diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index 0c092c2..0bd325a 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -6,6 +6,8 @@
 .. moduleauthor:: Guido van Rossum <guido@python.org>
 .. moduleauthor:: Mike Verdone <mike.verdone@gmail.com>
 .. moduleauthor:: Mark Russell <mark.russell@zen.co.uk>
+.. moduleauthor:: Antoine Pitrou <solipsis@pitrou.net>
+.. moduleauthor:: Amaury Forgeot d'Arc <amauryfa@gmail.com>
 .. sectionauthor:: Benjamin Peterson <benjamin@python.org>
 
 The :mod:`io` module provides the Python interfaces to stream handling.  The
@@ -364,6 +366,11 @@
       A :exc:`BlockingIOError` is raised if the underlying raw stream has no
       data at the moment.
 
+   .. method:: read1([n])
+
+      Read and return up to *n* bytes, with at most one call to the underlying
+      raw stream's :meth:`~RawIOBase.read` method.
+
    .. method:: readinto(b)
 
       Read up to len(b) bytes into bytearray *b* and return the number of bytes
@@ -501,7 +508,7 @@
 
    The constructor creates a :class:`BufferedWriter` for the given writeable
    *raw* stream.  If the *buffer_size* is not given, it defaults to
-   :data:`DEAFULT_BUFFER_SIZE`.  If *max_buffer_size* is omitted, it defaults to
+   :data:`DEFAULT_BUFFER_SIZE`.  If *max_buffer_size* is omitted, it defaults to
    twice the buffer size.
 
    :class:`BufferedWriter` provides or overrides these methods in addition to
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
new file mode 100644
index 0000000..5f2e400
--- /dev/null
+++ b/Lib/_pyio.py
@@ -0,0 +1,1831 @@
+"""
+Python implementation of the io module.
+"""
+
+import os
+import abc
+import codecs
+# Import _thread instead of threading to reduce startup cost
+try:
+    from _thread import allocate_lock as Lock
+except ImportError:
+    from _dummy_thread import allocate_lock as Lock
+
+import io
+from io import __all__
+
+# open() uses st_blksize whenever we can
+DEFAULT_BUFFER_SIZE = 8 * 1024  # bytes
+
+# NOTE: Base classes defined here are registered with the "official" ABCs
+# defined in io.py. We don't use real inheritance though, because we don't
+# want to inherit the C implementations.
+
+
+class BlockingIOError(IOError):
+
+    """Exception raised when I/O would block on a non-blocking I/O stream."""
+
+    def __init__(self, errno, strerror, characters_written=0):
+        super().__init__(errno, strerror)
+        if not isinstance(characters_written, int):
+            raise TypeError("characters_written must be a integer")
+        self.characters_written = characters_written
+
+
+def open(file, mode="r", buffering=None, encoding=None, errors=None,
+         newline=None, closefd=True):
+
+    r"""Open file and return a stream.  Raise IOError upon failure.
+
+    file is either a text or byte string giving the name (and the path
+    if the file isn't in the current working directory) of the file to
+    be opened or an integer file descriptor of the file to be
+    wrapped. (If a file descriptor is given, it is closed when the
+    returned I/O object is closed, unless closefd is set to False.)
+
+    mode is an optional string that specifies the mode in which the file
+    is opened. It defaults to 'r' which means open for reading in text
+    mode.  Other common values are 'w' for writing (truncating the file if
+    it already exists), and 'a' for appending (which on some Unix systems,
+    means that all writes append to the end of the file regardless of the
+    current seek position). In text mode, if encoding is not specified the
+    encoding used is platform dependent. (For reading and writing raw
+    bytes use binary mode and leave encoding unspecified.) The available
+    modes are:
+
+    ========= ===============================================================
+    Character Meaning
+    --------- ---------------------------------------------------------------
+    'r'       open for reading (default)
+    'w'       open for writing, truncating the file first
+    'a'       open for writing, appending to the end of the file if it exists
+    'b'       binary mode
+    't'       text mode (default)
+    '+'       open a disk file for updating (reading and writing)
+    'U'       universal newline mode (for backwards compatibility; unneeded
+              for new code)
+    ========= ===============================================================
+
+    The default mode is 'rt' (open for reading text). For binary random
+    access, the mode 'w+b' opens and truncates the file to 0 bytes, while
+    'r+b' opens the file without truncation.
+
+    Python distinguishes between files opened in binary and text modes,
+    even when the underlying operating system doesn't. Files opened in
+    binary mode (appending 'b' to the mode argument) return contents as
+    bytes objects without any decoding. In text mode (the default, or when
+    't' is appended to the mode argument), the contents of the file are
+    returned as strings, the bytes having been first decoded using a
+    platform-dependent encoding or using the specified encoding if given.
+
+    buffering is an optional integer used to set the buffering policy. By
+    default full buffering is on. Pass 0 to switch buffering off (only
+    allowed in binary mode), 1 to set line buffering, and an integer > 1
+    for full buffering.
+
+    encoding is the name of the encoding used to decode or encode the
+    file. This should only be used in text mode. The default encoding is
+    platform dependent, but any encoding supported by Python can be
+    passed.  See the codecs module for the list of supported encodings.
+
+    errors is an optional string that specifies how encoding errors are to
+    be handled---this argument should not be used in binary mode. Pass
+    'strict' to raise a ValueError exception if there is an encoding error
+    (the default of None has the same effect), or pass 'ignore' to ignore
+    errors. (Note that ignoring encoding errors can lead to data loss.)
+    See the documentation for codecs.register for a list of the permitted
+    encoding error strings.
+
+    newline controls how universal newlines works (it only applies to text
+    mode). It can be None, '', '\n', '\r', and '\r\n'.  It works as
+    follows:
+
+    * On input, if newline is None, universal newlines mode is
+      enabled. Lines in the input can end in '\n', '\r', or '\r\n', and
+      these are translated into '\n' before being returned to the
+      caller. If it is '', universal newline mode is enabled, but line
+      endings are returned to the caller untranslated. If it has any of
+      the other legal values, input lines are only terminated by the given
+      string, and the line ending is returned to the caller untranslated.
+
+    * On output, if newline is None, any '\n' characters written are
+      translated to the system default line separator, os.linesep. If
+      newline is '', no translation takes place. If newline is any of the
+      other legal values, any '\n' characters written are translated to
+      the given string.
+
+    If closefd is False, the underlying file descriptor will be kept open
+    when the file is closed. This does not work when a file name is given
+    and must be True in that case.
+
+    open() returns a file object whose type depends on the mode, and
+    through which the standard file operations such as reading and writing
+    are performed. When open() is used to open a file in a text mode ('w',
+    'r', 'wt', 'rt', etc.), it returns a TextIOWrapper. When used to open
+    a file in a binary mode, the returned class varies: in read binary
+    mode, it returns a BufferedReader; in write binary and append binary
+    modes, it returns a BufferedWriter, and in read/write mode, it returns
+    a BufferedRandom.
+
+    It is also possible to use a string or bytearray as a file for both
+    reading and writing. For strings StringIO can be used like a file
+    opened in a text mode, and for bytes a BytesIO can be used like a file
+    opened in a binary mode.
+    """
+    if not isinstance(file, (str, bytes, int)):
+        raise TypeError("invalid file: %r" % file)
+    if not isinstance(mode, str):
+        raise TypeError("invalid mode: %r" % mode)
+    if buffering is not None and not isinstance(buffering, int):
+        raise TypeError("invalid buffering: %r" % buffering)
+    if encoding is not None and not isinstance(encoding, str):
+        raise TypeError("invalid encoding: %r" % encoding)
+    if errors is not None and not isinstance(errors, str):
+        raise TypeError("invalid errors: %r" % errors)
+    modes = set(mode)
+    if modes - set("arwb+tU") or len(mode) > len(modes):
+        raise ValueError("invalid mode: %r" % mode)
+    reading = "r" in modes
+    writing = "w" in modes
+    appending = "a" in modes
+    updating = "+" in modes
+    text = "t" in modes
+    binary = "b" in modes
+    if "U" in modes:
+        if writing or appending:
+            raise ValueError("can't use U and writing mode at once")
+        reading = True
+    if text and binary:
+        raise ValueError("can't have text and binary mode at once")
+    if reading + writing + appending > 1:
+        raise ValueError("can't have read/write/append mode at once")
+    if not (reading or writing or appending):
+        raise ValueError("must have exactly one of read/write/append mode")
+    if binary and encoding is not None:
+        raise ValueError("binary mode doesn't take an encoding argument")
+    if binary and errors is not None:
+        raise ValueError("binary mode doesn't take an errors argument")
+    if binary and newline is not None:
+        raise ValueError("binary mode doesn't take a newline argument")
+    raw = FileIO(file,
+                 (reading and "r" or "") +
+                 (writing and "w" or "") +
+                 (appending and "a" or "") +
+                 (updating and "+" or ""),
+                 closefd)
+    if buffering is None:
+        buffering = -1
+    line_buffering = False
+    if buffering == 1 or buffering < 0 and raw.isatty():
+        buffering = -1
+        line_buffering = True
+    if buffering < 0:
+        buffering = DEFAULT_BUFFER_SIZE
+        try:
+            bs = os.fstat(raw.fileno()).st_blksize
+        except (os.error, AttributeError):
+            pass
+        else:
+            if bs > 1:
+                buffering = bs
+    if buffering < 0:
+        raise ValueError("invalid buffering size")
+    if buffering == 0:
+        if binary:
+            return raw
+        raise ValueError("can't have unbuffered text I/O")
+    if updating:
+        buffer = BufferedRandom(raw, buffering)
+    elif writing or appending:
+        buffer = BufferedWriter(raw, buffering)
+    elif reading:
+        buffer = BufferedReader(raw, buffering)
+    else:
+        raise ValueError("unknown mode: %r" % mode)
+    if binary:
+        return buffer
+    text = TextIOWrapper(buffer, encoding, errors, newline, line_buffering)
+    text.mode = mode
+    return text
+
+
+class DocDescriptor:
+    """Helper for builtins.open.__doc__
+    """
+    def __get__(self, obj, typ):
+        return (
+            "open(file, mode='r', buffering=None, encoding=None, "
+                 "errors=None, newline=None, closefd=True)\n\n" +
+            open.__doc__)
+
+class OpenWrapper:
+    """Wrapper for builtins.open
+
+    Trick so that open won't become a bound method when stored
+    as a class variable (as dbm.dumb does).
+
+    See initstdio() in Python/pythonrun.c.
+    """
+    __doc__ = DocDescriptor()
+
+    def __new__(cls, *args, **kwargs):
+        return open(*args, **kwargs)
+
+
+class UnsupportedOperation(ValueError, IOError):
+    pass
+
+
+class IOBase(metaclass=abc.ABCMeta):
+
+    """The abstract base class for all I/O classes, acting on streams of
+    bytes. There is no public constructor.
+
+    This class provides dummy implementations for many methods that
+    derived classes can override selectively; the default implementations
+    represent a file that cannot be read, written or seeked.
+
+    Even though IOBase does not declare read, readinto, or write because
+    their signatures will vary, implementations and clients should
+    consider those methods part of the interface. Also, implementations
+    may raise a IOError when operations they do not support are called.
+
+    The basic type used for binary data read from or written to a file is
+    bytes. bytearrays are accepted too, and in some cases (such as
+    readinto) needed. Text I/O classes work with str data.
+
+    Note that calling any method (even inquiries) on a closed stream is
+    undefined. Implementations may raise IOError in this case.
+
+    IOBase (and its subclasses) support the iterator protocol, meaning
+    that an IOBase object can be iterated over yielding the lines in a
+    stream.
+
+    IOBase also supports the :keyword:`with` statement. In this example,
+    fp is closed after the suite of the with statement is complete:
+
+    with open('spam.txt', 'r') as fp:
+        fp.write('Spam and eggs!')
+    """
+
+    ### Internal ###
+
+    def _unsupported(self, name: str) -> IOError:
+        """Internal: raise an exception for unsupported operations."""
+        raise UnsupportedOperation("%s.%s() not supported" %
+                                   (self.__class__.__name__, name))
+
+    ### Positioning ###
+
+    def seek(self, pos: int, whence: int = 0) -> int:
+        """Change stream position.
+
+        Change the stream position to byte offset offset. offset is
+        interpreted relative to the position indicated by whence.  Values
+        for whence are:
+
+        * 0 -- start of stream (the default); offset should be zero or positive
+        * 1 -- current stream position; offset may be negative
+        * 2 -- end of stream; offset is usually negative
+
+        Return the new absolute position.
+        """
+        self._unsupported("seek")
+
+    def tell(self) -> int:
+        """Return current stream position."""
+        return self.seek(0, 1)
+
+    def truncate(self, pos: int = None) -> int:
+        """Truncate file to size bytes.
+
+        Size defaults to the current IO position as reported by tell().  Return
+        the new size.
+        """
+        self._unsupported("truncate")
+
+    ### Flush and close ###
+
+    def flush(self) -> None:
+        """Flush write buffers, if applicable.
+
+        This is not implemented for read-only and non-blocking streams.
+        """
+        # XXX Should this return the number of bytes written???
+
+    __closed = False
+
+    def close(self) -> None:
+        """Flush and close the IO object.
+
+        This method has no effect if the file is already closed.
+        """
+        if not self.__closed:
+            try:
+                self.flush()
+            except IOError:
+                pass  # If flush() fails, just give up
+            self.__closed = True
+
+    def __del__(self) -> None:
+        """Destructor.  Calls close()."""
+        # The try/except block is in case this is called at program
+        # exit time, when it's possible that globals have already been
+        # deleted, and then the close() call might fail.  Since
+        # there's nothing we can do about such failures and they annoy
+        # the end users, we suppress the traceback.
+        try:
+            self.close()
+        except:
+            pass
+
+    ### Inquiries ###
+
+    def seekable(self) -> bool:
+        """Return whether object supports random access.
+
+        If False, seek(), tell() and truncate() will raise IOError.
+        This method may need to do a test seek().
+        """
+        return False
+
+    def _checkSeekable(self, msg=None):
+        """Internal: raise an IOError if file is not seekable
+        """
+        if not self.seekable():
+            raise IOError("File or stream is not seekable."
+                          if msg is None else msg)
+
+
+    def readable(self) -> bool:
+        """Return whether object was opened for reading.
+
+        If False, read() will raise IOError.
+        """
+        return False
+
+    def _checkReadable(self, msg=None):
+        """Internal: raise an IOError if file is not readable
+        """
+        if not self.readable():
+            raise IOError("File or stream is not readable."
+                          if msg is None else msg)
+
+    def writable(self) -> bool:
+        """Return whether object was opened for writing.
+
+        If False, write() and truncate() will raise IOError.
+        """
+        return False
+
+    def _checkWritable(self, msg=None):
+        """Internal: raise an IOError if file is not writable
+        """
+        if not self.writable():
+            raise IOError("File or stream is not writable."
+                          if msg is None else msg)
+
+    @property
+    def closed(self):
+        """closed: bool.  True iff the file has been closed.
+
+        For backwards compatibility, this is a property, not a predicate.
+        """
+        return self.__closed
+
+    def _checkClosed(self, msg=None):
+        """Internal: raise an ValueError if file is closed
+        """
+        if self.closed:
+            raise ValueError("I/O operation on closed file."
+                             if msg is None else msg)
+
+    ### Context manager ###
+
+    def __enter__(self) -> "IOBase":  # That's a forward reference
+        """Context management protocol.  Returns self."""
+        self._checkClosed()
+        return self
+
+    def __exit__(self, *args) -> None:
+        """Context management protocol.  Calls close()"""
+        self.close()
+
+    ### Lower-level APIs ###
+
+    # XXX Should these be present even if unimplemented?
+
+    def fileno(self) -> int:
+        """Returns underlying file descriptor if one exists.
+
+        An IOError is raised if the IO object does not use a file descriptor.
+        """
+        self._unsupported("fileno")
+
+    def isatty(self) -> bool:
+        """Return whether this is an 'interactive' stream.
+
+        Return False if it can't be determined.
+        """
+        self._checkClosed()
+        return False
+
+    ### Readline[s] and writelines ###
+
+    def readline(self, limit: int = -1) -> bytes:
+        r"""Read and return a line from the stream.
+
+        If limit is specified, at most limit bytes will be read.
+
+        The line terminator is always b'\n' for binary files; for text
+        files, the newlines argument to open can be used to select the line
+        terminator(s) recognized.
+        """
+        # For backwards compatibility, a (slowish) readline().
+        if hasattr(self, "peek"):
+            def nreadahead():
+                readahead = self.peek(1)
+                if not readahead:
+                    return 1
+                n = (readahead.find(b"\n") + 1) or len(readahead)
+                if limit >= 0:
+                    n = min(n, limit)
+                return n
+        else:
+            def nreadahead():
+                return 1
+        if limit is None:
+            limit = -1
+        res = bytearray()
+        while limit < 0 or len(res) < limit:
+            b = self.read(nreadahead())
+            if not b:
+                break
+            res += b
+            if res.endswith(b"\n"):
+                break
+        return bytes(res)
+
+    def __iter__(self):
+        self._checkClosed()
+        return self
+
+    def __next__(self):
+        line = self.readline()
+        if not line:
+            raise StopIteration
+        return line
+
+    def readlines(self, hint=None):
+        """Return a list of lines from the stream.
+
+        hint can be specified to control the number of lines read: no more
+        lines will be read if the total size (in bytes/characters) of all
+        lines so far exceeds hint.
+        """
+        if hint is None or hint <= 0:
+            return list(self)
+        n = 0
+        lines = []
+        for line in self:
+            lines.append(line)
+            n += len(line)
+            if n >= hint:
+                break
+        return lines
+
+    def writelines(self, lines):
+        self._checkClosed()
+        for line in lines:
+            self.write(line)
+
+io.IOBase.register(IOBase)
+
+
+class RawIOBase(IOBase):
+
+    """Base class for raw binary I/O."""
+
+    # The read() method is implemented by calling readinto(); derived
+    # classes that want to support read() only need to implement
+    # readinto() as a primitive operation.  In general, readinto() can be
+    # more efficient than read().
+
+    # (It would be tempting to also provide an implementation of
+    # readinto() in terms of read(), in case the latter is a more suitable
+    # primitive operation, but that would lead to nasty recursion in case
+    # a subclass doesn't implement either.)
+
+    def read(self, n: int = -1) -> bytes:
+        """Read and return up to n bytes.
+
+        Returns an empty bytes object on EOF, or None if the object is
+        set not to block and has no data to read.
+        """
+        if n is None:
+            n = -1
+        if n < 0:
+            return self.readall()
+        b = bytearray(n.__index__())
+        n = self.readinto(b)
+        del b[n:]
+        return bytes(b)
+
+    def readall(self):
+        """Read until EOF, using multiple read() call."""
+        res = bytearray()
+        while True:
+            data = self.read(DEFAULT_BUFFER_SIZE)
+            if not data:
+                break
+            res += data
+        return bytes(res)
+
+    def readinto(self, b: bytearray) -> int:
+        """Read up to len(b) bytes into b.
+
+        Returns number of bytes read (0 for EOF), or None if the object
+        is set not to block as has no data to read.
+        """
+        self._unsupported("readinto")
+
+    def write(self, b: bytes) -> int:
+        """Write the given buffer to the IO stream.
+
+        Returns the number of bytes written, which may be less than len(b).
+        """
+        self._unsupported("write")
+
+io.RawIOBase.register(RawIOBase)
+from _io import FileIO
+RawIOBase.register(FileIO)
+
+
+class BufferedIOBase(IOBase):
+
+    """Base class for buffered IO objects.
+
+    The main difference with RawIOBase is that the read() method
+    supports omitting the size argument, and does not have a default
+    implementation that defers to readinto().
+
+    In addition, read(), readinto() and write() may raise
+    BlockingIOError if the underlying raw stream is in non-blocking
+    mode and not ready; unlike their raw counterparts, they will never
+    return None.
+
+    A typical implementation should not inherit from a RawIOBase
+    implementation, but wrap one.
+    """
+
+    def read(self, n: int = None) -> bytes:
+        """Read and return up to n bytes.
+
+        If the argument is omitted, None, or negative, reads and
+        returns all data until EOF.
+
+        If the argument is positive, and the underlying raw stream is
+        not 'interactive', multiple raw reads may be issued to satisfy
+        the byte count (unless EOF is reached first).  But for
+        interactive raw streams (XXX and for pipes?), at most one raw
+        read will be issued, and a short result does not imply that
+        EOF is imminent.
+
+        Returns an empty bytes array on EOF.
+
+        Raises BlockingIOError if the underlying raw stream has no
+        data at the moment.
+        """
+        self._unsupported("read")
+
+    def read1(self, n: int=None) -> bytes:
+        """Read up to n bytes with at most one read() system call."""
+        self._unsupported("read1")
+
+    def readinto(self, b: bytearray) -> int:
+        """Read up to len(b) bytes into b.
+
+        Like read(), this may issue multiple reads to the underlying raw
+        stream, unless the latter is 'interactive'.
+
+        Returns the number of bytes read (0 for EOF).
+
+        Raises BlockingIOError if the underlying raw stream has no
+        data at the moment.
+        """
+        # XXX This ought to work with anything that supports the buffer API
+        data = self.read(len(b))
+        n = len(data)
+        try:
+            b[:n] = data
+        except TypeError as err:
+            import array
+            if not isinstance(b, array.array):
+                raise err
+            b[:n] = array.array('b', data)
+        return n
+
+    def write(self, b: bytes) -> int:
+        """Write the given buffer to the IO stream.
+
+        Return the number of bytes written, which is never less than
+        len(b).
+
+        Raises BlockingIOError if the buffer is full and the
+        underlying raw stream cannot accept more data at the moment.
+        """
+        self._unsupported("write")
+
+io.BufferedIOBase.register(BufferedIOBase)
+
+
+class _BufferedIOMixin(BufferedIOBase):
+
+    """A mixin implementation of BufferedIOBase with an underlying raw stream.
+
+    This passes most requests on to the underlying raw stream.  It
+    does *not* provide implementations of read(), readinto() or
+    write().
+    """
+
+    def __init__(self, raw):
+        self.raw = raw
+
+    ### Positioning ###
+
+    def seek(self, pos, whence=0):
+        new_position = self.raw.seek(pos, whence)
+        if new_position < 0:
+            raise IOError("seek() returned an invalid position")
+        return new_position
+
+    def tell(self):
+        pos = self.raw.tell()
+        if pos < 0:
+            raise IOError("tell() returned an invalid position")
+        return pos
+
+    def truncate(self, pos=None):
+        # Flush the stream.  We're mixing buffered I/O with lower-level I/O,
+        # and a flush may be necessary to synch both views of the current
+        # file state.
+        self.flush()
+
+        if pos is None:
+            pos = self.tell()
+        # XXX: Should seek() be used, instead of passing the position
+        # XXX  directly to truncate?
+        return self.raw.truncate(pos)
+
+    ### Flush and close ###
+
+    def flush(self):
+        self.raw.flush()
+
+    def close(self):
+        if not self.closed:
+            try:
+                self.flush()
+            except IOError:
+                pass  # If flush() fails, just give up
+            self.raw.close()
+
+    ### Inquiries ###
+
+    def seekable(self):
+        return self.raw.seekable()
+
+    def readable(self):
+        return self.raw.readable()
+
+    def writable(self):
+        return self.raw.writable()
+
+    @property
+    def closed(self):
+        return self.raw.closed
+
+    @property
+    def name(self):
+        return self.raw.name
+
+    @property
+    def mode(self):
+        return self.raw.mode
+
+    ### Lower-level APIs ###
+
+    def fileno(self):
+        return self.raw.fileno()
+
+    def isatty(self):
+        return self.raw.isatty()
+
+
+class BytesIO(BufferedIOBase):
+
+    """Buffered I/O implementation using an in-memory bytes buffer."""
+
+    def __init__(self, initial_bytes=None):
+        buf = bytearray()
+        if initial_bytes is not None:
+            buf += initial_bytes
+        self._buffer = buf
+        self._pos = 0
+
+    def getvalue(self):
+        """Return the bytes value (contents) of the buffer
+        """
+        if self.closed:
+            raise ValueError("getvalue on closed file")
+        return bytes(self._buffer)
+
+    def read(self, n=None):
+        if self.closed:
+            raise ValueError("read from closed file")
+        if n is None:
+            n = -1
+        if n < 0:
+            n = len(self._buffer)
+        if len(self._buffer) <= self._pos:
+            return b""
+        newpos = min(len(self._buffer), self._pos + n)
+        b = self._buffer[self._pos : newpos]
+        self._pos = newpos
+        return bytes(b)
+
+    def read1(self, n):
+        """This is the same as read.
+        """
+        return self.read(n)
+
+    def write(self, b):
+        if self.closed:
+            raise ValueError("write to closed file")
+        if isinstance(b, str):
+            raise TypeError("can't write str to binary stream")
+        n = len(b)
+        if n == 0:
+            return 0
+        pos = self._pos
+        if pos > len(self._buffer):
+            # Inserts null bytes between the current end of the file
+            # and the new write position.
+            padding = b'\x00' * (pos - len(self._buffer))
+            self._buffer += padding
+        self._buffer[pos:pos + n] = b
+        self._pos += n
+        return n
+
+    def seek(self, pos, whence=0):
+        if self.closed:
+            raise ValueError("seek on closed file")
+        try:
+            pos = pos.__index__()
+        except AttributeError as err:
+            raise TypeError("an integer is required") from err
+        if whence == 0:
+            if pos < 0:
+                raise ValueError("negative seek position %r" % (pos,))
+            self._pos = pos
+        elif whence == 1:
+            self._pos = max(0, self._pos + pos)
+        elif whence == 2:
+            self._pos = max(0, len(self._buffer) + pos)
+        else:
+            raise ValueError("invalid whence value")
+        return self._pos
+
+    def tell(self):
+        if self.closed:
+            raise ValueError("tell on closed file")
+        return self._pos
+
+    def truncate(self, pos=None):
+        if self.closed:
+            raise ValueError("truncate on closed file")
+        if pos is None:
+            pos = self._pos
+        elif pos < 0:
+            raise ValueError("negative truncate position %r" % (pos,))
+        del self._buffer[pos:]
+        return self.seek(pos)
+
+    def readable(self):
+        return True
+
+    def writable(self):
+        return True
+
+    def seekable(self):
+        return True
+
+
+class BufferedReader(_BufferedIOMixin):
+
+    """BufferedReader(raw[, buffer_size])
+
+    A buffer for a readable, sequential BaseRawIO object.
+
+    The constructor creates a BufferedReader for the given readable raw
+    stream and buffer_size. If buffer_size is omitted, DEFAULT_BUFFER_SIZE
+    is used.
+    """
+
+    def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE):
+        """Create a new buffered reader using the given readable raw IO object.
+        """
+        raw._checkReadable()
+        _BufferedIOMixin.__init__(self, raw)
+        if buffer_size <= 0:
+            raise ValueError("invalid buffer size")
+        self.buffer_size = buffer_size
+        self._reset_read_buf()
+        self._read_lock = Lock()
+
+    def _reset_read_buf(self):
+        self._read_buf = b""
+        self._read_pos = 0
+
+    def read(self, n=None):
+        """Read n bytes.
+
+        Returns exactly n bytes of data unless the underlying raw IO
+        stream reaches EOF or if the call would block in non-blocking
+        mode. If n is negative, read until EOF or until read() would
+        block.
+        """
+        if n is not None and n < -1:
+            raise ValueError("invalid number of bytes to read")
+        with self._read_lock:
+            return self._read_unlocked(n)
+
+    def _read_unlocked(self, n=None):
+        nodata_val = b""
+        empty_values = (b"", None)
+        buf = self._read_buf
+        pos = self._read_pos
+
+        # Special case for when the number of bytes to read is unspecified.
+        if n is None or n == -1:
+            self._reset_read_buf()
+            chunks = [buf[pos:]]  # Strip the consumed bytes.
+            current_size = 0
+            while True:
+                # Read until EOF or until read() would block.
+                chunk = self.raw.read()
+                if chunk in empty_values:
+                    nodata_val = chunk
+                    break
+                current_size += len(chunk)
+                chunks.append(chunk)
+            return b"".join(chunks) or nodata_val
+
+        # The number of bytes to read is specified, return at most n bytes.
+        avail = len(buf) - pos  # Length of the available buffered data.
+        if n <= avail:
+            # Fast path: the data to read is fully buffered.
+            self._read_pos += n
+            return buf[pos:pos+n]
+        # Slow path: read from the stream until enough bytes are read,
+        # or until an EOF occurs or until read() would block.
+        chunks = [buf[pos:]]
+        wanted = max(self.buffer_size, n)
+        while avail < n:
+            chunk = self.raw.read(wanted)
+            if chunk in empty_values:
+                nodata_val = chunk
+                break
+            avail += len(chunk)
+            chunks.append(chunk)
+        # n is more then avail only when an EOF occurred or when
+        # read() would have blocked.
+        n = min(n, avail)
+        out = b"".join(chunks)
+        self._read_buf = out[n:]  # Save the extra data in the buffer.
+        self._read_pos = 0
+        return out[:n] if out else nodata_val
+
+    def peek(self, n=0):
+        """Returns buffered bytes without advancing the position.
+
+        The argument indicates a desired minimal number of bytes; we
+        do at most one raw read to satisfy it.  We never return more
+        than self.buffer_size.
+        """
+        with self._read_lock:
+            return self._peek_unlocked(n)
+
+    def _peek_unlocked(self, n=0):
+        want = min(n, self.buffer_size)
+        have = len(self._read_buf) - self._read_pos
+        if have < want or have <= 0:
+            to_read = self.buffer_size - have
+            current = self.raw.read(to_read)
+            if current:
+                self._read_buf = self._read_buf[self._read_pos:] + current
+                self._read_pos = 0
+        return self._read_buf[self._read_pos:]
+
+    def read1(self, n):
+        """Reads up to n bytes, with at most one read() system call."""
+        # Returns up to n bytes.  If at least one byte is buffered, we
+        # only return buffered bytes.  Otherwise, we do one raw read.
+        if n < 0:
+            raise ValueError("number of bytes to read must be positive")
+        if n == 0:
+            return b""
+        with self._read_lock:
+            self._peek_unlocked(1)
+            return self._read_unlocked(
+                min(n, len(self._read_buf) - self._read_pos))
+
+    def tell(self):
+        return _BufferedIOMixin.tell(self) - len(self._read_buf) + self._read_pos
+
+    def seek(self, pos, whence=0):
+        if not (0 <= whence <= 2):
+            raise ValueError("invalid whence value")
+        with self._read_lock:
+            if whence == 1:
+                pos -= len(self._read_buf) - self._read_pos
+            pos = _BufferedIOMixin.seek(self, pos, whence)
+            self._reset_read_buf()
+            return pos
+
+class BufferedWriter(_BufferedIOMixin):
+
+    """A buffer for a writeable sequential RawIO object.
+
+    The constructor creates a BufferedWriter for the given writeable raw
+    stream. If the buffer_size is not given, it defaults to
+    DEFAULT_BUFFER_SIZE. If max_buffer_size is omitted, it defaults to
+    twice the buffer size.
+    """
+
+    def __init__(self, raw,
+                 buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):
+        raw._checkWritable()
+        _BufferedIOMixin.__init__(self, raw)
+        if buffer_size <= 0:
+            raise ValueError("invalid buffer size")
+        self.buffer_size = buffer_size
+        self.max_buffer_size = (2*buffer_size
+                                if max_buffer_size is None
+                                else max_buffer_size)
+        self._write_buf = bytearray()
+        self._write_lock = Lock()
+
+    def write(self, b):
+        if self.closed:
+            raise ValueError("write to closed file")
+        if isinstance(b, str):
+            raise TypeError("can't write str to binary stream")
+        with self._write_lock:
+            # XXX we can implement some more tricks to try and avoid
+            # partial writes
+            if len(self._write_buf) > self.buffer_size:
+                # We're full, so let's pre-flush the buffer
+                try:
+                    self._flush_unlocked()
+                except BlockingIOError as e:
+                    # We can't accept anything else.
+                    # XXX Why not just let the exception pass through?
+                    raise BlockingIOError(e.errno, e.strerror, 0)
+            before = len(self._write_buf)
+            self._write_buf.extend(b)
+            written = len(self._write_buf) - before
+            if len(self._write_buf) > self.buffer_size:
+                try:
+                    self._flush_unlocked()
+                except BlockingIOError as e:
+                    if len(self._write_buf) > self.max_buffer_size:
+                        # We've hit max_buffer_size. We have to accept a
+                        # partial write and cut back our buffer.
+                        overage = len(self._write_buf) - self.max_buffer_size
+                        written -= overage
+                        self._write_buf = self._write_buf[:self.max_buffer_size]
+                        raise BlockingIOError(e.errno, e.strerror, written)
+            return written
+
+    def truncate(self, pos=None):
+        with self._write_lock:
+            self._flush_unlocked()
+            if pos is None:
+                pos = self.raw.tell()
+            return self.raw.truncate(pos)
+
+    def flush(self):
+        with self._write_lock:
+            self._flush_unlocked()
+
+    def _flush_unlocked(self):
+        if self.closed:
+            raise ValueError("flush of closed file")
+        written = 0
+        try:
+            while self._write_buf:
+                n = self.raw.write(self._write_buf)
+                if n > len(self._write_buf) or n < 0:
+                    raise IOError("write() returned incorrect number of bytes")
+                del self._write_buf[:n]
+                written += n
+        except BlockingIOError as e:
+            n = e.characters_written
+            del self._write_buf[:n]
+            written += n
+            raise BlockingIOError(e.errno, e.strerror, written)
+
+    def tell(self):
+        return _BufferedIOMixin.tell(self) + len(self._write_buf)
+
+    def seek(self, pos, whence=0):
+        if not (0 <= whence <= 2):
+            raise ValueError("invalid whence")
+        with self._write_lock:
+            self._flush_unlocked()
+            return _BufferedIOMixin.seek(self, pos, whence)
+
+
+class BufferedRWPair(BufferedIOBase):
+
+    """A buffered reader and writer object together.
+
+    A buffered reader object and buffered writer object put together to
+    form a sequential IO object that can read and write. This is typically
+    used with a socket or two-way pipe.
+
+    reader and writer are RawIOBase objects that are readable and
+    writeable respectively. If the buffer_size is omitted it defaults to
+    DEFAULT_BUFFER_SIZE. The max_buffer_size (for the buffered writer)
+    defaults to twice the buffer size.
+    """
+
+    # XXX The usefulness of this (compared to having two separate IO
+    # objects) is questionable.
+
+    def __init__(self, reader, writer,
+                 buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):
+        """Constructor.
+
+        The arguments are two RawIO instances.
+        """
+        reader._checkReadable()
+        writer._checkWritable()
+        self.reader = BufferedReader(reader, buffer_size)
+        self.writer = BufferedWriter(writer, buffer_size, max_buffer_size)
+
+    def read(self, n=None):
+        if n is None:
+            n = -1
+        return self.reader.read(n)
+
+    def readinto(self, b):
+        return self.reader.readinto(b)
+
+    def write(self, b):
+        return self.writer.write(b)
+
+    def peek(self, n=0):
+        return self.reader.peek(n)
+
+    def read1(self, n):
+        return self.reader.read1(n)
+
+    def readable(self):
+        return self.reader.readable()
+
+    def writable(self):
+        return self.writer.writable()
+
+    def flush(self):
+        return self.writer.flush()
+
+    def close(self):
+        self.writer.close()
+        self.reader.close()
+
+    def isatty(self):
+        return self.reader.isatty() or self.writer.isatty()
+
+    @property
+    def closed(self):
+        return self.writer.closed
+
+
+class BufferedRandom(BufferedWriter, BufferedReader):
+
+    """A buffered interface to random access streams.
+
+    The constructor creates a reader and writer for a seekable stream,
+    raw, given in the first argument. If the buffer_size is omitted it
+    defaults to DEFAULT_BUFFER_SIZE. The max_buffer_size (for the buffered
+    writer) defaults to twice the buffer size.
+    """
+
+    def __init__(self, raw,
+                 buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):
+        raw._checkSeekable()
+        BufferedReader.__init__(self, raw, buffer_size)
+        BufferedWriter.__init__(self, raw, buffer_size, max_buffer_size)
+
+    def seek(self, pos, whence=0):
+        if not (0 <= whence <= 2):
+            raise ValueError("invalid whence")
+        self.flush()
+        if self._read_buf:
+            # Undo read ahead.
+            with self._read_lock:
+                self.raw.seek(self._read_pos - len(self._read_buf), 1)
+        # First do the raw seek, then empty the read buffer, so that
+        # if the raw seek fails, we don't lose buffered data forever.
+        pos = self.raw.seek(pos, whence)
+        with self._read_lock:
+            self._reset_read_buf()
+        if pos < 0:
+            raise IOError("seek() returned invalid position")
+        return pos
+
+    def tell(self):
+        if self._write_buf:
+            return BufferedWriter.tell(self)
+        else:
+            return BufferedReader.tell(self)
+
+    def truncate(self, pos=None):
+        if pos is None:
+            pos = self.tell()
+        # Use seek to flush the read buffer.
+        self.seek(pos)
+        return BufferedWriter.truncate(self)
+
+    def read(self, n=None):
+        if n is None:
+            n = -1
+        self.flush()
+        return BufferedReader.read(self, n)
+
+    def readinto(self, b):
+        self.flush()
+        return BufferedReader.readinto(self, b)
+
+    def peek(self, n=0):
+        self.flush()
+        return BufferedReader.peek(self, n)
+
+    def read1(self, n):
+        self.flush()
+        return BufferedReader.read1(self, n)
+
+    def write(self, b):
+        if self._read_buf:
+            # Undo readahead
+            with self._read_lock:
+                self.raw.seek(self._read_pos - len(self._read_buf), 1)
+                self._reset_read_buf()
+        return BufferedWriter.write(self, b)
+
+
+class TextIOBase(IOBase):
+
+    """Base class for text I/O.
+
+    This class provides a character and line based interface to stream
+    I/O. There is no readinto method because Python's character strings
+    are immutable. There is no public constructor.
+    """
+
+    def read(self, n: int = -1) -> str:
+        """Read at most n characters from stream.
+
+        Read from underlying buffer until we have n characters or we hit EOF.
+        If n is negative or omitted, read until EOF.
+        """
+        self._unsupported("read")
+
+    def write(self, s: str) -> int:
+        """Write string s to stream."""
+        self._unsupported("write")
+
+    def truncate(self, pos: int = None) -> int:
+        """Truncate size to pos."""
+        self._unsupported("truncate")
+
+    def readline(self) -> str:
+        """Read until newline or EOF.
+
+        Returns an empty string if EOF is hit immediately.
+        """
+        self._unsupported("readline")
+
+    @property
+    def encoding(self):
+        """Subclasses should override."""
+        return None
+
+    @property
+    def newlines(self):
+        """Line endings translated so far.
+
+        Only line endings translated during reading are considered.
+
+        Subclasses should override.
+        """
+        return None
+
+io.TextIOBase.register(TextIOBase)
+
+
+class IncrementalNewlineDecoder(codecs.IncrementalDecoder):
+    r"""Codec used when reading a file in universal newlines mode.  It wraps
+    another incremental decoder, translating \r\n and \r into \n.  It also
+    records the types of newlines encountered.  When used with
+    translate=False, it ensures that the newline sequence is returned in
+    one piece.
+    """
+    def __init__(self, decoder, translate, errors='strict'):
+        codecs.IncrementalDecoder.__init__(self, errors=errors)
+        self.translate = translate
+        self.decoder = decoder
+        self.seennl = 0
+        self.pendingcr = False
+
+    def decode(self, input, final=False):
+        # decode input (with the eventual \r from a previous pass)
+        if self.decoder is None:
+            output = input
+        else:
+            output = self.decoder.decode(input, final=final)
+        if self.pendingcr and (output or final):
+            output = "\r" + output
+            self.pendingcr = False
+
+        # retain last \r even when not translating data:
+        # then readline() is sure to get \r\n in one pass
+        if output.endswith("\r") and not final:
+            output = output[:-1]
+            self.pendingcr = True
+
+        # Record which newlines are read
+        crlf = output.count('\r\n')
+        cr = output.count('\r') - crlf
+        lf = output.count('\n') - crlf
+        self.seennl |= (lf and self._LF) | (cr and self._CR) \
+                    | (crlf and self._CRLF)
+
+        if self.translate:
+            if crlf:
+                output = output.replace("\r\n", "\n")
+            if cr:
+                output = output.replace("\r", "\n")
+
+        return output
+
+    def getstate(self):
+        if self.decoder is None:
+            buf = b""
+            flag = 0
+        else:
+            buf, flag = self.decoder.getstate()
+        flag <<= 1
+        if self.pendingcr:
+            flag |= 1
+        return buf, flag
+
+    def setstate(self, state):
+        buf, flag = state
+        self.pendingcr = bool(flag & 1)
+        if self.decoder is not None:
+            self.decoder.setstate((buf, flag >> 1))
+
+    def reset(self):
+        self.seennl = 0
+        self.pendingcr = False
+        if self.decoder is not None:
+            self.decoder.reset()
+
+    _LF = 1
+    _CR = 2
+    _CRLF = 4
+
+    @property
+    def newlines(self):
+        return (None,
+                "\n",
+                "\r",
+                ("\r", "\n"),
+                "\r\n",
+                ("\n", "\r\n"),
+                ("\r", "\r\n"),
+                ("\r", "\n", "\r\n")
+               )[self.seennl]
+
+
+class TextIOWrapper(TextIOBase):
+
+    r"""Character and line based layer over a BufferedIOBase object, buffer.
+
+    encoding gives the name of the encoding that the stream will be
+    decoded or encoded with. It defaults to locale.getpreferredencoding.
+
+    errors determines the strictness of encoding and decoding (see the
+    codecs.register) and defaults to "strict".
+
+    newline can be None, '', '\n', '\r', or '\r\n'.  It controls the
+    handling of line endings. If it is None, universal newlines is
+    enabled.  With this enabled, on input, the lines endings '\n', '\r',
+    or '\r\n' are translated to '\n' before being returned to the
+    caller. Conversely, on output, '\n' is translated to the system
+    default line seperator, os.linesep. If newline is any other of its
+    legal values, that newline becomes the newline when the file is read
+    and it is returned untranslated. On output, '\n' is converted to the
+    newline.
+
+    If line_buffering is True, a call to flush is implied when a call to
+    write contains a newline character.
+    """
+
+    _CHUNK_SIZE = 2048
+
+    def __init__(self, buffer, encoding=None, errors=None, newline=None,
+                 line_buffering=False):
+        if newline is not None and not isinstance(newline, str):
+            raise TypeError("illegal newline type: %r" % (type(newline),))
+        if newline not in (None, "", "\n", "\r", "\r\n"):
+            raise ValueError("illegal newline value: %r" % (newline,))
+        if encoding is None:
+            try:
+                encoding = os.device_encoding(buffer.fileno())
+            except (AttributeError, UnsupportedOperation):
+                pass
+            if encoding is None:
+                try:
+                    import locale
+                except ImportError:
+                    # Importing locale may fail if Python is being built
+                    encoding = "ascii"
+                else:
+                    encoding = locale.getpreferredencoding()
+
+        if not isinstance(encoding, str):
+            raise ValueError("invalid encoding: %r" % encoding)
+
+        if errors is None:
+            errors = "strict"
+        else:
+            if not isinstance(errors, str):
+                raise ValueError("invalid errors: %r" % errors)
+
+        self.buffer = buffer
+        self._line_buffering = line_buffering
+        self._encoding = encoding
+        self._errors = errors
+        self._readuniversal = not newline
+        self._readtranslate = newline is None
+        self._readnl = newline
+        self._writetranslate = newline != ''
+        self._writenl = newline or os.linesep
+        self._encoder = None
+        self._decoder = None
+        self._decoded_chars = ''  # buffer for text returned from decoder
+        self._decoded_chars_used = 0  # offset into _decoded_chars for read()
+        self._snapshot = None  # info for reconstructing decoder state
+        self._seekable = self._telling = self.buffer.seekable()
+
+    # self._snapshot is either None, or a tuple (dec_flags, next_input)
+    # where dec_flags is the second (integer) item of the decoder state
+    # and next_input is the chunk of input bytes that comes next after the
+    # snapshot point.  We use this to reconstruct decoder states in tell().
+
+    # Naming convention:
+    #   - "bytes_..." for integer variables that count input bytes
+    #   - "chars_..." for integer variables that count decoded characters
+
+    @property
+    def encoding(self):
+        return self._encoding
+
+    @property
+    def errors(self):
+        return self._errors
+
+    @property
+    def line_buffering(self):
+        return self._line_buffering
+
+    def seekable(self):
+        return self._seekable
+
+    def readable(self):
+        return self.buffer.readable()
+
+    def writable(self):
+        return self.buffer.writable()
+
+    def flush(self):
+        self.buffer.flush()
+        self._telling = self._seekable
+
+    def close(self):
+        try:
+            self.flush()
+        except:
+            pass  # If flush() fails, just give up
+        self.buffer.close()
+
+    @property
+    def closed(self):
+        return self.buffer.closed
+
+    @property
+    def name(self):
+        return self.buffer.name
+
+    def fileno(self):
+        return self.buffer.fileno()
+
+    def isatty(self):
+        return self.buffer.isatty()
+
+    def write(self, s: str):
+        if self.closed:
+            raise ValueError("write to closed file")
+        if not isinstance(s, str):
+            raise TypeError("can't write %s to text stream" %
+                            s.__class__.__name__)
+        length = len(s)
+        haslf = (self._writetranslate or self._line_buffering) and "\n" in s
+        if haslf and self._writetranslate and self._writenl != "\n":
+            s = s.replace("\n", self._writenl)
+        encoder = self._encoder or self._get_encoder()
+        # XXX What if we were just reading?
+        b = encoder.encode(s)
+        self.buffer.write(b)
+        if self._line_buffering and (haslf or "\r" in s):
+            self.flush()
+        self._snapshot = None
+        if self._decoder:
+            self._decoder.reset()
+        return length
+
+    def _get_encoder(self):
+        make_encoder = codecs.getincrementalencoder(self._encoding)
+        self._encoder = make_encoder(self._errors)
+        return self._encoder
+
+    def _get_decoder(self):
+        make_decoder = codecs.getincrementaldecoder(self._encoding)
+        decoder = make_decoder(self._errors)
+        if self._readuniversal:
+            decoder = IncrementalNewlineDecoder(decoder, self._readtranslate)
+        self._decoder = decoder
+        return decoder
+
+    # The following three methods implement an ADT for _decoded_chars.
+    # Text returned from the decoder is buffered here until the client
+    # requests it by calling our read() or readline() method.
+    def _set_decoded_chars(self, chars):
+        """Set the _decoded_chars buffer."""
+        self._decoded_chars = chars
+        self._decoded_chars_used = 0
+
+    def _get_decoded_chars(self, n=None):
+        """Advance into the _decoded_chars buffer."""
+        offset = self._decoded_chars_used
+        if n is None:
+            chars = self._decoded_chars[offset:]
+        else:
+            chars = self._decoded_chars[offset:offset + n]
+        self._decoded_chars_used += len(chars)
+        return chars
+
+    def _rewind_decoded_chars(self, n):
+        """Rewind the _decoded_chars buffer."""
+        if self._decoded_chars_used < n:
+            raise AssertionError("rewind decoded_chars out of bounds")
+        self._decoded_chars_used -= n
+
+    def _read_chunk(self):
+        """
+        Read and decode the next chunk of data from the BufferedReader.
+        """
+
+        # The return value is True unless EOF was reached.  The decoded
+        # string is placed in self._decoded_chars (replacing its previous
+        # value).  The entire input chunk is sent to the decoder, though
+        # some of it may remain buffered in the decoder, yet to be
+        # converted.
+
+        if self._decoder is None:
+            raise ValueError("no decoder")
+
+        if self._telling:
+            # To prepare for tell(), we need to snapshot a point in the
+            # file where the decoder's input buffer is empty.
+
+            dec_buffer, dec_flags = self._decoder.getstate()
+            # Given this, we know there was a valid snapshot point
+            # len(dec_buffer) bytes ago with decoder state (b'', dec_flags).
+
+        # Read a chunk, decode it, and put the result in self._decoded_chars.
+        input_chunk = self.buffer.read1(self._CHUNK_SIZE)
+        eof = not input_chunk
+        self._set_decoded_chars(self._decoder.decode(input_chunk, eof))
+
+        if self._telling:
+            # At the snapshot point, len(dec_buffer) bytes before the read,
+            # the next input to be decoded is dec_buffer + input_chunk.
+            self._snapshot = (dec_flags, dec_buffer + input_chunk)
+
+        return not eof
+
+    def _pack_cookie(self, position, dec_flags=0,
+                           bytes_to_feed=0, need_eof=0, chars_to_skip=0):
+        # The meaning of a tell() cookie is: seek to position, set the
+        # decoder flags to dec_flags, read bytes_to_feed bytes, feed them
+        # into the decoder with need_eof as the EOF flag, then skip
+        # chars_to_skip characters of the decoded result.  For most simple
+        # decoders, tell() will often just give a byte offset in the file.
+        return (position | (dec_flags<<64) | (bytes_to_feed<<128) |
+               (chars_to_skip<<192) | bool(need_eof)<<256)
+
+    def _unpack_cookie(self, bigint):
+        rest, position = divmod(bigint, 1<<64)
+        rest, dec_flags = divmod(rest, 1<<64)
+        rest, bytes_to_feed = divmod(rest, 1<<64)
+        need_eof, chars_to_skip = divmod(rest, 1<<64)
+        return position, dec_flags, bytes_to_feed, need_eof, chars_to_skip
+
+    def tell(self):
+        if not self._seekable:
+            raise IOError("underlying stream is not seekable")
+        if not self._telling:
+            raise IOError("telling position disabled by next() call")
+        self.flush()
+        position = self.buffer.tell()
+        decoder = self._decoder
+        if decoder is None or self._snapshot is None:
+            if self._decoded_chars:
+                # This should never happen.
+                raise AssertionError("pending decoded text")
+            return position
+
+        # Skip backward to the snapshot point (see _read_chunk).
+        dec_flags, next_input = self._snapshot
+        position -= len(next_input)
+
+        # How many decoded characters have been used up since the snapshot?
+        chars_to_skip = self._decoded_chars_used
+        if chars_to_skip == 0:
+            # We haven't moved from the snapshot point.
+            return self._pack_cookie(position, dec_flags)
+
+        # Starting from the snapshot position, we will walk the decoder
+        # forward until it gives us enough decoded characters.
+        saved_state = decoder.getstate()
+        try:
+            # Note our initial start point.
+            decoder.setstate((b'', dec_flags))
+            start_pos = position
+            start_flags, bytes_fed, chars_decoded = dec_flags, 0, 0
+            need_eof = 0
+
+            # Feed the decoder one byte at a time.  As we go, note the
+            # nearest "safe start point" before the current location
+            # (a point where the decoder has nothing buffered, so seek()
+            # can safely start from there and advance to this location).
+            next_byte = bytearray(1)
+            for next_byte[0] in next_input:
+                bytes_fed += 1
+                chars_decoded += len(decoder.decode(next_byte))
+                dec_buffer, dec_flags = decoder.getstate()
+                if not dec_buffer and chars_decoded <= chars_to_skip:
+                    # Decoder buffer is empty, so this is a safe start point.
+                    start_pos += bytes_fed
+                    chars_to_skip -= chars_decoded
+                    start_flags, bytes_fed, chars_decoded = dec_flags, 0, 0
+                if chars_decoded >= chars_to_skip:
+                    break
+            else:
+                # We didn't get enough decoded data; signal EOF to get more.
+                chars_decoded += len(decoder.decode(b'', final=True))
+                need_eof = 1
+                if chars_decoded < chars_to_skip:
+                    raise IOError("can't reconstruct logical file position")
+
+            # The returned cookie corresponds to the last safe start point.
+            return self._pack_cookie(
+                start_pos, start_flags, bytes_fed, need_eof, chars_to_skip)
+        finally:
+            decoder.setstate(saved_state)
+
+    def truncate(self, pos=None):
+        self.flush()
+        if pos is None:
+            pos = self.tell()
+        self.seek(pos)
+        return self.buffer.truncate()
+
+    def seek(self, cookie, whence=0):
+        if self.closed:
+            raise ValueError("tell on closed file")
+        if not self._seekable:
+            raise IOError("underlying stream is not seekable")
+        if whence == 1: # seek relative to current position
+            if cookie != 0:
+                raise IOError("can't do nonzero cur-relative seeks")
+            # Seeking to the current position should attempt to
+            # sync the underlying buffer with the current position.
+            whence = 0
+            cookie = self.tell()
+        if whence == 2: # seek relative to end of file
+            if cookie != 0:
+                raise IOError("can't do nonzero end-relative seeks")
+            self.flush()
+            position = self.buffer.seek(0, 2)
+            self._set_decoded_chars('')
+            self._snapshot = None
+            if self._decoder:
+                self._decoder.reset()
+            return position
+        if whence != 0:
+            raise ValueError("invalid whence (%r, should be 0, 1 or 2)" %
+                             (whence,))
+        if cookie < 0:
+            raise ValueError("negative seek position %r" % (cookie,))
+        self.flush()
+
+        # The strategy of seek() is to go back to the safe start point
+        # and replay the effect of read(chars_to_skip) from there.
+        start_pos, dec_flags, bytes_to_feed, need_eof, chars_to_skip = \
+            self._unpack_cookie(cookie)
+
+        # Seek back to the safe start point.
+        self.buffer.seek(start_pos)
+        self._set_decoded_chars('')
+        self._snapshot = None
+
+        # Restore the decoder to its state from the safe start point.
+        if self._decoder or dec_flags or chars_to_skip:
+            self._decoder = self._decoder or self._get_decoder()
+            self._decoder.setstate((b'', dec_flags))
+            self._snapshot = (dec_flags, b'')
+
+        if chars_to_skip:
+            # Just like _read_chunk, feed the decoder and save a snapshot.
+            input_chunk = self.buffer.read(bytes_to_feed)
+            self._set_decoded_chars(
+                self._decoder.decode(input_chunk, need_eof))
+            self._snapshot = (dec_flags, input_chunk)
+
+            # Skip chars_to_skip of the decoded characters.
+            if len(self._decoded_chars) < chars_to_skip:
+                raise IOError("can't restore logical file position")
+            self._decoded_chars_used = chars_to_skip
+
+        return cookie
+
+    def read(self, n=None):
+        if n is None:
+            n = -1
+        decoder = self._decoder or self._get_decoder()
+        if n < 0:
+            # Read everything.
+            result = (self._get_decoded_chars() +
+                      decoder.decode(self.buffer.read(), final=True))
+            self._set_decoded_chars('')
+            self._snapshot = None
+            return result
+        else:
+            # Keep reading chunks until we have n characters to return.
+            eof = False
+            result = self._get_decoded_chars(n)
+            while len(result) < n and not eof:
+                eof = not self._read_chunk()
+                result += self._get_decoded_chars(n - len(result))
+            return result
+
+    def __next__(self):
+        self._telling = False
+        line = self.readline()
+        if not line:
+            self._snapshot = None
+            self._telling = self._seekable
+            raise StopIteration
+        return line
+
+    def readline(self, limit=None):
+        if self.closed:
+            raise ValueError("read from closed file")
+        if limit is None:
+            limit = -1
+
+        # Grab all the decoded text (we will rewind any extra bits later).
+        line = self._get_decoded_chars()
+
+        start = 0
+        # Make the decoder if it doesn't already exist.
+        if not self._decoder:
+            self._get_decoder()
+
+        pos = endpos = None
+        while True:
+            if self._readtranslate:
+                # Newlines are already translated, only search for \n
+                pos = line.find('\n', start)
+                if pos >= 0:
+                    endpos = pos + 1
+                    break
+                else:
+                    start = len(line)
+
+            elif self._readuniversal:
+                # Universal newline search. Find any of \r, \r\n, \n
+                # The decoder ensures that \r\n are not split in two pieces
+
+                # In C we'd look for these in parallel of course.
+                nlpos = line.find("\n", start)
+                crpos = line.find("\r", start)
+                if crpos == -1:
+                    if nlpos == -1:
+                        # Nothing found
+                        start = len(line)
+                    else:
+                        # Found \n
+                        endpos = nlpos + 1
+                        break
+                elif nlpos == -1:
+                    # Found lone \r
+                    endpos = crpos + 1
+                    break
+                elif nlpos < crpos:
+                    # Found \n
+                    endpos = nlpos + 1
+                    break
+                elif nlpos == crpos + 1:
+                    # Found \r\n
+                    endpos = crpos + 2
+                    break
+                else:
+                    # Found \r
+                    endpos = crpos + 1
+                    break
+            else:
+                # non-universal
+                pos = line.find(self._readnl)
+                if pos >= 0:
+                    endpos = pos + len(self._readnl)
+                    break
+
+            if limit >= 0 and len(line) >= limit:
+                endpos = limit  # reached length limit
+                break
+
+            # No line ending seen yet - get more data'
+            while self._read_chunk():
+                if self._decoded_chars:
+                    break
+            if self._decoded_chars:
+                line += self._get_decoded_chars()
+            else:
+                # end of file
+                self._set_decoded_chars('')
+                self._snapshot = None
+                return line
+
+        if limit >= 0 and endpos > limit:
+            endpos = limit  # don't exceed limit
+
+        # Rewind _decoded_chars to just after the line ending we found.
+        self._rewind_decoded_chars(len(line) - endpos)
+        return line[:endpos]
+
+    @property
+    def newlines(self):
+        return self._decoder.newlines if self._decoder else None
+
+
+class StringIO(TextIOWrapper):
+    """Text I/O implementation using an in-memory buffer.
+
+    The initial_value argument sets the value of object.  The newline
+    argument is like the one of TextIOWrapper's constructor.
+    """
+
+    # XXX This is really slow, but fully functional
+
+    def __init__(self, initial_value="", newline="\n"):
+        super(StringIO, self).__init__(BytesIO(),
+                                       encoding="utf-8",
+                                       errors="strict",
+                                       newline=newline)
+        if initial_value:
+            if not isinstance(initial_value, str):
+                initial_value = str(initial_value)
+            self.write(initial_value)
+            self.seek(0)
+
+    def getvalue(self):
+        self.flush()
+        return self.buffer.getvalue().decode(self._encoding, self._errors)
diff --git a/Lib/importlib/__init__.py b/Lib/importlib/__init__.py
index 62e046e..7688ec2 100644
--- a/Lib/importlib/__init__.py
+++ b/Lib/importlib/__init__.py
@@ -93,12 +93,12 @@
         except ImportError:
             raise ImportError('posix, nt, or os2 module required for importlib')
 _bootstrap._os = _os
-import imp, sys, marshal, errno, _fileio
+import imp, sys, marshal, errno, _io
 _bootstrap.imp = imp
 _bootstrap.sys = sys
 _bootstrap.marshal = marshal
 _bootstrap.errno = errno
-_bootstrap._fileio = _fileio
+_bootstrap._io = _io
 import _warnings
 _bootstrap._warnings = _warnings
 
diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
index c61fe2d..c7cdfcf 100644
--- a/Lib/importlib/_bootstrap.py
+++ b/Lib/importlib/_bootstrap.py
@@ -473,7 +473,7 @@
         if source_path is None:
             return None
         import tokenize
-        with closing(_fileio._FileIO(source_path, 'r')) as file:
+        with closing(_io.FileIO(source_path, 'r')) as file:
             encoding, lines = tokenize.detect_encoding(file.readline)
         # XXX Will fail when passed to compile() if the encoding is
         # anything other than UTF-8.
@@ -527,7 +527,7 @@
         bytecode_path = self.bytecode_path(name)
         if not bytecode_path:
             bytecode_path = self._base_path + suffix_list(imp.PY_COMPILED)[0]
-        file = _fileio._FileIO(bytecode_path, 'w')
+        file = _io.FileIO(bytecode_path, 'w')
         try:
             with closing(file) as bytecode_file:
                 bytecode_file.write(data)
diff --git a/Lib/io.py b/Lib/io.py
index d41da60..a185a18 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -34,9 +34,6 @@
 """
 # New I/O library conforming to PEP 3116.
 
-# This is a prototype; hopefully eventually some of this will be
-# reimplemented in C.
-
 # XXX edge cases when switching between reading/writing
 # XXX need to support 1 meaning line-buffered
 # XXX whenever an argument is None, use the default value
@@ -48,2091 +45,58 @@
 
 __author__ = ("Guido van Rossum <guido@python.org>, "
               "Mike Verdone <mike.verdone@gmail.com>, "
-              "Mark Russell <mark.russell@zen.co.uk>")
+              "Mark Russell <mark.russell@zen.co.uk>, "
+              "Antoine Pitrou <solipsis@pitrou.net>, "
+              "Amaury Forgeotdarc <amauryfa@gmail.com>")
 
 __all__ = ["BlockingIOError", "open", "IOBase", "RawIOBase", "FileIO",
            "BytesIO", "StringIO", "BufferedIOBase",
            "BufferedReader", "BufferedWriter", "BufferedRWPair",
            "BufferedRandom", "TextIOBase", "TextIOWrapper"]
 
-import os
-import abc
-import codecs
-import _fileio
-# Import _thread instead of threading to reduce startup cost
-try:
-    from _thread import allocate_lock as Lock
-except ImportError:
-    from _dummy_thread import allocate_lock as Lock
 
+import _io
+import abc
 
 # open() uses st_blksize whenever we can
-DEFAULT_BUFFER_SIZE = 8 * 1024  # bytes
+DEFAULT_BUFFER_SIZE = _io.DEFAULT_BUFFER_SIZE
+BlockingIOError = _io.BlockingIOError
+UnsupportedOperation = _io.UnsupportedOperation
+open = _io.open
+OpenWrapper = _io.open
 
-
-class BlockingIOError(IOError):
-
-    """Exception raised when I/O would block on a non-blocking I/O stream."""
-
-    def __init__(self, errno, strerror, characters_written=0):
-        IOError.__init__(self, errno, strerror)
-        self.characters_written = characters_written
-
-
-def open(file, mode="r", buffering=None, encoding=None, errors=None,
-         newline=None, closefd=True):
-
-    r"""Open file and return a stream.  Raise IOError upon failure.
-
-    file is either a text or byte string giving the name (and the path
-    if the file isn't in the current working directory) of the file to
-    be opened or an integer file descriptor of the file to be
-    wrapped. (If a file descriptor is given, it is closed when the
-    returned I/O object is closed, unless closefd is set to False.)
-
-    mode is an optional string that specifies the mode in which the file
-    is opened. It defaults to 'r' which means open for reading in text
-    mode.  Other common values are 'w' for writing (truncating the file if
-    it already exists), and 'a' for appending (which on some Unix systems,
-    means that all writes append to the end of the file regardless of the
-    current seek position). In text mode, if encoding is not specified the
-    encoding used is platform dependent. (For reading and writing raw
-    bytes use binary mode and leave encoding unspecified.) The available
-    modes are:
-
-    ========= ===============================================================
-    Character Meaning
-    --------- ---------------------------------------------------------------
-    'r'       open for reading (default)
-    'w'       open for writing, truncating the file first
-    'a'       open for writing, appending to the end of the file if it exists
-    'b'       binary mode
-    't'       text mode (default)
-    '+'       open a disk file for updating (reading and writing)
-    'U'       universal newline mode (for backwards compatibility; unneeded
-              for new code)
-    ========= ===============================================================
-
-    The default mode is 'rt' (open for reading text). For binary random
-    access, the mode 'w+b' opens and truncates the file to 0 bytes, while
-    'r+b' opens the file without truncation.
-
-    Python distinguishes between files opened in binary and text modes,
-    even when the underlying operating system doesn't. Files opened in
-    binary mode (appending 'b' to the mode argument) return contents as
-    bytes objects without any decoding. In text mode (the default, or when
-    't' is appended to the mode argument), the contents of the file are
-    returned as strings, the bytes having been first decoded using a
-    platform-dependent encoding or using the specified encoding if given.
-
-    buffering is an optional integer used to set the buffering policy. By
-    default full buffering is on. Pass 0 to switch buffering off (only
-    allowed in binary mode), 1 to set line buffering, and an integer > 1
-    for full buffering.
-
-    encoding is the name of the encoding used to decode or encode the
-    file. This should only be used in text mode. The default encoding is
-    platform dependent, but any encoding supported by Python can be
-    passed.  See the codecs module for the list of supported encodings.
-
-    errors is an optional string that specifies how encoding errors are to
-    be handled---this argument should not be used in binary mode. Pass
-    'strict' to raise a ValueError exception if there is an encoding error
-    (the default of None has the same effect), or pass 'ignore' to ignore
-    errors. (Note that ignoring encoding errors can lead to data loss.)
-    See the documentation for codecs.register for a list of the permitted
-    encoding error strings.
-
-    newline controls how universal newlines works (it only applies to text
-    mode). It can be None, '', '\n', '\r', and '\r\n'.  It works as
-    follows:
-
-    * On input, if newline is None, universal newlines mode is
-      enabled. Lines in the input can end in '\n', '\r', or '\r\n', and
-      these are translated into '\n' before being returned to the
-      caller. If it is '', universal newline mode is enabled, but line
-      endings are returned to the caller untranslated. If it has any of
-      the other legal values, input lines are only terminated by the given
-      string, and the line ending is returned to the caller untranslated.
-
-    * On output, if newline is None, any '\n' characters written are
-      translated to the system default line separator, os.linesep. If
-      newline is '', no translation takes place. If newline is any of the
-      other legal values, any '\n' characters written are translated to
-      the given string.
-
-    If closefd is False, the underlying file descriptor will be kept open
-    when the file is closed. This does not work when a file name is given
-    and must be True in that case.
-
-    open() returns a file object whose type depends on the mode, and
-    through which the standard file operations such as reading and writing
-    are performed. When open() is used to open a file in a text mode ('w',
-    'r', 'wt', 'rt', etc.), it returns a TextIOWrapper. When used to open
-    a file in a binary mode, the returned class varies: in read binary
-    mode, it returns a BufferedReader; in write binary and append binary
-    modes, it returns a BufferedWriter, and in read/write mode, it returns
-    a BufferedRandom.
-
-    It is also possible to use a string or bytearray as a file for both
-    reading and writing. For strings StringIO can be used like a file
-    opened in a text mode, and for bytes a BytesIO can be used like a file
-    opened in a binary mode.
-    """
-    if not isinstance(file, (str, bytes, int)):
-        raise TypeError("invalid file: %r" % file)
-    if not isinstance(mode, str):
-        raise TypeError("invalid mode: %r" % mode)
-    if buffering is not None and not isinstance(buffering, int):
-        raise TypeError("invalid buffering: %r" % buffering)
-    if encoding is not None and not isinstance(encoding, str):
-        raise TypeError("invalid encoding: %r" % encoding)
-    if errors is not None and not isinstance(errors, str):
-        raise TypeError("invalid errors: %r" % errors)
-    modes = set(mode)
-    if modes - set("arwb+tU") or len(mode) > len(modes):
-        raise ValueError("invalid mode: %r" % mode)
-    reading = "r" in modes
-    writing = "w" in modes
-    appending = "a" in modes
-    updating = "+" in modes
-    text = "t" in modes
-    binary = "b" in modes
-    if "U" in modes:
-        if writing or appending:
-            raise ValueError("can't use U and writing mode at once")
-        reading = True
-    if text and binary:
-        raise ValueError("can't have text and binary mode at once")
-    if reading + writing + appending > 1:
-        raise ValueError("can't have read/write/append mode at once")
-    if not (reading or writing or appending):
-        raise ValueError("must have exactly one of read/write/append mode")
-    if binary and encoding is not None:
-        raise ValueError("binary mode doesn't take an encoding argument")
-    if binary and errors is not None:
-        raise ValueError("binary mode doesn't take an errors argument")
-    if binary and newline is not None:
-        raise ValueError("binary mode doesn't take a newline argument")
-    raw = FileIO(file,
-                 (reading and "r" or "") +
-                 (writing and "w" or "") +
-                 (appending and "a" or "") +
-                 (updating and "+" or ""),
-                 closefd)
-    if buffering is None:
-        buffering = -1
-    line_buffering = False
-    if buffering == 1 or buffering < 0 and raw.isatty():
-        buffering = -1
-        line_buffering = True
-    if buffering < 0:
-        buffering = DEFAULT_BUFFER_SIZE
-        try:
-            bs = os.fstat(raw.fileno()).st_blksize
-        except (os.error, AttributeError):
-            pass
-        else:
-            if bs > 1:
-                buffering = bs
-    if buffering < 0:
-        raise ValueError("invalid buffering size")
-    if buffering == 0:
-        if binary:
-            return raw
-        raise ValueError("can't have unbuffered text I/O")
-    if updating:
-        buffer = BufferedRandom(raw, buffering)
-    elif writing or appending:
-        buffer = BufferedWriter(raw, buffering)
-    elif reading:
-        buffer = BufferedReader(raw, buffering)
-    else:
-        raise ValueError("unknown mode: %r" % mode)
-    if binary:
-        return buffer
-    text = TextIOWrapper(buffer, encoding, errors, newline, line_buffering)
-    text.mode = mode
-    return text
-
-class _DocDescriptor:
-    """Helper for builtins.open.__doc__
-    """
-    def __get__(self, obj, typ):
-        return (
-            "open(file, mode='r', buffering=None, encoding=None, "
-                 "errors=None, newline=None, closefd=True)\n\n" +
-            open.__doc__)
-
-class OpenWrapper:
-    """Wrapper for builtins.open
-
-    Trick so that open won't become a bound method when stored
-    as a class variable (as dbm.dumb does).
-
-    See initstdio() in Python/pythonrun.c.
-    """
-    __doc__ = _DocDescriptor()
-
-    def __new__(cls, *args, **kwargs):
-        return open(*args, **kwargs)
-
-
-class UnsupportedOperation(ValueError, IOError):
+# Declaring ABCs in C is tricky so we do it here.
+# Method descriptions and default implementations are inherited from the C
+# version however.
+class IOBase(_io._IOBase, metaclass=abc.ABCMeta):
     pass
 
+class RawIOBase(_io._RawIOBase, IOBase):
+    pass
 
-class IOBase(metaclass=abc.ABCMeta):
+class BufferedIOBase(_io._BufferedIOBase, IOBase):
+    pass
 
-    """The abstract base class for all I/O classes, acting on streams of
-    bytes. There is no public constructor.
+class TextIOBase(_io._TextIOBase, IOBase):
+    pass
 
-    This class provides dummy implementations for many methods that
-    derived classes can override selectively; the default implementations
-    represent a file that cannot be read, written or seeked.
+FileIO = _io.FileIO
+BytesIO = _io.BytesIO
+StringIO = _io.StringIO
+BufferedReader = _io.BufferedReader
+BufferedWriter = _io.BufferedWriter
+BufferedRWPair = _io.BufferedRWPair
+BufferedRandom = _io.BufferedRandom
+IncrementalNewlineDecoder = _io.IncrementalNewlineDecoder
+TextIOWrapper = _io.TextIOWrapper
 
-    Even though IOBase does not declare read, readinto, or write because
-    their signatures will vary, implementations and clients should
-    consider those methods part of the interface. Also, implementations
-    may raise a IOError when operations they do not support are called.
+RawIOBase.register(FileIO)
 
-    The basic type used for binary data read from or written to a file is
-    bytes. bytearrays are accepted too, and in some cases (such as
-    readinto) needed. Text I/O classes work with str data.
+BufferedIOBase.register(BytesIO)
+BufferedIOBase.register(BufferedReader)
+BufferedIOBase.register(BufferedWriter)
+BufferedIOBase.register(BufferedRandom)
+BufferedIOBase.register(BufferedRWPair)
 
-    Note that calling any method (even inquiries) on a closed stream is
-    undefined. Implementations may raise IOError in this case.
-
-    IOBase (and its subclasses) support the iterator protocol, meaning
-    that an IOBase object can be iterated over yielding the lines in a
-    stream.
-
-    IOBase also supports the :keyword:`with` statement. In this example,
-    fp is closed after the suite of the with statment is complete:
-
-    with open('spam.txt', 'r') as fp:
-        fp.write('Spam and eggs!')
-    """
-
-    ### Internal ###
-
-    def _unsupported(self, name: str) -> IOError:
-        """Internal: raise an exception for unsupported operations."""
-        raise UnsupportedOperation("%s.%s() not supported" %
-                                   (self.__class__.__name__, name))
-
-    ### Positioning ###
-
-    def seek(self, pos: int, whence: int = 0) -> int:
-        """Change stream position.
-
-        Change the stream position to byte offset offset. offset is
-        interpreted relative to the position indicated by whence.  Values
-        for whence are:
-
-        * 0 -- start of stream (the default); offset should be zero or positive
-        * 1 -- current stream position; offset may be negative
-        * 2 -- end of stream; offset is usually negative
-
-        Return the new absolute position.
-        """
-        self._unsupported("seek")
-
-    def tell(self) -> int:
-        """Return current stream position."""
-        self._checkClosed()
-        return self.seek(0, 1)
-
-    def truncate(self, pos: int = None) -> int:
-        """Truncate file to size bytes.
-
-        Size defaults to the current IO position as reported by tell().  Return
-        the new size.
-        """
-        self._unsupported("truncate")
-
-    ### Flush and close ###
-
-    def flush(self) -> None:
-        """Flush write buffers, if applicable.
-
-        This is not implemented for read-only and non-blocking streams.
-        """
-        # XXX Should this return the number of bytes written???
-        if self.__closed:
-            raise ValueError("I/O operation on closed file.")
-
-    __closed = False
-
-    def close(self) -> None:
-        """Flush and close the IO object.
-
-        This method has no effect if the file is already closed.
-        """
-        if not self.__closed:
-            try:
-                self.flush()
-            except IOError:
-                pass  # If flush() fails, just give up
-            self.__closed = True
-
-    def __del__(self) -> None:
-        """Destructor.  Calls close()."""
-        # The try/except block is in case this is called at program
-        # exit time, when it's possible that globals have already been
-        # deleted, and then the close() call might fail.  Since
-        # there's nothing we can do about such failures and they annoy
-        # the end users, we suppress the traceback.
-        try:
-            self.close()
-        except:
-            pass
-
-    ### Inquiries ###
-
-    def seekable(self) -> bool:
-        """Return whether object supports random access.
-
-        If False, seek(), tell() and truncate() will raise IOError.
-        This method may need to do a test seek().
-        """
-        return False
-
-    def _checkSeekable(self, msg=None):
-        """Internal: raise an IOError if file is not seekable
-        """
-        if not self.seekable():
-            raise IOError("File or stream is not seekable."
-                          if msg is None else msg)
-
-
-    def readable(self) -> bool:
-        """Return whether object was opened for reading.
-
-        If False, read() will raise IOError.
-        """
-        return False
-
-    def _checkReadable(self, msg=None):
-        """Internal: raise an IOError if file is not readable
-        """
-        if not self.readable():
-            raise IOError("File or stream is not readable."
-                          if msg is None else msg)
-
-    def writable(self) -> bool:
-        """Return whether object was opened for writing.
-
-        If False, write() and truncate() will raise IOError.
-        """
-        return False
-
-    def _checkWritable(self, msg=None):
-        """Internal: raise an IOError if file is not writable
-        """
-        if not self.writable():
-            raise IOError("File or stream is not writable."
-                          if msg is None else msg)
-
-    @property
-    def closed(self):
-        """closed: bool.  True iff the file has been closed.
-
-        For backwards compatibility, this is a property, not a predicate.
-        """
-        return self.__closed
-
-    def _checkClosed(self, msg=None):
-        """Internal: raise an ValueError if file is closed
-        """
-        if self.closed:
-            raise ValueError("I/O operation on closed file."
-                             if msg is None else msg)
-
-    ### Context manager ###
-
-    def __enter__(self) -> "IOBase":  # That's a forward reference
-        """Context management protocol.  Returns self."""
-        self._checkClosed()
-        return self
-
-    def __exit__(self, *args) -> None:
-        """Context management protocol.  Calls close()"""
-        self.close()
-
-    ### Lower-level APIs ###
-
-    # XXX Should these be present even if unimplemented?
-
-    def fileno(self) -> int:
-        """Returns underlying file descriptor if one exists.
-
-        An IOError is raised if the IO object does not use a file descriptor.
-        """
-        self._unsupported("fileno")
-
-    def isatty(self) -> bool:
-        """Return whether this is an 'interactive' stream.
-
-        Return False if it can't be determined.
-        """
-        self._checkClosed()
-        return False
-
-    ### Readline[s] and writelines ###
-
-    def readline(self, limit: int = -1) -> bytes:
-        r"""Read and return a line from the stream.
-
-        If limit is specified, at most limit bytes will be read.
-
-        The line terminator is always b'\n' for binary files; for text
-        files, the newlines argument to open can be used to select the line
-        terminator(s) recognized.
-        """
-        # For backwards compatibility, a (slowish) readline().
-        if hasattr(self, "peek"):
-            def nreadahead():
-                readahead = self.peek(1)
-                if not readahead:
-                    return 1
-                n = (readahead.find(b"\n") + 1) or len(readahead)
-                if limit >= 0:
-                    n = min(n, limit)
-                return n
-        else:
-            def nreadahead():
-                return 1
-        if limit is None:
-            limit = -1
-        res = bytearray()
-        while limit < 0 or len(res) < limit:
-            b = self.read(nreadahead())
-            if not b:
-                break
-            res += b
-            if res.endswith(b"\n"):
-                break
-        return bytes(res)
-
-    def __iter__(self):
-        self._checkClosed()
-        return self
-
-    def __next__(self):
-        line = self.readline()
-        if not line:
-            raise StopIteration
-        return line
-
-    def readlines(self, hint=None):
-        """Return a list of lines from the stream.
-
-        hint can be specified to control the number of lines read: no more
-        lines will be read if the total size (in bytes/characters) of all
-        lines so far exceeds hint.
-        """
-        if hint is None or hint <= 0:
-            return list(self)
-        n = 0
-        lines = []
-        for line in self:
-            lines.append(line)
-            n += len(line)
-            if n >= hint:
-                break
-        return lines
-
-    def writelines(self, lines):
-        self._checkClosed()
-        for line in lines:
-            self.write(line)
-
-
-class RawIOBase(IOBase):
-
-    """Base class for raw binary I/O."""
-
-    # The read() method is implemented by calling readinto(); derived
-    # classes that want to support read() only need to implement
-    # readinto() as a primitive operation.  In general, readinto() can be
-    # more efficient than read().
-
-    # (It would be tempting to also provide an implementation of
-    # readinto() in terms of read(), in case the latter is a more suitable
-    # primitive operation, but that would lead to nasty recursion in case
-    # a subclass doesn't implement either.)
-
-    def read(self, n: int = -1) -> bytes:
-        """Read and return up to n bytes.
-
-        Returns an empty bytes object on EOF, or None if the object is
-        set not to block and has no data to read.
-        """
-        self._checkClosed()
-        if n is None:
-            n = -1
-        if n < 0:
-            return self.readall()
-        b = bytearray(n.__index__())
-        n = self.readinto(b)
-        del b[n:]
-        return bytes(b)
-
-    def readall(self):
-        """Read until EOF, using multiple read() call."""
-        self._checkClosed()
-        res = bytearray()
-        while True:
-            data = self.read(DEFAULT_BUFFER_SIZE)
-            if not data:
-                break
-            res += data
-        return bytes(res)
-
-    def readinto(self, b: bytearray) -> int:
-        """Read up to len(b) bytes into b.
-
-        Returns number of bytes read (0 for EOF), or None if the object
-        is set not to block as has no data to read.
-        """
-        self._unsupported("readinto")
-
-    def write(self, b: bytes) -> int:
-        """Write the given buffer to the IO stream.
-
-        Returns the number of bytes written, which may be less than len(b).
-        """
-        self._unsupported("write")
-
-
-class FileIO(_fileio._FileIO, RawIOBase):
-
-    """Raw I/O implementation for OS files."""
-
-    # This multiply inherits from _FileIO and RawIOBase to make
-    # isinstance(io.FileIO(), io.RawIOBase) return True without requiring
-    # that _fileio._FileIO inherits from io.RawIOBase (which would be hard
-    # to do since _fileio.c is written in C).
-
-    def __init__(self, name, mode="r", closefd=True):
-        _fileio._FileIO.__init__(self, name, mode, closefd)
-        self._name = name
-
-    def close(self):
-        _fileio._FileIO.close(self)
-        RawIOBase.close(self)
-
-    @property
-    def name(self):
-        return self._name
-
-
-class BufferedIOBase(IOBase):
-
-    """Base class for buffered IO objects.
-
-    The main difference with RawIOBase is that the read() method
-    supports omitting the size argument, and does not have a default
-    implementation that defers to readinto().
-
-    In addition, read(), readinto() and write() may raise
-    BlockingIOError if the underlying raw stream is in non-blocking
-    mode and not ready; unlike their raw counterparts, they will never
-    return None.
-
-    A typical implementation should not inherit from a RawIOBase
-    implementation, but wrap one.
-    """
-
-    def read(self, n: int = None) -> bytes:
-        """Read and return up to n bytes.
-
-        If the argument is omitted, None, or negative, reads and
-        returns all data until EOF.
-
-        If the argument is positive, and the underlying raw stream is
-        not 'interactive', multiple raw reads may be issued to satisfy
-        the byte count (unless EOF is reached first).  But for
-        interactive raw streams (XXX and for pipes?), at most one raw
-        read will be issued, and a short result does not imply that
-        EOF is imminent.
-
-        Returns an empty bytes array on EOF.
-
-        Raises BlockingIOError if the underlying raw stream has no
-        data at the moment.
-        """
-        self._unsupported("read")
-
-    def readinto(self, b: bytearray) -> int:
-        """Read up to len(b) bytes into b.
-
-        Like read(), this may issue multiple reads to the underlying raw
-        stream, unless the latter is 'interactive'.
-
-        Returns the number of bytes read (0 for EOF).
-
-        Raises BlockingIOError if the underlying raw stream has no
-        data at the moment.
-        """
-        # XXX This ought to work with anything that supports the buffer API
-        self._checkClosed()
-        data = self.read(len(b))
-        n = len(data)
-        try:
-            b[:n] = data
-        except TypeError as err:
-            import array
-            if not isinstance(b, array.array):
-                raise err
-            b[:n] = array.array('b', data)
-        return n
-
-    def write(self, b: bytes) -> int:
-        """Write the given buffer to the IO stream.
-
-        Return the number of bytes written, which is never less than
-        len(b).
-
-        Raises BlockingIOError if the buffer is full and the
-        underlying raw stream cannot accept more data at the moment.
-        """
-        self._unsupported("write")
-
-
-class _BufferedIOMixin(BufferedIOBase):
-
-    """A mixin implementation of BufferedIOBase with an underlying raw stream.
-
-    This passes most requests on to the underlying raw stream.  It
-    does *not* provide implementations of read(), readinto() or
-    write().
-    """
-
-    def __init__(self, raw):
-        self.raw = raw
-
-    ### Positioning ###
-
-    def seek(self, pos, whence=0):
-        return self.raw.seek(pos, whence)
-
-    def tell(self):
-        return self.raw.tell()
-
-    def truncate(self, pos=None):
-        # Flush the stream.  We're mixing buffered I/O with lower-level I/O,
-        # and a flush may be necessary to synch both views of the current
-        # file state.
-        self.flush()
-
-        if pos is None:
-            pos = self.tell()
-        # XXX: Should seek() be used, instead of passing the position
-        # XXX  directly to truncate?
-        return self.raw.truncate(pos)
-
-    ### Flush and close ###
-
-    def flush(self):
-        self.raw.flush()
-
-    def close(self):
-        if not self.closed:
-            try:
-                self.flush()
-            except IOError:
-                pass  # If flush() fails, just give up
-            self.raw.close()
-
-    ### Inquiries ###
-
-    def seekable(self):
-        return self.raw.seekable()
-
-    def readable(self):
-        return self.raw.readable()
-
-    def writable(self):
-        return self.raw.writable()
-
-    @property
-    def closed(self):
-        return self.raw.closed
-
-    @property
-    def name(self):
-        return self.raw.name
-
-    @property
-    def mode(self):
-        return self.raw.mode
-
-    ### Lower-level APIs ###
-
-    def fileno(self):
-        return self.raw.fileno()
-
-    def isatty(self):
-        return self.raw.isatty()
-
-
-class _BytesIO(BufferedIOBase):
-
-    """Buffered I/O implementation using an in-memory bytes buffer."""
-
-    def __init__(self, initial_bytes=None):
-        buf = bytearray()
-        if initial_bytes is not None:
-            buf += initial_bytes
-        self._buffer = buf
-        self._pos = 0
-
-    def getvalue(self):
-        """Return the bytes value (contents) of the buffer
-        """
-        self._checkClosed()
-        return bytes(self._buffer)
-
-    def read(self, n=None):
-        self._checkClosed()
-        if n is None:
-            n = -1
-        if n < 0:
-            n = len(self._buffer)
-        if len(self._buffer) <= self._pos:
-            return b""
-        newpos = min(len(self._buffer), self._pos + n)
-        b = self._buffer[self._pos : newpos]
-        self._pos = newpos
-        return bytes(b)
-
-    def read1(self, n):
-        """This is the same as read.
-        """
-        return self.read(n)
-
-    def write(self, b):
-        self._checkClosed()
-        if isinstance(b, str):
-            raise TypeError("can't write str to binary stream")
-        n = len(b)
-        if n == 0:
-            return 0
-        pos = self._pos
-        if pos > len(self._buffer):
-            # Inserts null bytes between the current end of the file
-            # and the new write position.
-            padding = b'\x00' * (pos - len(self._buffer))
-            self._buffer += padding
-        self._buffer[pos:pos + n] = b
-        self._pos += n
-        return n
-
-    def seek(self, pos, whence=0):
-        self._checkClosed()
-        try:
-            pos = pos.__index__()
-        except AttributeError as err:
-            raise TypeError("an integer is required") from err
-        if whence == 0:
-            if pos < 0:
-                raise ValueError("negative seek position %r" % (pos,))
-            self._pos = pos
-        elif whence == 1:
-            self._pos = max(0, self._pos + pos)
-        elif whence == 2:
-            self._pos = max(0, len(self._buffer) + pos)
-        else:
-            raise ValueError("invalid whence value")
-        return self._pos
-
-    def tell(self):
-        self._checkClosed()
-        return self._pos
-
-    def truncate(self, pos=None):
-        self._checkClosed()
-        if pos is None:
-            pos = self._pos
-        elif pos < 0:
-            raise ValueError("negative truncate position %r" % (pos,))
-        del self._buffer[pos:]
-        return self.seek(pos)
-
-    def readable(self):
-        return True
-
-    def writable(self):
-        return True
-
-    def seekable(self):
-        return True
-
-# Use the faster implementation of BytesIO if available
-try:
-    import _bytesio
-
-    class BytesIO(_bytesio._BytesIO, BufferedIOBase):
-        __doc__ = _bytesio._BytesIO.__doc__
-
-except ImportError:
-    BytesIO = _BytesIO
-
-
-class BufferedReader(_BufferedIOMixin):
-
-    """BufferedReader(raw[, buffer_size])
-
-    A buffer for a readable, sequential BaseRawIO object.
-
-    The constructor creates a BufferedReader for the given readable raw
-    stream and buffer_size. If buffer_size is omitted, DEFAULT_BUFFER_SIZE
-    is used.
-    """
-
-    def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE):
-        """Create a new buffered reader using the given readable raw IO object.
-        """
-        raw._checkReadable()
-        _BufferedIOMixin.__init__(self, raw)
-        self.buffer_size = buffer_size
-        self._reset_read_buf()
-        self._read_lock = Lock()
-
-    def _reset_read_buf(self):
-        self._read_buf = b""
-        self._read_pos = 0
-
-    def read(self, n=None):
-        """Read n bytes.
-
-        Returns exactly n bytes of data unless the underlying raw IO
-        stream reaches EOF or if the call would block in non-blocking
-        mode. If n is negative, read until EOF or until read() would
-        block.
-        """
-        self._checkClosed()
-        with self._read_lock:
-            return self._read_unlocked(n)
-
-    def _read_unlocked(self, n=None):
-        nodata_val = b""
-        empty_values = (b"", None)
-        buf = self._read_buf
-        pos = self._read_pos
-
-        # Special case for when the number of bytes to read is unspecified.
-        if n is None or n == -1:
-            self._reset_read_buf()
-            chunks = [buf[pos:]]  # Strip the consumed bytes.
-            current_size = 0
-            while True:
-                # Read until EOF or until read() would block.
-                chunk = self.raw.read()
-                if chunk in empty_values:
-                    nodata_val = chunk
-                    break
-                current_size += len(chunk)
-                chunks.append(chunk)
-            return b"".join(chunks) or nodata_val
-
-        # The number of bytes to read is specified, return at most n bytes.
-        avail = len(buf) - pos  # Length of the available buffered data.
-        if n <= avail:
-            # Fast path: the data to read is fully buffered.
-            self._read_pos += n
-            return buf[pos:pos+n]
-        # Slow path: read from the stream until enough bytes are read,
-        # or until an EOF occurs or until read() would block.
-        chunks = [buf[pos:]]
-        wanted = max(self.buffer_size, n)
-        while avail < n:
-            chunk = self.raw.read(wanted)
-            if chunk in empty_values:
-                nodata_val = chunk
-                break
-            avail += len(chunk)
-            chunks.append(chunk)
-        # n is more then avail only when an EOF occurred or when
-        # read() would have blocked.
-        n = min(n, avail)
-        out = b"".join(chunks)
-        self._read_buf = out[n:]  # Save the extra data in the buffer.
-        self._read_pos = 0
-        return out[:n] if out else nodata_val
-
-    def peek(self, n=0):
-        """Returns buffered bytes without advancing the position.
-
-        The argument indicates a desired minimal number of bytes; we
-        do at most one raw read to satisfy it.  We never return more
-        than self.buffer_size.
-        """
-        self._checkClosed()
-        with self._read_lock:
-            return self._peek_unlocked(n)
-
-    def _peek_unlocked(self, n=0):
-        want = min(n, self.buffer_size)
-        have = len(self._read_buf) - self._read_pos
-        if have < want:
-            to_read = self.buffer_size - have
-            current = self.raw.read(to_read)
-            if current:
-                self._read_buf = self._read_buf[self._read_pos:] + current
-                self._read_pos = 0
-        return self._read_buf[self._read_pos:]
-
-    def read1(self, n):
-        """Reads up to n bytes, with at most one read() system call."""
-        # Returns up to n bytes.  If at least one byte is buffered, we
-        # only return buffered bytes.  Otherwise, we do one raw read.
-        self._checkClosed()
-        if n <= 0:
-            return b""
-        with self._read_lock:
-            self._peek_unlocked(1)
-            return self._read_unlocked(
-                min(n, len(self._read_buf) - self._read_pos))
-
-    def tell(self):
-        self._checkClosed()
-        return self.raw.tell() - len(self._read_buf) + self._read_pos
-
-    def seek(self, pos, whence=0):
-        self._checkClosed()
-        with self._read_lock:
-            if whence == 1:
-                pos -= len(self._read_buf) - self._read_pos
-            pos = self.raw.seek(pos, whence)
-            self._reset_read_buf()
-            return pos
-
-
-class BufferedWriter(_BufferedIOMixin):
-
-    """A buffer for a writeable sequential RawIO object.
-
-    The constructor creates a BufferedWriter for the given writeable raw
-    stream. If the buffer_size is not given, it defaults to
-    DEAFULT_BUFFER_SIZE. If max_buffer_size is omitted, it defaults to
-    twice the buffer size.
-    """
-
-    def __init__(self, raw,
-                 buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):
-        raw._checkWritable()
-        _BufferedIOMixin.__init__(self, raw)
-        self.buffer_size = buffer_size
-        self.max_buffer_size = (2*buffer_size
-                                if max_buffer_size is None
-                                else max_buffer_size)
-        self._write_buf = bytearray()
-        self._write_lock = Lock()
-
-    def write(self, b):
-        self._checkClosed()
-        if isinstance(b, str):
-            raise TypeError("can't write str to binary stream")
-        with self._write_lock:
-            # XXX we can implement some more tricks to try and avoid
-            # partial writes
-            if len(self._write_buf) > self.buffer_size:
-                # We're full, so let's pre-flush the buffer
-                try:
-                    self._flush_unlocked()
-                except BlockingIOError as e:
-                    # We can't accept anything else.
-                    # XXX Why not just let the exception pass through?
-                    raise BlockingIOError(e.errno, e.strerror, 0)
-            before = len(self._write_buf)
-            self._write_buf.extend(b)
-            written = len(self._write_buf) - before
-            if len(self._write_buf) > self.buffer_size:
-                try:
-                    self._flush_unlocked()
-                except BlockingIOError as e:
-                    if len(self._write_buf) > self.max_buffer_size:
-                        # We've hit max_buffer_size. We have to accept a
-                        # partial write and cut back our buffer.
-                        overage = len(self._write_buf) - self.max_buffer_size
-                        self._write_buf = self._write_buf[:self.max_buffer_size]
-                        raise BlockingIOError(e.errno, e.strerror, overage)
-            return written
-
-    def truncate(self, pos=None):
-        self._checkClosed()
-        with self._write_lock:
-            self._flush_unlocked()
-            if pos is None:
-                pos = self.raw.tell()
-            return self.raw.truncate(pos)
-
-    def flush(self):
-        self._checkClosed()
-        with self._write_lock:
-            self._flush_unlocked()
-
-    def _flush_unlocked(self):
-        written = 0
-        try:
-            while self._write_buf:
-                n = self.raw.write(self._write_buf)
-                del self._write_buf[:n]
-                written += n
-        except BlockingIOError as e:
-            n = e.characters_written
-            del self._write_buf[:n]
-            written += n
-            raise BlockingIOError(e.errno, e.strerror, written)
-
-    def tell(self):
-        self._checkClosed()
-        return self.raw.tell() + len(self._write_buf)
-
-    def seek(self, pos, whence=0):
-        self._checkClosed()
-        with self._write_lock:
-            self._flush_unlocked()
-            return self.raw.seek(pos, whence)
-
-
-class BufferedRWPair(BufferedIOBase):
-
-    """A buffered reader and writer object together.
-
-    A buffered reader object and buffered writer object put together to
-    form a sequential IO object that can read and write. This is typically
-    used with a socket or two-way pipe.
-
-    reader and writer are RawIOBase objects that are readable and
-    writeable respectively. If the buffer_size is omitted it defaults to
-    DEFAULT_BUFFER_SIZE. The max_buffer_size (for the buffered writer)
-    defaults to twice the buffer size.
-    """
-
-    # XXX The usefulness of this (compared to having two separate IO
-    # objects) is questionable.
-
-    def __init__(self, reader, writer,
-                 buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):
-        """Constructor.
-
-        The arguments are two RawIO instances.
-        """
-        reader._checkReadable()
-        writer._checkWritable()
-        self.reader = BufferedReader(reader, buffer_size)
-        self.writer = BufferedWriter(writer, buffer_size, max_buffer_size)
-
-    def read(self, n=None):
-        if n is None:
-            n = -1
-        return self.reader.read(n)
-
-    def readinto(self, b):
-        return self.reader.readinto(b)
-
-    def write(self, b):
-        return self.writer.write(b)
-
-    def peek(self, n=0):
-        return self.reader.peek(n)
-
-    def read1(self, n):
-        return self.reader.read1(n)
-
-    def readable(self):
-        return self.reader.readable()
-
-    def writable(self):
-        return self.writer.writable()
-
-    def flush(self):
-        return self.writer.flush()
-
-    def close(self):
-        self.writer.close()
-        self.reader.close()
-
-    def isatty(self):
-        return self.reader.isatty() or self.writer.isatty()
-
-    @property
-    def closed(self):
-        return self.writer.closed
-
-
-class BufferedRandom(BufferedWriter, BufferedReader):
-
-    """A buffered interface to random access streams.
-
-    The constructor creates a reader and writer for a seekable stream,
-    raw, given in the first argument. If the buffer_size is omitted it
-    defaults to DEFAULT_BUFFER_SIZE. The max_buffer_size (for the buffered
-    writer) defaults to twice the buffer size.
-    """
-
-    def __init__(self, raw,
-                 buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):
-        raw._checkSeekable()
-        BufferedReader.__init__(self, raw, buffer_size)
-        BufferedWriter.__init__(self, raw, buffer_size, max_buffer_size)
-
-    def seek(self, pos, whence=0):
-        self.flush()
-        # First do the raw seek, then empty the read buffer, so that
-        # if the raw seek fails, we don't lose buffered data forever.
-        pos = self.raw.seek(pos, whence)
-        with self._read_lock:
-            self._reset_read_buf()
-        return pos
-
-    def tell(self):
-        self._checkClosed()
-        if self._write_buf:
-            return self.raw.tell() + len(self._write_buf)
-        else:
-            return BufferedReader.tell(self)
-
-    def truncate(self, pos=None):
-        if pos is None:
-            pos = self.tell()
-        # Use seek to flush the read buffer.
-        self.seek(pos)
-        return BufferedWriter.truncate(self)
-
-    def read(self, n=None):
-        if n is None:
-            n = -1
-        self.flush()
-        return BufferedReader.read(self, n)
-
-    def readinto(self, b):
-        self.flush()
-        return BufferedReader.readinto(self, b)
-
-    def peek(self, n=0):
-        self.flush()
-        return BufferedReader.peek(self, n)
-
-    def read1(self, n):
-        self.flush()
-        return BufferedReader.read1(self, n)
-
-    def write(self, b):
-        self._checkClosed()
-        if self._read_buf:
-            # Undo readahead
-            with self._read_lock:
-                self.raw.seek(self._read_pos - len(self._read_buf), 1)
-                self._reset_read_buf()
-        return BufferedWriter.write(self, b)
-
-
-class TextIOBase(IOBase):
-
-    """Base class for text I/O.
-
-    This class provides a character and line based interface to stream
-    I/O. There is no readinto method because Python's character strings
-    are immutable. There is no public constructor.
-    """
-
-    def read(self, n: int = -1) -> str:
-        """Read at most n characters from stream.
-
-        Read from underlying buffer until we have n characters or we hit EOF.
-        If n is negative or omitted, read until EOF.
-        """
-        self._unsupported("read")
-
-    def write(self, s: str) -> int:
-        """Write string s to stream."""
-        self._unsupported("write")
-
-    def truncate(self, pos: int = None) -> int:
-        """Truncate size to pos."""
-        self._unsupported("truncate")
-
-    def readline(self) -> str:
-        """Read until newline or EOF.
-
-        Returns an empty string if EOF is hit immediately.
-        """
-        self._unsupported("readline")
-
-    @property
-    def encoding(self):
-        """Subclasses should override."""
-        return None
-
-    @property
-    def newlines(self):
-        """Line endings translated so far.
-
-        Only line endings translated during reading are considered.
-
-        Subclasses should override.
-        """
-        return None
-
-
-class IncrementalNewlineDecoder(codecs.IncrementalDecoder):
-    r"""Codec used when reading a file in universal newlines mode.  It wraps
-    another incremental decoder, translating \r\n and \r into \n.  It also
-    records the types of newlines encountered.  When used with
-    translate=False, it ensures that the newline sequence is returned in
-    one piece.
-    """
-    def __init__(self, decoder, translate, errors='strict'):
-        codecs.IncrementalDecoder.__init__(self, errors=errors)
-        self.translate = translate
-        self.decoder = decoder
-        self.seennl = 0
-        self.pendingcr = False
-
-    def decode(self, input, final=False):
-        # decode input (with the eventual \r from a previous pass)
-        output = self.decoder.decode(input, final=final)
-        if self.pendingcr and (output or final):
-            output = "\r" + output
-            self.pendingcr = False
-
-        # retain last \r even when not translating data:
-        # then readline() is sure to get \r\n in one pass
-        if output.endswith("\r") and not final:
-            output = output[:-1]
-            self.pendingcr = True
-
-        # Record which newlines are read
-        crlf = output.count('\r\n')
-        cr = output.count('\r') - crlf
-        lf = output.count('\n') - crlf
-        self.seennl |= (lf and self._LF) | (cr and self._CR) \
-                    | (crlf and self._CRLF)
-
-        if self.translate:
-            if crlf:
-                output = output.replace("\r\n", "\n")
-            if cr:
-                output = output.replace("\r", "\n")
-
-        return output
-
-    def getstate(self):
-        buf, flag = self.decoder.getstate()
-        flag <<= 1
-        if self.pendingcr:
-            flag |= 1
-        return buf, flag
-
-    def setstate(self, state):
-        buf, flag = state
-        self.pendingcr = bool(flag & 1)
-        self.decoder.setstate((buf, flag >> 1))
-
-    def reset(self):
-        self.seennl = 0
-        self.pendingcr = False
-        self.decoder.reset()
-
-    _LF = 1
-    _CR = 2
-    _CRLF = 4
-
-    @property
-    def newlines(self):
-        return (None,
-                "\n",
-                "\r",
-                ("\r", "\n"),
-                "\r\n",
-                ("\n", "\r\n"),
-                ("\r", "\r\n"),
-                ("\r", "\n", "\r\n")
-               )[self.seennl]
-
-
-class TextIOWrapper(TextIOBase):
-
-    r"""Character and line based layer over a BufferedIOBase object, buffer.
-
-    encoding gives the name of the encoding that the stream will be
-    decoded or encoded with. It defaults to locale.getpreferredencoding.
-
-    errors determines the strictness of encoding and decoding (see the
-    codecs.register) and defaults to "strict".
-
-    newline can be None, '', '\n', '\r', or '\r\n'.  It controls the
-    handling of line endings. If it is None, universal newlines is
-    enabled.  With this enabled, on input, the lines endings '\n', '\r',
-    or '\r\n' are translated to '\n' before being returned to the
-    caller. Conversely, on output, '\n' is translated to the system
-    default line separator, os.linesep. If newline is any other of its
-    legal values, that newline becomes the newline when the file is read
-    and it is returned untranslated. On output, '\n' is converted to the
-    newline.
-
-    If line_buffering is True, a call to flush is implied when a call to
-    write contains a newline character.
-    """
-
-    _CHUNK_SIZE = 2048
-
-    def __init__(self, buffer, encoding=None, errors=None, newline=None,
-                 line_buffering=False):
-        if newline not in (None, "", "\n", "\r", "\r\n"):
-            raise ValueError("illegal newline value: %r" % (newline,))
-        if encoding is None:
-            try:
-                encoding = os.device_encoding(buffer.fileno())
-            except (AttributeError, UnsupportedOperation):
-                pass
-            if encoding is None:
-                try:
-                    import locale
-                except ImportError:
-                    # Importing locale may fail if Python is being built
-                    encoding = "ascii"
-                else:
-                    encoding = locale.getpreferredencoding()
-
-        if not isinstance(encoding, str):
-            raise ValueError("invalid encoding: %r" % encoding)
-
-        if errors is None:
-            errors = "strict"
-        else:
-            if not isinstance(errors, str):
-                raise ValueError("invalid errors: %r" % errors)
-
-        self.buffer = buffer
-        self._line_buffering = line_buffering
-        self._encoding = encoding
-        self._errors = errors
-        self._readuniversal = not newline
-        self._readtranslate = newline is None
-        self._readnl = newline
-        self._writetranslate = newline != ''
-        self._writenl = newline or os.linesep
-        self._encoder = None
-        self._decoder = None
-        self._decoded_chars = ''  # buffer for text returned from decoder
-        self._decoded_chars_used = 0  # offset into _decoded_chars for read()
-        self._snapshot = None  # info for reconstructing decoder state
-        self._seekable = self._telling = self.buffer.seekable()
-
-    # self._snapshot is either None, or a tuple (dec_flags, next_input)
-    # where dec_flags is the second (integer) item of the decoder state
-    # and next_input is the chunk of input bytes that comes next after the
-    # snapshot point.  We use this to reconstruct decoder states in tell().
-
-    # Naming convention:
-    #   - "bytes_..." for integer variables that count input bytes
-    #   - "chars_..." for integer variables that count decoded characters
-
-    @property
-    def encoding(self):
-        return self._encoding
-
-    @property
-    def errors(self):
-        return self._errors
-
-    @property
-    def line_buffering(self):
-        return self._line_buffering
-
-    def seekable(self):
-        return self._seekable
-
-    def readable(self):
-        return self.buffer.readable()
-
-    def writable(self):
-        return self.buffer.writable()
-
-    def flush(self):
-        self.buffer.flush()
-        self._telling = self._seekable
-
-    def close(self):
-        try:
-            self.flush()
-        except:
-            pass  # If flush() fails, just give up
-        self.buffer.close()
-
-    @property
-    def closed(self):
-        return self.buffer.closed
-
-    @property
-    def name(self):
-        return self.buffer.name
-
-    def fileno(self):
-        return self.buffer.fileno()
-
-    def isatty(self):
-        return self.buffer.isatty()
-
-    def write(self, s: str):
-        self._checkClosed()
-        if not isinstance(s, str):
-            raise TypeError("can't write %s to text stream" %
-                            s.__class__.__name__)
-        length = len(s)
-        haslf = (self._writetranslate or self._line_buffering) and "\n" in s
-        if haslf and self._writetranslate and self._writenl != "\n":
-            s = s.replace("\n", self._writenl)
-        encoder = self._encoder or self._get_encoder()
-        # XXX What if we were just reading?
-        b = encoder.encode(s)
-        self.buffer.write(b)
-        if self._line_buffering and (haslf or "\r" in s):
-            self.flush()
-        self._snapshot = None
-        if self._decoder:
-            self._decoder.reset()
-        return length
-
-    def _get_encoder(self):
-        make_encoder = codecs.getincrementalencoder(self._encoding)
-        self._encoder = make_encoder(self._errors)
-        return self._encoder
-
-    def _get_decoder(self):
-        make_decoder = codecs.getincrementaldecoder(self._encoding)
-        decoder = make_decoder(self._errors)
-        if self._readuniversal:
-            decoder = IncrementalNewlineDecoder(decoder, self._readtranslate)
-        self._decoder = decoder
-        return decoder
-
-    # The following three methods implement an ADT for _decoded_chars.
-    # Text returned from the decoder is buffered here until the client
-    # requests it by calling our read() or readline() method.
-    def _set_decoded_chars(self, chars):
-        """Set the _decoded_chars buffer."""
-        self._decoded_chars = chars
-        self._decoded_chars_used = 0
-
-    def _get_decoded_chars(self, n=None):
-        """Advance into the _decoded_chars buffer."""
-        offset = self._decoded_chars_used
-        if n is None:
-            chars = self._decoded_chars[offset:]
-        else:
-            chars = self._decoded_chars[offset:offset + n]
-        self._decoded_chars_used += len(chars)
-        return chars
-
-    def _rewind_decoded_chars(self, n):
-        """Rewind the _decoded_chars buffer."""
-        if self._decoded_chars_used < n:
-            raise AssertionError("rewind decoded_chars out of bounds")
-        self._decoded_chars_used -= n
-
-    def _read_chunk(self):
-        """
-        Read and decode the next chunk of data from the BufferedReader.
-        """
-
-        # The return value is True unless EOF was reached.  The decoded
-        # string is placed in self._decoded_chars (replacing its previous
-        # value).  The entire input chunk is sent to the decoder, though
-        # some of it may remain buffered in the decoder, yet to be
-        # converted.
-
-        if self._decoder is None:
-            raise ValueError("no decoder")
-
-        if self._telling:
-            # To prepare for tell(), we need to snapshot a point in the
-            # file where the decoder's input buffer is empty.
-
-            dec_buffer, dec_flags = self._decoder.getstate()
-            # Given this, we know there was a valid snapshot point
-            # len(dec_buffer) bytes ago with decoder state (b'', dec_flags).
-
-        # Read a chunk, decode it, and put the result in self._decoded_chars.
-        input_chunk = self.buffer.read1(self._CHUNK_SIZE)
-        eof = not input_chunk
-        self._set_decoded_chars(self._decoder.decode(input_chunk, eof))
-
-        if self._telling:
-            # At the snapshot point, len(dec_buffer) bytes before the read,
-            # the next input to be decoded is dec_buffer + input_chunk.
-            self._snapshot = (dec_flags, dec_buffer + input_chunk)
-
-        return not eof
-
-    def _pack_cookie(self, position, dec_flags=0,
-                           bytes_to_feed=0, need_eof=0, chars_to_skip=0):
-        # The meaning of a tell() cookie is: seek to position, set the
-        # decoder flags to dec_flags, read bytes_to_feed bytes, feed them
-        # into the decoder with need_eof as the EOF flag, then skip
-        # chars_to_skip characters of the decoded result.  For most simple
-        # decoders, tell() will often just give a byte offset in the file.
-        return (position | (dec_flags<<64) | (bytes_to_feed<<128) |
-               (chars_to_skip<<192) | bool(need_eof)<<256)
-
-    def _unpack_cookie(self, bigint):
-        rest, position = divmod(bigint, 1<<64)
-        rest, dec_flags = divmod(rest, 1<<64)
-        rest, bytes_to_feed = divmod(rest, 1<<64)
-        need_eof, chars_to_skip = divmod(rest, 1<<64)
-        return position, dec_flags, bytes_to_feed, need_eof, chars_to_skip
-
-    def tell(self):
-        self._checkClosed()
-        if not self._seekable:
-            raise IOError("underlying stream is not seekable")
-        if not self._telling:
-            raise IOError("telling position disabled by next() call")
-        self.flush()
-        position = self.buffer.tell()
-        decoder = self._decoder
-        if decoder is None or self._snapshot is None:
-            if self._decoded_chars:
-                # This should never happen.
-                raise AssertionError("pending decoded text")
-            return position
-
-        # Skip backward to the snapshot point (see _read_chunk).
-        dec_flags, next_input = self._snapshot
-        position -= len(next_input)
-
-        # How many decoded characters have been used up since the snapshot?
-        chars_to_skip = self._decoded_chars_used
-        if chars_to_skip == 0:
-            # We haven't moved from the snapshot point.
-            return self._pack_cookie(position, dec_flags)
-
-        # Starting from the snapshot position, we will walk the decoder
-        # forward until it gives us enough decoded characters.
-        saved_state = decoder.getstate()
-        try:
-            # Note our initial start point.
-            decoder.setstate((b'', dec_flags))
-            start_pos = position
-            start_flags, bytes_fed, chars_decoded = dec_flags, 0, 0
-            need_eof = 0
-
-            # Feed the decoder one byte at a time.  As we go, note the
-            # nearest "safe start point" before the current location
-            # (a point where the decoder has nothing buffered, so seek()
-            # can safely start from there and advance to this location).
-            next_byte = bytearray(1)
-            for next_byte[0] in next_input:
-                bytes_fed += 1
-                chars_decoded += len(decoder.decode(next_byte))
-                dec_buffer, dec_flags = decoder.getstate()
-                if not dec_buffer and chars_decoded <= chars_to_skip:
-                    # Decoder buffer is empty, so this is a safe start point.
-                    start_pos += bytes_fed
-                    chars_to_skip -= chars_decoded
-                    start_flags, bytes_fed, chars_decoded = dec_flags, 0, 0
-                if chars_decoded >= chars_to_skip:
-                    break
-            else:
-                # We didn't get enough decoded data; signal EOF to get more.
-                chars_decoded += len(decoder.decode(b'', final=True))
-                need_eof = 1
-                if chars_decoded < chars_to_skip:
-                    raise IOError("can't reconstruct logical file position")
-
-            # The returned cookie corresponds to the last safe start point.
-            return self._pack_cookie(
-                start_pos, start_flags, bytes_fed, need_eof, chars_to_skip)
-        finally:
-            decoder.setstate(saved_state)
-
-    def truncate(self, pos=None):
-        self.flush()
-        if pos is None:
-            pos = self.tell()
-        self.seek(pos)
-        return self.buffer.truncate()
-
-    def seek(self, cookie, whence=0):
-        self._checkClosed()
-        if not self._seekable:
-            raise IOError("underlying stream is not seekable")
-        if whence == 1: # seek relative to current position
-            if cookie != 0:
-                raise IOError("can't do nonzero cur-relative seeks")
-            # Seeking to the current position should attempt to
-            # sync the underlying buffer with the current position.
-            whence = 0
-            cookie = self.tell()
-        if whence == 2: # seek relative to end of file
-            if cookie != 0:
-                raise IOError("can't do nonzero end-relative seeks")
-            self.flush()
-            position = self.buffer.seek(0, 2)
-            self._set_decoded_chars('')
-            self._snapshot = None
-            if self._decoder:
-                self._decoder.reset()
-            return position
-        if whence != 0:
-            raise ValueError("invalid whence (%r, should be 0, 1 or 2)" %
-                             (whence,))
-        if cookie < 0:
-            raise ValueError("negative seek position %r" % (cookie,))
-        self.flush()
-
-        # The strategy of seek() is to go back to the safe start point
-        # and replay the effect of read(chars_to_skip) from there.
-        start_pos, dec_flags, bytes_to_feed, need_eof, chars_to_skip = \
-            self._unpack_cookie(cookie)
-
-        # Seek back to the safe start point.
-        self.buffer.seek(start_pos)
-        self._set_decoded_chars('')
-        self._snapshot = None
-
-        # Restore the decoder to its state from the safe start point.
-        if self._decoder or dec_flags or chars_to_skip:
-            self._decoder = self._decoder or self._get_decoder()
-            self._decoder.setstate((b'', dec_flags))
-            self._snapshot = (dec_flags, b'')
-
-        if chars_to_skip:
-            # Just like _read_chunk, feed the decoder and save a snapshot.
-            input_chunk = self.buffer.read(bytes_to_feed)
-            self._set_decoded_chars(
-                self._decoder.decode(input_chunk, need_eof))
-            self._snapshot = (dec_flags, input_chunk)
-
-            # Skip chars_to_skip of the decoded characters.
-            if len(self._decoded_chars) < chars_to_skip:
-                raise IOError("can't restore logical file position")
-            self._decoded_chars_used = chars_to_skip
-
-        return cookie
-
-    def read(self, n=None):
-        self._checkClosed()
-        if n is None:
-            n = -1
-        decoder = self._decoder or self._get_decoder()
-        if n < 0:
-            # Read everything.
-            result = (self._get_decoded_chars() +
-                      decoder.decode(self.buffer.read(), final=True))
-            self._set_decoded_chars('')
-            self._snapshot = None
-            return result
-        else:
-            # Keep reading chunks until we have n characters to return.
-            eof = False
-            result = self._get_decoded_chars(n)
-            while len(result) < n and not eof:
-                eof = not self._read_chunk()
-                result += self._get_decoded_chars(n - len(result))
-            return result
-
-    def __next__(self):
-        self._checkClosed()
-        self._telling = False
-        line = self.readline()
-        if not line:
-            self._snapshot = None
-            self._telling = self._seekable
-            raise StopIteration
-        return line
-
-    def readline(self, limit=None):
-        self._checkClosed()
-        if limit is None:
-            limit = -1
-
-        # Grab all the decoded text (we will rewind any extra bits later).
-        line = self._get_decoded_chars()
-
-        start = 0
-        decoder = self._decoder or self._get_decoder()
-
-        pos = endpos = None
-        while True:
-            if self._readtranslate:
-                # Newlines are already translated, only search for \n
-                pos = line.find('\n', start)
-                if pos >= 0:
-                    endpos = pos + 1
-                    break
-                else:
-                    start = len(line)
-
-            elif self._readuniversal:
-                # Universal newline search. Find any of \r, \r\n, \n
-                # The decoder ensures that \r\n are not split in two pieces
-
-                # In C we'd look for these in parallel of course.
-                nlpos = line.find("\n", start)
-                crpos = line.find("\r", start)
-                if crpos == -1:
-                    if nlpos == -1:
-                        # Nothing found
-                        start = len(line)
-                    else:
-                        # Found \n
-                        endpos = nlpos + 1
-                        break
-                elif nlpos == -1:
-                    # Found lone \r
-                    endpos = crpos + 1
-                    break
-                elif nlpos < crpos:
-                    # Found \n
-                    endpos = nlpos + 1
-                    break
-                elif nlpos == crpos + 1:
-                    # Found \r\n
-                    endpos = crpos + 2
-                    break
-                else:
-                    # Found \r
-                    endpos = crpos + 1
-                    break
-            else:
-                # non-universal
-                pos = line.find(self._readnl)
-                if pos >= 0:
-                    endpos = pos + len(self._readnl)
-                    break
-
-            if limit >= 0 and len(line) >= limit:
-                endpos = limit  # reached length limit
-                break
-
-            # No line ending seen yet - get more data
-            more_line = ''
-            while self._read_chunk():
-                if self._decoded_chars:
-                    break
-            if self._decoded_chars:
-                line += self._get_decoded_chars()
-            else:
-                # end of file
-                self._set_decoded_chars('')
-                self._snapshot = None
-                return line
-
-        if limit >= 0 and endpos > limit:
-            endpos = limit  # don't exceed limit
-
-        # Rewind _decoded_chars to just after the line ending we found.
-        self._rewind_decoded_chars(len(line) - endpos)
-        return line[:endpos]
-
-    @property
-    def newlines(self):
-        return self._decoder.newlines if self._decoder else None
-
-class _StringIO(TextIOWrapper):
-    """Text I/O implementation using an in-memory buffer.
-
-    The initial_value argument sets the value of object.  The newline
-    argument is like the one of TextIOWrapper's constructor.
-    """
-
-    # XXX This is really slow, but fully functional
-
-    def __init__(self, initial_value="", newline="\n"):
-        super(_StringIO, self).__init__(BytesIO(),
-                                        encoding="utf-8",
-                                        errors="strict",
-                                        newline=newline)
-        if initial_value:
-            if not isinstance(initial_value, str):
-                initial_value = str(initial_value)
-            self.write(initial_value)
-            self.seek(0)
-
-    def getvalue(self):
-        self.flush()
-        return self.buffer.getvalue().decode(self._encoding, self._errors)
-
-try:
-    import _stringio
-
-    # This subclass is a reimplementation of the TextIOWrapper
-    # interface without any of its text decoding facilities. All the
-    # stored data is manipulated with the efficient
-    # _stringio._StringIO extension type. Also, the newline decoding
-    # mechanism of IncrementalNewlineDecoder is reimplemented here for
-    # efficiency. Doing otherwise, would require us to implement a
-    # fake decoder which would add an additional and unnecessary layer
-    # on top of the _StringIO methods.
-
-    class StringIO(_stringio._StringIO, TextIOBase):
-        """Text I/O implementation using an in-memory buffer.
-
-        The initial_value argument sets the value of object.  The newline
-        argument is like the one of TextIOWrapper's constructor.
-        """
-
-        _CHUNK_SIZE = 4096
-
-        def __init__(self, initial_value="", newline="\n"):
-            if newline not in (None, "", "\n", "\r", "\r\n"):
-                raise ValueError("illegal newline value: %r" % (newline,))
-
-            self._readuniversal = not newline
-            self._readtranslate = newline is None
-            self._readnl = newline
-            self._writetranslate = newline != ""
-            self._writenl = newline or os.linesep
-            self._pending = ""
-            self._seennl = 0
-
-            # Reset the buffer first, in case __init__ is called
-            # multiple times.
-            self.truncate(0)
-            if initial_value is None:
-                initial_value = ""
-            self.write(initial_value)
-            self.seek(0)
-
-        @property
-        def buffer(self):
-            raise UnsupportedOperation("%s.buffer attribute is unsupported" %
-                                       self.__class__.__name__)
-
-        # XXX Cruft to support the TextIOWrapper API. This would only
-        # be meaningful if StringIO supported the buffer attribute.
-        # Hopefully, a better solution, than adding these pseudo-attributes,
-        # will be found.
-        @property
-        def encoding(self):
-            return "utf-8"
-
-        @property
-        def errors(self):
-            return "strict"
-
-        @property
-        def line_buffering(self):
-            return False
-
-        def _decode_newlines(self, input, final=False):
-            # decode input (with the eventual \r from a previous pass)
-            if self._pending:
-                input = self._pending + input
-
-            # retain last \r even when not translating data:
-            # then readline() is sure to get \r\n in one pass
-            if input.endswith("\r") and not final:
-                input = input[:-1]
-                self._pending = "\r"
-            else:
-                self._pending = ""
-
-            # Record which newlines are read
-            crlf = input.count('\r\n')
-            cr = input.count('\r') - crlf
-            lf = input.count('\n') - crlf
-            self._seennl |= (lf and self._LF) | (cr and self._CR) \
-                         | (crlf and self._CRLF)
-
-            if self._readtranslate:
-                if crlf:
-                    output = input.replace("\r\n", "\n")
-                if cr:
-                    output = input.replace("\r", "\n")
-            else:
-                output = input
-
-            return output
-
-        def writable(self):
-            return True
-
-        def readable(self):
-            return True
-
-        def seekable(self):
-            return True
-
-        _read = _stringio._StringIO.read
-        _write = _stringio._StringIO.write
-        _tell = _stringio._StringIO.tell
-        _seek = _stringio._StringIO.seek
-        _truncate = _stringio._StringIO.truncate
-        _getvalue = _stringio._StringIO.getvalue
-
-        def getvalue(self) -> str:
-            """Retrieve the entire contents of the object."""
-            self._checkClosed()
-            return self._getvalue()
-
-        def write(self, s: str) -> int:
-            """Write string s to file.
-
-            Returns the number of characters written.
-            """
-            self._checkClosed()
-            if not isinstance(s, str):
-                raise TypeError("can't write %s to text stream" %
-                                s.__class__.__name__)
-            length = len(s)
-            if self._writetranslate and self._writenl != "\n":
-                s = s.replace("\n", self._writenl)
-            self._pending = ""
-            self._write(s)
-            return length
-
-        def read(self, n: int = None) -> str:
-            """Read at most n characters, returned as a string.
-
-            If the argument is negative or omitted, read until EOF
-            is reached. Return an empty string at EOF.
-            """
-            self._checkClosed()
-            if n is None:
-                n = -1
-            res = self._pending
-            if n < 0:
-                res += self._decode_newlines(self._read(), True)
-                self._pending = ""
-                return res
-            else:
-                res = self._decode_newlines(self._read(n), True)
-                self._pending = res[n:]
-                return res[:n]
-
-        def tell(self) -> int:
-            """Tell the current file position."""
-            self._checkClosed()
-            if self._pending:
-                return self._tell() - len(self._pending)
-            else:
-                return self._tell()
-
-        def seek(self, pos: int = None, whence: int = 0) -> int:
-            """Change stream position.
-
-            Seek to character offset pos relative to position indicated by whence:
-                0  Start of stream (the default).  pos should be >= 0;
-                1  Current position - pos must be 0;
-                2  End of stream - pos must be 0.
-            Returns the new absolute position.
-            """
-            self._checkClosed()
-            self._pending = ""
-            return self._seek(pos, whence)
-
-        def truncate(self, pos: int = None) -> int:
-            """Truncate size to pos.
-
-            The pos argument defaults to the current file position, as
-            returned by tell().  Imply an absolute seek to pos.
-            Returns the new absolute position.
-            """
-            self._checkClosed()
-            self._pending = ""
-            return self._truncate(pos)
-
-        def readline(self, limit: int = None) -> str:
-            self._checkClosed()
-            if limit is None:
-                limit = -1
-            if limit >= 0:
-                # XXX: Hack to support limit argument, for backwards
-                # XXX  compatibility
-                line = self.readline()
-                if len(line) <= limit:
-                    return line
-                line, self._pending = line[:limit], line[limit:] + self._pending
-                return line
-
-            line = self._pending
-            self._pending = ""
-
-            start = 0
-            pos = endpos = None
-            while True:
-                if self._readtranslate:
-                    # Newlines are already translated, only search for \n
-                    pos = line.find('\n', start)
-                    if pos >= 0:
-                        endpos = pos + 1
-                        break
-                    else:
-                        start = len(line)
-
-                elif self._readuniversal:
-                    # Universal newline search. Find any of \r, \r\n, \n
-                    # The decoder ensures that \r\n are not split in two pieces
-
-                    # In C we'd look for these in parallel of course.
-                    nlpos = line.find("\n", start)
-                    crpos = line.find("\r", start)
-                    if crpos == -1:
-                        if nlpos == -1:
-                            # Nothing found
-                            start = len(line)
-                        else:
-                            # Found \n
-                            endpos = nlpos + 1
-                            break
-                    elif nlpos == -1:
-                        # Found lone \r
-                        endpos = crpos + 1
-                        break
-                    elif nlpos < crpos:
-                        # Found \n
-                        endpos = nlpos + 1
-                        break
-                    elif nlpos == crpos + 1:
-                        # Found \r\n
-                        endpos = crpos + 2
-                        break
-                    else:
-                        # Found \r
-                        endpos = crpos + 1
-                        break
-                else:
-                    # non-universal
-                    pos = line.find(self._readnl)
-                    if pos >= 0:
-                        endpos = pos + len(self._readnl)
-                        break
-
-                # No line ending seen yet - get more data
-                more_line = self.read(self._CHUNK_SIZE)
-                if more_line:
-                    line += more_line
-                else:
-                    # end of file
-                    return line
-
-            self._pending = line[endpos:]
-            return line[:endpos]
-
-        _LF = 1
-        _CR = 2
-        _CRLF = 4
-
-        @property
-        def newlines(self):
-            return (None,
-                    "\n",
-                    "\r",
-                    ("\r", "\n"),
-                    "\r\n",
-                    ("\n", "\r\n"),
-                    ("\r", "\r\n"),
-                    ("\r", "\n", "\r\n")
-                   )[self._seennl]
-
-
-except ImportError:
-    StringIO = _StringIO
+TextIOBase.register(StringIO)
+TextIOBase.register(TextIOWrapper)
diff --git a/Lib/test/test_bufio.py b/Lib/test/test_bufio.py
index e65951d..7d617d3 100644
--- a/Lib/test/test_bufio.py
+++ b/Lib/test/test_bufio.py
@@ -1,9 +1,12 @@
 import unittest
 from test import support
 
-# Simple test to ensure that optimizations in fileobject.c deliver
-# the expected results.  For best testing, run this under a debug-build
-# Python too (to exercise asserts in the C code).
+import io # C implementation.
+import _pyio as pyio # Python implementation.
+
+# Simple test to ensure that optimizations in the IO library deliver the
+# expected results.  For best testing, run this under a debug-build Python too
+# (to exercise asserts in the C code).
 
 lengths = list(range(1, 257)) + [512, 1000, 1024, 2048, 4096, 8192, 10000,
                                  16384, 32768, 65536, 1000000]
@@ -18,7 +21,7 @@
 
         # Since C doesn't guarantee we can write/read arbitrary bytes in text
         # files, use binary mode.
-        f = open(support.TESTFN, "wb")
+        f = self.open(support.TESTFN, "wb")
         try:
             # write once with \n and once without
             f.write(s)
@@ -58,8 +61,16 @@
     def test_nullpat(self):
         self.drive_one(bytes(1000))
 
+
+class CBufferSizeTest(BufferSizeTest):
+    open = io.open
+
+class PyBufferSizeTest(BufferSizeTest):
+    open = staticmethod(pyio.open)
+
+
 def test_main():
-    support.run_unittest(BufferSizeTest)
+    support.run_unittest(CBufferSizeTest, PyBufferSizeTest)
 
 if __name__ == "__main__":
     test_main()
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 8d43d7a..0554fc2 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -2605,10 +2605,10 @@
 
     def test_descrdoc(self):
         # Testing descriptor doc strings...
-        from _fileio import _FileIO
+        from _io import FileIO
         def check(descr, what):
             self.assertEqual(descr.__doc__, what)
-        check(_FileIO.closed, "True if the file is closed") # getset descriptor
+        check(FileIO.closed, "True if the file is closed") # getset descriptor
         check(complex.real, "the real part of a complex number") # member descriptor
 
     def test_doc_descriptor(self):
diff --git a/Lib/test/test_file.py b/Lib/test/test_file.py
index 7a68b2f..3360121 100644
--- a/Lib/test/test_file.py
+++ b/Lib/test/test_file.py
@@ -4,6 +4,9 @@
 from array import array
 from weakref import proxy
 
+import io
+import _pyio as pyio
+
 from test.support import TESTFN, findfile, run_unittest
 from collections import UserList
 
@@ -11,7 +14,7 @@
     # file tests for which a test file is automatically set up
 
     def setUp(self):
-        self.f = open(TESTFN, 'wb')
+        self.f = self.open(TESTFN, 'wb')
 
     def tearDown(self):
         if self.f:
@@ -39,7 +42,7 @@
         self.f.write(b'12')
         self.f.close()
         a = array('b', b'x'*10)
-        self.f = open(TESTFN, 'rb')
+        self.f = self.open(TESTFN, 'rb')
         n = self.f.readinto(a)
         self.assertEquals(b'12', a.tostring()[:n])
 
@@ -47,7 +50,7 @@
         # verify readinto refuses text files
         a = array('b', b'x'*10)
         self.f.close()
-        self.f = open(TESTFN, 'r')
+        self.f = self.open(TESTFN, 'r')
         if hasattr(self.f, "readinto"):
             self.assertRaises(TypeError, self.f.readinto, a)
 
@@ -56,7 +59,7 @@
         l = UserList([b'1', b'2'])
         self.f.writelines(l)
         self.f.close()
-        self.f = open(TESTFN, 'rb')
+        self.f = self.open(TESTFN, 'rb')
         buf = self.f.read()
         self.assertEquals(buf, b'12')
 
@@ -126,13 +129,20 @@
     def testReadWhenWriting(self):
         self.assertRaises(IOError, self.f.read)
 
+class CAutoFileTests(AutoFileTests):
+    open = io.open
+
+class PyAutoFileTests(AutoFileTests):
+    open = staticmethod(pyio.open)
+
+
 class OtherFileTests(unittest.TestCase):
 
     def testModeStrings(self):
         # check invalid mode strings
         for mode in ("", "aU", "wU+"):
             try:
-                f = open(TESTFN, mode)
+                f = self.open(TESTFN, mode)
             except ValueError:
                 pass
             else:
@@ -153,7 +163,7 @@
         # verify that we get a sensible error message for bad mode argument
         bad_mode = "qwerty"
         try:
-            f = open(TESTFN, bad_mode)
+            f = self.open(TESTFN, bad_mode)
         except ValueError as msg:
             if msg.args[0] != 0:
                 s = str(msg)
@@ -170,11 +180,11 @@
         # misbehaviour especially with repeated close() calls
         for s in (-1, 0, 1, 512):
             try:
-                f = open(TESTFN, 'wb', s)
+                f = self.open(TESTFN, 'wb', s)
                 f.write(str(s).encode("ascii"))
                 f.close()
                 f.close()
-                f = open(TESTFN, 'rb', s)
+                f = self.open(TESTFN, 'rb', s)
                 d = int(f.read().decode("ascii"))
                 f.close()
                 f.close()
@@ -187,13 +197,13 @@
         # "file.truncate fault on windows"
 
         os.unlink(TESTFN)
-        f = open(TESTFN, 'wb')
+        f = self.open(TESTFN, 'wb')
 
         try:
             f.write(b'12345678901')   # 11 bytes
             f.close()
 
-            f = open(TESTFN,'rb+')
+            f = self.open(TESTFN,'rb+')
             data = f.read(5)
             if data != b'12345':
                 self.fail("Read on file opened for update failed %r" % data)
@@ -233,13 +243,13 @@
 
         try:
             # Prepare the testfile
-            bag = open(TESTFN, "wb")
+            bag = self.open(TESTFN, "wb")
             bag.write(filler * nchunks)
             bag.writelines(testlines)
             bag.close()
             # Test for appropriate errors mixing read* and iteration
             for methodname, args in methods:
-                f = open(TESTFN, 'rb')
+                f = self.open(TESTFN, 'rb')
                 if next(f) != filler:
                     self.fail, "Broken testfile"
                 meth = getattr(f, methodname)
@@ -253,7 +263,7 @@
             # ("h", "a", "m", "\n"), so 4096 lines of that should get us
             # exactly on the buffer boundary for any power-of-2 buffersize
             # between 4 and 16384 (inclusive).
-            f = open(TESTFN, 'rb')
+            f = self.open(TESTFN, 'rb')
             for i in range(nchunks):
                 next(f)
             testline = testlines.pop(0)
@@ -295,7 +305,7 @@
                 self.fail("readlines() after next() with empty buffer "
                           "failed. Got %r, expected %r" % (line, testline))
             # Reading after iteration hit EOF shouldn't hurt either
-            f = open(TESTFN, 'rb')
+            f = self.open(TESTFN, 'rb')
             try:
                 for line in f:
                     pass
@@ -311,12 +321,19 @@
         finally:
             os.unlink(TESTFN)
 
+class COtherFileTests(OtherFileTests):
+    open = io.open
+
+class PyOtherFileTests(OtherFileTests):
+    open = staticmethod(pyio.open)
+
 
 def test_main():
     # Historically, these tests have been sloppy about removing TESTFN.
     # So get rid of it no matter what.
     try:
-        run_unittest(AutoFileTests, OtherFileTests)
+        run_unittest(CAutoFileTests, PyAutoFileTests,
+                     COtherFileTests, PyOtherFileTests)
     finally:
         if os.path.exists(TESTFN):
             os.unlink(TESTFN)
diff --git a/Lib/test/test_fileio.py b/Lib/test/test_fileio.py
index 497914f..615361e 100644
--- a/Lib/test/test_fileio.py
+++ b/Lib/test/test_fileio.py
@@ -10,13 +10,13 @@
                           make_bad_fd)
 from collections import UserList
 
-import _fileio
+from _io import FileIO as _FileIO
 
 class AutoFileTests(unittest.TestCase):
     # file tests for which a test file is automatically set up
 
     def setUp(self):
-        self.f = _fileio._FileIO(TESTFN, 'w')
+        self.f = _FileIO(TESTFN, 'w')
 
     def tearDown(self):
         if self.f:
@@ -63,13 +63,13 @@
         self.f.write(bytes([1, 2]))
         self.f.close()
         a = array('b', b'x'*10)
-        self.f = _fileio._FileIO(TESTFN, 'r')
+        self.f = _FileIO(TESTFN, 'r')
         n = self.f.readinto(a)
         self.assertEquals(array('b', [1, 2]), a[:n])
 
     def testRepr(self):
         self.assertEquals(repr(self.f),
-                          "_fileio._FileIO(%d, %s)" % (self.f.fileno(),
+                          "io.FileIO(%d, %s)" % (self.f.fileno(),
                                                        repr(self.f.mode)))
 
     def testErrors(self):
@@ -80,7 +80,7 @@
         self.assertRaises(ValueError, f.read, 10) # Open for reading
         f.close()
         self.assert_(f.closed)
-        f = _fileio._FileIO(TESTFN, 'r')
+        f = _FileIO(TESTFN, 'r')
         self.assertRaises(TypeError, f.readinto, "")
         self.assert_(not f.closed)
         f.close()
@@ -106,7 +106,7 @@
         # Windows always returns "[Errno 13]: Permission denied
         # Unix calls dircheck() and returns "[Errno 21]: Is a directory"
         try:
-            _fileio._FileIO('.', 'r')
+            _FileIO('.', 'r')
         except IOError as e:
             self.assertNotEqual(e.errno, 0)
             self.assertEqual(e.filename, ".")
@@ -118,19 +118,19 @@
 
     def testAbles(self):
         try:
-            f = _fileio._FileIO(TESTFN, "w")
+            f = _FileIO(TESTFN, "w")
             self.assertEquals(f.readable(), False)
             self.assertEquals(f.writable(), True)
             self.assertEquals(f.seekable(), True)
             f.close()
 
-            f = _fileio._FileIO(TESTFN, "r")
+            f = _FileIO(TESTFN, "r")
             self.assertEquals(f.readable(), True)
             self.assertEquals(f.writable(), False)
             self.assertEquals(f.seekable(), True)
             f.close()
 
-            f = _fileio._FileIO(TESTFN, "a+")
+            f = _FileIO(TESTFN, "a+")
             self.assertEquals(f.readable(), True)
             self.assertEquals(f.writable(), True)
             self.assertEquals(f.seekable(), True)
@@ -139,14 +139,14 @@
 
             if sys.platform != "win32":
                 try:
-                    f = _fileio._FileIO("/dev/tty", "a")
+                    f = _FileIO("/dev/tty", "a")
                 except EnvironmentError:
                     # When run in a cron job there just aren't any
                     # ttys, so skip the test.  This also handles other
                     # OS'es that don't support /dev/tty.
                     pass
                 else:
-                    f = _fileio._FileIO("/dev/tty", "a")
+                    f = _FileIO("/dev/tty", "a")
                     self.assertEquals(f.readable(), False)
                     self.assertEquals(f.writable(), True)
                     if sys.platform != "darwin" and \
@@ -163,7 +163,7 @@
         # check invalid mode strings
         for mode in ("", "aU", "wU+", "rw", "rt"):
             try:
-                f = _fileio._FileIO(TESTFN, mode)
+                f = _FileIO(TESTFN, mode)
             except ValueError:
                 pass
             else:
@@ -172,10 +172,26 @@
 
     def testUnicodeOpen(self):
         # verify repr works for unicode too
-        f = _fileio._FileIO(str(TESTFN), "w")
+        f = _FileIO(str(TESTFN), "w")
         f.close()
         os.unlink(TESTFN)
 
+    def testBytesOpen(self):
+        # Opening a bytes filename
+        try:
+            fn = TESTFN.encode("ascii")
+        except UnicodeEncodeError:
+            # Skip test
+            return
+        f = _FileIO(fn, "w")
+        try:
+            f.write(b"abc")
+            f.close()
+            with open(TESTFN, "rb") as f:
+                self.assertEquals(f.read(), b"abc")
+        finally:
+            os.unlink(TESTFN)
+
     def testInvalidFd(self):
         self.assertRaises(ValueError, _fileio._FileIO, -10)
         self.assertRaises(OSError, _fileio._FileIO, make_bad_fd())
@@ -184,7 +200,7 @@
         # verify that we get a sensible error message for bad mode argument
         bad_mode = "qwerty"
         try:
-            f = _fileio._FileIO(TESTFN, bad_mode)
+            f = _FileIO(TESTFN, bad_mode)
         except ValueError as msg:
             if msg.args[0] != 0:
                 s = str(msg)
@@ -200,11 +216,11 @@
         def bug801631():
             # SF bug <http://www.python.org/sf/801631>
             # "file.truncate fault on windows"
-            f = _fileio._FileIO(TESTFN, 'w')
+            f = _FileIO(TESTFN, 'w')
             f.write(bytes(range(11)))
             f.close()
 
-            f = _fileio._FileIO(TESTFN,'r+')
+            f = _FileIO(TESTFN,'r+')
             data = f.read(5)
             if data != bytes(range(5)):
                 self.fail("Read on file opened for update failed %r" % data)
@@ -244,14 +260,14 @@
                 pass
 
     def testInvalidInit(self):
-        self.assertRaises(TypeError, _fileio._FileIO, "1", 0, 0)
+        self.assertRaises(TypeError, _FileIO, "1", 0, 0)
 
     def testWarnings(self):
         with check_warnings() as w:
             self.assertEqual(w.warnings, [])
-            self.assertRaises(TypeError, _fileio._FileIO, [])
+            self.assertRaises(TypeError, _FileIO, [])
             self.assertEqual(w.warnings, [])
-            self.assertRaises(ValueError, _fileio._FileIO, "/some/invalid/name", "rt")
+            self.assertRaises(ValueError, _FileIO, "/some/invalid/name", "rt")
             self.assertEqual(w.warnings, [])
 
 
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 30869ac..58f33a2 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -1,4 +1,23 @@
-"""Unit tests for io.py."""
+"""Unit tests for the io module."""
+
+# Tests of io are scattered over the test suite:
+# * test_bufio - tests file buffering
+# * test_memoryio - tests BytesIO and StringIO
+# * test_fileio - tests FileIO
+# * test_file - tests the file interface
+# * test_io - tests everything else in the io module
+# * test_univnewlines - tests universal newline support
+# * test_largefile - tests operations on a file greater than 2**32 bytes
+#     (only enabled with -ulargefile)
+
+################################################################################
+# ATTENTION TEST WRITERS!!!
+################################################################################
+# When writing tests for io, it's important to test both the C and Python
+# implementations. This is usually done by writing a base test that refers to
+# the type it is testing as a attribute. Then it provides custom subclasses to
+# test both implementations. This file has lots of examples.
+################################################################################
 
 import os
 import sys
@@ -7,27 +26,40 @@
 import threading
 import random
 import unittest
-from itertools import chain, cycle
+import weakref
+import gc
+import abc
+from itertools import chain, cycle, count
+from collections import deque
 from test import support
 
 import codecs
-import io  # The module under test
+import io  # C implementation of io
+import _pyio as pyio # Python implementation of io
 
 
-class MockRawIO(io.RawIOBase):
+def _default_chunk_size():
+    """Get the default TextIOWrapper chunk size"""
+    with open(__file__, "r", encoding="latin1") as f:
+        return f._CHUNK_SIZE
+
+
+class MockRawIO:
 
     def __init__(self, read_stack=()):
         self._read_stack = list(read_stack)
         self._write_stack = []
+        self._reads = 0
 
     def read(self, n=None):
+        self._reads += 1
         try:
             return self._read_stack.pop(0)
         except:
             return b""
 
     def write(self, b):
-        self._write_stack.append(b[:])
+        self._write_stack.append(bytes(b))
         return len(b)
 
     def writable(self):
@@ -43,41 +75,148 @@
         return True
 
     def seek(self, pos, whence):
-        pass
+        return 0   # wrong but we gotta return something
 
     def tell(self):
-        return 42
+        return 0   # same comment as above
+
+    def readinto(self, buf):
+        self._reads += 1
+        max_len = len(buf)
+        try:
+            data = self._read_stack[0]
+        except IndexError:
+            return 0
+        if data is None:
+            del self._read_stack[0]
+            return None
+        n = len(data)
+        if len(data) <= max_len:
+            del self._read_stack[0]
+            buf[:n] = data
+            return n
+        else:
+            buf[:] = data[:max_len]
+            self._read_stack[0] = data[max_len:]
+            return max_len
+
+    def truncate(self, pos=None):
+        return pos
+
+class CMockRawIO(MockRawIO, io.RawIOBase):
+    pass
+
+class PyMockRawIO(MockRawIO, pyio.RawIOBase):
+    pass
 
 
-class MockFileIO(io.BytesIO):
+class MisbehavedRawIO(MockRawIO):
+    def write(self, b):
+        return super().write(b) * 2
+
+    def read(self, n=None):
+        return super().read(n) * 2
+
+    def seek(self, pos, whence):
+        return -123
+
+    def tell(self):
+        return -456
+
+    def readinto(self, buf):
+        super().readinto(buf)
+        return len(buf) * 5
+
+class CMisbehavedRawIO(MisbehavedRawIO, io.RawIOBase):
+    pass
+
+class PyMisbehavedRawIO(MisbehavedRawIO, pyio.RawIOBase):
+    pass
+
+
+class CloseFailureIO(MockRawIO):
+    closed = 0
+
+    def close(self):
+        if not self.closed:
+            self.closed = 1
+            raise IOError
+
+class CCloseFailureIO(CloseFailureIO, io.RawIOBase):
+    pass
+
+class PyCloseFailureIO(CloseFailureIO, pyio.RawIOBase):
+    pass
+
+
+class MockFileIO:
 
     def __init__(self, data):
         self.read_history = []
-        io.BytesIO.__init__(self, data)
+        super().__init__(data)
 
     def read(self, n=None):
-        res = io.BytesIO.read(self, n)
+        res = super().read(n)
         self.read_history.append(None if res is None else len(res))
         return res
 
+    def readinto(self, b):
+        res = super().readinto(b)
+        self.read_history.append(res)
+        return res
 
-class MockNonBlockWriterIO(io.RawIOBase):
+class CMockFileIO(MockFileIO, io.BytesIO):
+    pass
 
-    def __init__(self, blocking_script):
-        self._blocking_script = list(blocking_script)
+class PyMockFileIO(MockFileIO, pyio.BytesIO):
+    pass
+
+
+class MockNonBlockWriterIO:
+
+    def __init__(self):
         self._write_stack = []
+        self._blocker_char = None
 
-    def write(self, b):
-        self._write_stack.append(b[:])
-        n = self._blocking_script.pop(0)
-        if (n < 0):
-            raise io.BlockingIOError(0, "test blocking", -n)
-        else:
-            return n
+    def pop_written(self):
+        s = b"".join(self._write_stack)
+        self._write_stack[:] = []
+        return s
+
+    def block_on(self, char):
+        """Block when a given char is encountered."""
+        self._blocker_char = char
+
+    def readable(self):
+        return True
+
+    def seekable(self):
+        return True
 
     def writable(self):
         return True
 
+    def write(self, b):
+        b = bytes(b)
+        n = -1
+        if self._blocker_char:
+            try:
+                n = b.index(self._blocker_char)
+            except ValueError:
+                pass
+            else:
+                self._blocker_char = None
+                self._write_stack.append(b[:n])
+                raise self.BlockingIOError(0, "test blocking", n)
+        self._write_stack.append(b)
+        return len(b)
+
+class CMockNonBlockWriterIO(MockNonBlockWriterIO, io.RawIOBase):
+    BlockingIOError = io.BlockingIOError
+
+class PyMockNonBlockWriterIO(MockNonBlockWriterIO, pyio.RawIOBase):
+    BlockingIOError = pyio.BlockingIOError
+
 
 class IOTest(unittest.TestCase):
 
@@ -151,13 +290,13 @@
         self.assertEqual(f.read(2), b"x")
 
     def test_raw_file_io(self):
-        f = io.open(support.TESTFN, "wb", buffering=0)
+        f = self.open(support.TESTFN, "wb", buffering=0)
         self.assertEqual(f.readable(), False)
         self.assertEqual(f.writable(), True)
         self.assertEqual(f.seekable(), True)
         self.write_ops(f)
         f.close()
-        f = io.open(support.TESTFN, "rb", buffering=0)
+        f = self.open(support.TESTFN, "rb", buffering=0)
         self.assertEqual(f.readable(), True)
         self.assertEqual(f.writable(), False)
         self.assertEqual(f.seekable(), True)
@@ -165,13 +304,13 @@
         f.close()
 
     def test_buffered_file_io(self):
-        f = io.open(support.TESTFN, "wb")
+        f = self.open(support.TESTFN, "wb")
         self.assertEqual(f.readable(), False)
         self.assertEqual(f.writable(), True)
         self.assertEqual(f.seekable(), True)
         self.write_ops(f)
         f.close()
-        f = io.open(support.TESTFN, "rb")
+        f = self.open(support.TESTFN, "rb")
         self.assertEqual(f.readable(), True)
         self.assertEqual(f.writable(), False)
         self.assertEqual(f.seekable(), True)
@@ -180,22 +319,23 @@
 
     def test_readline(self):
         f = io.open(support.TESTFN, "wb")
-        f.write(b"abc\ndef\nxyzzy\nfoo")
+        f.write(b"abc\ndef\nxyzzy\nfoo\x00bar\nanother line")
         f.close()
-        f = io.open(support.TESTFN, "rb")
+        f = self.open(support.TESTFN, "rb")
         self.assertEqual(f.readline(), b"abc\n")
         self.assertEqual(f.readline(10), b"def\n")
         self.assertEqual(f.readline(2), b"xy")
         self.assertEqual(f.readline(4), b"zzy\n")
-        self.assertEqual(f.readline(), b"foo")
+        self.assertEqual(f.readline(), b"foo\x00bar\n")
+        self.assertEqual(f.readline(), b"another line")
         f.close()
 
     def test_raw_bytes_io(self):
-        f = io.BytesIO()
+        f = self.BytesIO()
         self.write_ops(f)
         data = f.getvalue()
         self.assertEqual(data, b"hello world\n")
-        f = io.BytesIO(data)
+        f = self.BytesIO(data)
         self.read_ops(f, True)
 
     def test_large_file_ops(self):
@@ -211,12 +351,10 @@
                 print("Use 'regrtest.py -u largefile test_io' to run it.",
                       file=sys.stderr)
                 return
-        f = io.open(support.TESTFN, "w+b", 0)
-        self.large_file_ops(f)
-        f.close()
-        f = io.open(support.TESTFN, "w+b")
-        self.large_file_ops(f)
-        f.close()
+        with self.open(support.TESTFN, "w+b", 0) as f:
+            self.large_file_ops(f)
+        with self.open(support.TESTFN, "w+b") as f:
+            self.large_file_ops(f)
 
     def test_with_open(self):
         for bufsize in (0, 1, 100):
@@ -235,59 +373,107 @@
 
     # issue 5008
     def test_append_mode_tell(self):
-        with io.open(support.TESTFN, "wb") as f:
+        with self.open(support.TESTFN, "wb") as f:
             f.write(b"xxx")
-        with io.open(support.TESTFN, "ab", buffering=0) as f:
+        with self.open(support.TESTFN, "ab", buffering=0) as f:
             self.assertEqual(f.tell(), 3)
-        with io.open(support.TESTFN, "ab") as f:
+        with self.open(support.TESTFN, "ab") as f:
             self.assertEqual(f.tell(), 3)
-        with io.open(support.TESTFN, "a") as f:
+        with self.open(support.TESTFN, "a") as f:
             self.assert_(f.tell() > 0)
 
     def test_destructor(self):
         record = []
-        class MyFileIO(io.FileIO):
+        class MyFileIO(self.FileIO):
             def __del__(self):
                 record.append(1)
-                io.FileIO.__del__(self)
+                try:
+                    f = super().__del__
+                except AttributeError:
+                    pass
+                else:
+                    f()
             def close(self):
                 record.append(2)
-                io.FileIO.close(self)
+                super().close()
             def flush(self):
                 record.append(3)
-                io.FileIO.flush(self)
-        f = MyFileIO(support.TESTFN, "w")
-        f.write("xxx")
+                super().flush()
+        f = MyFileIO(support.TESTFN, "wb")
+        f.write(b"xxx")
+        del f
+        self.assertEqual(record, [1, 2, 3])
+        f = open(support.TESTFN, "rb")
+        self.assertEqual(f.read(), b"xxx")
+
+    def _check_base_destructor(self, base):
+        record = []
+        class MyIO(base):
+            def __init__(self):
+                # This exercises the availability of attributes on object
+                # destruction.
+                # (in the C version, close() is called by the tp_dealloc
+                # function, not by __del__)
+                self.on_del = 1
+                self.on_close = 2
+                self.on_flush = 3
+            def __del__(self):
+                record.append(self.on_del)
+                try:
+                    f = super().__del__
+                except AttributeError:
+                    pass
+                else:
+                    f()
+            def close(self):
+                record.append(self.on_close)
+                super().close()
+            def flush(self):
+                record.append(self.on_flush)
+                super().flush()
+        f = MyIO()
         del f
         self.assertEqual(record, [1, 2, 3])
 
+    def test_IOBase_destructor(self):
+        self._check_base_destructor(self.IOBase)
+
+    def test_RawIOBase_destructor(self):
+        self._check_base_destructor(self.RawIOBase)
+
+    def test_BufferedIOBase_destructor(self):
+        self._check_base_destructor(self.BufferedIOBase)
+
+    def test_TextIOBase_destructor(self):
+        self._check_base_destructor(self.TextIOBase)
+
     def test_close_flushes(self):
-        f = io.open(support.TESTFN, "wb")
+        f = self.open(support.TESTFN, "wb")
         f.write(b"xxx")
         f.close()
-        f = io.open(support.TESTFN, "rb")
+        f = self.open(support.TESTFN, "rb")
         self.assertEqual(f.read(), b"xxx")
         f.close()
 
     def test_array_writes(self):
         a = array.array('i', range(10))
         n = len(a.tostring())
-        f = io.open(support.TESTFN, "wb", 0)
+        f = self.open(support.TESTFN, "wb", 0)
         self.assertEqual(f.write(a), n)
         f.close()
-        f = io.open(support.TESTFN, "wb")
+        f = self.open(support.TESTFN, "wb")
         self.assertEqual(f.write(a), n)
         f.close()
 
     def test_closefd(self):
-        self.assertRaises(ValueError, io.open, support.TESTFN, 'w',
+        self.assertRaises(ValueError, self.open, support.TESTFN, 'w',
                           closefd=False)
 
-    def testReadClosed(self):
-        with io.open(support.TESTFN, "w") as f:
+    def test_read_closed(self):
+        with self.open(support.TESTFN, "w") as f:
             f.write("egg\n")
-        with io.open(support.TESTFN, "r") as f:
-            file = io.open(f.fileno(), "r", closefd=False)
+        with self.open(support.TESTFN, "r") as f:
+            file = self.open(f.fileno(), "r", closefd=False)
             self.assertEqual(file.read(), "egg\n")
             file.seek(0)
             file.close()
@@ -295,85 +481,168 @@
 
     def test_no_closefd_with_filename(self):
         # can't use closefd in combination with a file name
-        self.assertRaises(ValueError, io.open, support.TESTFN, "r", closefd=False)
+        self.assertRaises(ValueError, self.open, support.TESTFN, "r", closefd=False)
 
     def test_closefd_attr(self):
-        with io.open(support.TESTFN, "wb") as f:
+        with self.open(support.TESTFN, "wb") as f:
             f.write(b"egg\n")
-        with io.open(support.TESTFN, "r") as f:
+        with self.open(support.TESTFN, "r") as f:
             self.assertEqual(f.buffer.raw.closefd, True)
-            file = io.open(f.fileno(), "r", closefd=False)
+            file = self.open(f.fileno(), "r", closefd=False)
             self.assertEqual(file.buffer.raw.closefd, False)
 
+    def test_garbage_collection(self):
+        # FileIO objects are collected, and collecting them flushes
+        # all data to disk.
+        f = self.FileIO(support.TESTFN, "wb")
+        f.write(b"abcxxx")
+        f.f = f
+        wr = weakref.ref(f)
+        del f
+        gc.collect()
+        self.assert_(wr() is None, wr)
+        with open(support.TESTFN, "rb") as f:
+            self.assertEqual(f.read(), b"abcxxx")
 
-class MemorySeekTestMixin:
+class CIOTest(IOTest):
+    pass
 
-    def testInit(self):
-        buf = self.buftype("1234567890")
-        bytesIo = self.ioclass(buf)
-
-    def testRead(self):
-        buf = self.buftype("1234567890")
-        bytesIo = self.ioclass(buf)
-
-        self.assertEquals(buf[:1], bytesIo.read(1))
-        self.assertEquals(buf[1:5], bytesIo.read(4))
-        self.assertEquals(buf[5:], bytesIo.read(900))
-        self.assertEquals(self.EOF, bytesIo.read())
-
-    def testReadNoArgs(self):
-        buf = self.buftype("1234567890")
-        bytesIo = self.ioclass(buf)
-
-        self.assertEquals(buf, bytesIo.read())
-        self.assertEquals(self.EOF, bytesIo.read())
-
-    def testSeek(self):
-        buf = self.buftype("1234567890")
-        bytesIo = self.ioclass(buf)
-
-        bytesIo.read(5)
-        bytesIo.seek(0)
-        self.assertEquals(buf, bytesIo.read())
-
-        bytesIo.seek(3)
-        self.assertEquals(buf[3:], bytesIo.read())
-        self.assertRaises(TypeError, bytesIo.seek, 0.0)
-
-    def testTell(self):
-        buf = self.buftype("1234567890")
-        bytesIo = self.ioclass(buf)
-
-        self.assertEquals(0, bytesIo.tell())
-        bytesIo.seek(5)
-        self.assertEquals(5, bytesIo.tell())
-        bytesIo.seek(10000)
-        self.assertEquals(10000, bytesIo.tell())
+class PyIOTest(IOTest):
+    pass
 
 
-class BytesIOTest(MemorySeekTestMixin, unittest.TestCase):
-    @staticmethod
-    def buftype(s):
-        return s.encode("utf-8")
-    ioclass = io.BytesIO
-    EOF = b""
+class CommonBufferedTests:
+    # Tests common to BufferedReader, BufferedWriter and BufferedRandom
+
+    def test_fileno(self):
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+
+        self.assertEquals(42, bufio.fileno())
+
+    def test_no_fileno(self):
+        # XXX will we always have fileno() function? If so, kill
+        # this test. Else, write it.
+        pass
+
+    def test_invalid_args(self):
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+        # Invalid whence
+        self.assertRaises(ValueError, bufio.seek, 0, -1)
+        self.assertRaises(ValueError, bufio.seek, 0, 3)
+
+    def test_override_destructor(self):
+        tp = self.tp
+        record = []
+        class MyBufferedIO(tp):
+            def __del__(self):
+                record.append(1)
+                try:
+                    f = super().__del__
+                except AttributeError:
+                    pass
+                else:
+                    f()
+            def close(self):
+                record.append(2)
+                super().close()
+            def flush(self):
+                record.append(3)
+                super().flush()
+        rawio = self.MockRawIO()
+        bufio = MyBufferedIO(rawio)
+        writable = bufio.writable()
+        del bufio
+        if writable:
+            self.assertEqual(record, [1, 2, 3])
+        else:
+            self.assertEqual(record, [1, 2])
+
+    def test_context_manager(self):
+        # Test usability as a context manager
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+        def _with():
+            with bufio:
+                pass
+        _with()
+        # bufio should now be closed, and using it a second time should raise
+        # a ValueError.
+        self.assertRaises(ValueError, _with)
+
+    def test_error_through_destructor(self):
+        # Test that the exception state is not modified by a destructor,
+        # even if close() fails.
+        rawio = self.CloseFailureIO()
+        def f():
+            self.tp(rawio).xyzzy
+        with support.captured_output("stderr") as s:
+            self.assertRaises(AttributeError, f)
+        s = s.getvalue().strip()
+        if s:
+            # The destructor *may* have printed an unraisable error, check it
+            self.assertEqual(len(s.splitlines()), 1)
+            self.assert_(s.startswith("Exception IOError: "), s)
+            self.assert_(s.endswith(" ignored"), s)
 
 
-class StringIOTest(MemorySeekTestMixin, unittest.TestCase):
-    buftype = str
-    ioclass = io.StringIO
-    EOF = ""
+class BufferedReaderTest(unittest.TestCase, CommonBufferedTests):
+    read_mode = "rb"
 
+    def test_constructor(self):
+        rawio = self.MockRawIO([b"abc"])
+        bufio = self.tp(rawio)
+        bufio.__init__(rawio)
+        bufio.__init__(rawio, buffer_size=1024)
+        bufio.__init__(rawio, buffer_size=16)
+        self.assertEquals(b"abc", bufio.read())
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
+        rawio = self.MockRawIO([b"abc"])
+        bufio.__init__(rawio)
+        self.assertEquals(b"abc", bufio.read())
 
-class BufferedReaderTest(unittest.TestCase):
-
-    def testRead(self):
-        rawio = MockRawIO((b"abc", b"d", b"efg"))
-        bufio = io.BufferedReader(rawio)
-
+    def test_read(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
         self.assertEquals(b"abcdef", bufio.read(6))
+        # Invalid args
+        self.assertRaises(ValueError, bufio.read, -2)
 
-    def testBuffering(self):
+    def test_read1(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+        self.assertEquals(b"a", bufio.read(1))
+        self.assertEquals(b"b", bufio.read1(1))
+        self.assertEquals(rawio._reads, 1)
+        self.assertEquals(b"c", bufio.read1(100))
+        self.assertEquals(rawio._reads, 1)
+        self.assertEquals(b"d", bufio.read1(100))
+        self.assertEquals(rawio._reads, 2)
+        self.assertEquals(b"efg", bufio.read1(100))
+        self.assertEquals(rawio._reads, 3)
+        self.assertEquals(b"", bufio.read1(100))
+        # Invalid args
+        self.assertRaises(ValueError, bufio.read1, -1)
+
+    def test_readinto(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+        b = bytearray(2)
+        self.assertEquals(bufio.readinto(b), 2)
+        self.assertEquals(b, b"ab")
+        self.assertEquals(bufio.readinto(b), 2)
+        self.assertEquals(b, b"cd")
+        self.assertEquals(bufio.readinto(b), 2)
+        self.assertEquals(b, b"ef")
+        self.assertEquals(bufio.readinto(b), 1)
+        self.assertEquals(b, b"gf")
+        self.assertEquals(bufio.readinto(b), 0)
+        self.assertEquals(b, b"gf")
+
+    def test_buffering(self):
         data = b"abcdefghi"
         dlen = len(data)
 
@@ -384,49 +653,40 @@
         ]
 
         for bufsize, buf_read_sizes, raw_read_sizes in tests:
-            rawio = MockFileIO(data)
-            bufio = io.BufferedReader(rawio, buffer_size=bufsize)
+            rawio = self.MockFileIO(data)
+            bufio = self.tp(rawio, buffer_size=bufsize)
             pos = 0
             for nbytes in buf_read_sizes:
                 self.assertEquals(bufio.read(nbytes), data[pos:pos+nbytes])
                 pos += nbytes
+            # this is mildly implementation-dependent
             self.assertEquals(rawio.read_history, raw_read_sizes)
 
-    def testReadNonBlocking(self):
+    def test_read_non_blocking(self):
         # Inject some None's in there to simulate EWOULDBLOCK
-        rawio = MockRawIO((b"abc", b"d", None, b"efg", None, None))
-        bufio = io.BufferedReader(rawio)
+        rawio = self.MockRawIO((b"abc", b"d", None, b"efg", None, None, None))
+        bufio = self.tp(rawio)
 
         self.assertEquals(b"abcd", bufio.read(6))
         self.assertEquals(b"e", bufio.read(1))
         self.assertEquals(b"fg", bufio.read())
+        self.assertEquals(b"", bufio.peek(1))
         self.assert_(None is bufio.read())
         self.assertEquals(b"", bufio.read())
 
-    def testReadToEof(self):
-        rawio = MockRawIO((b"abc", b"d", b"efg"))
-        bufio = io.BufferedReader(rawio)
+    def test_read_past_eof(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
 
         self.assertEquals(b"abcdefg", bufio.read(9000))
 
-    def testReadNoArgs(self):
-        rawio = MockRawIO((b"abc", b"d", b"efg"))
-        bufio = io.BufferedReader(rawio)
+    def test_read_all(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
 
         self.assertEquals(b"abcdefg", bufio.read())
 
-    def testFileno(self):
-        rawio = MockRawIO((b"abc", b"d", b"efg"))
-        bufio = io.BufferedReader(rawio)
-
-        self.assertEquals(42, bufio.fileno())
-
-    def testFilenoNoFileno(self):
-        # XXX will we always have fileno() function? If so, kill
-        # this test. Else, write it.
-        pass
-
-    def testThreads(self):
+    def test_threads(self):
         try:
             # Write out many bytes with exactly the same number of 0's,
             # 1's... 255's. This will help us check that concurrent reading
@@ -437,8 +697,8 @@
             s = bytes(bytearray(l))
             with io.open(support.TESTFN, "wb") as f:
                 f.write(s)
-            with io.open(support.TESTFN, "rb", buffering=0) as raw:
-                bufio = io.BufferedReader(raw, 8)
+            with io.open(support.TESTFN, self.read_mode, buffering=0) as raw:
+                bufio = self.tp(raw, 8)
                 errors = []
                 results = []
                 def f():
@@ -468,80 +728,230 @@
         finally:
             support.unlink(support.TESTFN)
 
+    def test_misbehaved_io(self):
+        rawio = self.MisbehavedRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+        self.assertRaises(IOError, bufio.seek, 0)
+        self.assertRaises(IOError, bufio.tell)
+
+class CBufferedReaderTest(BufferedReaderTest):
+    tp = io.BufferedReader
+
+    def test_constructor(self):
+        BufferedReaderTest.test_constructor(self)
+        # The allocation can succeed on 32-bit builds, e.g. with more
+        # than 2GB RAM and a 64-bit kernel.
+        if sys.maxsize > 0x7FFFFFFF:
+            rawio = self.MockRawIO()
+            bufio = self.tp(rawio)
+            self.assertRaises((OverflowError, MemoryError, ValueError),
+                bufio.__init__, rawio, sys.maxsize)
+
+    def test_initialization(self):
+        rawio = self.MockRawIO([b"abc"])
+        bufio = self.tp(rawio)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
+        self.assertRaises(ValueError, bufio.read)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
+        self.assertRaises(ValueError, bufio.read)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
+        self.assertRaises(ValueError, bufio.read)
+
+    def test_misbehaved_io_read(self):
+        rawio = self.MisbehavedRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+        # _pyio.BufferedReader seems to implement reading different, so that
+        # checking this is not so easy.
+        self.assertRaises(IOError, bufio.read, 10)
+
+    def test_garbage_collection(self):
+        # C BufferedReader objects are collected.
+        # The Python version has __del__, so it ends into gc.garbage instead
+        rawio = self.FileIO(support.TESTFN, "w+b")
+        f = self.tp(rawio)
+        f.f = f
+        wr = weakref.ref(f)
+        del f
+        gc.collect()
+        self.assert_(wr() is None, wr)
+
+class PyBufferedReaderTest(BufferedReaderTest):
+    tp = pyio.BufferedReader
 
 
-class BufferedWriterTest(unittest.TestCase):
+class BufferedWriterTest(unittest.TestCase, CommonBufferedTests):
+    write_mode = "wb"
 
-    def testWrite(self):
+    def test_constructor(self):
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+        bufio.__init__(rawio)
+        bufio.__init__(rawio, buffer_size=1024)
+        bufio.__init__(rawio, buffer_size=16)
+        self.assertEquals(3, bufio.write(b"abc"))
+        bufio.flush()
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
+        bufio.__init__(rawio)
+        self.assertEquals(3, bufio.write(b"ghi"))
+        bufio.flush()
+        self.assertEquals(b"".join(rawio._write_stack), b"abcghi")
+
+    def test_write(self):
         # Write to the buffered IO but don't overflow the buffer.
-        writer = MockRawIO()
-        bufio = io.BufferedWriter(writer, 8)
-
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
         bufio.write(b"abc")
-
         self.assertFalse(writer._write_stack)
 
-    def testWriteOverflow(self):
-        writer = MockRawIO()
-        bufio = io.BufferedWriter(writer, 8)
+    def test_write_overflow(self):
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
+        contents = b"abcdefghijklmnop"
+        for n in range(0, len(contents), 3):
+            bufio.write(contents[n:n+3])
+        flushed = b"".join(writer._write_stack)
+        # At least (total - 8) bytes were implicitly flushed, perhaps more
+        # depending on the implementation.
+        self.assert_(flushed.startswith(contents[:-8]), flushed)
 
-        bufio.write(b"abc")
-        bufio.write(b"defghijkl")
+    def check_writes(self, intermediate_func):
+        # Lots of writes, test the flushed output is as expected.
+        contents = bytes(range(256)) * 1000
+        n = 0
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 13)
+        # Generator of write sizes: repeat each N 15 times then proceed to N+1
+        def gen_sizes():
+            for size in count(1):
+                for i in range(15):
+                    yield size
+        sizes = gen_sizes()
+        while n < len(contents):
+            size = min(next(sizes), len(contents) - n)
+            self.assertEquals(bufio.write(contents[n:n+size]), size)
+            intermediate_func(bufio)
+            n += size
+        bufio.flush()
+        self.assertEquals(contents, b"".join(writer._write_stack))
 
-        self.assertEquals(b"abcdefghijkl", writer._write_stack[0])
+    def test_writes(self):
+        self.check_writes(lambda bufio: None)
 
-    def testWriteNonBlocking(self):
-        raw = MockNonBlockWriterIO((9, 2, 22, -6, 10, 12, 12))
-        bufio = io.BufferedWriter(raw, 8, 16)
+    def test_writes_and_flushes(self):
+        self.check_writes(lambda bufio: bufio.flush())
 
-        bufio.write(b"asdf")
-        bufio.write(b"asdfa")
-        self.assertEquals(b"asdfasdfa", raw._write_stack[0])
+    def test_writes_and_seeks(self):
+        def _seekabs(bufio):
+            pos = bufio.tell()
+            bufio.seek(pos + 1, 0)
+            bufio.seek(pos - 1, 0)
+            bufio.seek(pos, 0)
+        self.check_writes(_seekabs)
+        def _seekrel(bufio):
+            pos = bufio.seek(0, 1)
+            bufio.seek(+1, 1)
+            bufio.seek(-1, 1)
+            bufio.seek(pos, 0)
+        self.check_writes(_seekrel)
 
-        bufio.write(b"asdfasdfasdf")
-        self.assertEquals(b"asdfasdfasdf", raw._write_stack[1])
-        bufio.write(b"asdfasdfasdf")
-        self.assertEquals(b"dfasdfasdf", raw._write_stack[2])
-        self.assertEquals(b"asdfasdfasdf", raw._write_stack[3])
+    def test_writes_and_truncates(self):
+        self.check_writes(lambda bufio: bufio.truncate(bufio.tell()))
 
-        bufio.write(b"asdfasdfasdf")
+    def test_write_non_blocking(self):
+        raw = self.MockNonBlockWriterIO()
+        bufio = self.tp(raw, 8, 8)
 
-        # XXX I don't like this test. It relies too heavily on how the
-        # algorithm actually works, which we might change. Refactor
-        # later.
+        self.assertEquals(bufio.write(b"abcd"), 4)
+        self.assertEquals(bufio.write(b"efghi"), 5)
+        # 1 byte will be written, the rest will be buffered
+        raw.block_on(b"k")
+        self.assertEquals(bufio.write(b"jklmn"), 5)
 
-    def testFileno(self):
-        rawio = MockRawIO((b"abc", b"d", b"efg"))
-        bufio = io.BufferedWriter(rawio)
+        # 8 bytes will be written, 8 will be buffered and the rest will be lost
+        raw.block_on(b"0")
+        try:
+            bufio.write(b"opqrwxyz0123456789")
+        except self.BlockingIOError as e:
+            written = e.characters_written
+        else:
+            self.fail("BlockingIOError should have been raised")
+        self.assertEquals(written, 16)
+        self.assertEquals(raw.pop_written(),
+            b"abcdefghijklmnopqrwxyz")
 
-        self.assertEquals(42, bufio.fileno())
+        self.assertEquals(bufio.write(b"ABCDEFGHI"), 9)
+        s = raw.pop_written()
+        # Previously buffered bytes were flushed
+        self.assertTrue(s.startswith(b"01234567A"), s)
 
-    def testFlush(self):
-        writer = MockRawIO()
-        bufio = io.BufferedWriter(writer, 8)
+    def test_write_and_rewind(self):
+        raw = io.BytesIO()
+        bufio = self.tp(raw, 4)
+        self.assertEqual(bufio.write(b"abcdef"), 6)
+        self.assertEqual(bufio.tell(), 6)
+        bufio.seek(0, 0)
+        self.assertEqual(bufio.write(b"XY"), 2)
+        bufio.seek(6, 0)
+        self.assertEqual(raw.getvalue(), b"XYcdef")
+        self.assertEqual(bufio.write(b"123456"), 6)
+        bufio.flush()
+        self.assertEqual(raw.getvalue(), b"XYcdef123456")
 
+    def test_flush(self):
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
         bufio.write(b"abc")
         bufio.flush()
-
         self.assertEquals(b"abc", writer._write_stack[0])
 
-    def testThreads(self):
-        # BufferedWriter should not raise exceptions or crash
-        # when called from multiple threads.
+    def test_destructor(self):
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
+        bufio.write(b"abc")
+        del bufio
+        self.assertEquals(b"abc", writer._write_stack[0])
+
+    def test_truncate(self):
+        # Truncate implicitly flushes the buffer.
+        with io.open(support.TESTFN, self.write_mode, buffering=0) as raw:
+            bufio = self.tp(raw, 8)
+            bufio.write(b"abcdef")
+            self.assertEqual(bufio.truncate(3), 3)
+            self.assertEqual(bufio.tell(), 3)
+        with io.open(support.TESTFN, "rb", buffering=0) as f:
+            self.assertEqual(f.read(), b"abc")
+
+    def test_threads(self):
         try:
+            # Write out many bytes from many threads and test they were
+            # all flushed.
+            N = 1000
+            contents = bytes(range(256)) * N
+            sizes = cycle([1, 19])
+            n = 0
+            queue = deque()
+            while n < len(contents):
+                size = next(sizes)
+                queue.append(contents[n:n+size])
+                n += size
+            del contents
             # We use a real file object because it allows us to
             # exercise situations where the GIL is released before
             # writing the buffer to the raw streams. This is in addition
             # to concurrency issues due to switching threads in the middle
             # of Python code.
-            with io.open(support.TESTFN, "wb", buffering=0) as raw:
-                bufio = io.BufferedWriter(raw, 8)
+            with io.open(support.TESTFN, self.write_mode, buffering=0) as raw:
+                bufio = self.tp(raw, 8)
                 errors = []
                 def f():
                     try:
-                        # Write enough bytes to flush the buffer
-                        s = b"a" * 19
-                        for i in range(50):
+                        while True:
+                            try:
+                                s = queue.popleft()
+                            except IndexError:
+                                return
                             bufio.write(s)
                     except Exception as e:
                         errors.append(e)
@@ -554,37 +964,102 @@
                     t.join()
                 self.assertFalse(errors,
                     "the following exceptions were caught: %r" % errors)
+                bufio.close()
+            with io.open(support.TESTFN, "rb") as f:
+                s = f.read()
+            for i in range(256):
+                self.assertEquals(s.count(bytes([i])), N)
         finally:
             support.unlink(support.TESTFN)
 
+    def test_misbehaved_io(self):
+        rawio = self.MisbehavedRawIO()
+        bufio = self.tp(rawio, 5)
+        self.assertRaises(IOError, bufio.seek, 0)
+        self.assertRaises(IOError, bufio.tell)
+        self.assertRaises(IOError, bufio.write, b"abcdef")
+
+class CBufferedWriterTest(BufferedWriterTest):
+    tp = io.BufferedWriter
+
+    def test_constructor(self):
+        BufferedWriterTest.test_constructor(self)
+        # The allocation can succeed on 32-bit builds, e.g. with more
+        # than 2GB RAM and a 64-bit kernel.
+        if sys.maxsize > 0x7FFFFFFF:
+            rawio = self.MockRawIO()
+            bufio = self.tp(rawio)
+            self.assertRaises((OverflowError, MemoryError, ValueError),
+                bufio.__init__, rawio, sys.maxsize)
+
+    def test_initialization(self):
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
+        self.assertRaises(ValueError, bufio.write, b"def")
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
+        self.assertRaises(ValueError, bufio.write, b"def")
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
+        self.assertRaises(ValueError, bufio.write, b"def")
+
+    def test_garbage_collection(self):
+        # C BufferedWriter objects are collected, and collecting them flushes
+        # all data to disk.
+        # The Python version has __del__, so it ends into gc.garbage instead
+        rawio = self.FileIO(support.TESTFN, "w+b")
+        f = self.tp(rawio)
+        f.write(b"123xxx")
+        f.x = f
+        wr = weakref.ref(f)
+        del f
+        gc.collect()
+        self.assert_(wr() is None, wr)
+        with open(support.TESTFN, "rb") as f:
+            self.assertEqual(f.read(), b"123xxx")
+
+
+class PyBufferedWriterTest(BufferedWriterTest):
+    tp = pyio.BufferedWriter
 
 class BufferedRWPairTest(unittest.TestCase):
 
-    def testRWPair(self):
-        r = MockRawIO(())
-        w = MockRawIO()
-        pair = io.BufferedRWPair(r, w)
+    def test_basic(self):
+        r = self.MockRawIO(())
+        w = self.MockRawIO()
+        pair = self.tp(r, w)
         self.assertFalse(pair.closed)
 
         # XXX More Tests
 
+class CBufferedRWPairTest(BufferedRWPairTest):
+    tp = io.BufferedRWPair
 
-class BufferedRandomTest(unittest.TestCase):
+class PyBufferedRWPairTest(BufferedRWPairTest):
+    tp = pyio.BufferedRWPair
 
-    def testReadAndWrite(self):
-        raw = MockRawIO((b"asdf", b"ghjk"))
-        rw = io.BufferedRandom(raw, 8, 12)
+
+class BufferedRandomTest(BufferedReaderTest, BufferedWriterTest):
+    read_mode = "rb+"
+    write_mode = "wb+"
+
+    def test_constructor(self):
+        BufferedReaderTest.test_constructor(self)
+        BufferedWriterTest.test_constructor(self)
+
+    def test_read_and_write(self):
+        raw = self.MockRawIO((b"asdf", b"ghjk"))
+        rw = self.tp(raw, 8, 12)
 
         self.assertEqual(b"as", rw.read(2))
         rw.write(b"ddd")
         rw.write(b"eee")
         self.assertFalse(raw._write_stack) # Buffer writes
-        self.assertEqual(b"ghjk", rw.read()) # This read forces write flush
+        self.assertEqual(b"ghjk", rw.read())
         self.assertEquals(b"dddeee", raw._write_stack[0])
 
-    def testSeekAndTell(self):
-        raw = io.BytesIO(b"asdfghjkl")
-        rw = io.BufferedRandom(raw)
+    def test_seek_and_tell(self):
+        raw = self.BytesIO(b"asdfghjkl")
+        rw = self.tp(raw)
 
         self.assertEquals(b"as", rw.read(2))
         self.assertEquals(2, rw.tell())
@@ -602,6 +1077,115 @@
         self.assertEquals(b"fl", rw.read(11))
         self.assertRaises(TypeError, rw.seek, 0.0)
 
+    def check_flush_and_read(self, read_func):
+        raw = self.BytesIO(b"abcdefghi")
+        bufio = self.tp(raw)
+
+        self.assertEquals(b"ab", read_func(bufio, 2))
+        bufio.write(b"12")
+        self.assertEquals(b"ef", read_func(bufio, 2))
+        self.assertEquals(6, bufio.tell())
+        bufio.flush()
+        self.assertEquals(6, bufio.tell())
+        self.assertEquals(b"ghi", read_func(bufio))
+        raw.seek(0, 0)
+        raw.write(b"XYZ")
+        # flush() resets the read buffer
+        bufio.flush()
+        bufio.seek(0, 0)
+        self.assertEquals(b"XYZ", read_func(bufio, 3))
+
+    def test_flush_and_read(self):
+        self.check_flush_and_read(lambda bufio, *args: bufio.read(*args))
+
+    def test_flush_and_readinto(self):
+        def _readinto(bufio, n=-1):
+            b = bytearray(n if n >= 0 else 9999)
+            n = bufio.readinto(b)
+            return bytes(b[:n])
+        self.check_flush_and_read(_readinto)
+
+    def test_flush_and_peek(self):
+        def _peek(bufio, n=-1):
+            # This relies on the fact that the buffer can contain the whole
+            # raw stream, otherwise peek() can return less.
+            b = bufio.peek(n)
+            if n != -1:
+                b = b[:n]
+            bufio.seek(len(b), 1)
+            return b
+        self.check_flush_and_read(_peek)
+
+    def test_flush_and_write(self):
+        raw = self.BytesIO(b"abcdefghi")
+        bufio = self.tp(raw)
+
+        bufio.write(b"123")
+        bufio.flush()
+        bufio.write(b"45")
+        bufio.flush()
+        bufio.seek(0, 0)
+        self.assertEquals(b"12345fghi", raw.getvalue())
+        self.assertEquals(b"12345fghi", bufio.read())
+
+    def test_threads(self):
+        BufferedReaderTest.test_threads(self)
+        BufferedWriterTest.test_threads(self)
+
+    def test_writes_and_peek(self):
+        def _peek(bufio):
+            bufio.peek(1)
+        self.check_writes(_peek)
+        def _peek(bufio):
+            pos = bufio.tell()
+            bufio.seek(-1, 1)
+            bufio.peek(1)
+            bufio.seek(pos, 0)
+        self.check_writes(_peek)
+
+    def test_writes_and_reads(self):
+        def _read(bufio):
+            bufio.seek(-1, 1)
+            bufio.read(1)
+        self.check_writes(_read)
+
+    def test_writes_and_read1s(self):
+        def _read1(bufio):
+            bufio.seek(-1, 1)
+            bufio.read1(1)
+        self.check_writes(_read1)
+
+    def test_writes_and_readintos(self):
+        def _read(bufio):
+            bufio.seek(-1, 1)
+            bufio.readinto(bytearray(1))
+        self.check_writes(_read)
+
+    def test_misbehaved_io(self):
+        BufferedReaderTest.test_misbehaved_io(self)
+        BufferedWriterTest.test_misbehaved_io(self)
+
+class CBufferedRandomTest(BufferedRandomTest):
+    tp = io.BufferedRandom
+
+    def test_constructor(self):
+        BufferedRandomTest.test_constructor(self)
+        # The allocation can succeed on 32-bit builds, e.g. with more
+        # than 2GB RAM and a 64-bit kernel.
+        if sys.maxsize > 0x7FFFFFFF:
+            rawio = self.MockRawIO()
+            bufio = self.tp(rawio)
+            self.assertRaises((OverflowError, MemoryError, ValueError),
+                bufio.__init__, rawio, sys.maxsize)
+
+    def test_garbage_collection(self):
+        CBufferedReaderTest.test_garbage_collection(self)
+        CBufferedWriterTest.test_garbage_collection(self)
+
+class PyBufferedRandomTest(BufferedRandomTest):
+    tp = pyio.BufferedRandom
+
+
 # To fully exercise seek/tell, the StatefulIncrementalDecoder has these
 # properties:
 #   - A single output character can correspond to many bytes of input.
@@ -735,7 +1319,7 @@
          'm--------------.')
     ]
 
-    def testDecoder(self):
+    def test_decoder(self):
         # Try a few one-shot test cases.
         for input, eof, output in self.test_cases:
             d = StatefulIncrementalDecoder()
@@ -756,10 +1340,24 @@
     def tearDown(self):
         support.unlink(support.TESTFN)
 
-    def testLineBuffering(self):
-        r = io.BytesIO()
-        b = io.BufferedWriter(r, 1000)
-        t = io.TextIOWrapper(b, newline="\n", line_buffering=True)
+    def test_constructor(self):
+        r = self.BytesIO(b"\xc3\xa9\n\n")
+        b = self.BufferedReader(r, 1000)
+        t = self.TextIOWrapper(b)
+        t.__init__(b, encoding="latin1", newline="\r\n")
+        self.assertEquals(t.encoding, "latin1")
+        self.assertEquals(t.line_buffering, False)
+        t.__init__(b, encoding="utf8", line_buffering=True)
+        self.assertEquals(t.encoding, "utf8")
+        self.assertEquals(t.line_buffering, True)
+        self.assertEquals("\xe9\n", t.readline())
+        self.assertRaises(TypeError, t.__init__, b, newline=42)
+        self.assertRaises(ValueError, t.__init__, b, newline='xyzzy')
+
+    def test_line_buffering(self):
+        r = self.BytesIO()
+        b = self.BufferedWriter(r, 1000)
+        t = self.TextIOWrapper(b, newline="\n", line_buffering=True)
         t.write("X")
         self.assertEquals(r.getvalue(), b"")  # No flush happened
         t.write("Y\nZ")
@@ -767,83 +1365,58 @@
         t.write("A\rB")
         self.assertEquals(r.getvalue(), b"XY\nZA\rB")
 
-    def testEncodingErrorsReading(self):
+    def test_encoding(self):
+        # Check the encoding attribute is always set, and valid
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="utf8")
+        self.assertEqual(t.encoding, "utf8")
+        t = self.TextIOWrapper(b)
+        self.assert_(t.encoding is not None)
+        codecs.lookup(t.encoding)
+
+    def test_encoding_errors_reading(self):
         # (1) default
-        b = io.BytesIO(b"abc\n\xff\n")
-        t = io.TextIOWrapper(b, encoding="ascii")
+        b = self.BytesIO(b"abc\n\xff\n")
+        t = self.TextIOWrapper(b, encoding="ascii")
         self.assertRaises(UnicodeError, t.read)
         # (2) explicit strict
-        b = io.BytesIO(b"abc\n\xff\n")
-        t = io.TextIOWrapper(b, encoding="ascii", errors="strict")
+        b = self.BytesIO(b"abc\n\xff\n")
+        t = self.TextIOWrapper(b, encoding="ascii", errors="strict")
         self.assertRaises(UnicodeError, t.read)
         # (3) ignore
-        b = io.BytesIO(b"abc\n\xff\n")
-        t = io.TextIOWrapper(b, encoding="ascii", errors="ignore")
+        b = self.BytesIO(b"abc\n\xff\n")
+        t = self.TextIOWrapper(b, encoding="ascii", errors="ignore")
         self.assertEquals(t.read(), "abc\n\n")
         # (4) replace
-        b = io.BytesIO(b"abc\n\xff\n")
-        t = io.TextIOWrapper(b, encoding="ascii", errors="replace")
+        b = self.BytesIO(b"abc\n\xff\n")
+        t = self.TextIOWrapper(b, encoding="ascii", errors="replace")
         self.assertEquals(t.read(), "abc\n\ufffd\n")
 
-    def testEncodingErrorsWriting(self):
+    def test_encoding_errors_writing(self):
         # (1) default
-        b = io.BytesIO()
-        t = io.TextIOWrapper(b, encoding="ascii")
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii")
         self.assertRaises(UnicodeError, t.write, "\xff")
         # (2) explicit strict
-        b = io.BytesIO()
-        t = io.TextIOWrapper(b, encoding="ascii", errors="strict")
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii", errors="strict")
         self.assertRaises(UnicodeError, t.write, "\xff")
         # (3) ignore
-        b = io.BytesIO()
-        t = io.TextIOWrapper(b, encoding="ascii", errors="ignore",
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii", errors="ignore",
                              newline="\n")
         t.write("abc\xffdef\n")
         t.flush()
         self.assertEquals(b.getvalue(), b"abcdef\n")
         # (4) replace
-        b = io.BytesIO()
-        t = io.TextIOWrapper(b, encoding="ascii", errors="replace",
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii", errors="replace",
                              newline="\n")
         t.write("abc\xffdef\n")
         t.flush()
         self.assertEquals(b.getvalue(), b"abc?def\n")
 
-    def testNewlinesInput(self):
-        testdata = b"AAA\nBBB\nCCC\rDDD\rEEE\r\nFFF\r\nGGG"
-        normalized = testdata.replace(b"\r\n", b"\n").replace(b"\r", b"\n")
-        for newline, expected in [
-            (None, normalized.decode("ascii").splitlines(True)),
-            ("", testdata.decode("ascii").splitlines(True)),
-            ("\n", ["AAA\n", "BBB\n", "CCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
-            ("\r\n", ["AAA\nBBB\nCCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
-            ("\r",  ["AAA\nBBB\nCCC\r", "DDD\r", "EEE\r", "\nFFF\r", "\nGGG"]),
-            ]:
-            buf = io.BytesIO(testdata)
-            txt = io.TextIOWrapper(buf, encoding="ascii", newline=newline)
-            self.assertEquals(txt.readlines(), expected)
-            txt.seek(0)
-            self.assertEquals(txt.read(), "".join(expected))
-
-    def testNewlinesOutput(self):
-        testdict = {
-            "": b"AAA\nBBB\nCCC\nX\rY\r\nZ",
-            "\n": b"AAA\nBBB\nCCC\nX\rY\r\nZ",
-            "\r": b"AAA\rBBB\rCCC\rX\rY\r\rZ",
-            "\r\n": b"AAA\r\nBBB\r\nCCC\r\nX\rY\r\r\nZ",
-            }
-        tests = [(None, testdict[os.linesep])] + sorted(testdict.items())
-        for newline, expected in tests:
-            buf = io.BytesIO()
-            txt = io.TextIOWrapper(buf, encoding="ascii", newline=newline)
-            txt.write("AAA\nB")
-            txt.write("BB\nCCC\n")
-            txt.write("X\rY\r\nZ")
-            txt.flush()
-            self.assertEquals(buf.closed, False)
-            self.assertEquals(buf.getvalue(), expected)
-
-    def testNewlines(self):
+    def test_newlines(self):
         input_lines = [ "unix\n", "windows\r\n", "os9\r", "last\n", "nonl" ]
 
         tests = [
@@ -867,8 +1440,8 @@
             for do_reads in (False, True):
                 for bufsize in range(1, 10):
                     for newline, exp_lines in tests:
-                        bufio = io.BufferedReader(io.BytesIO(data), bufsize)
-                        textio = io.TextIOWrapper(bufio, newline=newline,
+                        bufio = self.BufferedReader(self.BytesIO(data), bufsize)
+                        textio = self.TextIOWrapper(bufio, newline=newline,
                                                   encoding=encoding)
                         if do_reads:
                             got_lines = []
@@ -885,60 +1458,100 @@
                             self.assertEquals(got_line, exp_line)
                         self.assertEquals(len(got_lines), len(exp_lines))
 
-    def testNewlinesInput(self):
-        testdata = b"AAA\nBBB\nCCC\rDDD\rEEE\r\nFFF\r\nGGG"
+    def test_newlines_input(self):
+        testdata = b"AAA\nBB\x00B\nCCC\rDDD\rEEE\r\nFFF\r\nGGG"
         normalized = testdata.replace(b"\r\n", b"\n").replace(b"\r", b"\n")
         for newline, expected in [
             (None, normalized.decode("ascii").splitlines(True)),
             ("", testdata.decode("ascii").splitlines(True)),
-            ("\n", ["AAA\n", "BBB\n", "CCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
-            ("\r\n", ["AAA\nBBB\nCCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
-            ("\r",  ["AAA\nBBB\nCCC\r", "DDD\r", "EEE\r", "\nFFF\r", "\nGGG"]),
+            ("\n", ["AAA\n", "BB\x00B\n", "CCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
+            ("\r\n", ["AAA\nBB\x00B\nCCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
+            ("\r",  ["AAA\nBB\x00B\nCCC\r", "DDD\r", "EEE\r", "\nFFF\r", "\nGGG"]),
             ]:
-            buf = io.BytesIO(testdata)
-            txt = io.TextIOWrapper(buf, encoding="ascii", newline=newline)
+            buf = self.BytesIO(testdata)
+            txt = self.TextIOWrapper(buf, encoding="ascii", newline=newline)
             self.assertEquals(txt.readlines(), expected)
             txt.seek(0)
             self.assertEquals(txt.read(), "".join(expected))
 
-    def testNewlinesOutput(self):
-        data = "AAA\nBBB\rCCC\n"
-        data_lf = b"AAA\nBBB\rCCC\n"
-        data_cr = b"AAA\rBBB\rCCC\r"
-        data_crlf = b"AAA\r\nBBB\rCCC\r\n"
-        save_linesep = os.linesep
-        try:
-            for os.linesep, newline, expected in [
-                ("\n", None, data_lf),
-                ("\r\n", None, data_crlf),
-                ("\n", "", data_lf),
-                ("\r\n", "", data_lf),
-                ("\n", "\n", data_lf),
-                ("\r\n", "\n", data_lf),
-                ("\n", "\r", data_cr),
-                ("\r\n", "\r", data_cr),
-                ("\n", "\r\n", data_crlf),
-                ("\r\n", "\r\n", data_crlf),
-                ]:
-                buf = io.BytesIO()
-                txt = io.TextIOWrapper(buf, encoding="ascii", newline=newline)
-                txt.write(data)
-                txt.close()
-                self.assertEquals(buf.closed, True)
-                self.assertRaises(ValueError, buf.getvalue)
-        finally:
-            os.linesep = save_linesep
+    def test_newlines_output(self):
+        testdict = {
+            "": b"AAA\nBBB\nCCC\nX\rY\r\nZ",
+            "\n": b"AAA\nBBB\nCCC\nX\rY\r\nZ",
+            "\r": b"AAA\rBBB\rCCC\rX\rY\r\rZ",
+            "\r\n": b"AAA\r\nBBB\r\nCCC\r\nX\rY\r\r\nZ",
+            }
+        tests = [(None, testdict[os.linesep])] + sorted(testdict.items())
+        for newline, expected in tests:
+            buf = self.BytesIO()
+            txt = self.TextIOWrapper(buf, encoding="ascii", newline=newline)
+            txt.write("AAA\nB")
+            txt.write("BB\nCCC\n")
+            txt.write("X\rY\r\nZ")
+            txt.flush()
+            self.assertEquals(buf.closed, False)
+            self.assertEquals(buf.getvalue(), expected)
+
+    def test_destructor(self):
+        l = []
+        base = self.BytesIO
+        class MyBytesIO(base):
+            def close(self):
+                l.append(self.getvalue())
+                base.close(self)
+        b = MyBytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii")
+        t.write("abc")
+        del t
+        self.assertEquals([b"abc"], l)
+
+    def test_override_destructor(self):
+        record = []
+        class MyTextIO(self.TextIOWrapper):
+            def __del__(self):
+                record.append(1)
+                try:
+                    f = super().__del__
+                except AttributeError:
+                    pass
+                else:
+                    f()
+            def close(self):
+                record.append(2)
+                super().close()
+            def flush(self):
+                record.append(3)
+                super().flush()
+        b = self.BytesIO()
+        t = MyTextIO(b, encoding="ascii")
+        del t
+        self.assertEqual(record, [1, 2, 3])
+
+    def test_error_through_destructor(self):
+        # Test that the exception state is not modified by a destructor,
+        # even if close() fails.
+        rawio = self.CloseFailureIO()
+        def f():
+            self.TextIOWrapper(rawio).xyzzy
+        with support.captured_output("stderr") as s:
+            self.assertRaises(AttributeError, f)
+        s = s.getvalue().strip()
+        if s:
+            # The destructor *may* have printed an unraisable error, check it
+            self.assertEqual(len(s.splitlines()), 1)
+            self.assert_(s.startswith("Exception IOError: "), s)
+            self.assert_(s.endswith(" ignored"), s)
 
     # Systematic tests of the text I/O API
 
-    def testBasicIO(self):
+    def test_basic_io(self):
         for chunksize in (1, 2, 3, 4, 5, 15, 16, 17, 31, 32, 33, 63, 64, 65):
             for enc in "ascii", "latin1", "utf8" :# , "utf-16-be", "utf-16-le":
-                f = io.open(support.TESTFN, "w+", encoding=enc)
+                f = self.open(support.TESTFN, "w+", encoding=enc)
                 f._CHUNK_SIZE = chunksize
                 self.assertEquals(f.write("abc"), 3)
                 f.close()
-                f = io.open(support.TESTFN, "r+", encoding=enc)
+                f = self.open(support.TESTFN, "r+", encoding=enc)
                 f._CHUNK_SIZE = chunksize
                 self.assertEquals(f.tell(), 0)
                 self.assertEquals(f.read(), "abc")
@@ -980,8 +1593,8 @@
             rlines.append((pos, line))
         self.assertEquals(rlines, wlines)
 
-    def testTelling(self):
-        f = io.open(support.TESTFN, "w+", encoding="utf8")
+    def test_telling(self):
+        f = self.open(support.TESTFN, "w+", encoding="utf8")
         p0 = f.tell()
         f.write("\xff\n")
         p1 = f.tell()
@@ -1000,8 +1613,8 @@
         self.assertEquals(f.tell(), p2)
         f.close()
 
-    def testSeeking(self):
-        chunk_size = io.TextIOWrapper._CHUNK_SIZE
+    def test_seeking(self):
+        chunk_size = _default_chunk_size()
         prefix_size = chunk_size - 2
         u_prefix = "a" * prefix_size
         prefix = bytes(u_prefix.encode("utf-8"))
@@ -1009,48 +1622,46 @@
         u_suffix = "\u8888\n"
         suffix = bytes(u_suffix.encode("utf-8"))
         line = prefix + suffix
-        f = io.open(support.TESTFN, "wb")
+        f = self.open(support.TESTFN, "wb")
         f.write(line*2)
         f.close()
-        f = io.open(support.TESTFN, "r", encoding="utf-8")
+        f = self.open(support.TESTFN, "r", encoding="utf-8")
         s = f.read(prefix_size)
         self.assertEquals(s, str(prefix, "ascii"))
         self.assertEquals(f.tell(), prefix_size)
         self.assertEquals(f.readline(), u_suffix)
 
-    def testSeekingToo(self):
+    def test_seeking_too(self):
         # Regression test for a specific bug
         data = b'\xe0\xbf\xbf\n'
-        f = io.open(support.TESTFN, "wb")
+        f = self.open(support.TESTFN, "wb")
         f.write(data)
         f.close()
-        f = io.open(support.TESTFN, "r", encoding="utf-8")
+        f = self.open(support.TESTFN, "r", encoding="utf-8")
         f._CHUNK_SIZE  # Just test that it exists
         f._CHUNK_SIZE = 2
         f.readline()
         f.tell()
 
-    def testSeekAndTell(self):
-        """Test seek/tell using the StatefulIncrementalDecoder."""
-        # Make this test faster by forcing a smaller (but large enough)
-        # chunk size. The bigger the chunker size, the slower seek() is,
-        # as it tries to replay character decoding one byte at a time.
-        CHUNK_SIZE = 256
+    def test_seek_and_tell(self):
+        #Test seek/tell using the StatefulIncrementalDecoder.
+        # Make test faster by doing smaller seeks
+        CHUNK_SIZE = 128
 
         def testSeekAndTellWithData(data, min_pos=0):
             """Tell/seek to various points within a data stream and ensure
             that the decoded data returned by read() is consistent."""
-            f = io.open(support.TESTFN, 'wb')
+            f = self.open(support.TESTFN, 'wb')
             f.write(data)
             f.close()
-            f = io.open(support.TESTFN, encoding='test_decoder')
+            f = self.open(support.TESTFN, encoding='test_decoder')
+            f._CHUNK_SIZE = CHUNK_SIZE
             decoded = f.read()
             f.close()
 
             for i in range(min_pos, len(decoded) + 1): # seek positions
                 for j in [1, 5, len(decoded) - i]: # read lengths
-                    f = io.open(support.TESTFN, encoding='test_decoder')
-                    f._CHUNK_SIZE = CHUNK_SIZE
+                    f = self.open(support.TESTFN, encoding='test_decoder')
                     self.assertEquals(f.read(i), decoded[:i])
                     cookie = f.tell()
                     self.assertEquals(f.read(j), decoded[i:i + j])
@@ -1079,7 +1690,7 @@
         finally:
             StatefulIncrementalDecoder.codecEnabled = 0
 
-    def testEncodedWrites(self):
+    def test_encoded_writes(self):
         data = "1234567890"
         tests = ("utf-16",
                  "utf-16-le",
@@ -1088,8 +1699,8 @@
                  "utf-32-le",
                  "utf-32-be")
         for encoding in tests:
-            buf = io.BytesIO()
-            f = io.TextIOWrapper(buf, encoding=encoding)
+            buf = self.BytesIO()
+            f = self.TextIOWrapper(buf, encoding=encoding)
             # Check if the BOM is written only once (see issue1753).
             f.write(data)
             f.write(data)
@@ -1097,45 +1708,8 @@
             self.assertEquals(f.read(), data * 2)
             self.assertEquals(buf.getvalue(), (data * 2).encode(encoding))
 
-    def timingTest(self):
-        timer = time.time
-        enc = "utf8"
-        line = "\0\x0f\xff\u0fff\uffff\U000fffff\U0010ffff"*3 + "\n"
-        nlines = 10000
-        nchars = len(line)
-        nbytes = len(line.encode(enc))
-        for chunk_size in (32, 64, 128, 256):
-            f = io.open(support.TESTFN, "w+", encoding=enc)
-            f._CHUNK_SIZE = chunk_size
-            t0 = timer()
-            for i in range(nlines):
-                f.write(line)
-            f.flush()
-            t1 = timer()
-            f.seek(0)
-            for line in f:
-                pass
-            t2 = timer()
-            f.seek(0)
-            while f.readline():
-                pass
-            t3 = timer()
-            f.seek(0)
-            while f.readline():
-                f.tell()
-            t4 = timer()
-            f.close()
-            if support.verbose:
-                print("\nTiming test: %d lines of %d characters (%d bytes)" %
-                      (nlines, nchars, nbytes))
-                print("File chunk size:          %6s" % f._CHUNK_SIZE)
-                print("Writing:                  %6.3f seconds" % (t1-t0))
-                print("Reading using iteration:  %6.3f seconds" % (t2-t1))
-                print("Reading using readline(): %6.3f seconds" % (t3-t2))
-                print("Using readline()+tell():  %6.3f seconds" % (t4-t3))
-
-    def testReadOneByOne(self):
-        txt = io.TextIOWrapper(io.BytesIO(b"AA\r\nBB"))
+    def test_read_one_by_one(self):
+        txt = self.TextIOWrapper(self.BytesIO(b"AA\r\nBB"))
         reads = ""
         while True:
             c = txt.read(1)
@@ -1145,9 +1719,9 @@
         self.assertEquals(reads, "AA\nBB")
 
     # read in amounts equal to TextIOWrapper._CHUNK_SIZE which is 128.
-    def testReadByChunk(self):
+    def test_read_by_chunk(self):
         # make sure "\r\n" straddles 128 char boundary.
-        txt = io.TextIOWrapper(io.BytesIO(b"A" * 127 + b"\r\nB"))
+        txt = self.TextIOWrapper(self.BytesIO(b"A" * 127 + b"\r\nB"))
         reads = ""
         while True:
             c = txt.read(128)
@@ -1157,7 +1731,7 @@
         self.assertEquals(reads, "A"*127+"\nB")
 
     def test_issue1395_1(self):
-        txt = io.TextIOWrapper(io.BytesIO(self.testdata), encoding="ascii")
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
 
         # read one char at a time
         reads = ""
@@ -1169,7 +1743,7 @@
         self.assertEquals(reads, self.normalized)
 
     def test_issue1395_2(self):
-        txt = io.TextIOWrapper(io.BytesIO(self.testdata), encoding="ascii")
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
         txt._CHUNK_SIZE = 4
 
         reads = ""
@@ -1181,7 +1755,7 @@
         self.assertEquals(reads, self.normalized)
 
     def test_issue1395_3(self):
-        txt = io.TextIOWrapper(io.BytesIO(self.testdata), encoding="ascii")
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
         txt._CHUNK_SIZE = 4
 
         reads = txt.read(4)
@@ -1192,7 +1766,7 @@
         self.assertEquals(reads, self.normalized)
 
     def test_issue1395_4(self):
-        txt = io.TextIOWrapper(io.BytesIO(self.testdata), encoding="ascii")
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
         txt._CHUNK_SIZE = 4
 
         reads = txt.read(4)
@@ -1200,7 +1774,7 @@
         self.assertEquals(reads, self.normalized)
 
     def test_issue1395_5(self):
-        txt = io.TextIOWrapper(io.BytesIO(self.testdata), encoding="ascii")
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
         txt._CHUNK_SIZE = 4
 
         reads = txt.read(4)
@@ -1210,12 +1784,45 @@
         self.assertEquals(txt.read(4), "BBB\n")
 
     def test_issue2282(self):
-        buffer = io.BytesIO(self.testdata)
-        txt = io.TextIOWrapper(buffer, encoding="ascii")
+        buffer = self.BytesIO(self.testdata)
+        txt = self.TextIOWrapper(buffer, encoding="ascii")
 
         self.assertEqual(buffer.seekable(), txt.seekable())
 
-    def check_newline_decoder_utf8(self, decoder):
+class CTextIOWrapperTest(TextIOWrapperTest):
+
+    def test_initialization(self):
+        r = self.BytesIO(b"\xc3\xa9\n\n")
+        b = self.BufferedReader(r, 1000)
+        t = self.TextIOWrapper(b)
+        self.assertRaises(TypeError, t.__init__, b, newline=42)
+        self.assertRaises(ValueError, t.read)
+        self.assertRaises(ValueError, t.__init__, b, newline='xyzzy')
+        self.assertRaises(ValueError, t.read)
+
+    def test_garbage_collection(self):
+        # C TextIOWrapper objects are collected, and collecting them flushes
+        # all data to disk.
+        # The Python version has __del__, so it ends in gc.garbage instead.
+        rawio = io.FileIO(support.TESTFN, "wb")
+        b = self.BufferedWriter(rawio)
+        t = self.TextIOWrapper(b, encoding="ascii")
+        t.write("456def")
+        t.x = t
+        wr = weakref.ref(t)
+        del t
+        gc.collect()
+        self.assert_(wr() is None, wr)
+        with open(support.TESTFN, "rb") as f:
+            self.assertEqual(f.read(), b"456def")
+
+class PyTextIOWrapperTest(TextIOWrapperTest):
+    pass
+
+
+class IncrementalNewlineDecoderTest(unittest.TestCase):
+
+    def check_newline_decoding_utf8(self, decoder):
         # UTF-8 specific tests for a newline decoder
         def _check_decode(b, s, **kwargs):
             # We exercise getstate() / setstate() as well as decode()
@@ -1257,12 +1864,20 @@
         _check_decode(b'\xe8\xa2\x88\r', "\u8888")
         _check_decode(b'\n', "\n")
 
-    def check_newline_decoder(self, decoder, encoding):
+    def check_newline_decoding(self, decoder, encoding):
         result = []
-        encoder = codecs.getincrementalencoder(encoding)()
-        def _decode_bytewise(s):
-            for b in encoder.encode(s):
-                result.append(decoder.decode(bytes([b])))
+        if encoding is not None:
+            encoder = codecs.getincrementalencoder(encoding)()
+            def _decode_bytewise(s):
+                # Decode one byte at a time
+                for b in encoder.encode(s):
+                    result.append(decoder.decode(bytes([b])))
+        else:
+            encoder = None
+            def _decode_bytewise(s):
+                # Decode one char at a time
+                for c in s:
+                    result.append(decoder.decode(c))
         self.assertEquals(decoder.newlines, None)
         _decode_bytewise("abc\n\r")
         self.assertEquals(decoder.newlines, '\n')
@@ -1275,22 +1890,34 @@
         _decode_bytewise("abc\r")
         self.assertEquals("".join(result), "abc\n\nabcabc\nabcabc")
         decoder.reset()
-        self.assertEquals(decoder.decode("abc".encode(encoding)), "abc")
+        input = "abc"
+        if encoder is not None:
+            encoder.reset()
+            input = encoder.encode(input)
+        self.assertEquals(decoder.decode(input), "abc")
         self.assertEquals(decoder.newlines, None)
 
     def test_newline_decoder(self):
         encodings = (
-            'utf-8', 'latin-1',
+            # None meaning the IncrementalNewlineDecoder takes unicode input
+            # rather than bytes input
+            None, 'utf-8', 'latin-1',
             'utf-16', 'utf-16-le', 'utf-16-be',
             'utf-32', 'utf-32-le', 'utf-32-be',
         )
         for enc in encodings:
-            decoder = codecs.getincrementaldecoder(enc)()
-            decoder = io.IncrementalNewlineDecoder(decoder, translate=True)
-            self.check_newline_decoder(decoder, enc)
+            decoder = enc and codecs.getincrementaldecoder(enc)()
+            decoder = self.IncrementalNewlineDecoder(decoder, translate=True)
+            self.check_newline_decoding(decoder, enc)
         decoder = codecs.getincrementaldecoder("utf-8")()
-        decoder = io.IncrementalNewlineDecoder(decoder, translate=True)
-        self.check_newline_decoder_utf8(decoder)
+        decoder = self.IncrementalNewlineDecoder(decoder, translate=True)
+        self.check_newline_decoding_utf8(decoder)
+
+class CIncrementalNewlineDecoderTest(IncrementalNewlineDecoderTest):
+    pass
+
+class PyIncrementalNewlineDecoderTest(IncrementalNewlineDecoderTest):
+    pass
 
 
 # XXX Tests for open()
@@ -1300,24 +1927,23 @@
     def tearDown(self):
         support.unlink(support.TESTFN)
 
-    def testImport__all__(self):
-        for name in io.__all__:
-            obj = getattr(io, name, None)
+    def test___all__(self):
+        for name in self.io.__all__:
+            obj = getattr(self.io, name, None)
             self.assert_(obj is not None, name)
             if name == "open":
                 continue
             elif "error" in name.lower():
                 self.assert_(issubclass(obj, Exception), name)
             else:
-                self.assert_(issubclass(obj, io.IOBase))
-
+                self.assert_(issubclass(obj, self.IOBase), name)
 
     def test_attributes(self):
-        f = io.open(support.TESTFN, "wb", buffering=0)
+        f = self.open(support.TESTFN, "wb", buffering=0)
         self.assertEquals(f.mode, "wb")
         f.close()
 
-        f = io.open(support.TESTFN, "U")
+        f = self.open(support.TESTFN, "U")
         self.assertEquals(f.name,            support.TESTFN)
         self.assertEquals(f.buffer.name,     support.TESTFN)
         self.assertEquals(f.buffer.raw.name, support.TESTFN)
@@ -1326,12 +1952,12 @@
         self.assertEquals(f.buffer.raw.mode, "rb")
         f.close()
 
-        f = io.open(support.TESTFN, "w+")
+        f = self.open(support.TESTFN, "w+")
         self.assertEquals(f.mode,            "w+")
         self.assertEquals(f.buffer.mode,     "rb+") # Does it really matter?
         self.assertEquals(f.buffer.raw.mode, "rb+")
 
-        g = io.open(f.fileno(), "wb", closefd=False)
+        g = self.open(f.fileno(), "wb", closefd=False)
         self.assertEquals(g.mode,     "wb")
         self.assertEquals(g.raw.mode, "wb")
         self.assertEquals(g.name,     f.fileno())
@@ -1357,13 +1983,12 @@
                 {"mode": "w+", "buffering": 2},
                 {"mode": "w+b", "buffering": 0},
             ]:
-            f = io.open(support.TESTFN, **kwargs)
+            f = self.open(support.TESTFN, **kwargs)
             f.close()
             self.assertRaises(ValueError, f.flush)
             self.assertRaises(ValueError, f.fileno)
             self.assertRaises(ValueError, f.isatty)
             self.assertRaises(ValueError, f.__iter__)
-            self.assertRaises(ValueError, next, f)
             if hasattr(f, "peek"):
                 self.assertRaises(ValueError, f.peek, 1)
             self.assertRaises(ValueError, f.read)
@@ -1376,16 +2001,101 @@
             self.assertRaises(ValueError, f.seek, 0)
             self.assertRaises(ValueError, f.tell)
             self.assertRaises(ValueError, f.truncate)
-            self.assertRaises(ValueError, f.write, "")
+            self.assertRaises(ValueError, f.write,
+                              b"" if "b" in kwargs['mode'] else "")
             self.assertRaises(ValueError, f.writelines, [])
+            self.assertRaises(ValueError, next, f)
 
+    def test_blockingioerror(self):
+        # Various BlockingIOError issues
+        self.assertRaises(TypeError, self.BlockingIOError)
+        self.assertRaises(TypeError, self.BlockingIOError, 1)
+        self.assertRaises(TypeError, self.BlockingIOError, 1, 2, 3, 4)
+        self.assertRaises(TypeError, self.BlockingIOError, 1, "", None)
+        b = self.BlockingIOError(1, "")
+        self.assertEqual(b.characters_written, 0)
+        class C(str):
+            pass
+        c = C("")
+        b = self.BlockingIOError(1, c)
+        c.b = b
+        b.c = c
+        wr = weakref.ref(c)
+        del c, b
+        gc.collect()
+        self.assert_(wr() is None, wr)
+
+    def test_abcs(self):
+        # Test the visible base classes are ABCs.
+        self.assertTrue(isinstance(self.IOBase, abc.ABCMeta))
+        self.assertTrue(isinstance(self.RawIOBase, abc.ABCMeta))
+        self.assertTrue(isinstance(self.BufferedIOBase, abc.ABCMeta))
+        self.assertTrue(isinstance(self.TextIOBase, abc.ABCMeta))
+
+    def _check_abc_inheritance(self, abcmodule):
+        with self.open(support.TESTFN, "wb", buffering=0) as f:
+            self.assertTrue(isinstance(f, abcmodule.IOBase))
+            self.assertTrue(isinstance(f, abcmodule.RawIOBase))
+            self.assertFalse(isinstance(f, abcmodule.BufferedIOBase))
+            self.assertFalse(isinstance(f, abcmodule.TextIOBase))
+        with self.open(support.TESTFN, "wb") as f:
+            self.assertTrue(isinstance(f, abcmodule.IOBase))
+            self.assertFalse(isinstance(f, abcmodule.RawIOBase))
+            self.assertTrue(isinstance(f, abcmodule.BufferedIOBase))
+            self.assertFalse(isinstance(f, abcmodule.TextIOBase))
+        with self.open(support.TESTFN, "w") as f:
+            self.assertTrue(isinstance(f, abcmodule.IOBase))
+            self.assertFalse(isinstance(f, abcmodule.RawIOBase))
+            self.assertFalse(isinstance(f, abcmodule.BufferedIOBase))
+            self.assertTrue(isinstance(f, abcmodule.TextIOBase))
+
+    def test_abc_inheritance(self):
+        # Test implementations inherit from their respective ABCs
+        self._check_abc_inheritance(self)
+
+    def test_abc_inheritance_official(self):
+        # Test implementations inherit from the official ABCs of the
+        # baseline "io" module.
+        self._check_abc_inheritance(io)
+
+class CMiscIOTest(MiscIOTest):
+    io = io
+
+class PyMiscIOTest(MiscIOTest):
+    io = pyio
 
 def test_main():
-    support.run_unittest(IOTest, BytesIOTest, StringIOTest,
-                              BufferedReaderTest, BufferedWriterTest,
-                              BufferedRWPairTest, BufferedRandomTest,
-                              StatefulIncrementalDecoderTest,
-                              TextIOWrapperTest, MiscIOTest)
+    tests = (CIOTest, PyIOTest,
+             CBufferedReaderTest, PyBufferedReaderTest,
+             CBufferedWriterTest, PyBufferedWriterTest,
+             CBufferedRWPairTest, PyBufferedRWPairTest,
+             CBufferedRandomTest, PyBufferedRandomTest,
+             StatefulIncrementalDecoderTest,
+             CIncrementalNewlineDecoderTest, PyIncrementalNewlineDecoderTest,
+             CTextIOWrapperTest, PyTextIOWrapperTest,
+             CMiscIOTest, PyMiscIOTest,)
+
+    # Put the namespaces of the IO module we are testing and some useful mock
+    # classes in the __dict__ of each test.
+    mocks = (MockRawIO, MisbehavedRawIO, MockFileIO, CloseFailureIO,
+             MockNonBlockWriterIO)
+    all_members = io.__all__ + ["IncrementalNewlineDecoder"]
+    c_io_ns = {name : getattr(io, name) for name in all_members}
+    py_io_ns = {name : getattr(pyio, name) for name in all_members}
+    globs = globals()
+    c_io_ns.update((x.__name__, globs["C" + x.__name__]) for x in mocks)
+    py_io_ns.update((x.__name__, globs["Py" + x.__name__]) for x in mocks)
+    # Avoid turning open into a bound method.
+    py_io_ns["open"] = pyio.OpenWrapper
+    for test in tests:
+        if test.__name__.startswith("C"):
+            for name, obj in c_io_ns.items():
+                setattr(test, name, obj)
+        elif test.__name__.startswith("Py"):
+            for name, obj in py_io_ns.items():
+                setattr(test, name, obj)
+
+    support.run_unittest(*tests)
 
 if __name__ == "__main__":
-    unittest.main()
+    test_main()
diff --git a/Lib/test/test_largefile.py b/Lib/test/test_largefile.py
index 8060ea0..584a206 100644
--- a/Lib/test/test_largefile.py
+++ b/Lib/test/test_largefile.py
@@ -7,6 +7,8 @@
 import unittest
 from test.support import run_unittest, TESTFN, verbose, requires, \
                               TestSkipped, unlink
+import io  # C implementation of io
+import _pyio as pyio # Python implementation of io
 
 try:
     import signal
@@ -21,7 +23,7 @@
 size = 2500000000
 
 
-class TestCase(unittest.TestCase):
+class LargeFileTest(unittest.TestCase):
     """Test that each file function works as expected for a large
     (i.e. > 2GB, do  we have to check > 4GB) files.
 
@@ -34,7 +36,7 @@
     def test_seek(self):
         if verbose:
             print('create large file via seek (may be sparse file) ...')
-        with open(TESTFN, 'wb') as f:
+        with self.open(TESTFN, 'wb') as f:
             f.write(b'z')
             f.seek(0)
             f.seek(size)
@@ -52,7 +54,7 @@
     def test_seek_read(self):
         if verbose:
             print('play around with seek() and read() with the built largefile')
-        with open(TESTFN, 'rb') as f:
+        with self.open(TESTFN, 'rb') as f:
             self.assertEqual(f.tell(), 0)
             self.assertEqual(f.read(1), b'z')
             self.assertEqual(f.tell(), 1)
@@ -85,7 +87,7 @@
     def test_lseek(self):
         if verbose:
             print('play around with os.lseek() with the built largefile')
-        with open(TESTFN, 'rb') as f:
+        with self.open(TESTFN, 'rb') as f:
             self.assertEqual(os.lseek(f.fileno(), 0, 0), 0)
             self.assertEqual(os.lseek(f.fileno(), 42, 0), 42)
             self.assertEqual(os.lseek(f.fileno(), 42, 1), 84)
@@ -100,7 +102,7 @@
     def test_truncate(self):
         if verbose:
             print('try truncate')
-        with open(TESTFN, 'r+b') as f:
+        with self.open(TESTFN, 'r+b') as f:
             # this is already decided before start running the test suite
             # but we do it anyway for extra protection
             if not hasattr(f, 'truncate'):
@@ -143,7 +145,7 @@
         # Only run if the current filesystem supports large files.
         # (Skip this test on Windows, since we now always support
         # large files.)
-        f = open(TESTFN, 'wb')
+        f = open(TESTFN, 'wb', buffering=0)
         try:
             # 2**31 == 2147483648
             f.seek(2147483649)
@@ -158,14 +160,19 @@
         else:
             f.close()
     suite = unittest.TestSuite()
-    suite.addTest(TestCase('test_seek'))
-    suite.addTest(TestCase('test_osstat'))
-    suite.addTest(TestCase('test_seek_read'))
-    suite.addTest(TestCase('test_lseek'))
-    with open(TESTFN, 'w') as f:
-        if hasattr(f, 'truncate'):
-            suite.addTest(TestCase('test_truncate'))
-    unlink(TESTFN)
+    for _open, prefix in [(io.open, 'C'), (pyio.open, 'Py')]:
+        class TestCase(LargeFileTest):
+            pass
+        TestCase.open = staticmethod(_open)
+        TestCase.__name__ = prefix + LargeFileTest.__name__
+        suite.addTest(TestCase('test_seek'))
+        suite.addTest(TestCase('test_osstat'))
+        suite.addTest(TestCase('test_seek_read'))
+        suite.addTest(TestCase('test_lseek'))
+        with _open(TESTFN, 'wb') as f:
+            if hasattr(f, 'truncate'):
+                suite.addTest(TestCase('test_truncate'))
+        unlink(TESTFN)
     try:
         run_unittest(suite)
     finally:
diff --git a/Lib/test/test_memoryio.py b/Lib/test/test_memoryio.py
index d1745bc..b3fc042 100644
--- a/Lib/test/test_memoryio.py
+++ b/Lib/test/test_memoryio.py
@@ -7,13 +7,52 @@
 from test import support
 
 import io
+import _pyio as pyio
 import sys
 
-try:
-    import _bytesio, _stringio
-    has_c_implementation = True
-except ImportError:
-    has_c_implementation = False
+class MemorySeekTestMixin:
+
+    def testInit(self):
+        buf = self.buftype("1234567890")
+        bytesIo = self.ioclass(buf)
+
+    def testRead(self):
+        buf = self.buftype("1234567890")
+        bytesIo = self.ioclass(buf)
+
+        self.assertEquals(buf[:1], bytesIo.read(1))
+        self.assertEquals(buf[1:5], bytesIo.read(4))
+        self.assertEquals(buf[5:], bytesIo.read(900))
+        self.assertEquals(self.EOF, bytesIo.read())
+
+    def testReadNoArgs(self):
+        buf = self.buftype("1234567890")
+        bytesIo = self.ioclass(buf)
+
+        self.assertEquals(buf, bytesIo.read())
+        self.assertEquals(self.EOF, bytesIo.read())
+
+    def testSeek(self):
+        buf = self.buftype("1234567890")
+        bytesIo = self.ioclass(buf)
+
+        bytesIo.read(5)
+        bytesIo.seek(0)
+        self.assertEquals(buf, bytesIo.read())
+
+        bytesIo.seek(3)
+        self.assertEquals(buf[3:], bytesIo.read())
+        self.assertRaises(TypeError, bytesIo.seek, 0.0)
+
+    def testTell(self):
+        buf = self.buftype("1234567890")
+        bytesIo = self.ioclass(buf)
+
+        self.assertEquals(0, bytesIo.tell())
+        bytesIo.seek(5)
+        self.assertEquals(5, bytesIo.tell())
+        bytesIo.seek(10000)
+        self.assertEquals(10000, bytesIo.tell())
 
 
 class MemoryTestMixin:
@@ -148,7 +187,7 @@
         self.assertEqual(memio.readline(), self.EOF)
         memio.seek(0)
         self.assertEqual(type(memio.readline()), type(buf))
-        self.assertEqual(memio.readline(None), buf)
+        self.assertEqual(memio.readline(), buf)
         self.assertRaises(TypeError, memio.readline, '')
         memio.close()
         self.assertRaises(ValueError,  memio.readline)
@@ -296,11 +335,11 @@
         self.assertEqual(test2(), buf)
 
 
-class PyBytesIOTest(MemoryTestMixin, unittest.TestCase):
+class PyBytesIOTest(MemoryTestMixin, MemorySeekTestMixin, unittest.TestCase):
     @staticmethod
     def buftype(s):
         return s.encode("ascii")
-    ioclass = io._BytesIO
+    ioclass = pyio.BytesIO
     EOF = b""
 
     def test_read1(self):
@@ -371,11 +410,32 @@
         self.assertEqual(memio.getvalue(), buf)
 
 
-class PyStringIOTest(MemoryTestMixin, unittest.TestCase):
+class PyStringIOTest(MemoryTestMixin, MemorySeekTestMixin, unittest.TestCase):
     buftype = str
-    ioclass = io._StringIO
+    ioclass = pyio.StringIO
     EOF = ""
 
+    # TextIO-specific behaviour.
+
+    def test_newlines_property(self):
+        memio = self.ioclass(newline=None)
+        # The C StringIO decodes newlines in write() calls, but the Python
+        # implementation only does when reading.  This function forces them to
+        # be decoded for testing.
+        def force_decode():
+            memio.seek(0)
+            memio.read()
+        self.assertEqual(memio.newlines, None)
+        memio.write("a\n")
+        force_decode()
+        self.assertEqual(memio.newlines, "\n")
+        memio.write("b\r\n")
+        force_decode()
+        self.assertEqual(memio.newlines, ("\n", "\r\n"))
+        memio.write("c\rd")
+        force_decode()
+        self.assertEqual(memio.newlines, ("\r", "\n", "\r\n"))
+
     def test_relative_seek(self):
         memio = self.ioclass()
 
@@ -386,32 +446,99 @@
         self.assertRaises(IOError, memio.seek, 1, 1)
         self.assertRaises(IOError, memio.seek, 1, 2)
 
+    def test_textio_properties(self):
+        memio = self.ioclass()
+
+        # These are just dummy values but we nevertheless check them for fear
+        # of unexpected breakage.
+        self.assertEqual(memio.encoding, "utf-8")
+        self.assertEqual(memio.errors, "strict")
+        self.assertEqual(memio.line_buffering, False)
+
+    def test_newline_none(self):
+        # newline=None
+        memio = self.ioclass("a\nb\r\nc\rd", newline=None)
+        self.assertEqual(list(memio), ["a\n", "b\n", "c\n", "d"])
+        memio.seek(0)
+        self.assertEqual(memio.read(1), "a")
+        self.assertEqual(memio.read(2), "\nb")
+        self.assertEqual(memio.read(2), "\nc")
+        self.assertEqual(memio.read(1), "\n")
+        memio = self.ioclass(newline=None)
+        self.assertEqual(2, memio.write("a\n"))
+        self.assertEqual(3, memio.write("b\r\n"))
+        self.assertEqual(3, memio.write("c\rd"))
+        memio.seek(0)
+        self.assertEqual(memio.read(), "a\nb\nc\nd")
+        memio = self.ioclass("a\r\nb", newline=None)
+        self.assertEqual(memio.read(3), "a\nb")
+
+    def test_newline_empty(self):
+        # newline=""
+        memio = self.ioclass("a\nb\r\nc\rd", newline="")
+        self.assertEqual(list(memio), ["a\n", "b\r\n", "c\r", "d"])
+        memio.seek(0)
+        self.assertEqual(memio.read(4), "a\nb\r")
+        self.assertEqual(memio.read(2), "\nc")
+        self.assertEqual(memio.read(1), "\r")
+        memio = self.ioclass(newline="")
+        self.assertEqual(2, memio.write("a\n"))
+        self.assertEqual(2, memio.write("b\r"))
+        self.assertEqual(2, memio.write("\nc"))
+        self.assertEqual(2, memio.write("\rd"))
+        memio.seek(0)
+        self.assertEqual(list(memio), ["a\n", "b\r\n", "c\r", "d"])
+
+    def test_newline_lf(self):
+        # newline="\n"
+        memio = self.ioclass("a\nb\r\nc\rd")
+        self.assertEqual(list(memio), ["a\n", "b\r\n", "c\rd"])
+
+    def test_newline_cr(self):
+        # newline="\r"
+        memio = self.ioclass("a\nb\r\nc\rd", newline="\r")
+        memio.seek(0)
+        self.assertEqual(memio.read(), "a\rb\r\rc\rd")
+        memio.seek(0)
+        self.assertEqual(list(memio), ["a\r", "b\r", "\r", "c\r", "d"])
+
+    def test_newline_crlf(self):
+        # newline="\r\n"
+        memio = self.ioclass("a\nb\r\nc\rd", newline="\r\n")
+        memio.seek(0)
+        self.assertEqual(memio.read(), "a\r\nb\r\r\nc\rd")
+        memio.seek(0)
+        self.assertEqual(list(memio), ["a\r\n", "b\r\r\n", "c\rd"])
+
+    def test_issue5265(self):
+        # StringIO can duplicate newlines in universal newlines mode
+        memio = self.ioclass("a\r\nb\r\n", newline=None)
+        self.assertEqual(memio.read(5), "a\nb\n")
+
+
+class CBytesIOTest(PyBytesIOTest):
+    ioclass = io.BytesIO
+
+class CStringIOTest(PyStringIOTest):
+    ioclass = io.StringIO
+
     # XXX: For the Python version of io.StringIO, this is highly
     # dependent on the encoding used for the underlying buffer.
-    # def test_widechar(self):
-    #     buf = self.buftype("\U0002030a\U00020347")
-    #     memio = self.ioclass(buf)
-    #
-    #     self.assertEqual(memio.getvalue(), buf)
-    #     self.assertEqual(memio.write(buf), len(buf))
-    #     self.assertEqual(memio.tell(), len(buf))
-    #     self.assertEqual(memio.getvalue(), buf)
-    #     self.assertEqual(memio.write(buf), len(buf))
-    #     self.assertEqual(memio.tell(), len(buf) * 2)
-    #     self.assertEqual(memio.getvalue(), buf + buf)
+    def test_widechar(self):
+        buf = self.buftype("\U0002030a\U00020347")
+        memio = self.ioclass(buf)
 
-if has_c_implementation:
-    class CBytesIOTest(PyBytesIOTest):
-        ioclass = io.BytesIO
-
-    class CStringIOTest(PyStringIOTest):
-        ioclass = io.StringIO
+        self.assertEqual(memio.getvalue(), buf)
+        self.assertEqual(memio.write(buf), len(buf))
+        self.assertEqual(memio.tell(), len(buf))
+        self.assertEqual(memio.getvalue(), buf)
+        self.assertEqual(memio.write(buf), len(buf))
+        self.assertEqual(memio.tell(), len(buf) * 2)
+        self.assertEqual(memio.getvalue(), buf + buf)
 
 
 def test_main():
-    tests = [PyBytesIOTest, PyStringIOTest]
-    if has_c_implementation:
-        tests.extend([CBytesIOTest, CStringIOTest])
+    tests = [PyBytesIOTest, PyStringIOTest, CBytesIOTest, CStringIOTest]
     support.run_unittest(*tests)
 
 if __name__ == '__main__':
diff --git a/Lib/test/test_univnewlines.py b/Lib/test/test_univnewlines.py
index c4e4a3f..a6b9909 100644
--- a/Lib/test/test_univnewlines.py
+++ b/Lib/test/test_univnewlines.py
@@ -1,4 +1,6 @@
 # Tests universal newline support for both reading and parsing files.
+import io
+import _pyio as pyio
 import unittest
 import os
 import sys
@@ -35,7 +37,7 @@
     WRITEMODE = 'wb'
 
     def setUp(self):
-        fp = open(support.TESTFN, self.WRITEMODE)
+        fp = self.open(support.TESTFN, self.WRITEMODE)
         data = self.DATA
         if "b" in self.WRITEMODE:
             data = data.encode("ascii")
@@ -49,19 +51,19 @@
             pass
 
     def test_read(self):
-        fp = open(support.TESTFN, self.READMODE)
+        fp = self.open(support.TESTFN, self.READMODE)
         data = fp.read()
         self.assertEqual(data, DATA_LF)
         self.assertEqual(repr(fp.newlines), repr(self.NEWLINE))
 
     def test_readlines(self):
-        fp = open(support.TESTFN, self.READMODE)
+        fp = self.open(support.TESTFN, self.READMODE)
         data = fp.readlines()
         self.assertEqual(data, DATA_SPLIT)
         self.assertEqual(repr(fp.newlines), repr(self.NEWLINE))
 
     def test_readline(self):
-        fp = open(support.TESTFN, self.READMODE)
+        fp = self.open(support.TESTFN, self.READMODE)
         data = []
         d = fp.readline()
         while d:
@@ -71,7 +73,7 @@
         self.assertEqual(repr(fp.newlines), repr(self.NEWLINE))
 
     def test_seek(self):
-        fp = open(support.TESTFN, self.READMODE)
+        fp = self.open(support.TESTFN, self.READMODE)
         fp.readline()
         pos = fp.tell()
         data = fp.readlines()
@@ -94,7 +96,7 @@
     DATA = DATA_CRLF
 
     def test_tell(self):
-        fp = open(support.TESTFN, self.READMODE)
+        fp = self.open(support.TESTFN, self.READMODE)
         self.assertEqual(repr(fp.newlines), repr(None))
         data = fp.readline()
         pos = fp.tell()
@@ -106,12 +108,22 @@
 
 
 def test_main():
-    support.run_unittest(
-        TestCRNewlines,
-        TestLFNewlines,
-        TestCRLFNewlines,
-        TestMixedNewlines
-     )
+    base_tests = (TestCRNewlines,
+                  TestLFNewlines,
+                  TestCRLFNewlines,
+                  TestMixedNewlines)
+    tests = []
+    # Test the C and Python implementations.
+    for test in base_tests:
+        class CTest(test):
+            open = io.open
+        CTest.__name__ = "C" + test.__name__
+        class PyTest(test):
+            open = staticmethod(pyio.open)
+        PyTest.__name__ = "Py" + test.__name__
+        tests.append(CTest)
+        tests.append(PyTest)
+    support.run_unittest(*tests)
 
 if __name__ == '__main__':
     test_main()
diff --git a/Lib/test/test_uu.py b/Lib/test/test_uu.py
index d2b6e73..a54f2c1 100644
--- a/Lib/test/test_uu.py
+++ b/Lib/test/test_uu.py
@@ -32,6 +32,8 @@
                                      encoding=encoding,
                                      errors=errors,
                                      newline=newline)
+        self._encoding = encoding
+        self._errors = errors
         if initial_value:
             if not isinstance(initial_value, str):
                 initial_value = str(initial_value)
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 8f3384b..0f84c88 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -193,6 +193,15 @@
 # Used of signalmodule.o is not available
 SIGNAL_OBJS=	@SIGNAL_OBJS@
 
+IO_H=		Modules/_iomodule.h
+
+IO_OBJS=	\
+		Modules/io.o \
+		Modules/_iobase.o \
+		Modules/_fileio.o \
+		Modules/_bufferedio.o \
+		Modules/_textio.o \
+		Modules/_bytesio.o
 
 ##########################################################################
 # Grammar
@@ -521,6 +530,7 @@
 Modules/python.o: $(srcdir)/Modules/python.c
 	$(MAINCC) -c $(PY_CFLAGS) -o $@ $(srcdir)/Modules/python.c
 
+$(IO_OBJS): $(IO_H)
 
 $(GRAMMAR_H) $(GRAMMAR_C): $(PGEN) $(GRAMMAR_INPUT)
 		-@$(INSTALL) -d Include
diff --git a/Misc/NEWS b/Misc/NEWS
index 702e02f..83e5874 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -14,6 +14,8 @@
 
 =======
 
+- The io module has been reimplemented in C for speed.
+
 - Give dict views an informative __repr__.
 
 - Issue #5247: Improve error message when unknown format codes are
diff --git a/Modules/Setup.dist b/Modules/Setup.dist
index ef85db3..bfd74b5 100644
--- a/Modules/Setup.dist
+++ b/Modules/Setup.dist
@@ -111,10 +111,10 @@
 				# if $HOME is not set
 _sre _sre.c			# Fredrik Lundh's new regular expressions
 _codecs _codecsmodule.c		# access to the builtin codecs and codec registry
-_fileio _fileio.c		# Standard I/O baseline
 _weakref _weakref.c		# weak references
-_bytesio _bytesio.c		# For Lib/io.py
-_stringio _stringio.c		# For Lib/io.py
+
+# Standard I/O baseline
+_io io.c _iobase.c _fileio.c _bytesio.c _bufferedio.c _textio.c _stringio.c
 
 # The zipimport module is always imported at startup. Having it as a
 # builtin module avoids some bootstrapping problems and reduces overhead.
@@ -164,7 +164,6 @@
 #_collections _collectionsmodule.c # Container types
 #itertools itertoolsmodule.c	# Functions creating iterators for efficient looping 
 #atexit atexitmodule.c      # Register functions to be run at interpreter-shutdown
-#_functools _functoolsmodule.c	# Tools for working with functions and callable objects
 #_elementtree -I$(srcdir)/Modules/expat -DHAVE_EXPAT_CONFIG_H -DUSE_PYEXPAT_CAPI _elementtree.c	# elementtree accelerator
 #_pickle _pickle.c	# pickle accelerator
 #datetime datetimemodule.c	# date/time type
diff --git a/Modules/_bufferedio.c b/Modules/_bufferedio.c
new file mode 100644
index 0000000..88f4fbc
--- /dev/null
+++ b/Modules/_bufferedio.c
@@ -0,0 +1,2130 @@
+/*
+    An implementation of Buffered I/O as defined by PEP 3116 - "New I/O"
+    
+    Classes defined here: BufferedIOBase, BufferedReader, BufferedWriter,
+    BufferedRandom.
+    
+    Written by Amaury Forgeot d'Arc and Antoine Pitrou
+*/
+
+#define PY_SSIZE_T_CLEAN
+#include "Python.h"
+#include "structmember.h"
+#include "pythread.h"
+#include "_iomodule.h"
+
+/*
+ * BufferedIOBase class, inherits from IOBase.
+ */
+PyDoc_STRVAR(BufferedIOBase_doc,
+    "Base class for buffered IO objects.\n"
+    "\n"
+    "The main difference with RawIOBase is that the read() method\n"
+    "supports omitting the size argument, and does not have a default\n"
+    "implementation that defers to readinto().\n"
+    "\n"
+    "In addition, read(), readinto() and write() may raise\n"
+    "BlockingIOError if the underlying raw stream is in non-blocking\n"
+    "mode and not ready; unlike their raw counterparts, they will never\n"
+    "return None.\n"
+    "\n"
+    "A typical implementation should not inherit from a RawIOBase\n"
+    "implementation, but wrap one.\n"
+    );
+
+static PyObject *
+BufferedIOBase_readinto(PyObject *self, PyObject *args)
+{
+    Py_buffer buf;
+    Py_ssize_t len;
+    PyObject *data;
+
+    if (!PyArg_ParseTuple(args, "w*:readinto", &buf)) {
+        return NULL;
+    }
+
+    data = PyObject_CallMethod(self, "read", "n", buf.len);
+    if (data == NULL)
+        goto error;
+
+    if (!PyBytes_Check(data)) {
+        Py_DECREF(data);
+        PyErr_SetString(PyExc_TypeError, "read() should return bytes");
+        goto error;
+    }
+
+    len = Py_SIZE(data);
+    memcpy(buf.buf, PyBytes_AS_STRING(data), len);
+
+    PyBuffer_Release(&buf);
+    Py_DECREF(data);
+
+    return PyLong_FromSsize_t(len);
+
+  error:
+    PyBuffer_Release(&buf);
+    return NULL;
+}
+
+static PyObject *
+BufferedIOBase_unsupported(const char *message)
+{
+    PyErr_SetString(IO_STATE->unsupported_operation, message);
+    return NULL;
+}
+
+PyDoc_STRVAR(BufferedIOBase_read_doc,
+    "Read and return up to n bytes.\n"
+    "\n"
+    "If the argument is omitted, None, or negative, reads and\n"
+    "returns all data until EOF.\n"
+    "\n"
+    "If the argument is positive, and the underlying raw stream is\n"
+    "not 'interactive', multiple raw reads may be issued to satisfy\n"
+    "the byte count (unless EOF is reached first).  But for\n"
+    "interactive raw streams (as well as sockets and pipes), at most\n"
+    "one raw read will be issued, and a short result does not imply\n"
+    "that EOF is imminent.\n"
+    "\n"
+    "Returns an empty bytes object on EOF.\n"
+    "\n"
+    "Returns None if the underlying raw stream was open in non-blocking\n"
+    "mode and no data is available at the moment.\n");
+
+static PyObject *
+BufferedIOBase_read(PyObject *self, PyObject *args)
+{
+    return BufferedIOBase_unsupported("read");
+}
+
+PyDoc_STRVAR(BufferedIOBase_read1_doc,
+    "Read and return up to n bytes, with at most one read() call\n"
+    "to the underlying raw stream. A short result does not imply\n"
+    "that EOF is imminent.\n"
+    "\n"
+    "Returns an empty bytes object on EOF.\n");
+
+static PyObject *
+BufferedIOBase_read1(PyObject *self, PyObject *args)
+{
+    return BufferedIOBase_unsupported("read1");
+}
+
+PyDoc_STRVAR(BufferedIOBase_write_doc,
+    "Write the given buffer to the IO stream.\n"
+    "\n"
+    "Returns the number of bytes written, which is never less than\n"
+    "len(b).\n"
+    "\n"
+    "Raises BlockingIOError if the buffer is full and the\n"
+    "underlying raw stream cannot accept more data at the moment.\n");
+
+static PyObject *
+BufferedIOBase_write(PyObject *self, PyObject *args)
+{
+    return BufferedIOBase_unsupported("write");
+}
+
+
+static PyMethodDef BufferedIOBase_methods[] = {
+    {"read", BufferedIOBase_read, METH_VARARGS, BufferedIOBase_read_doc},
+    {"read1", BufferedIOBase_read1, METH_VARARGS, BufferedIOBase_read1_doc},
+    {"readinto", BufferedIOBase_readinto, METH_VARARGS, NULL},
+    {"write", BufferedIOBase_write, METH_VARARGS, BufferedIOBase_write_doc},
+    {NULL, NULL}
+};
+
+PyTypeObject PyBufferedIOBase_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io._BufferedIOBase",      /*tp_name*/
+    0,                          /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    0,                          /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
+    BufferedIOBase_doc,         /* tp_doc */
+    0,                          /* tp_traverse */
+    0,                          /* tp_clear */
+    0,                          /* tp_richcompare */
+    0,                          /* tp_weaklistoffset */
+    0,                          /* tp_iter */
+    0,                          /* tp_iternext */
+    BufferedIOBase_methods,     /* tp_methods */
+    0,                          /* tp_members */
+    0,                          /* tp_getset */
+    &PyIOBase_Type,             /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    0,                          /* tp_dictoffset */
+    0,                          /* tp_init */
+    0,                          /* tp_alloc */
+    0,                          /* tp_new */
+};
+
+
+typedef struct {
+    PyObject_HEAD
+
+    PyObject *raw;
+    int ok;    /* Initialized? */
+    int readable;
+    int writable;
+
+    /* Absolute position inside the raw stream (-1 if unknown). */
+    Py_off_t abs_pos;
+
+    /* A static buffer of size `buffer_size` */
+    char *buffer;
+    /* Current logical position in the buffer. */
+    Py_off_t pos;
+    /* Position of the raw stream in the buffer. */
+    Py_off_t raw_pos;
+
+    /* Just after the last buffered byte in the buffer, or -1 if the buffer
+       isn't ready for reading. */
+    Py_off_t read_end;
+
+    /* Just after the last byte actually written */
+    Py_off_t write_pos;
+    /* Just after the last byte waiting to be written, or -1 if the buffer
+       isn't ready for writing. */
+    Py_off_t write_end;
+
+    PyThread_type_lock lock;
+
+    Py_ssize_t buffer_size;
+    Py_ssize_t buffer_mask;
+
+    PyObject *dict;
+    PyObject *weakreflist;
+} BufferedObject;
+
+/*
+    Implementation notes:
+    
+    * BufferedReader, BufferedWriter and BufferedRandom try to share most
+      methods (this is helped by the members `readable` and `writable`, which
+      are initialized in the respective constructors)
+    * They also share a single buffer for reading and writing. This enables
+      interleaved reads and writes without flushing. It also makes the logic
+      a bit trickier to get right.
+    * The absolute position of the raw stream is cached, if possible, in the
+      `abs_pos` member. It must be updated every time an operation is done
+      on the raw stream. If not sure, it can be reinitialized by calling
+      _Buffered_raw_tell(), which queries the raw stream (_Buffered_raw_seek()
+      also does it). To read it, use RAW_TELL().
+    * Three helpers, _BufferedReader_raw_read, _BufferedWriter_raw_write and
+      _BufferedWriter_flush_unlocked do a lot of useful housekeeping.
+
+    NOTE: we should try to maintain block alignment of reads and writes to the
+    raw stream (according to the buffer size), but for now it is only done
+    in read() and friends.
+    
+    XXX: method naming is a bit messy.
+*/
+
+/* These macros protect the BufferedObject against concurrent operations. */
+
+#define ENTER_BUFFERED(self) \
+    Py_BEGIN_ALLOW_THREADS \
+    PyThread_acquire_lock(self->lock, 1); \
+    Py_END_ALLOW_THREADS
+
+#define LEAVE_BUFFERED(self) \
+    PyThread_release_lock(self->lock);
+
+#define CHECK_INITIALIZED(self) \
+    if (self->ok <= 0) { \
+        PyErr_SetString(PyExc_ValueError, \
+            "I/O operation on uninitialized object"); \
+        return NULL; \
+    }
+
+#define CHECK_INITIALIZED_INT(self) \
+    if (self->ok <= 0) { \
+        PyErr_SetString(PyExc_ValueError, \
+            "I/O operation on uninitialized object"); \
+        return -1; \
+    }
+
+#define VALID_READ_BUFFER(self) \
+    (self->readable && self->read_end != -1)
+
+#define VALID_WRITE_BUFFER(self) \
+    (self->writable && self->write_end != -1)
+
+#define ADJUST_POSITION(self, _new_pos) \
+    do { \
+        self->pos = _new_pos; \
+        if (VALID_READ_BUFFER(self) && self->read_end < self->pos) \
+            self->read_end = self->pos; \
+    } while(0)
+
+#define READAHEAD(self) \
+    ((self->readable && VALID_READ_BUFFER(self)) \
+        ? (self->read_end - self->pos) : 0)
+
+#define RAW_OFFSET(self) \
+    (((VALID_READ_BUFFER(self) || VALID_WRITE_BUFFER(self)) \
+        && self->raw_pos >= 0) ? self->raw_pos - self->pos : 0)
+
+#define RAW_TELL(self) \
+    (self->abs_pos != -1 ? self->abs_pos : _Buffered_raw_tell(self))
+
+#define MINUS_LAST_BLOCK(self, size) \
+    (self->buffer_mask ? \
+        (size & ~self->buffer_mask) : \
+        (self->buffer_size * (size / self->buffer_size)))
+
+
+static void
+BufferedObject_dealloc(BufferedObject *self)
+{
+    if (self->ok && _PyIOBase_finalize((PyObject *) self) < 0)
+        return;
+    _PyObject_GC_UNTRACK(self);
+    self->ok = 0;
+    if (self->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *)self);
+    Py_CLEAR(self->raw);
+    if (self->buffer) {
+        PyMem_Free(self->buffer);
+        self->buffer = NULL;
+    }
+    if (self->lock) {
+        PyThread_free_lock(self->lock);
+        self->lock = NULL;
+    }
+    Py_CLEAR(self->dict);
+    Py_TYPE(self)->tp_free((PyObject *)self);
+}
+
+static int
+Buffered_traverse(BufferedObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->raw);
+    Py_VISIT(self->dict);
+    return 0;
+}
+
+static int
+Buffered_clear(BufferedObject *self)
+{
+    if (self->ok && _PyIOBase_finalize((PyObject *) self) < 0)
+        return -1;
+    self->ok = 0;
+    Py_CLEAR(self->raw);
+    Py_CLEAR(self->dict);
+    return 0;
+}
+
+/*
+ * _BufferedIOMixin methods
+ * This is not a class, just a collection of methods that will be reused
+ * by BufferedReader and BufferedWriter
+ */
+
+/* Flush and close */
+
+static PyObject *
+BufferedIOMixin_flush(BufferedObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self)
+    return PyObject_CallMethodObjArgs(self->raw, _PyIO_str_flush, NULL);
+}
+
+static int
+BufferedIOMixin_closed(BufferedObject *self)
+{
+    int closed;
+    PyObject *res;
+    CHECK_INITIALIZED_INT(self)
+    res = PyObject_GetAttr(self->raw, _PyIO_str_closed);
+    if (res == NULL)
+        return -1;
+    closed = PyObject_IsTrue(res);
+    Py_DECREF(res);
+    return closed;
+}
+
+static PyObject *
+BufferedIOMixin_closed_get(BufferedObject *self, void *context)
+{
+    CHECK_INITIALIZED(self)
+    return PyObject_GetAttr(self->raw, _PyIO_str_closed);
+}
+
+static PyObject *
+BufferedIOMixin_close(BufferedObject *self, PyObject *args)
+{
+    PyObject *res = NULL;
+    int r;
+
+    CHECK_INITIALIZED(self)
+    ENTER_BUFFERED(self)
+
+    r = BufferedIOMixin_closed(self);
+    if (r < 0)
+        goto end;
+    if (r > 0) {
+        res = Py_None;
+        Py_INCREF(res);
+        goto end;
+    }
+    /* flush() will most probably re-take the lock, so drop it first */
+    LEAVE_BUFFERED(self)
+    res = PyObject_CallMethodObjArgs((PyObject *)self, _PyIO_str_flush, NULL);
+    ENTER_BUFFERED(self)
+    if (res == NULL) {
+        /* If flush() fails, just give up */
+        if (PyErr_ExceptionMatches(PyExc_IOError))
+            PyErr_Clear();
+        else
+            goto end;
+    }
+    Py_XDECREF(res);
+
+    res = PyObject_CallMethodObjArgs(self->raw, _PyIO_str_close, NULL);
+
+end:
+    LEAVE_BUFFERED(self)
+    return res;
+}
+
+/* Inquiries */
+
+static PyObject *
+BufferedIOMixin_seekable(BufferedObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self)
+    return PyObject_CallMethodObjArgs(self->raw, _PyIO_str_seekable, NULL);
+}
+
+static PyObject *
+BufferedIOMixin_readable(BufferedObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self)
+    return PyObject_CallMethodObjArgs(self->raw, _PyIO_str_readable, NULL);
+}
+
+static PyObject *
+BufferedIOMixin_writable(BufferedObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self)
+    return PyObject_CallMethodObjArgs(self->raw, _PyIO_str_writable, NULL);
+}
+
+static PyObject *
+BufferedIOMixin_name_get(BufferedObject *self, void *context)
+{
+    CHECK_INITIALIZED(self)
+    return PyObject_GetAttrString(self->raw, "name");
+}
+
+static PyObject *
+BufferedIOMixin_mode_get(BufferedObject *self, void *context)
+{
+    CHECK_INITIALIZED(self)
+    return PyObject_GetAttrString(self->raw, "mode");
+}
+
+/* Lower-level APIs */
+
+static PyObject *
+BufferedIOMixin_fileno(BufferedObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self)
+    return PyObject_CallMethodObjArgs(self->raw, _PyIO_str_fileno, NULL);
+}
+
+static PyObject *
+BufferedIOMixin_isatty(BufferedObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self)
+    return PyObject_CallMethodObjArgs(self->raw, _PyIO_str_isatty, NULL);
+}
+
+
+/* Forward decls */
+static PyObject *
+_BufferedWriter_flush_unlocked(BufferedObject *, int);
+static Py_ssize_t
+_BufferedReader_fill_buffer(BufferedObject *self);
+static void
+_BufferedReader_reset_buf(BufferedObject *self);
+static void
+_BufferedWriter_reset_buf(BufferedObject *self);
+static PyObject *
+_BufferedReader_peek_unlocked(BufferedObject *self, Py_ssize_t);
+static PyObject *
+_BufferedReader_read_unlocked(BufferedObject *self, Py_ssize_t);
+
+
+/*
+ * Helpers
+ */
+
+/* Returns the address of the `written` member if a BlockingIOError was
+   raised, NULL otherwise. The error is always re-raised. */
+static Py_ssize_t *
+_Buffered_check_blocking_error(void)
+{
+    PyObject *t, *v, *tb;
+    PyBlockingIOErrorObject *err;
+
+    PyErr_Fetch(&t, &v, &tb);
+    if (v == NULL || !PyErr_GivenExceptionMatches(v, PyExc_BlockingIOError)) {
+        PyErr_Restore(t, v, tb);
+        return NULL;
+    }
+    err = (PyBlockingIOErrorObject *) v;
+    /* TODO: sanity check (err->written >= 0) */
+    PyErr_Restore(t, v, tb);
+    return &err->written;
+}
+
+static Py_off_t
+_Buffered_raw_tell(BufferedObject *self)
+{
+    PyObject *res;
+    Py_off_t n;
+    res = PyObject_CallMethodObjArgs(self->raw, _PyIO_str_tell, NULL);
+    if (res == NULL)
+        return -1;
+    n = PyNumber_AsOff_t(res, PyExc_ValueError);
+    Py_DECREF(res);
+    if (n < 0) {
+        if (!PyErr_Occurred())
+            PyErr_Format(PyExc_IOError,
+                         "Raw stream returned invalid position %zd", n);
+        return -1;
+    }
+    self->abs_pos = n;
+    return n;
+}
+
+static Py_off_t
+_Buffered_raw_seek(BufferedObject *self, Py_off_t target, int whence)
+{
+    PyObject *res, *posobj, *whenceobj;
+    Py_off_t n;
+
+    posobj = PyLong_FromOff_t(target);
+    if (posobj == NULL)
+        return -1;
+    whenceobj = PyLong_FromLong(whence);
+    if (whenceobj == NULL) {
+        Py_DECREF(posobj);
+        return -1;
+    }
+    res = PyObject_CallMethodObjArgs(self->raw, _PyIO_str_seek,
+                                     posobj, whenceobj, NULL);
+    Py_DECREF(posobj);
+    Py_DECREF(whenceobj);
+    if (res == NULL)
+        return -1;
+    n = PyNumber_AsOff_t(res, PyExc_ValueError);
+    Py_DECREF(res);
+    if (n < 0) {
+        if (!PyErr_Occurred())
+            PyErr_Format(PyExc_IOError,
+                         "Raw stream returned invalid position %zd", n);
+        return -1;
+    }
+    self->abs_pos = n;
+    return n;
+}
+
+static int
+_Buffered_init(BufferedObject *self)
+{
+    Py_ssize_t n;
+    if (self->buffer_size <= 0) {
+        PyErr_SetString(PyExc_ValueError,
+            "buffer size must be strictly positive");
+        return -1;
+    }
+    if (self->buffer)
+        PyMem_Free(self->buffer);
+    self->buffer = PyMem_Malloc(self->buffer_size);
+    if (self->buffer == NULL) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    self->lock = PyThread_allocate_lock();
+    if (self->lock == NULL) {
+        PyErr_SetString(PyExc_RuntimeError, "can't allocate read lock");
+        return -1;
+    }
+    /* Find out whether buffer_size is a power of 2 */
+    /* XXX is this optimization useful? */
+    for (n = self->buffer_size - 1; n & 1; n >>= 1)
+        ;
+    if (n == 0)
+        self->buffer_mask = self->buffer_size - 1;
+    else
+        self->buffer_mask = 0;
+    if (_Buffered_raw_tell(self) == -1)
+        PyErr_Clear();
+    return 0;
+}
+
+/*
+ * Shared methods and wrappers
+ */
+
+static PyObject *
+Buffered_flush(BufferedObject *self, PyObject *args)
+{
+    PyObject *res;
+
+    CHECK_INITIALIZED(self)
+    if (BufferedIOMixin_closed(self)) {
+        PyErr_SetString(PyExc_ValueError, "flush of closed file");
+        return NULL;
+    }
+
+    ENTER_BUFFERED(self)
+    res = _BufferedWriter_flush_unlocked(self, 0);
+    if (res != NULL && self->readable) {
+        /* Rewind the raw stream so that its position corresponds to
+           the current logical position. */
+        Py_off_t n;
+        n = _Buffered_raw_seek(self, -RAW_OFFSET(self), 1);
+        if (n == -1)
+            Py_CLEAR(res);
+        _BufferedReader_reset_buf(self);
+    }
+    LEAVE_BUFFERED(self)
+
+    return res;
+}
+
+static PyObject *
+Buffered_peek(BufferedObject *self, PyObject *args)
+{
+    Py_ssize_t n = 0;
+    PyObject *res = NULL;
+
+    CHECK_INITIALIZED(self)
+    if (!PyArg_ParseTuple(args, "|n:peek", &n)) {
+        return NULL;
+    }
+
+    ENTER_BUFFERED(self)
+
+    if (self->writable) {
+        res = _BufferedWriter_flush_unlocked(self, 1);
+        if (res == NULL)
+            goto end;
+        Py_CLEAR(res);
+    }
+    res = _BufferedReader_peek_unlocked(self, n);
+
+end:
+    LEAVE_BUFFERED(self)
+    return res;
+}
+
+static PyObject *
+Buffered_read(BufferedObject *self, PyObject *args)
+{
+    Py_ssize_t n = -1;
+    PyObject *res;
+
+    CHECK_INITIALIZED(self)
+    if (!PyArg_ParseTuple(args, "|n:read", &n)) {
+        return NULL;
+    }
+    if (n < -1) {
+        PyErr_SetString(PyExc_ValueError,
+                        "read length must be positive or -1");
+        return NULL;
+    }
+
+    if (BufferedIOMixin_closed(self)) {
+        PyErr_SetString(PyExc_ValueError, "read of closed file");
+        return NULL;
+    }
+
+    ENTER_BUFFERED(self)
+    res = _BufferedReader_read_unlocked(self, n);
+    LEAVE_BUFFERED(self)
+
+    return res;
+}
+
+static PyObject *
+Buffered_read1(BufferedObject *self, PyObject *args)
+{
+    Py_ssize_t n, have, r;
+    PyObject *res = NULL;
+
+    CHECK_INITIALIZED(self)
+    if (!PyArg_ParseTuple(args, "n:read1", &n)) {
+        return NULL;
+    }
+
+    if (n < 0) {
+        PyErr_SetString(PyExc_ValueError,
+                        "read length must be positive");
+        return NULL;
+    }
+    if (n == 0)
+        return PyBytes_FromStringAndSize(NULL, 0);
+
+    ENTER_BUFFERED(self)
+    
+    if (self->writable) {
+        res = _BufferedWriter_flush_unlocked(self, 1);
+        if (res == NULL)
+            goto end;
+        Py_CLEAR(res);
+    }
+
+    /* Return up to n bytes.  If at least one byte is buffered, we
+       only return buffered bytes.  Otherwise, we do one raw read. */
+
+    /* XXX: this mimicks the io.py implementation but is probably wrong.
+       If we need to read from the raw stream, then we could actually read
+       all `n` bytes asked by the caller (and possibly more, so as to fill
+       our buffer for the next reads). */
+
+    have = Py_SAFE_DOWNCAST(READAHEAD(self), Py_off_t, Py_ssize_t);
+    if (have > 0) {
+        if (n > have)
+            n = have;
+        res = PyBytes_FromStringAndSize(self->buffer + self->pos, n);
+        if (res == NULL)
+            goto end;
+        self->pos += n;
+        goto end;
+    }
+
+    /* Fill the buffer from the raw stream, and copy it to the result. */
+    _BufferedReader_reset_buf(self);
+    r = _BufferedReader_fill_buffer(self);
+    if (r == -1)
+        goto end;
+    if (r == -2)
+        r = 0;
+    if (n > r)
+        n = r;
+    res = PyBytes_FromStringAndSize(self->buffer, n);
+    if (res == NULL)
+        goto end;
+    self->pos = n;
+
+end:
+    LEAVE_BUFFERED(self)
+    return res;
+}
+
+static PyObject *
+Buffered_readinto(BufferedObject *self, PyObject *args)
+{
+    PyObject *res = NULL;
+
+    CHECK_INITIALIZED(self)
+    
+    /* TODO: use raw.readinto() instead! */
+    if (self->writable) {
+        ENTER_BUFFERED(self)
+        res = _BufferedWriter_flush_unlocked(self, 0);
+        LEAVE_BUFFERED(self)
+        if (res == NULL)
+            goto end;
+        Py_DECREF(res);
+    }
+    res = BufferedIOBase_readinto((PyObject *)self, args);
+
+end:
+    return res;
+}
+
+static PyObject *
+_Buffered_readline(BufferedObject *self, Py_ssize_t limit)
+{
+    PyObject *res = NULL;
+    PyObject *chunks = NULL;
+    Py_ssize_t n, written = 0;
+    const char *start, *s, *end;
+
+    if (BufferedIOMixin_closed(self)) {
+        PyErr_SetString(PyExc_ValueError, "readline of closed file");
+        return NULL;
+    }
+
+    ENTER_BUFFERED(self)
+
+    /* First, try to find a line in the buffer */
+    n = Py_SAFE_DOWNCAST(READAHEAD(self), Py_off_t, Py_ssize_t);
+    if (limit >= 0 && n > limit)
+        n = limit;
+    start = self->buffer + self->pos;
+    end = start + n;
+    s = start;
+    while (s < end) {
+        if (*s++ == '\n') {
+            res = PyBytes_FromStringAndSize(start, s - start);
+            if (res != NULL)
+                self->pos += s - start;
+            goto end;
+        }
+    }
+    if (n == limit) {
+        res = PyBytes_FromStringAndSize(start, n);
+        if (res != NULL)
+            self->pos += n;
+        goto end;
+    }
+
+    /* Now we try to get some more from the raw stream */
+    if (self->writable) {
+        res = _BufferedWriter_flush_unlocked(self, 1);
+        if (res == NULL)
+            goto end;
+        Py_CLEAR(res);
+    }
+    chunks = PyList_New(0);
+    if (chunks == NULL)
+        goto end;
+    if (n > 0) {
+        res = PyBytes_FromStringAndSize(start, n);
+        if (res == NULL)
+            goto end;
+        if (PyList_Append(chunks, res) < 0) {
+            Py_CLEAR(res);
+            goto end;
+        }
+        Py_CLEAR(res);
+        written += n;
+        if (limit >= 0)
+            limit -= n;
+    }
+
+    for (;;) {
+        _BufferedReader_reset_buf(self);
+        n = _BufferedReader_fill_buffer(self);
+        if (n == -1)
+            goto end;
+        if (n <= 0)
+            break;
+        if (limit >= 0 && n > limit)
+            n = limit;
+        start = self->buffer;
+        end = start + n;
+        s = start;
+        while (s < end) {
+            if (*s++ == '\n') {
+                res = PyBytes_FromStringAndSize(start, s - start);
+                if (res == NULL)
+                    goto end;
+                self->pos = s - start;
+                goto found;
+            }
+        }
+        res = PyBytes_FromStringAndSize(start, n);
+        if (res == NULL)
+            goto end;
+        if (n == limit) {
+            self->pos = n;
+            break;
+        }
+        if (PyList_Append(chunks, res) < 0) {
+            Py_CLEAR(res);
+            goto end;
+        }
+        Py_CLEAR(res);
+        written += n;
+        if (limit >= 0)
+            limit -= n;
+    }
+found:
+    if (res != NULL && PyList_Append(chunks, res) < 0) {
+        Py_CLEAR(res);
+        goto end;
+    }
+    Py_CLEAR(res);
+    res = _PyBytes_Join(_PyIO_empty_bytes, chunks);
+
+end:
+    LEAVE_BUFFERED(self)
+    Py_XDECREF(chunks);
+    return res;
+}
+
+static PyObject *
+Buffered_readline(BufferedObject *self, PyObject *args)
+{
+    Py_ssize_t limit = -1;
+
+    CHECK_INITIALIZED(self)
+
+    if (!PyArg_ParseTuple(args, "|n:readline", &limit)) {
+        return NULL;
+    }
+    return _Buffered_readline(self, limit);
+}
+
+
+static PyObject *
+Buffered_tell(BufferedObject *self, PyObject *args)
+{
+    Py_off_t pos;
+
+    CHECK_INITIALIZED(self)
+    pos = _Buffered_raw_tell(self);
+    if (pos == -1)
+        return NULL;
+    pos -= RAW_OFFSET(self);
+    /* TODO: sanity check (pos >= 0) */
+    return PyLong_FromOff_t(pos);
+}
+
+static PyObject *
+Buffered_seek(BufferedObject *self, PyObject *args)
+{
+    Py_off_t target, n;
+    int whence = 0;
+    PyObject *targetobj, *res = NULL;
+
+    CHECK_INITIALIZED(self)
+    if (!PyArg_ParseTuple(args, "O|i:seek", &targetobj, &whence)) {
+        return NULL;
+    }
+    
+    if (whence < 0 || whence > 2) {
+        PyErr_Format(PyExc_ValueError,
+                     "whence must be between 0 and 2, not %d", whence);
+        return NULL;
+    }
+    target = PyNumber_AsOff_t(targetobj, PyExc_ValueError);
+    if (target == -1 && PyErr_Occurred())
+        return NULL;
+
+    ENTER_BUFFERED(self)
+
+    if (whence != 2 && self->readable) {
+        Py_off_t current, avail;
+        /* Check if seeking leaves us inside the current buffer,
+           so as to return quickly if possible.
+           Don't know how to do that when whence == 2, though. */
+        current = RAW_TELL(self);
+        avail = READAHEAD(self);
+        if (avail > 0) {
+            Py_off_t offset;
+            if (whence == 0)
+                offset = target - (current - RAW_OFFSET(self));
+            else
+                offset = target;
+            if (offset >= -self->pos && offset <= avail) {
+                self->pos += offset;
+                res = PyLong_FromOff_t(current - avail + offset);
+                goto end;
+            }
+        }
+    }
+
+    /* Fallback: invoke raw seek() method and clear buffer */
+    if (self->writable) {
+        res = _BufferedWriter_flush_unlocked(self, 0);
+        if (res == NULL)
+            goto end;
+        Py_CLEAR(res);
+        _BufferedWriter_reset_buf(self);
+    }
+
+    /* TODO: align on block boundary and read buffer if needed? */
+    if (whence == 1)
+        target -= RAW_OFFSET(self);
+    n = _Buffered_raw_seek(self, target, whence);
+    if (n == -1)
+        goto end;
+    self->raw_pos = -1;
+    res = PyLong_FromOff_t(n);
+    if (res != NULL && self->readable)
+        _BufferedReader_reset_buf(self);
+
+end:
+    LEAVE_BUFFERED(self)
+    return res;
+}
+
+static PyObject *
+Buffered_truncate(BufferedObject *self, PyObject *args)
+{
+    PyObject *pos = Py_None;
+    PyObject *res = NULL;
+
+    CHECK_INITIALIZED(self)
+    if (!PyArg_ParseTuple(args, "|O:truncate", &pos)) {
+        return NULL;
+    }
+
+    ENTER_BUFFERED(self)
+
+    if (self->writable) {
+        res = _BufferedWriter_flush_unlocked(self, 0);
+        if (res == NULL)
+            goto end;
+        Py_CLEAR(res);
+    }
+    if (self->readable) {
+        if (pos == Py_None) {
+            /* Rewind the raw stream so that its position corresponds to
+               the current logical position. */
+            if (_Buffered_raw_seek(self, -RAW_OFFSET(self), 1) == -1)
+                goto end;
+        }
+        _BufferedReader_reset_buf(self);
+    }
+    res = PyObject_CallMethodObjArgs(self->raw, _PyIO_str_truncate, pos, NULL);
+    if (res == NULL)
+        goto end;
+    /* Reset cached position */
+    if (_Buffered_raw_tell(self) == -1)
+        PyErr_Clear();
+
+end:
+    LEAVE_BUFFERED(self)
+    return res;
+}
+
+static PyObject *
+Buffered_iternext(BufferedObject *self)
+{
+    PyObject *line;
+    PyTypeObject *tp;
+
+    CHECK_INITIALIZED(self);
+
+    tp = Py_TYPE(self);
+    if (tp == &PyBufferedReader_Type ||
+        tp == &PyBufferedRandom_Type) {
+        /* Skip method call overhead for speed */
+        line = _Buffered_readline(self, -1);
+    }
+    else {
+        line = PyObject_CallMethodObjArgs((PyObject *)self,
+                                           _PyIO_str_readline, NULL);
+        if (line && !PyBytes_Check(line)) {
+            PyErr_Format(PyExc_IOError,
+                         "readline() should have returned a bytes object, "
+                         "not '%.200s'", Py_TYPE(line)->tp_name);
+            Py_DECREF(line);
+            return NULL;
+        }
+    }
+
+    if (line == NULL)
+        return NULL;
+
+    if (PyBytes_GET_SIZE(line) == 0) {
+        /* Reached EOF or would have blocked */
+        Py_DECREF(line);
+        return NULL;
+    }
+
+    return line;
+}
+
+/*
+ * class BufferedReader
+ */
+
+PyDoc_STRVAR(BufferedReader_doc,
+             "Create a new buffered reader using the given readable raw IO object.");
+
+static void _BufferedReader_reset_buf(BufferedObject *self)
+{
+    self->read_end = -1;
+}
+
+static int
+BufferedReader_init(BufferedObject *self, PyObject *args, PyObject *kwds)
+{
+    char *kwlist[] = {"raw", "buffer_size", NULL};
+    Py_ssize_t buffer_size = DEFAULT_BUFFER_SIZE;
+    PyObject *raw;
+
+    self->ok = 0;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|n:BufferedReader", kwlist,
+                                     &raw, &buffer_size)) {
+        return -1;
+    }
+
+    if (_PyIOBase_checkReadable(raw, Py_True) == NULL)
+        return -1;
+
+    Py_CLEAR(self->raw);
+    Py_INCREF(raw);
+    self->raw = raw;
+    self->buffer_size = buffer_size;
+    self->readable = 1;
+    self->writable = 0;
+
+    if (_Buffered_init(self) < 0)
+        return -1;
+    _BufferedReader_reset_buf(self);
+
+    self->ok = 1;
+    return 0;
+}
+
+static Py_ssize_t
+_BufferedReader_raw_read(BufferedObject *self, char *start, Py_ssize_t len)
+{
+    Py_buffer buf;
+    PyObject *memobj, *res;
+    Py_ssize_t n;
+    /* NOTE: the buffer needn't be released as its object is NULL. */
+    if (PyBuffer_FillInfo(&buf, NULL, start, len, 0, PyBUF_CONTIG) == -1)
+        return -1;
+    memobj = PyMemoryView_FromBuffer(&buf);
+    if (memobj == NULL)
+        return -1;
+    res = PyObject_CallMethodObjArgs(self->raw, _PyIO_str_readinto, memobj, NULL);
+    Py_DECREF(memobj);
+    if (res == NULL)
+        return -1;
+    if (res == Py_None) {
+        /* Non-blocking stream would have blocked. Special return code! */
+        Py_DECREF(res);
+        return -2;
+    }
+    n = PyNumber_AsSsize_t(res, PyExc_ValueError);
+    Py_DECREF(res);
+    if (n < 0 || n > len) {
+        PyErr_Format(PyExc_IOError,
+                     "raw readinto() returned invalid length %zd "
+                     "(should have been between 0 and %zd)", n, len);
+        return -1;
+    }
+    if (n > 0 && self->abs_pos != -1)
+        self->abs_pos += n;
+    return n;
+}
+
+static Py_ssize_t
+_BufferedReader_fill_buffer(BufferedObject *self)
+{
+    Py_ssize_t start, len, n;
+    if (VALID_READ_BUFFER(self))
+        start = Py_SAFE_DOWNCAST(self->read_end, Py_off_t, Py_ssize_t);
+    else
+        start = 0;
+    len = self->buffer_size - start;
+    n = _BufferedReader_raw_read(self, self->buffer + start, len);
+    if (n <= 0)
+        return n;
+    self->read_end = start + n;
+    self->raw_pos = start + n;
+    return n;
+}
+
+static PyObject *
+_BufferedReader_read_unlocked(BufferedObject *self, Py_ssize_t n)
+{
+    PyObject *data, *res = NULL;
+    Py_ssize_t current_size, remaining, written;
+    char *out;
+    static PyObject *sep = NULL;
+
+    /* Special case for when the number of bytes to read is unspecified. */
+    if (n == -1) {
+        PyObject *chunks = PyList_New(0);
+        if (chunks == NULL)
+            return NULL;
+
+        /* First copy what we have in the current buffer. */
+        current_size = Py_SAFE_DOWNCAST(READAHEAD(self), Py_off_t, Py_ssize_t);
+        data = NULL;
+        if (current_size) {
+            data = PyBytes_FromStringAndSize(
+                self->buffer + self->pos, current_size);
+            if (data == NULL) {
+                Py_DECREF(chunks);
+                return NULL;
+            }
+        }
+        _BufferedReader_reset_buf(self);
+        /* We're going past the buffer's bounds, flush it */
+        if (self->writable) {
+            res = _BufferedWriter_flush_unlocked(self, 1);
+            if (res == NULL) {
+                Py_DECREF(chunks);
+                return NULL;
+            }
+            Py_CLEAR(res);
+        }
+        while (1) {
+            if (data) {
+                if (PyList_Append(chunks, data) < 0) {
+                    Py_DECREF(data);
+                    Py_DECREF(chunks);
+                    return NULL;
+                }
+                Py_DECREF(data);
+            }
+
+            /* Read until EOF or until read() would block. */
+            data = PyObject_CallMethodObjArgs(self->raw, _PyIO_str_read, NULL);
+            if (data == NULL) {
+                Py_DECREF(chunks);
+                return NULL;
+            }
+            if (data != Py_None && !PyBytes_Check(data)) {
+                Py_DECREF(data);
+                Py_DECREF(chunks);
+                PyErr_SetString(PyExc_TypeError, "read() should return bytes");
+                return NULL;
+            }
+            if (data == Py_None || PyBytes_GET_SIZE(data) == 0) {
+                if (current_size == 0) {
+                    Py_DECREF(chunks);
+                    return data;
+                }
+                else {
+                    if (sep == NULL) {
+                        sep = PyBytes_FromStringAndSize(NULL, 0);
+                        if (sep == NULL) {
+                            Py_DECREF(data);
+                            Py_DECREF(chunks);
+                            return NULL;
+                        }
+                    }
+                    res =_PyBytes_Join(sep, chunks);
+                    Py_DECREF(data);
+                    Py_DECREF(chunks);
+                    return res;
+                }
+            }
+            current_size += PyBytes_GET_SIZE(data);
+            if (self->abs_pos != -1)
+                self->abs_pos += PyBytes_GET_SIZE(data);
+        }
+    }
+
+    /* The number of bytes to read is specified, return at most n bytes. */
+    current_size = Py_SAFE_DOWNCAST(READAHEAD(self), Py_off_t, Py_ssize_t);
+    if (n <= current_size) {
+        /* Fast path: the data to read is fully buffered. */
+        res = PyBytes_FromStringAndSize(self->buffer + self->pos, n);
+        if (res == NULL)
+            goto error;
+        self->pos += n;
+        return res;
+    }
+
+    /* Slow path: read from the stream until enough bytes are read,
+     * or until an EOF occurs or until read() would block.
+     */
+    res = PyBytes_FromStringAndSize(NULL, n);
+    if (res == NULL)
+        goto error;
+    out = PyBytes_AS_STRING(res);
+    remaining = n;
+    written = 0;
+    if (current_size > 0) {
+        memcpy(out, self->buffer + self->pos, current_size);
+        remaining -= current_size;
+        written += current_size;
+    }
+    _BufferedReader_reset_buf(self);
+    while (remaining > 0) {
+        /* We want to read a whole block at the end into buffer.
+           If we had readv() we could do this in one pass. */
+        Py_ssize_t r = MINUS_LAST_BLOCK(self, remaining);
+        if (r == 0)
+            break;
+        r = _BufferedReader_raw_read(self, out + written, r);
+        if (r == -1)
+            goto error;
+        if (r == 0 || r == -2) {
+            /* EOF occurred or read() would block. */
+            if (r == 0 || written > 0) {
+                if (_PyBytes_Resize(&res, written))
+                    goto error;
+                return res;
+            }
+            Py_DECREF(res);
+            Py_INCREF(Py_None);
+            return Py_None;
+        }
+        remaining -= r;
+        written += r;
+    }
+    assert(remaining <= self->buffer_size);
+    self->pos = 0;
+    self->raw_pos = 0;
+    self->read_end = 0;
+    while (self->read_end < self->buffer_size) {
+        Py_ssize_t r = _BufferedReader_fill_buffer(self);
+        if (r == -1)
+            goto error;
+        if (r == 0 || r == -2) {
+            /* EOF occurred or read() would block. */
+            if (r == 0 || written > 0) {
+                if (_PyBytes_Resize(&res, written))
+                    goto error;
+                return res;
+            }
+            Py_DECREF(res);
+            Py_INCREF(Py_None);
+            return Py_None;
+        }
+        if (remaining > r) {
+            memcpy(out + written, self->buffer + self->pos, r);
+            written += r;
+            self->pos += r;
+            remaining -= r;
+        }
+        else if (remaining > 0) {
+            memcpy(out + written, self->buffer + self->pos, remaining);
+            written += remaining;
+            self->pos += remaining;
+            remaining = 0;
+        }
+        if (remaining == 0)
+            break;
+    }
+
+    return res;
+
+error:
+    Py_XDECREF(res);
+    return NULL;
+}
+
+static PyObject *
+_BufferedReader_peek_unlocked(BufferedObject *self, Py_ssize_t n)
+{
+    Py_ssize_t have, r;
+
+    have = Py_SAFE_DOWNCAST(READAHEAD(self), Py_off_t, Py_ssize_t);
+    /* Constraints:
+       1. we don't want to advance the file position.
+       2. we don't want to lose block alignment, so we can't shift the buffer
+          to make some place.
+       Therefore, we either return `have` bytes (if > 0), or a full buffer.
+    */
+    if (have > 0) {
+        return PyBytes_FromStringAndSize(self->buffer + self->pos, have);
+    }
+
+    /* Fill the buffer from the raw stream, and copy it to the result. */
+    _BufferedReader_reset_buf(self);
+    r = _BufferedReader_fill_buffer(self);
+    if (r == -1)
+        return NULL;
+    if (r == -2)
+        r = 0;
+    self->pos = 0;
+    return PyBytes_FromStringAndSize(self->buffer, r);
+}
+
+static PyMethodDef BufferedReader_methods[] = {
+    /* BufferedIOMixin methods */
+    {"flush", (PyCFunction)BufferedIOMixin_flush, METH_NOARGS},
+    {"close", (PyCFunction)BufferedIOMixin_close, METH_NOARGS},
+    {"seekable", (PyCFunction)BufferedIOMixin_seekable, METH_NOARGS},
+    {"readable", (PyCFunction)BufferedIOMixin_readable, METH_NOARGS},
+    {"writable", (PyCFunction)BufferedIOMixin_writable, METH_NOARGS},
+    {"fileno", (PyCFunction)BufferedIOMixin_fileno, METH_NOARGS},
+    {"isatty", (PyCFunction)BufferedIOMixin_isatty, METH_NOARGS},
+
+    {"read", (PyCFunction)Buffered_read, METH_VARARGS},
+    {"peek", (PyCFunction)Buffered_peek, METH_VARARGS},
+    {"read1", (PyCFunction)Buffered_read1, METH_VARARGS},
+    {"readline", (PyCFunction)Buffered_readline, METH_VARARGS},
+    {"seek", (PyCFunction)Buffered_seek, METH_VARARGS},
+    {"tell", (PyCFunction)Buffered_tell, METH_NOARGS},
+    {"truncate", (PyCFunction)Buffered_truncate, METH_VARARGS},
+    {NULL, NULL}
+};
+
+static PyMemberDef BufferedReader_members[] = {
+    {"raw", T_OBJECT, offsetof(BufferedObject, raw), 0},
+    {NULL}
+};
+
+static PyGetSetDef BufferedReader_getset[] = {
+    {"closed", (getter)BufferedIOMixin_closed_get, NULL, NULL},
+    {"name", (getter)BufferedIOMixin_name_get, NULL, NULL},
+    {"mode", (getter)BufferedIOMixin_mode_get, NULL, NULL},
+    {0}
+};
+
+
+PyTypeObject PyBufferedReader_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io.BufferedReader",       /*tp_name*/
+    sizeof(BufferedObject),     /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    (destructor)BufferedObject_dealloc,     /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+            | Py_TPFLAGS_HAVE_GC, /*tp_flags*/
+    BufferedReader_doc,         /* tp_doc */
+    (traverseproc)Buffered_traverse, /* tp_traverse */
+    (inquiry)Buffered_clear,    /* tp_clear */
+    0,                          /* tp_richcompare */
+    offsetof(BufferedObject, weakreflist), /*tp_weaklistoffset*/
+    0,                          /* tp_iter */
+    (iternextfunc)Buffered_iternext, /* tp_iternext */
+    BufferedReader_methods,     /* tp_methods */
+    BufferedReader_members,     /* tp_members */
+    BufferedReader_getset,      /* tp_getset */
+    0,                          /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    offsetof(BufferedObject, dict), /* tp_dictoffset */
+    (initproc)BufferedReader_init, /* tp_init */
+    0,                          /* tp_alloc */
+    PyType_GenericNew,          /* tp_new */
+};
+
+
+/*
+ * class BufferedWriter
+ */
+PyDoc_STRVAR(BufferedWriter_doc,
+    "A buffer for a writeable sequential RawIO object.\n"
+    "\n"
+    "The constructor creates a BufferedWriter for the given writeable raw\n"
+    "stream. If the buffer_size is not given, it defaults to\n"
+    "DEFAULT_BUFFER_SIZE. max_buffer_size isn't used anymore.\n"
+    );
+
+static void
+_BufferedWriter_reset_buf(BufferedObject *self)
+{
+    self->write_pos = 0;
+    self->write_end = -1;
+}
+
+static int
+BufferedWriter_init(BufferedObject *self, PyObject *args, PyObject *kwds)
+{
+    /* TODO: properly deprecate max_buffer_size */
+    char *kwlist[] = {"raw", "buffer_size", "max_buffer_size", NULL};
+    Py_ssize_t buffer_size = DEFAULT_BUFFER_SIZE;
+    Py_ssize_t max_buffer_size = -1;
+    PyObject *raw;
+
+    self->ok = 0;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|nn:BufferedReader", kwlist,
+                                     &raw, &buffer_size, &max_buffer_size)) {
+        return -1;
+    }
+
+    if (_PyIOBase_checkWritable(raw, Py_True) == NULL)
+        return -1;
+
+    Py_CLEAR(self->raw);
+    Py_INCREF(raw);
+    self->raw = raw;
+    self->readable = 0;
+    self->writable = 1;
+
+    self->buffer_size = buffer_size;
+    if (_Buffered_init(self) < 0)
+        return -1;
+    _BufferedWriter_reset_buf(self);
+    self->pos = 0;
+
+    self->ok = 1;
+    return 0;
+}
+
+static Py_ssize_t
+_BufferedWriter_raw_write(BufferedObject *self, char *start, Py_ssize_t len)
+{
+    Py_buffer buf;
+    PyObject *memobj, *res;
+    Py_ssize_t n;
+    /* NOTE: the buffer needn't be released as its object is NULL. */
+    if (PyBuffer_FillInfo(&buf, NULL, start, len, 1, PyBUF_CONTIG_RO) == -1)
+        return -1;
+    memobj = PyMemoryView_FromBuffer(&buf);
+    if (memobj == NULL)
+        return -1;
+    res = PyObject_CallMethodObjArgs(self->raw, _PyIO_str_write, memobj, NULL);
+    Py_DECREF(memobj);
+    if (res == NULL)
+        return -1;
+    n = PyNumber_AsSsize_t(res, PyExc_ValueError);
+    Py_DECREF(res);
+    if (n < 0 || n > len) {
+        PyErr_Format(PyExc_IOError,
+                     "raw write() returned invalid length %zd "
+                     "(should have been between 0 and %zd)", n, len);
+        return -1;
+    }
+    if (n > 0 && self->abs_pos != -1)
+        self->abs_pos += n;
+    return n;
+}
+
+/* `restore_pos` is 1 if we need to restore the raw stream position at
+   the end, 0 otherwise. */
+static PyObject *
+_BufferedWriter_flush_unlocked(BufferedObject *self, int restore_pos)
+{
+    Py_ssize_t written = 0;
+    Py_off_t n, rewind;
+
+    if (!VALID_WRITE_BUFFER(self) || self->write_pos == self->write_end)
+        goto end;
+    /* First, rewind */
+    rewind = RAW_OFFSET(self) + (self->pos - self->write_pos);
+    if (rewind != 0) {
+        n = _Buffered_raw_seek(self, -rewind, 1);
+        if (n < 0) {
+            goto error;
+        }
+        self->raw_pos -= rewind;
+    }
+    while (self->write_pos < self->write_end) {
+        n = _BufferedWriter_raw_write(self,
+            self->buffer + self->write_pos,
+            Py_SAFE_DOWNCAST(self->write_end - self->write_pos,
+                             Py_off_t, Py_ssize_t));
+        if (n == -1) {
+            Py_ssize_t *w = _Buffered_check_blocking_error();
+            if (w == NULL)
+                goto error;
+            self->write_pos += *w;
+            self->raw_pos = self->write_pos;
+            written += *w;
+            *w = written;
+            /* Already re-raised */
+            goto error;
+        }
+        self->write_pos += n;
+        self->raw_pos = self->write_pos;
+        written += Py_SAFE_DOWNCAST(n, Py_off_t, Py_ssize_t);
+    }
+
+    if (restore_pos) {
+        Py_off_t forward = rewind - written;
+        if (forward != 0) {
+            n = _Buffered_raw_seek(self, forward, 1);
+            if (n < 0) {
+                goto error;
+            }
+            self->raw_pos += forward;
+        }
+    }
+    _BufferedWriter_reset_buf(self);
+
+end:
+    Py_RETURN_NONE;
+
+error:
+    return NULL;
+}
+
+static PyObject *
+BufferedWriter_write(BufferedObject *self, PyObject *args)
+{
+    PyObject *res = NULL;
+    Py_buffer buf;
+    Py_ssize_t written, avail, remaining, n;
+
+    CHECK_INITIALIZED(self)
+    if (!PyArg_ParseTuple(args, "y*:write", &buf)) {
+        return NULL;
+    }
+
+    if (BufferedIOMixin_closed(self)) {
+        PyErr_SetString(PyExc_ValueError, "write to closed file");
+        PyBuffer_Release(&buf);
+        return NULL;
+    }
+
+    ENTER_BUFFERED(self)
+
+    /* Fast path: the data to write can be fully buffered. */
+    if (!VALID_READ_BUFFER(self) && !VALID_WRITE_BUFFER(self)) {
+        self->pos = 0;
+        self->raw_pos = 0;
+    }
+    avail = Py_SAFE_DOWNCAST(self->buffer_size - self->pos, Py_off_t, Py_ssize_t);
+    if (buf.len <= avail) {
+        memcpy(self->buffer + self->pos, buf.buf, buf.len);
+        if (!VALID_WRITE_BUFFER(self)) {
+            self->write_pos = self->pos;
+        }
+        ADJUST_POSITION(self, self->pos + buf.len);
+        if (self->pos > self->write_end)
+            self->write_end = self->pos;
+        written = buf.len;
+        goto end;
+    }
+
+    /* First write the current buffer */
+    res = _BufferedWriter_flush_unlocked(self, 0);
+    if (res == NULL) {
+        Py_ssize_t *w = _Buffered_check_blocking_error();
+        if (w == NULL)
+            goto error;
+        if (self->readable)
+            _BufferedReader_reset_buf(self);
+        /* Make some place by shifting the buffer. */
+        assert(VALID_WRITE_BUFFER(self));
+        memmove(self->buffer, self->buffer + self->write_pos,
+                Py_SAFE_DOWNCAST(self->write_end - self->write_pos,
+                                 Py_off_t, Py_ssize_t));
+        self->write_end -= self->write_pos;
+        self->raw_pos -= self->write_pos;
+        self->pos -= self->write_pos;
+        self->write_pos = 0;
+        avail = Py_SAFE_DOWNCAST(self->buffer_size - self->write_end,
+                                 Py_off_t, Py_ssize_t);
+        if (buf.len <= avail) {
+            /* Everything can be buffered */
+            PyErr_Clear();
+            memcpy(self->buffer + self->write_end, buf.buf, buf.len);
+            self->write_end += buf.len;
+            written = buf.len;
+            goto end;
+        }
+        /* Buffer as much as possible. */
+        memcpy(self->buffer + self->write_end, buf.buf, avail);
+        self->write_end += avail;
+        /* Already re-raised */
+        *w = avail;
+        goto error;
+    }
+    Py_CLEAR(res);
+
+    /* Then write buf itself. At this point the buffer has been emptied. */
+    remaining = buf.len;
+    written = 0;
+    while (remaining > self->buffer_size) {
+        n = _BufferedWriter_raw_write(
+            self, (char *) buf.buf + written, buf.len - written);
+        if (n == -1) {
+            Py_ssize_t *w = _Buffered_check_blocking_error();
+            if (w == NULL)
+                goto error;
+            written += *w;
+            remaining -= *w;
+            if (remaining > self->buffer_size) {
+                /* Can't buffer everything, still buffer as much as possible */
+                memcpy(self->buffer,
+                       (char *) buf.buf + written, self->buffer_size);
+                self->raw_pos = 0;
+                ADJUST_POSITION(self, self->buffer_size);
+                self->write_end = self->buffer_size;
+                *w = written + self->buffer_size;
+                /* Already re-raised */
+                goto error;
+            }
+            PyErr_Clear();
+            break;
+        }
+        written += n;
+        remaining -= n;
+    }
+    if (self->readable)
+        _BufferedReader_reset_buf(self);
+    if (remaining > 0) {
+        memcpy(self->buffer, (char *) buf.buf + written, remaining);
+        written += remaining;
+    }
+    self->write_pos = 0;
+    /* TODO: sanity check (remaining >= 0) */
+    self->write_end = remaining;
+    ADJUST_POSITION(self, remaining);
+    self->raw_pos = 0;
+
+end:
+    res = PyLong_FromSsize_t(written);
+
+error:
+    LEAVE_BUFFERED(self)
+    PyBuffer_Release(&buf);
+    return res;
+}
+
+static PyMethodDef BufferedWriter_methods[] = {
+    /* BufferedIOMixin methods */
+    {"close", (PyCFunction)BufferedIOMixin_close, METH_NOARGS},
+    {"seekable", (PyCFunction)BufferedIOMixin_seekable, METH_NOARGS},
+    {"readable", (PyCFunction)BufferedIOMixin_readable, METH_NOARGS},
+    {"writable", (PyCFunction)BufferedIOMixin_writable, METH_NOARGS},
+    {"fileno", (PyCFunction)BufferedIOMixin_fileno, METH_NOARGS},
+    {"isatty", (PyCFunction)BufferedIOMixin_isatty, METH_NOARGS},
+
+    {"write", (PyCFunction)BufferedWriter_write, METH_VARARGS},
+    {"truncate", (PyCFunction)Buffered_truncate, METH_VARARGS},
+    {"flush", (PyCFunction)Buffered_flush, METH_NOARGS},
+    {"seek", (PyCFunction)Buffered_seek, METH_VARARGS},
+    {"tell", (PyCFunction)Buffered_tell, METH_NOARGS},
+    {NULL, NULL}
+};
+
+static PyMemberDef BufferedWriter_members[] = {
+    {"raw", T_OBJECT, offsetof(BufferedObject, raw), 0},
+    {NULL}
+};
+
+static PyGetSetDef BufferedWriter_getset[] = {
+    {"closed", (getter)BufferedIOMixin_closed_get, NULL, NULL},
+    {"name", (getter)BufferedIOMixin_name_get, NULL, NULL},
+    {"mode", (getter)BufferedIOMixin_mode_get, NULL, NULL},
+    {0}
+};
+
+
+PyTypeObject PyBufferedWriter_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io.BufferedWriter",       /*tp_name*/
+    sizeof(BufferedObject),     /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    (destructor)BufferedObject_dealloc,     /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+        | Py_TPFLAGS_HAVE_GC,   /*tp_flags*/
+    BufferedWriter_doc,         /* tp_doc */
+    (traverseproc)Buffered_traverse, /* tp_traverse */
+    (inquiry)Buffered_clear,    /* tp_clear */
+    0,                          /* tp_richcompare */
+    offsetof(BufferedObject, weakreflist), /*tp_weaklistoffset*/
+    0,                          /* tp_iter */
+    0,                          /* tp_iternext */
+    BufferedWriter_methods,     /* tp_methods */
+    BufferedWriter_members,     /* tp_members */
+    BufferedWriter_getset,      /* tp_getset */
+    0,                          /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    offsetof(BufferedObject, dict), /* tp_dictoffset */
+    (initproc)BufferedWriter_init, /* tp_init */
+    0,                          /* tp_alloc */
+    PyType_GenericNew,          /* tp_new */
+};
+
+
+
+/*
+ * BufferedRWPair
+ */
+
+PyDoc_STRVAR(BufferedRWPair_doc,
+    "A buffered reader and writer object together.\n"
+    "\n"
+    "A buffered reader object and buffered writer object put together to\n"
+    "form a sequential IO object that can read and write. This is typically\n"
+    "used with a socket or two-way pipe.\n"
+    "\n"
+    "reader and writer are RawIOBase objects that are readable and\n"
+    "writeable respectively. If the buffer_size is omitted it defaults to\n"
+    "DEFAULT_BUFFER_SIZE. The max_buffer_size (for the buffered writer)\n"
+    "defaults to twice the buffer size.\n"
+    );
+
+/* XXX The usefulness of this (compared to having two separate IO objects) is
+ * questionable.
+ */
+
+typedef struct {
+    PyObject_HEAD
+    BufferedObject *reader;
+    BufferedObject *writer;
+    PyObject *dict;
+    PyObject *weakreflist;
+} BufferedRWPairObject;
+
+static int
+BufferedRWPair_init(BufferedRWPairObject *self, PyObject *args,
+                     PyObject *kwds)
+{
+    PyObject *reader, *writer;
+    Py_ssize_t buffer_size = DEFAULT_BUFFER_SIZE;
+    Py_ssize_t max_buffer_size = -1;
+
+    if (!PyArg_ParseTuple(args, "OO|nn:BufferedRWPair", &reader, &writer,
+                          &buffer_size, &max_buffer_size)) {
+        return -1;
+    }
+
+    if (_PyIOBase_checkReadable(reader, Py_True) == NULL)
+        return -1;
+    if (_PyIOBase_checkWritable(writer, Py_True) == NULL)
+        return -1;
+
+    args = Py_BuildValue("(n)", buffer_size);
+    if (args == NULL) {
+        Py_CLEAR(self->reader);
+        return -1;
+    }
+    self->reader = (BufferedObject *)PyType_GenericNew(
+            &PyBufferedReader_Type, args, NULL);
+    Py_DECREF(args);
+    if (self->reader == NULL)
+        return -1;
+
+    args = Py_BuildValue("(nn)", buffer_size, max_buffer_size);
+    if (args == NULL) {
+        Py_CLEAR(self->reader);
+        return -1;
+    }
+    self->writer = (BufferedObject *)PyType_GenericNew(
+            &PyBufferedWriter_Type, args, NULL);
+    Py_DECREF(args);
+    if (self->writer == NULL) {
+        Py_CLEAR(self->reader);
+        return -1;
+    }
+    return 0;
+}
+
+static int
+BufferedRWPair_traverse(BufferedRWPairObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->dict);
+    return 0;
+}
+
+static int
+BufferedRWPair_clear(BufferedRWPairObject *self)
+{
+    Py_CLEAR(self->reader);
+    Py_CLEAR(self->writer);
+    Py_CLEAR(self->dict);
+    return 0;
+}
+
+static void
+BufferedRWPair_dealloc(BufferedRWPairObject *self)
+{
+    _PyObject_GC_UNTRACK(self);
+    Py_CLEAR(self->reader);
+    Py_CLEAR(self->writer);
+    Py_CLEAR(self->dict);
+    Py_TYPE(self)->tp_free((PyObject *) self);
+}
+
+static PyObject *
+_forward_call(BufferedObject *self, const char *name, PyObject *args)
+{
+    PyObject *func = PyObject_GetAttrString((PyObject *)self, name);
+    PyObject *ret;
+
+    if (func == NULL) {
+        PyErr_SetString(PyExc_AttributeError, name);
+        return NULL;
+    }
+
+    ret = PyObject_CallObject(func, args);
+    Py_DECREF(func);
+    return ret;
+}
+
+static PyObject *
+BufferedRWPair_read(BufferedRWPairObject *self, PyObject *args)
+{
+    return _forward_call(self->reader, "read", args);
+}
+
+static PyObject *
+BufferedRWPair_peek(BufferedRWPairObject *self, PyObject *args)
+{
+    return _forward_call(self->reader, "peek", args);
+}
+
+static PyObject *
+BufferedRWPair_read1(BufferedRWPairObject *self, PyObject *args)
+{
+    return _forward_call(self->reader, "read1", args);
+}
+
+static PyObject *
+BufferedRWPair_write(BufferedRWPairObject *self, PyObject *args)
+{
+    return _forward_call(self->writer, "write", args);
+}
+
+static PyObject *
+BufferedRWPair_flush(BufferedRWPairObject *self, PyObject *args)
+{
+    return _forward_call(self->writer, "flush", args);
+}
+
+static PyObject *
+BufferedRWPair_readable(BufferedRWPairObject *self, PyObject *args)
+{
+    return _forward_call(self->reader, "readable", args);
+}
+
+static PyObject *
+BufferedRWPair_writable(BufferedRWPairObject *self, PyObject *args)
+{
+    return _forward_call(self->writer, "writable", args);
+}
+
+static PyObject *
+BufferedRWPair_close(BufferedRWPairObject *self, PyObject *args)
+{
+    PyObject *ret = _forward_call(self->writer, "close", args);
+    if (ret == NULL)
+        return NULL;
+    Py_DECREF(ret);
+
+    return _forward_call(self->reader, "close", args);
+}
+
+static PyObject *
+BufferedRWPair_isatty(BufferedRWPairObject *self, PyObject *args)
+{
+    PyObject *ret = _forward_call(self->writer, "isatty", args);
+
+    if (ret != Py_False) {
+        /* either True or exception */
+        return ret;
+    }
+    Py_DECREF(ret);
+
+    return _forward_call(self->reader, "isatty", args);
+}
+
+
+static PyMethodDef BufferedRWPair_methods[] = {
+    {"read", (PyCFunction)BufferedRWPair_read, METH_VARARGS},
+    {"peek", (PyCFunction)BufferedRWPair_peek, METH_VARARGS},
+    {"read1", (PyCFunction)BufferedRWPair_read1, METH_VARARGS},
+    {"readinto", (PyCFunction)Buffered_readinto, METH_VARARGS},
+
+    {"write", (PyCFunction)BufferedRWPair_write, METH_VARARGS},
+    {"flush", (PyCFunction)BufferedRWPair_flush, METH_NOARGS},
+
+    {"readable", (PyCFunction)BufferedRWPair_readable, METH_NOARGS},
+    {"writable", (PyCFunction)BufferedRWPair_writable, METH_NOARGS},
+
+    {"close", (PyCFunction)BufferedRWPair_close, METH_NOARGS},
+    {"isatty", (PyCFunction)BufferedRWPair_isatty, METH_NOARGS},
+
+    {NULL, NULL}
+};
+
+PyTypeObject PyBufferedRWPair_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io.BufferedRWPair",       /*tp_name*/
+    sizeof(BufferedRWPairObject), /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    (destructor)BufferedRWPair_dealloc,     /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+        | Py_TPFLAGS_HAVE_GC,   /* tp_flags */
+    BufferedRWPair_doc,         /* tp_doc */
+    (traverseproc)BufferedRWPair_traverse, /* tp_traverse */
+    (inquiry)BufferedRWPair_clear, /* tp_clear */
+    0,                          /* tp_richcompare */
+    offsetof(BufferedRWPairObject, weakreflist), /*tp_weaklistoffset*/
+    0,                          /* tp_iter */
+    0,                          /* tp_iternext */
+    BufferedRWPair_methods,     /* tp_methods */
+    0,                          /* tp_members */
+    0,                          /* tp_getset */
+    0,                          /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    offsetof(BufferedRWPairObject, dict), /* tp_dictoffset */
+    (initproc)BufferedRWPair_init, /* tp_init */
+    0,                          /* tp_alloc */
+    PyType_GenericNew,          /* tp_new */
+};
+
+
+
+/*
+ * BufferedRandom
+ */
+
+PyDoc_STRVAR(BufferedRandom_doc,
+    "A buffered interface to random access streams.\n"
+    "\n"
+    "The constructor creates a reader and writer for a seekable stream,\n"
+    "raw, given in the first argument. If the buffer_size is omitted it\n"
+    "defaults to DEFAULT_BUFFER_SIZE. max_buffer_size isn't used anymore.\n"
+    );
+
+static int
+BufferedRandom_init(BufferedObject *self, PyObject *args, PyObject *kwds)
+{
+    char *kwlist[] = {"raw", "buffer_size", "max_buffer_size", NULL};
+    Py_ssize_t buffer_size = DEFAULT_BUFFER_SIZE;
+    Py_ssize_t max_buffer_size = -1;
+    PyObject *raw;
+
+    self->ok = 0;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|nn:BufferedReader", kwlist,
+                                     &raw, &buffer_size, &max_buffer_size)) {
+        return -1;
+    }
+
+    if (_PyIOBase_checkSeekable(raw, Py_True) == NULL)
+        return -1;
+    if (_PyIOBase_checkReadable(raw, Py_True) == NULL)
+        return -1;
+    if (_PyIOBase_checkWritable(raw, Py_True) == NULL)
+        return -1;
+
+    Py_CLEAR(self->raw);
+    Py_INCREF(raw);
+    self->raw = raw;
+    self->buffer_size = buffer_size;
+    self->readable = 1;
+    self->writable = 1;
+
+    if (_Buffered_init(self) < 0)
+        return -1;
+    _BufferedReader_reset_buf(self);
+    _BufferedWriter_reset_buf(self);
+    self->pos = 0;
+
+    self->ok = 1;
+    return 0;
+}
+
+static PyMethodDef BufferedRandom_methods[] = {
+    /* BufferedIOMixin methods */
+    {"close", (PyCFunction)BufferedIOMixin_close, METH_NOARGS},
+    {"seekable", (PyCFunction)BufferedIOMixin_seekable, METH_NOARGS},
+    {"readable", (PyCFunction)BufferedIOMixin_readable, METH_NOARGS},
+    {"writable", (PyCFunction)BufferedIOMixin_writable, METH_NOARGS},
+    {"fileno", (PyCFunction)BufferedIOMixin_fileno, METH_NOARGS},
+    {"isatty", (PyCFunction)BufferedIOMixin_isatty, METH_NOARGS},
+
+    {"flush", (PyCFunction)Buffered_flush, METH_NOARGS},
+
+    {"seek", (PyCFunction)Buffered_seek, METH_VARARGS},
+    {"tell", (PyCFunction)Buffered_tell, METH_NOARGS},
+    {"truncate", (PyCFunction)Buffered_truncate, METH_VARARGS},
+    {"read", (PyCFunction)Buffered_read, METH_VARARGS},
+    {"read1", (PyCFunction)Buffered_read1, METH_VARARGS},
+    {"readinto", (PyCFunction)Buffered_readinto, METH_VARARGS},
+    {"readline", (PyCFunction)Buffered_readline, METH_VARARGS},
+    {"peek", (PyCFunction)Buffered_peek, METH_VARARGS},
+    {"write", (PyCFunction)BufferedWriter_write, METH_VARARGS},
+    {NULL, NULL}
+};
+
+static PyMemberDef BufferedRandom_members[] = {
+    {"raw", T_OBJECT, offsetof(BufferedObject, raw), 0},
+    {NULL}
+};
+
+static PyGetSetDef BufferedRandom_getset[] = {
+    {"closed", (getter)BufferedIOMixin_closed_get, NULL, NULL},
+    {"name", (getter)BufferedIOMixin_name_get, NULL, NULL},
+    {"mode", (getter)BufferedIOMixin_mode_get, NULL, NULL},
+    {0}
+};
+
+
+PyTypeObject PyBufferedRandom_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io.BufferedRandom",       /*tp_name*/
+    sizeof(BufferedObject),     /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    (destructor)BufferedObject_dealloc,     /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+        | Py_TPFLAGS_HAVE_GC,   /*tp_flags*/
+    BufferedRandom_doc,         /* tp_doc */
+    (traverseproc)Buffered_traverse, /* tp_traverse */
+    (inquiry)Buffered_clear,    /* tp_clear */
+    0,                          /* tp_richcompare */
+    offsetof(BufferedObject, weakreflist), /*tp_weaklistoffset*/
+    0,                          /* tp_iter */
+    (iternextfunc)Buffered_iternext, /* tp_iternext */
+    BufferedRandom_methods,     /* tp_methods */
+    BufferedRandom_members,     /* tp_members */
+    BufferedRandom_getset,      /* tp_getset */
+    0,                          /* tp_base */
+    0,                          /*tp_dict*/
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    offsetof(BufferedObject, dict), /*tp_dictoffset*/
+    (initproc)BufferedRandom_init, /* tp_init */
+    0,                          /* tp_alloc */
+    PyType_GenericNew,          /* tp_new */
+};
+
diff --git a/Modules/_bytesio.c b/Modules/_bytesio.c
index 2cea0fc..0068cb7 100644
--- a/Modules/_bytesio.c
+++ b/Modules/_bytesio.c
@@ -1,4 +1,6 @@
 #include "Python.h"
+#include "structmember.h"       /* for offsetof() */
+#include "_iomodule.h"
 
 typedef struct {
     PyObject_HEAD
@@ -6,6 +8,8 @@
     Py_ssize_t pos;
     Py_ssize_t string_size;
     size_t buf_size;
+    PyObject *dict;
+    PyObject *weakreflist;
 } BytesIOObject;
 
 #define CHECK_CLOSED(self)                                  \
@@ -144,10 +148,12 @@
 static PyObject *
 bytesio_get_closed(BytesIOObject *self)
 {
-    if (self->buf == NULL)
+    if (self->buf == NULL) {
         Py_RETURN_TRUE;
-    else
+    }
+    else {
         Py_RETURN_FALSE;
+    }
 }
 
 /* Generic getter for the writable, readable and seekable properties */
@@ -532,22 +538,22 @@
 static PyObject *
 bytesio_write(BytesIOObject *self, PyObject *obj)
 {
-    const char *bytes;
-    Py_ssize_t size;
     Py_ssize_t n = 0;
+    Py_buffer buf;
+    PyObject *result = NULL;
 
     CHECK_CLOSED(self);
 
-    if (PyObject_AsReadBuffer(obj, (void *)&bytes, &size) < 0)
+    if (PyObject_GetBuffer(obj, &buf, PyBUF_CONTIG_RO) < 0)
         return NULL;
 
-    if (size != 0) {
-        n = write_bytes(self, bytes, size);
-        if (n < 0)
-            return NULL;
-    }
+    if (buf.len != 0)
+        n = write_bytes(self, buf.buf, buf.len);
+    if (n >= 0)
+        result = PyLong_FromSsize_t(n);
 
-    return PyLong_FromSsize_t(n);
+    PyBuffer_Release(&buf);
+    return result;
 }
 
 PyDoc_STRVAR(writelines_doc,
@@ -607,6 +613,7 @@
         PyMem_Free(self->buf);
         self->buf = NULL;
     }
+    Py_TYPE(self)->tp_clear((PyObject *)self);
     Py_TYPE(self)->tp_free(self);
 }
 
@@ -656,6 +663,24 @@
     return 0;
 }
 
+static int
+bytesio_traverse(BytesIOObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->dict);
+    Py_VISIT(self->weakreflist);
+    return 0;
+}
+
+static int
+bytesio_clear(BytesIOObject *self)
+{
+    Py_CLEAR(self->dict);
+    if (self->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *)self);
+    return 0;
+}
+
+
 static PyGetSetDef bytesio_getsetlist[] = {
     {"closed",  (getter)bytesio_get_closed, NULL,
      "True if the file is closed."},
@@ -689,9 +714,9 @@
 "Create a buffered I/O implementation using an in-memory bytes\n"
 "buffer, ready for reading and writing.");
 
-static PyTypeObject BytesIO_Type = {
+PyTypeObject PyBytesIO_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
-    "_bytesio._BytesIO",                       /*tp_name*/
+    "_io.BytesIO",                             /*tp_name*/
     sizeof(BytesIOObject),                     /*tp_basicsize*/
     0,                                         /*tp_itemsize*/
     (destructor)bytesio_dealloc,               /*tp_dealloc*/
@@ -709,12 +734,13 @@
     0,                                         /*tp_getattro*/
     0,                                         /*tp_setattro*/
     0,                                         /*tp_as_buffer*/
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+    Py_TPFLAGS_HAVE_GC,                        /*tp_flags*/
     bytesio_doc,                               /*tp_doc*/
-    0,                                         /*tp_traverse*/
-    0,                                         /*tp_clear*/
+    (traverseproc)bytesio_traverse,            /*tp_traverse*/
+    (inquiry)bytesio_clear,                    /*tp_clear*/
     0,                                         /*tp_richcompare*/
-    0,                                         /*tp_weaklistoffset*/
+    offsetof(BytesIOObject, weakreflist),      /*tp_weaklistoffset*/
     PyObject_SelfIter,                         /*tp_iter*/
     (iternextfunc)bytesio_iternext,            /*tp_iternext*/
     bytesio_methods,                           /*tp_methods*/
@@ -724,36 +750,8 @@
     0,                                         /*tp_dict*/
     0,                                         /*tp_descr_get*/
     0,                                         /*tp_descr_set*/
-    0,                                         /*tp_dictoffset*/
+    offsetof(BytesIOObject, dict),             /*tp_dictoffset*/
     (initproc)bytesio_init,                    /*tp_init*/
     0,                                         /*tp_alloc*/
     bytesio_new,                               /*tp_new*/
 };
-
-
-static struct PyModuleDef _bytesiomodule = {
-	PyModuleDef_HEAD_INIT,
-	"_bytesio",
-	NULL,
-	-1,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL
-};
-
-PyMODINIT_FUNC
-PyInit__bytesio(void)
-{
-    PyObject *m;
-
-    if (PyType_Ready(&BytesIO_Type) < 0)
-        return NULL;
-    m = PyModule_Create(&_bytesiomodule);
-    if (m == NULL)
-        return NULL;
-    Py_INCREF(&BytesIO_Type);
-    PyModule_AddObject(m, "_BytesIO", (PyObject *)&BytesIO_Type);
-    return m;
-}
diff --git a/Modules/_fileio.c b/Modules/_fileio.c
index 1ed6417..d6c14c6 100644
--- a/Modules/_fileio.c
+++ b/Modules/_fileio.c
@@ -6,6 +6,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <stddef.h> /* For offsetof */
+#include "_iomodule.h"
 
 /*
  * Known likely problems:
@@ -49,14 +50,19 @@
 	int seekable : 2; /* -1 means unknown */
 	int closefd : 1;
 	PyObject *weakreflist;
+	PyObject *dict;
 } PyFileIOObject;
 
 PyTypeObject PyFileIO_Type;
 
 #define PyFileIO_Check(op) (PyObject_TypeCheck((op), &PyFileIO_Type))
 
-static PyObject *
-portable_lseek(int fd, PyObject *posobj, int whence);
+
+int
+_PyFileIO_closed(PyObject *self)
+{
+	return ((PyFileIOObject *)self)->fd < 0;
+}
 
 /* Returns 0 on success, -1 with exception set on failure. */
 static int
@@ -88,14 +94,18 @@
 		self->fd = -1;
 		Py_RETURN_NONE;
 	}
-	if (internal_close(self))
+	errno = internal_close(self);
+	if (errno < 0) {
+		PyErr_SetFromErrno(PyExc_IOError);
 		return NULL;
+	}
 
-	Py_RETURN_NONE;
+	return PyObject_CallMethod((PyObject*)&PyRawIOBase_Type,
+				   "close", "O", self);
 }
 
 static PyObject *
-fileio_new(PyTypeObject *type, PyObject *args, PyObject *kews)
+fileio_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 {
 	PyFileIOObject *self;
 
@@ -119,7 +129,7 @@
    directories, so we need a check.  */
 
 static int
-dircheck(PyFileIOObject* self, char *name)
+dircheck(PyFileIOObject* self, const char *name)
 {
 #if defined(HAVE_FSTAT) && defined(S_IFDIR) && defined(EISDIR)
 	struct stat buf;
@@ -146,7 +156,7 @@
 {
 #if defined(HAVE_FSTAT)
 	struct stat buf;
-	if (!_PyVerify_fd(fd) || (fstat(fd, &buf) < 0 && errno == EBADF)) {
+	if (fstat(fd, &buf) < 0 && errno == EBADF) {
 		PyObject *exc;
 		char *msg = strerror(EBADF);
 		exc = PyObject_CallFunction(PyExc_OSError, "(is)",
@@ -165,7 +175,8 @@
 {
 	PyFileIOObject *self = (PyFileIOObject *) oself;
 	static char *kwlist[] = {"file", "mode", "closefd", NULL};
-	char *name = NULL;
+	const char *name = NULL;
+	PyObject *nameobj;
 	char *mode = "r";
 	char *s;
 #ifdef MS_WINDOWS
@@ -184,42 +195,58 @@
 			return -1;
 	}
 
-	if (PyArg_ParseTupleAndKeywords(args, kwds, "i|si:fileio",
-					kwlist, &fd, &mode, &closefd)) {
-		if (fd < 0) {
+	if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|si:fileio",
+					 kwlist, &nameobj, &mode, &closefd))
+		return -1;
+
+	if (PyFloat_Check(nameobj)) {
+		PyErr_SetString(PyExc_TypeError,
+				"integer argument expected, got float");
+		return -1;
+	}
+
+	fd = PyLong_AsLong(nameobj);
+	if (fd < 0) {
+		if (!PyErr_Occurred()) {
 			PyErr_SetString(PyExc_ValueError,
 					"Negative filedescriptor");
 			return -1;
 		}
-		if (check_fd(fd))
-			return -1;
-	}
-	else {
 		PyErr_Clear();
+	}
 
 #ifdef Py_WIN_WIDE_FILENAMES
-	    if (GetVersion() < 0x80000000) {
+	if (GetVersion() < 0x80000000) {
 		/* On NT, so wide API available */
-		PyObject *po;
-		if (PyArg_ParseTupleAndKeywords(args, kwds, "U|si:fileio",
-						kwlist, &po, &mode, &closefd)
-						) {
-			widename = PyUnicode_AS_UNICODE(po);
-		} else {
-			/* Drop the argument parsing error as narrow
-			   strings are also valid. */
-			PyErr_Clear();
-		}
-	    }
-	    if (widename == NULL)
+		if (PyUnicode_Check(nameobj))
+			widename = PyUnicode_AS_UNICODE(nameobj);
+	}
+	if (widename == NULL)
 #endif
-	    {
-		if (!PyArg_ParseTupleAndKeywords(args, kwds, "et|si:fileio",
-						 kwlist,
-						 Py_FileSystemDefaultEncoding,
-						 &name, &mode, &closefd))
-			return -1;
-	    }
+	if (fd < 0)
+	{
+		if (PyBytes_Check(nameobj) || PyByteArray_Check(nameobj)) {
+			if (PyObject_AsCharBuffer(nameobj, &name, NULL) < 0)
+				return -1;
+		}
+		else {
+			PyObject *s;
+			PyObject *u = PyUnicode_FromObject(nameobj);
+
+			if (u == NULL)
+				return -1;
+
+			s = PyUnicode_AsEncodedString(
+				u, Py_FileSystemDefaultEncoding, NULL);
+			Py_DECREF(u);
+			if (s == NULL)
+				return -1;
+			if (!PyBytes_Check(s)) {
+				PyErr_SetString(PyExc_TypeError,
+						"encoder failed to return bytes");
+			}
+			name = PyBytes_AS_STRING(s);
+		}
 	}
 
 	s = mode;
@@ -287,6 +314,8 @@
 	if (fd >= 0) {
 		self->fd = fd;
 		self->closefd = closefd;
+		if (check_fd(fd))
+			goto error;
 	}
 	else {
 		self->closefd = 1;
@@ -318,15 +347,8 @@
 			goto error;
 	}
 
-	if (append) {
-		/* For consistent behaviour, we explicitly seek to the
-		   end of file (otherwise, it might be done only on the
-		   first write()). */
-		PyObject *pos = portable_lseek(self->fd, NULL, 2);
-		if (pos == NULL)
-			goto error;
-		Py_DECREF(pos);
-	}
+	if (PyObject_SetAttrString((PyObject *)self, "name", nameobj) < 0)
+		goto error;
 
 	goto done;
 
@@ -334,21 +356,32 @@
 	ret = -1;
 
  done:
-	PyMem_Free(name);
 	return ret;
 }
 
+static int
+fileio_traverse(PyFileIOObject *self, visitproc visit, void *arg)
+{
+	Py_VISIT(self->dict);
+	return 0;
+}
+
+static int
+fileio_clear(PyFileIOObject *self)
+{
+	Py_CLEAR(self->dict);
+	return 0;
+}
+
 static void
 fileio_dealloc(PyFileIOObject *self)
 {
+	if (_PyIOBase_finalize((PyObject *) self) < 0)
+		return;
+	_PyObject_GC_UNTRACK(self);
 	if (self->weakreflist != NULL)
 		PyObject_ClearWeakRefs((PyObject *) self);
-
-	if (self->fd >= 0 && self->closefd) {
-		if(internal_close(self))
-			PyErr_WriteUnraisable((PyObject*)self);
-	}
-
+	Py_CLEAR(self->dict);
 	Py_TYPE(self)->tp_free((PyObject *)self);
 }
 
@@ -437,6 +470,31 @@
 	return PyLong_FromSsize_t(n);
 }
 
+static size_t
+new_buffersize(PyFileIOObject *self, size_t currentsize)
+{
+#ifdef HAVE_FSTAT
+	off_t pos, end;
+	struct stat st;
+	if (fstat(self->fd, &st) == 0) {
+		end = st.st_size;
+		pos = lseek(self->fd, 0L, SEEK_CUR);
+		if (end >= pos && pos >= 0)
+			return currentsize + end - pos + 1;
+		/* Add 1 so if the file were to grow we'd notice. */
+	}
+#endif
+	if (currentsize > SMALLCHUNK) {
+		/* Keep doubling until we reach BIGCHUNK;
+		   then keep adding BIGCHUNK. */
+		if (currentsize <= BIGCHUNK)
+			return currentsize + currentsize;
+		else
+			return currentsize + BIGCHUNK;
+	}
+	return currentsize + SMALLCHUNK;
+}
+
 static PyObject *
 fileio_readall(PyFileIOObject *self)
 {
@@ -449,17 +507,7 @@
 		return NULL;
 
 	while (1) {
-		Py_ssize_t newsize = (total < SMALLCHUNK) ? SMALLCHUNK : total;
-
-		/* Keep doubling until we reach BIGCHUNK;
-		   then keep adding BIGCHUNK. */
-		if (newsize <= BIGCHUNK) {
-			newsize += newsize;
-		}
-		else {
-			/* NOTE: overflow impossible due to limits on BUFSIZ */
-			newsize += BIGCHUNK;
-		}
+		Py_ssize_t newsize = new_buffersize(self, total);
 
 		if (PyBytes_GET_SIZE(result) < newsize) {
 			if (_PyBytes_Resize(&result, newsize) < 0) {
@@ -583,12 +631,6 @@
 
 /* XXX Windows support below is likely incomplete */
 
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
-typedef PY_LONG_LONG Py_off_t;
-#else
-typedef off_t Py_off_t;
-#endif
-
 /* Cribbed from posix_lseek() */
 static PyObject *
 portable_lseek(int fd, PyObject *posobj, int whence)
@@ -755,9 +797,9 @@
 fileio_repr(PyFileIOObject *self)
 {
         if (self->fd < 0)
-		return PyUnicode_FromFormat("_fileio._FileIO(-1)");
+		return PyUnicode_FromFormat("io.FileIO(-1)");
 
-	return PyUnicode_FromFormat("_fileio._FileIO(%d, '%s')",
+	return PyUnicode_FromFormat("io.FileIO(%d, '%s')",
 				   self->fd, mode_string(self));
 }
 
@@ -899,15 +941,15 @@
 };
 
 PyTypeObject PyFileIO_Type = {
-	PyVarObject_HEAD_INIT(&PyType_Type, 0)
-	"_FileIO",
+	PyVarObject_HEAD_INIT(NULL, 0)
+	"FileIO",
 	sizeof(PyFileIOObject),
 	0,
 	(destructor)fileio_dealloc,		/* tp_dealloc */
 	0,					/* tp_print */
 	0,					/* tp_getattr */
 	0,					/* tp_setattr */
-	0,					/* tp_reserved */
+	0,					/* tp_compare */
 	(reprfunc)fileio_repr,			/* tp_repr */
 	0,					/* tp_as_number */
 	0,					/* tp_as_sequence */
@@ -918,10 +960,11 @@
 	PyObject_GenericGetAttr,		/* tp_getattro */
 	0,					/* tp_setattro */
 	0,					/* tp_as_buffer */
-	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /* tp_flags */
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+			| Py_TPFLAGS_HAVE_GC,	/* tp_flags */
 	fileio_doc,				/* tp_doc */
-	0,					/* tp_traverse */
-	0,					/* tp_clear */
+	(traverseproc)fileio_traverse,		/* tp_traverse */
+	(inquiry)fileio_clear,			/* tp_clear */
 	0,					/* tp_richcompare */
 	offsetof(PyFileIOObject, weakreflist),	/* tp_weaklistoffset */
 	0,					/* tp_iter */
@@ -933,40 +976,9 @@
 	0,					/* tp_dict */
 	0,					/* tp_descr_get */
 	0,					/* tp_descr_set */
-	0,					/* tp_dictoffset */
+	offsetof(PyFileIOObject, dict),         /* tp_dictoffset */
 	fileio_init,				/* tp_init */
 	PyType_GenericAlloc,			/* tp_alloc */
 	fileio_new,				/* tp_new */
-	PyObject_Del,				/* tp_free */
+	PyObject_GC_Del,			/* tp_free */
 };
-
-static PyMethodDef module_methods[] = {
-	{NULL, NULL}
-};
-
-static struct PyModuleDef fileiomodule = {
-	PyModuleDef_HEAD_INIT,
-	"_fileio",
-	"Fast implementation of io.FileIO.",
-	-1,
-	module_methods,
-	NULL,
-	NULL,
-	NULL,
-	NULL
-};
-
-PyMODINIT_FUNC
-PyInit__fileio(void)
-{
-	PyObject *m;	/* a module object */
-
-	m = PyModule_Create(&fileiomodule);
-	if (m == NULL)
-		return NULL;
-	if (PyType_Ready(&PyFileIO_Type) < 0)
-		return NULL;
-	Py_INCREF(&PyFileIO_Type);
-	PyModule_AddObject(m, "_FileIO", (PyObject *) &PyFileIO_Type);
-	return m;
-}
diff --git a/Modules/_iobase.c b/Modules/_iobase.c
new file mode 100644
index 0000000..9ee2326
--- /dev/null
+++ b/Modules/_iobase.c
@@ -0,0 +1,905 @@
+/*
+    An implementation of the I/O abstract base classes hierarchy
+    as defined by PEP 3116 - "New I/O"
+    
+    Classes defined here: IOBase, RawIOBase.
+    
+    Written by Amaury Forgeot d'Arc and Antoine Pitrou
+*/
+
+
+#define PY_SSIZE_T_CLEAN
+#include "Python.h"
+#include "structmember.h"
+#include "_iomodule.h"
+
+/*
+ * IOBase class, an abstract class
+ */
+
+typedef struct {
+    PyObject_HEAD
+    
+    PyObject *dict;
+    PyObject *weakreflist;
+} IOBaseObject;
+
+PyDoc_STRVAR(IOBase_doc,
+    "The abstract base class for all I/O classes, acting on streams of\n"
+    "bytes. There is no public constructor.\n"
+    "\n"
+    "This class provides dummy implementations for many methods that\n"
+    "derived classes can override selectively; the default implementations\n"
+    "represent a file that cannot be read, written or seeked.\n"
+    "\n"
+    "Even though IOBase does not declare read, readinto, or write because\n"
+    "their signatures will vary, implementations and clients should\n"
+    "consider those methods part of the interface. Also, implementations\n"
+    "may raise a IOError when operations they do not support are called.\n"
+    "\n"
+    "The basic type used for binary data read from or written to a file is\n"
+    "bytes. bytearrays are accepted too, and in some cases (such as\n"
+    "readinto) needed. Text I/O classes work with str data.\n"
+    "\n"
+    "Note that calling any method (even inquiries) on a closed stream is\n"
+    "undefined. Implementations may raise IOError in this case.\n"
+    "\n"
+    "IOBase (and its subclasses) support the iterator protocol, meaning\n"
+    "that an IOBase object can be iterated over yielding the lines in a\n"
+    "stream.\n"
+    "\n"
+    "IOBase also supports the :keyword:`with` statement. In this example,\n"
+    "fp is closed after the suite of the with statment is complete:\n"
+    "\n"
+    "with open('spam.txt', 'r') as fp:\n"
+    "    fp.write('Spam and eggs!')\n");
+
+/* Use this macro whenever you want to check the internal `closed` status
+   of the IOBase object rather than the virtual `closed` attribute as returned
+   by whatever subclass. */
+
+#define IS_CLOSED(self) \
+    PyObject_HasAttrString(self, "__IOBase_closed")
+
+/* Internal methods */
+static PyObject *
+IOBase_unsupported(const char *message)
+{
+    PyErr_SetString(IO_STATE->unsupported_operation, message);
+    return NULL;
+}
+
+/* Positionning */
+
+PyDoc_STRVAR(IOBase_seek_doc,
+    "Change stream position.\n"
+    "\n"
+    "Change the stream position to byte offset offset. offset is\n"
+    "interpreted relative to the position indicated by whence.  Values\n"
+    "for whence are:\n"
+    "\n"
+    "* 0 -- start of stream (the default); offset should be zero or positive\n"
+    "* 1 -- current stream position; offset may be negative\n"
+    "* 2 -- end of stream; offset is usually negative\n"
+    "\n"
+    "Return the new absolute position.");
+
+static PyObject *
+IOBase_seek(PyObject *self, PyObject *args)
+{
+    return IOBase_unsupported("seek");
+}
+
+PyDoc_STRVAR(IOBase_tell_doc,
+             "Return current stream position.");
+
+static PyObject *
+IOBase_tell(PyObject *self, PyObject *args)
+{
+    return PyObject_CallMethod(self, "seek", "ii", 0, 1);
+}
+
+PyDoc_STRVAR(IOBase_truncate_doc,
+    "Truncate file to size bytes.\n"
+    "\n"
+    "Size defaults to the current IO position as reported by tell().  Return\n"
+    "the new size.");
+
+static PyObject *
+IOBase_truncate(PyObject *self, PyObject *args)
+{
+    return IOBase_unsupported("truncate");
+}
+
+/* Flush and close methods */
+
+PyDoc_STRVAR(IOBase_flush_doc,
+    "Flush write buffers, if applicable.\n"
+    "\n"
+    "This is not implemented for read-only and non-blocking streams.\n");
+
+static PyObject *
+IOBase_flush(PyObject *self, PyObject *args)
+{
+    /* XXX Should this return the number of bytes written??? */
+    if (IS_CLOSED(self)) {
+        PyErr_SetString(PyExc_ValueError, "I/O operation on closed file.");
+        return NULL;
+    }
+    Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(IOBase_close_doc,
+    "Flush and close the IO object.\n"
+    "\n"
+    "This method has no effect if the file is already closed.\n");
+
+static int
+IOBase_closed(PyObject *self)
+{
+    PyObject *res;
+    int closed;
+    /* This gets the derived attribute, which is *not* __IOBase_closed
+       in most cases! */
+    res = PyObject_GetAttr(self, _PyIO_str_closed);
+    if (res == NULL)
+        return 0;
+    closed = PyObject_IsTrue(res);
+    Py_DECREF(res);
+    return closed;
+}
+
+static PyObject *
+IOBase_closed_get(PyObject *self, void *context)
+{
+    return PyBool_FromLong(IS_CLOSED(self));
+}
+
+PyObject *
+_PyIOBase_checkClosed(PyObject *self, PyObject *args)
+{
+    if (IOBase_closed(self)) {
+        PyErr_SetString(PyExc_ValueError, "I/O operation on closed file.");
+        return NULL;
+    }
+    if (args == Py_True)
+        return Py_None;
+    else
+        Py_RETURN_NONE;
+}
+
+/* XXX: IOBase thinks it has to maintain its own internal state in
+   `__IOBase_closed` and call flush() by itself, but it is redundant with
+   whatever behaviour a non-trivial derived class will implement. */
+
+static PyObject *
+IOBase_close(PyObject *self, PyObject *args)
+{
+    PyObject *res;
+
+    if (IS_CLOSED(self))
+        Py_RETURN_NONE;
+
+    res = PyObject_CallMethodObjArgs(self, _PyIO_str_flush, NULL);
+    PyObject_SetAttrString(self, "__IOBase_closed", Py_True);
+    if (res == NULL) {
+        /* If flush() fails, just give up */
+        if (PyErr_ExceptionMatches(PyExc_IOError))
+            PyErr_Clear();
+        else
+            return NULL;
+    }
+    Py_XDECREF(res);
+    Py_RETURN_NONE;
+}
+
+/* Finalization and garbage collection support */
+
+int
+_PyIOBase_finalize(PyObject *self)
+{
+    PyObject *res;
+    PyObject *tp, *v, *tb;
+    int closed = 1;
+    int is_zombie;
+
+    /* If _PyIOBase_finalize() is called from a destructor, we need to
+       resurrect the object as calling close() can invoke arbitrary code. */
+    is_zombie = (Py_REFCNT(self) == 0);
+    if (is_zombie) {
+        ++Py_REFCNT(self);
+    }
+    PyErr_Fetch(&tp, &v, &tb);
+    /* If `closed` doesn't exist or can't be evaluated as bool, then the
+       object is probably in an unusable state, so ignore. */
+    res = PyObject_GetAttr(self, _PyIO_str_closed);
+    if (res == NULL)
+        PyErr_Clear();
+    else {
+        closed = PyObject_IsTrue(res);
+        Py_DECREF(res);
+        if (closed == -1)
+            PyErr_Clear();
+    }
+    if (closed == 0) {
+        res = PyObject_CallMethodObjArgs((PyObject *) self, _PyIO_str_close,
+                                          NULL);
+        /* Silencing I/O errors is bad, but printing spurious tracebacks is
+           equally as bad, and potentially more frequent (because of
+           shutdown issues). */
+        if (res == NULL)
+            PyErr_Clear();
+        else
+            Py_DECREF(res);
+    }
+    PyErr_Restore(tp, v, tb);
+    if (is_zombie) {
+        if (--Py_REFCNT(self) != 0) {
+            /* The object lives again. The following code is taken from
+               slot_tp_del in typeobject.c. */
+            Py_ssize_t refcnt = Py_REFCNT(self);
+            _Py_NewReference(self);
+            Py_REFCNT(self) = refcnt;
+            /* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
+             * we need to undo that. */
+            _Py_DEC_REFTOTAL;
+            /* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
+             * chain, so no more to do there.
+             * If COUNT_ALLOCS, the original decref bumped tp_frees, and
+             * _Py_NewReference bumped tp_allocs:  both of those need to be
+             * undone.
+             */
+#ifdef COUNT_ALLOCS
+            --Py_TYPE(self)->tp_frees;
+            --Py_TYPE(self)->tp_allocs;
+#endif
+            return -1;
+        }
+    }
+    return 0;
+}
+
+static int
+IOBase_traverse(IOBaseObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->dict);
+    return 0;
+}
+
+static int
+IOBase_clear(IOBaseObject *self)
+{
+    if (_PyIOBase_finalize((PyObject *) self) < 0)
+        return -1;
+    Py_CLEAR(self->dict);
+    return 0;
+}
+
+/* Destructor */
+
+static void
+IOBase_dealloc(IOBaseObject *self)
+{
+    /* NOTE: since IOBaseObject has its own dict, Python-defined attributes
+       are still available here for close() to use.
+       However, if the derived class declares a __slots__, those slots are
+       already gone.
+    */
+    if (_PyIOBase_finalize((PyObject *) self) < 0) {
+        /* When called from a heap type's dealloc, the type will be
+           decref'ed on return (see e.g. subtype_dealloc in typeobject.c). */
+        if (PyType_HasFeature(Py_TYPE(self), Py_TPFLAGS_HEAPTYPE))
+            Py_INCREF(Py_TYPE(self));
+        return;
+    }
+    _PyObject_GC_UNTRACK(self);
+    if (self->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *) self);
+    Py_CLEAR(self->dict);
+    Py_TYPE(self)->tp_free((PyObject *) self);
+}
+
+/* Inquiry methods */
+
+PyDoc_STRVAR(IOBase_seekable_doc,
+    "Return whether object supports random access.\n"
+    "\n"
+    "If False, seek(), tell() and truncate() will raise IOError.\n"
+    "This method may need to do a test seek().");
+
+static PyObject *
+IOBase_seekable(PyObject *self, PyObject *args)
+{
+    Py_RETURN_FALSE;
+}
+
+PyObject *
+_PyIOBase_checkSeekable(PyObject *self, PyObject *args)
+{
+    PyObject *res  = PyObject_CallMethodObjArgs(self, _PyIO_str_seekable, NULL);
+    if (res == NULL)
+        return NULL;
+    if (res != Py_True) {
+        Py_CLEAR(res);
+        PyErr_SetString(PyExc_IOError, "File or stream is not seekable.");
+        return NULL;
+    }
+    if (args == Py_True) {
+        Py_DECREF(res);
+    }
+    return res;
+}
+
+PyDoc_STRVAR(IOBase_readable_doc,
+    "Return whether object was opened for reading.\n"
+    "\n"
+    "If False, read() will raise IOError.");
+
+static PyObject *
+IOBase_readable(PyObject *self, PyObject *args)
+{
+    Py_RETURN_FALSE;
+}
+
+/* May be called with any object */
+PyObject *
+_PyIOBase_checkReadable(PyObject *self, PyObject *args)
+{
+    PyObject *res  = PyObject_CallMethodObjArgs(self, _PyIO_str_readable, NULL);
+    if (res == NULL)
+        return NULL;
+    if (res != Py_True) {
+        Py_CLEAR(res);
+        PyErr_SetString(PyExc_IOError, "File or stream is not readable.");
+        return NULL;
+    }
+    if (args == Py_True) {
+        Py_DECREF(res);
+    }
+    return res;
+}
+
+PyDoc_STRVAR(IOBase_writable_doc,
+    "Return whether object was opened for writing.\n"
+    "\n"
+    "If False, read() will raise IOError.");
+
+static PyObject *
+IOBase_writable(PyObject *self, PyObject *args)
+{
+    Py_RETURN_FALSE;
+}
+
+/* May be called with any object */
+PyObject *
+_PyIOBase_checkWritable(PyObject *self, PyObject *args)
+{
+    PyObject *res  = PyObject_CallMethodObjArgs(self, _PyIO_str_writable, NULL);
+    if (res == NULL)
+        return NULL;
+    if (res != Py_True) {
+        Py_CLEAR(res);
+        PyErr_SetString(PyExc_IOError, "File or stream is not writable.");
+        return NULL;
+    }
+    if (args == Py_True) {
+        Py_DECREF(res);
+    }
+    return res;
+}
+
+/* Context manager */
+
+static PyObject *
+IOBase_enter(PyObject *self, PyObject *args)
+{
+    if (_PyIOBase_checkClosed(self, Py_True) == NULL)
+        return NULL;
+
+    Py_INCREF(self);
+    return self;
+}
+
+static PyObject *
+IOBase_exit(PyObject *self, PyObject *args)
+{
+    return PyObject_CallMethodObjArgs(self, _PyIO_str_close, NULL);
+}
+
+/* Lower-level APIs */
+
+/* XXX Should these be present even if unimplemented? */
+
+PyDoc_STRVAR(IOBase_fileno_doc,
+    "Returns underlying file descriptor if one exists.\n"
+    "\n"
+    "An IOError is raised if the IO object does not use a file descriptor.\n");
+
+static PyObject *
+IOBase_fileno(PyObject *self, PyObject *args)
+{
+    return IOBase_unsupported("fileno");
+}
+
+PyDoc_STRVAR(IOBase_isatty_doc,
+    "Return whether this is an 'interactive' stream.\n"
+    "\n"
+    "Return False if it can't be determined.\n");
+
+static PyObject *
+IOBase_isatty(PyObject *self, PyObject *args)
+{
+    if (_PyIOBase_checkClosed(self, Py_True) == NULL)
+        return NULL;
+    Py_RETURN_FALSE;
+}
+
+/* Readline(s) and writelines */
+
+PyDoc_STRVAR(IOBase_readline_doc,
+    "Read and return a line from the stream.\n"
+    "\n"
+    "If limit is specified, at most limit bytes will be read.\n"
+    "\n"
+    "The line terminator is always b'\n' for binary files; for text\n"
+    "files, the newlines argument to open can be used to select the line\n"
+    "terminator(s) recognized.\n");
+
+static PyObject *
+IOBase_readline(PyObject *self, PyObject *args)
+{
+    /* For backwards compatibility, a (slowish) readline(). */
+
+    Py_ssize_t limit = -1;
+    int has_peek = 0;
+    PyObject *buffer, *result;
+    Py_ssize_t old_size = -1;
+
+    if (!PyArg_ParseTuple(args, "|n:readline", &limit)) {
+        return NULL;
+    }
+
+    if (_PyIOBase_checkClosed(self, Py_True) == NULL)
+        return NULL;
+
+    if (PyObject_HasAttrString(self, "peek"))
+        has_peek = 1;
+
+    buffer = PyByteArray_FromStringAndSize(NULL, 0);
+    if (buffer == NULL)
+        return NULL;
+
+    while (limit < 0 || Py_SIZE(buffer) < limit) {
+        Py_ssize_t nreadahead = 1;
+        PyObject *b;
+
+        if (has_peek) {
+            PyObject *readahead = PyObject_CallMethod(self, "peek", "i", 1);
+            if (readahead == NULL)
+                goto fail;
+            if (!PyBytes_Check(readahead)) {
+                PyErr_Format(PyExc_IOError,
+                             "peek() should have returned a bytes object, "
+                             "not '%.200s'", Py_TYPE(readahead)->tp_name);
+                Py_DECREF(readahead);
+                goto fail;
+            }
+            if (PyBytes_GET_SIZE(readahead) > 0) {
+                Py_ssize_t n = 0;
+                const char *buf = PyBytes_AS_STRING(readahead);
+                if (limit >= 0) {
+                    do {
+                        if (n >= PyBytes_GET_SIZE(readahead) || n >= limit)
+                            break;
+                        if (buf[n++] == '\n')
+                            break;
+                    } while (1);
+                }
+                else {
+                    do {
+                        if (n >= PyBytes_GET_SIZE(readahead))
+                            break;
+                        if (buf[n++] == '\n')
+                            break;
+                    } while (1);
+                }
+                nreadahead = n;
+            }
+            Py_DECREF(readahead);
+        }
+
+        b = PyObject_CallMethod(self, "read", "n", nreadahead);
+        if (b == NULL)
+            goto fail;
+        if (!PyBytes_Check(b)) {
+            PyErr_Format(PyExc_IOError,
+                         "read() should have returned a bytes object, "
+                         "not '%.200s'", Py_TYPE(b)->tp_name);
+            Py_DECREF(b);
+            goto fail;
+        }
+        if (PyBytes_GET_SIZE(b) == 0) {
+            Py_DECREF(b);
+            break;
+        }
+
+        old_size = PyByteArray_GET_SIZE(buffer);
+        PyByteArray_Resize(buffer, old_size + PyBytes_GET_SIZE(b));
+        memcpy(PyByteArray_AS_STRING(buffer) + old_size,
+               PyBytes_AS_STRING(b), PyBytes_GET_SIZE(b));
+
+        Py_DECREF(b);
+
+        if (PyByteArray_AS_STRING(buffer)[PyByteArray_GET_SIZE(buffer) - 1] == '\n')
+            break;
+    }
+
+    result = PyBytes_FromStringAndSize(PyByteArray_AS_STRING(buffer),
+                                       PyByteArray_GET_SIZE(buffer));
+    Py_DECREF(buffer);
+    return result;
+  fail:
+    Py_DECREF(buffer);
+    return NULL;
+}
+
+static PyObject *
+IOBase_iter(PyObject *self)
+{
+    if (_PyIOBase_checkClosed(self, Py_True) == NULL)
+        return NULL;
+
+    Py_INCREF(self);
+    return self;
+}
+
+static PyObject *
+IOBase_iternext(PyObject *self)
+{
+    PyObject *line = PyObject_CallMethodObjArgs(self, _PyIO_str_readline, NULL);
+
+    if (line == NULL)
+        return NULL;
+
+    if (PyObject_Size(line) == 0) {
+        Py_DECREF(line);
+        return NULL;
+    }
+
+    return line;
+}
+
+PyDoc_STRVAR(IOBase_readlines_doc,
+    "Return a list of lines from the stream.\n"
+    "\n"
+    "hint can be specified to control the number of lines read: no more\n"
+    "lines will be read if the total size (in bytes/characters) of all\n"
+    "lines so far exceeds hint.");
+
+static PyObject *
+IOBase_readlines(PyObject *self, PyObject *args)
+{
+    Py_ssize_t hint = -1, length = 0;
+    PyObject *hintobj = Py_None, *result;
+
+    if (!PyArg_ParseTuple(args, "|O:readlines", &hintobj)) {
+        return NULL;
+    }
+    if (hintobj != Py_None) {
+        hint = PyNumber_AsSsize_t(hintobj, PyExc_ValueError);
+        if (hint == -1 && PyErr_Occurred())
+            return NULL;
+    }
+
+    result = PyList_New(0);
+    if (result == NULL)
+        return NULL;
+
+    if (hint <= 0) {
+        /* XXX special-casing this made sense in the Python version in order
+           to remove the bytecode interpretation overhead, but it could
+           probably be removed here. */
+        PyObject *ret = PyObject_CallMethod(result, "extend", "O", self);
+        if (ret == NULL) {
+            Py_DECREF(result);
+            return NULL;
+        }
+        Py_DECREF(ret);
+        return result;
+    }
+
+    while (1) {
+        PyObject *line = PyIter_Next(self);
+        if (line == NULL) {
+            if (PyErr_Occurred()) {
+                Py_DECREF(result);
+                return NULL;
+            }
+            else
+                break; /* StopIteration raised */
+        }
+
+        if (PyList_Append(result, line) < 0) {
+            Py_DECREF(line);
+            Py_DECREF(result);
+            return NULL;
+        }
+        length += PyObject_Size(line);
+        Py_DECREF(line);
+
+        if (length > hint)
+            break;
+    }
+    return result;
+}
+
+static PyObject *
+IOBase_writelines(PyObject *self, PyObject *args)
+{
+    PyObject *lines, *iter, *res;
+
+    if (!PyArg_ParseTuple(args, "O:writelines", &lines)) {
+        return NULL;
+    }
+
+    if (_PyIOBase_checkClosed(self, Py_True) == NULL)
+        return NULL;
+
+    iter = PyObject_GetIter(lines);
+    if (iter == NULL)
+        return NULL;
+
+    while (1) {
+        PyObject *line = PyIter_Next(iter);
+        if (line == NULL) {
+            if (PyErr_Occurred()) {
+                Py_DECREF(iter);
+                return NULL;
+            }
+            else
+                break; /* Stop Iteration */
+        }
+
+        res = PyObject_CallMethodObjArgs(self, _PyIO_str_write, line, NULL);
+        Py_DECREF(line);
+        if (res == NULL) {
+            Py_DECREF(iter);
+            return NULL;
+        }
+        Py_DECREF(res);
+    }
+    Py_DECREF(iter);
+    Py_RETURN_NONE;
+}
+
+static PyMethodDef IOBase_methods[] = {
+    {"seek", IOBase_seek, METH_VARARGS, IOBase_seek_doc},
+    {"tell", IOBase_tell, METH_NOARGS, IOBase_tell_doc},
+    {"truncate", IOBase_truncate, METH_VARARGS, IOBase_truncate_doc},
+    {"flush", IOBase_flush, METH_NOARGS, IOBase_flush_doc},
+    {"close", IOBase_close, METH_NOARGS, IOBase_close_doc},
+
+    {"seekable", IOBase_seekable, METH_NOARGS, IOBase_seekable_doc},
+    {"readable", IOBase_readable, METH_NOARGS, IOBase_readable_doc},
+    {"writable", IOBase_writable, METH_NOARGS, IOBase_writable_doc},
+
+    {"_checkClosed",   _PyIOBase_checkClosed, METH_NOARGS},
+    {"_checkSeekable", _PyIOBase_checkSeekable, METH_NOARGS},
+    {"_checkReadable", _PyIOBase_checkReadable, METH_NOARGS},
+    {"_checkWritable", _PyIOBase_checkWritable, METH_NOARGS},
+
+    {"fileno", IOBase_fileno, METH_NOARGS, IOBase_fileno_doc},
+    {"isatty", IOBase_isatty, METH_NOARGS, IOBase_isatty_doc},
+
+    {"__enter__", IOBase_enter, METH_NOARGS},
+    {"__exit__", IOBase_exit, METH_VARARGS},
+
+    {"readline", IOBase_readline, METH_VARARGS, IOBase_readline_doc},
+    {"readlines", IOBase_readlines, METH_VARARGS, IOBase_readlines_doc},
+    {"writelines", IOBase_writelines, METH_VARARGS},
+
+    {NULL, NULL}
+};
+
+static PyGetSetDef IOBase_getset[] = {
+    {"closed", (getter)IOBase_closed_get, NULL, NULL},
+    {0}
+};
+
+
+PyTypeObject PyIOBase_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io._IOBase",              /*tp_name*/
+    sizeof(IOBaseObject),       /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    (destructor)IOBase_dealloc, /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+        | Py_TPFLAGS_HAVE_GC,   /*tp_flags*/
+    IOBase_doc,                 /* tp_doc */
+    (traverseproc)IOBase_traverse, /* tp_traverse */
+    (inquiry)IOBase_clear,      /* tp_clear */
+    0,                          /* tp_richcompare */
+    offsetof(IOBaseObject, weakreflist), /* tp_weaklistoffset */
+    IOBase_iter,                /* tp_iter */
+    IOBase_iternext,            /* tp_iternext */
+    IOBase_methods,             /* tp_methods */
+    0,                          /* tp_members */
+    IOBase_getset,              /* tp_getset */
+    0,                          /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    offsetof(IOBaseObject, dict), /* tp_dictoffset */
+    0,                          /* tp_init */
+    0,                          /* tp_alloc */
+    PyType_GenericNew,          /* tp_new */
+};
+
+
+/*
+ * RawIOBase class, Inherits from IOBase.
+ */
+PyDoc_STRVAR(RawIOBase_doc,
+             "Base class for raw binary I/O.");
+
+/*
+ * The read() method is implemented by calling readinto(); derived classes
+ * that want to support read() only need to implement readinto() as a
+ * primitive operation.  In general, readinto() can be more efficient than
+ * read().
+ *
+ * (It would be tempting to also provide an implementation of readinto() in
+ * terms of read(), in case the latter is a more suitable primitive operation,
+ * but that would lead to nasty recursion in case a subclass doesn't implement
+ * either.)
+*/
+
+static PyObject *
+RawIOBase_read(PyObject *self, PyObject *args)
+{
+    Py_ssize_t n = -1;
+    PyObject *b, *res;
+
+    if (!PyArg_ParseTuple(args, "|n:read", &n)) {
+        return NULL;
+    }
+
+    if (n < 0)
+        return PyObject_CallMethod(self, "readall", NULL);
+
+    /* TODO: allocate a bytes object directly instead and manually construct
+       a writable memoryview pointing to it. */
+    b = PyByteArray_FromStringAndSize(NULL, n);
+    if (b == NULL)
+        return NULL;
+
+    res = PyObject_CallMethodObjArgs(self, _PyIO_str_readinto, b, NULL);
+    if (res == NULL) {
+        Py_DECREF(b);
+        return NULL;
+    }
+
+    n = PyNumber_AsSsize_t(res, PyExc_ValueError);
+    Py_DECREF(res);
+    if (n == -1 && PyErr_Occurred()) {
+        Py_DECREF(b);
+        return NULL;
+    }
+
+    res = PyBytes_FromStringAndSize(PyByteArray_AsString(b), n);
+    Py_DECREF(b);
+    return res;
+}
+
+
+PyDoc_STRVAR(RawIOBase_readall_doc,
+             "Read until EOF, using multiple read() call.");
+
+static PyObject *
+RawIOBase_readall(PyObject *self, PyObject *args)
+{
+    PyObject *b = NULL;
+    Py_ssize_t cursize = 0;
+
+    while (1) {
+        Py_ssize_t length;
+        PyObject *data = PyObject_CallMethod(self, "read",
+                                             "i", DEFAULT_BUFFER_SIZE);
+
+        if (!data) {
+            Py_XDECREF(b);
+            return NULL;
+        }
+
+        if (!PyBytes_Check(data)) {
+            Py_XDECREF(b);
+            Py_DECREF(data);
+            PyErr_SetString(PyExc_TypeError, "read() should return bytes");
+            return NULL;
+        }
+
+        length = Py_SIZE(data);
+
+        if (b == NULL)
+            b = data;
+        else if (length != 0) {
+
+            _PyBytes_Resize(&b, cursize + length);
+            if (b == NULL) {
+                Py_DECREF(data);
+                return NULL;
+            }
+
+            memcpy(PyBytes_AS_STRING(b) + cursize,
+                   PyBytes_AS_STRING(data), length);
+            Py_DECREF(data);
+        }
+
+        if (length == 0)
+            break;
+    }
+
+    return b;
+
+}
+
+static PyMethodDef RawIOBase_methods[] = {
+    {"read", RawIOBase_read, METH_VARARGS},
+    {"readall", RawIOBase_readall, METH_NOARGS, RawIOBase_readall_doc},
+    {NULL, NULL}
+};
+
+PyTypeObject PyRawIOBase_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io._RawIOBase",                /*tp_name*/
+    0,                          /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    0,                          /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
+    RawIOBase_doc,              /* tp_doc */
+    0,                          /* tp_traverse */
+    0,                          /* tp_clear */
+    0,                          /* tp_richcompare */
+    0,                          /* tp_weaklistoffset */
+    0,                          /* tp_iter */
+    0,                          /* tp_iternext */
+    RawIOBase_methods,          /* tp_methods */
+    0,                          /* tp_members */
+    0,                          /* tp_getset */
+    &PyIOBase_Type,             /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    0,                          /* tp_dictoffset */
+    0,                          /* tp_init */
+    0,                          /* tp_alloc */
+    0,                          /* tp_new */
+};
diff --git a/Modules/_iomodule.h b/Modules/_iomodule.h
new file mode 100644
index 0000000..a2f2413
--- /dev/null
+++ b/Modules/_iomodule.h
@@ -0,0 +1,150 @@
+/*
+ * Declarations shared between the different parts of the io module
+ */
+
+/* ABCs */
+extern PyTypeObject PyIOBase_Type;
+extern PyTypeObject PyRawIOBase_Type;
+extern PyTypeObject PyBufferedIOBase_Type;
+extern PyTypeObject PyTextIOBase_Type;
+
+/* Concrete classes */
+extern PyTypeObject PyFileIO_Type;
+extern PyTypeObject PyBytesIO_Type;
+extern PyTypeObject PyStringIO_Type;
+extern PyTypeObject PyBufferedReader_Type;
+extern PyTypeObject PyBufferedWriter_Type;
+extern PyTypeObject PyBufferedRWPair_Type;
+extern PyTypeObject PyBufferedRandom_Type;
+extern PyTypeObject PyTextIOWrapper_Type;
+extern PyTypeObject PyIncrementalNewlineDecoder_Type;
+
+/* These functions are used as METH_NOARGS methods, are normally called
+ * with args=NULL, and return a new reference.
+ * BUT when args=Py_True is passed, they return a borrowed reference.
+ */
+extern PyObject* _PyIOBase_checkReadable(PyObject *self, PyObject *args);
+extern PyObject* _PyIOBase_checkWritable(PyObject *self, PyObject *args);
+extern PyObject* _PyIOBase_checkSeekable(PyObject *self, PyObject *args);
+extern PyObject* _PyIOBase_checkClosed(PyObject *self, PyObject *args);
+
+/* Helper for finalization.
+   This function will revive an object ready to be deallocated and try to
+   close() it. It returns 0 if the object can be destroyed, or -1 if it
+   is alive again. */
+extern int _PyIOBase_finalize(PyObject *self);
+
+/* Returns true if the given FileIO object is closed.
+   Doesn't check the argument type, so be careful! */
+extern int _PyFileIO_closed(PyObject *self);
+
+/* Shortcut to the core of the IncrementalNewlineDecoder.decode method */
+extern PyObject *_PyIncrementalNewlineDecoder_decode(
+    PyObject *self, PyObject *input, int final);
+
+/* Finds the first line ending between `start` and `end`.
+   If found, returns the index after the line ending and doesn't touch
+   `*consumed`.
+   If not found, returns -1 and sets `*consumed` to the number of characters
+   which can be safely put aside until another search.
+   
+   NOTE: for performance reasons, `end` must point to a NUL character ('\0'). 
+   Otherwise, the function will scan further and return garbage. */
+extern Py_ssize_t _PyIO_find_line_ending(
+    int translated, int universal, PyObject *readnl,
+    Py_UNICODE *start, Py_UNICODE *end, Py_ssize_t *consumed);
+
+
+#define DEFAULT_BUFFER_SIZE (8 * 1024)  /* bytes */
+
+typedef struct {
+    PyException_HEAD
+    PyObject *myerrno;
+    PyObject *strerror;
+    PyObject *filename; /* Not used, but part of the IOError object */
+    Py_ssize_t written;
+} PyBlockingIOErrorObject;
+PyObject *PyExc_BlockingIOError;
+
+/*
+ * Offset type for positioning.
+ */
+
+#if defined(MS_WIN64) || defined(MS_WINDOWS)
+
+/* Windows uses long long for offsets */
+typedef PY_LONG_LONG Py_off_t;
+# define PyLong_AsOff_t     PyLong_AsLongLong
+# define PyLong_FromOff_t   PyLong_FromLongLong
+# define PY_OFF_T_MAX       PY_LLONG_MAX
+# define PY_OFF_T_MIN       PY_LLONG_MIN
+
+#else
+
+/* Other platforms use off_t */
+typedef off_t Py_off_t;
+#if (SIZEOF_OFF_T == SIZEOF_SIZE_T)
+# define PyLong_AsOff_t     PyLong_AsSsize_t
+# define PyLong_FromOff_t   PyLong_FromSsize_t
+# define PY_OFF_T_MAX       PY_SSIZE_T_MAX
+# define PY_OFF_T_MIN       PY_SSIZE_T_MIN
+#elif (SIZEOF_OFF_T == SIZEOF_LONG_LONG)
+# define PyLong_AsOff_t     PyLong_AsLongLong
+# define PyLong_FromOff_t   PyLong_FromLongLong
+# define PY_OFF_T_MAX       PY_LLONG_MAX
+# define PY_OFF_T_MIN       PY_LLONG_MIN
+#elif (SIZEOF_OFF_T == SIZEOF_LONG)
+# define PyLong_AsOff_t     PyLong_AsLong
+# define PyLong_FromOff_t   PyLong_FromLong
+# define PY_OFF_T_MAX       LONG_MAX
+# define PY_OFF_T_MIN       LONG_MIN
+#else
+# error off_t does not match either size_t, long, or long long!
+#endif
+
+#endif
+
+extern Py_off_t PyNumber_AsOff_t(PyObject *item, PyObject *err);
+
+/* Implementation details */
+
+/* IO module structure */
+
+extern PyModuleDef _PyIO_Module;
+
+typedef struct {
+    int initialized;
+    PyObject *os_module;
+    PyObject *locale_module;
+
+    PyObject *unsupported_operation;
+} _PyIO_State;
+
+#define IO_MOD_STATE(mod) ((_PyIO_State *)PyModule_GetState(mod))
+#define IO_STATE IO_MOD_STATE(PyState_FindModule(&_PyIO_Module))
+
+extern PyObject *_PyIO_str_close;
+extern PyObject *_PyIO_str_closed;
+extern PyObject *_PyIO_str_decode;
+extern PyObject *_PyIO_str_encode;
+extern PyObject *_PyIO_str_fileno;
+extern PyObject *_PyIO_str_flush;
+extern PyObject *_PyIO_str_getstate;
+extern PyObject *_PyIO_str_isatty;
+extern PyObject *_PyIO_str_newlines;
+extern PyObject *_PyIO_str_nl;
+extern PyObject *_PyIO_str_read;
+extern PyObject *_PyIO_str_read1;
+extern PyObject *_PyIO_str_readable;
+extern PyObject *_PyIO_str_readinto;
+extern PyObject *_PyIO_str_readline;
+extern PyObject *_PyIO_str_reset;
+extern PyObject *_PyIO_str_seek;
+extern PyObject *_PyIO_str_seekable;
+extern PyObject *_PyIO_str_tell;
+extern PyObject *_PyIO_str_truncate;
+extern PyObject *_PyIO_str_writable;
+extern PyObject *_PyIO_str_write;
+
+extern PyObject *_PyIO_empty_str;
+extern PyObject *_PyIO_empty_bytes;
diff --git a/Modules/_stringio.c b/Modules/_stringio.c
index e627258..a88fcb7 100644
--- a/Modules/_stringio.c
+++ b/Modules/_stringio.c
@@ -1,8 +1,11 @@
+#define PY_SSIZE_T_CLEAN
 #include "Python.h"
+#include "structmember.h"
+#include "_iomodule.h"
 
-/* This module is a stripped down version of _bytesio.c with a Py_UNICODE
-   buffer. Most of the functionality is provided by subclassing _StringIO. */
-
+/* Implementation note: the buffer is always at least one character longer
+   than the enclosed string, for proper functioning of _PyIO_find_line_ending.
+*/
 
 typedef struct {
     PyObject_HEAD
@@ -10,8 +13,39 @@
     Py_ssize_t pos;
     Py_ssize_t string_size;
     size_t buf_size;
+
+    char ok; /* initialized? */
+    char closed;
+    char readuniversal;
+    char readtranslate;
+    PyObject *decoder;
+    PyObject *readnl;
+    PyObject *writenl;
+    
+    PyObject *dict;
+    PyObject *weakreflist;
 } StringIOObject;
 
+#define CHECK_INITIALIZED(self) \
+    if (self->ok <= 0) { \
+        PyErr_SetString(PyExc_ValueError, \
+            "I/O operation on uninitialized object"); \
+        return NULL; \
+    }
+
+#define CHECK_CLOSED(self) \
+    if (self->closed) { \
+        PyErr_SetString(PyExc_ValueError, \
+            "I/O operation on closed file"); \
+        return NULL; \
+    }
+
+PyDoc_STRVAR(stringio_doc,
+    "Text I/O implementation using an in-memory buffer.\n"
+    "\n"
+    "The initial_value argument sets the value of object.  The newline\n"
+    "argument is like the one of TextIOWrapper's constructor.");
+
 
 /* Internal routine for changing the size, in terms of characters, of the
    buffer of StringIO objects.  The caller should ensure that the 'size'
@@ -26,6 +60,8 @@
 
     assert(self->buf != NULL);
 
+    /* Reserve one more char for line ending detection. */
+    size = size + 1;
     /* For simplicity, stay in the range of the signed type. Anyway, Python
        doesn't allow strings to be longer than this. */
     if (size > PY_SSIZE_T_MAX)
@@ -67,13 +103,38 @@
     return -1;
 }
 
-/* Internal routine for writing a string of characters to the buffer of a
-   StringIO object. Returns the number of bytes wrote, or -1 on error. */
+/* Internal routine for writing a whole PyUnicode object to the buffer of a
+   StringIO object. Returns 0 on success, or -1 on error. */
 static Py_ssize_t
-write_str(StringIOObject *self, const Py_UNICODE *str, Py_ssize_t len)
+write_str(StringIOObject *self, PyObject *obj)
 {
+    Py_UNICODE *str;
+    Py_ssize_t len;
+    PyObject *decoded = NULL;
     assert(self->buf != NULL);
     assert(self->pos >= 0);
+
+    if (self->decoder != NULL) {
+        decoded = _PyIncrementalNewlineDecoder_decode(
+            self->decoder, obj, 1 /* always final */);
+    }
+    else {
+        decoded = obj;
+        Py_INCREF(decoded);
+    }
+    if (self->writenl) {
+        PyObject *translated = PyUnicode_Replace(
+            decoded, _PyIO_str_nl, self->writenl, -1);
+        Py_DECREF(decoded);
+        decoded = translated;
+    }
+    if (decoded == NULL)
+        return -1;
+
+    assert(PyUnicode_Check(decoded));
+    str = PyUnicode_AS_UNICODE(decoded);
+    len = PyUnicode_GET_SIZE(decoded);
+
     assert(len >= 0);
 
     /* This overflow check is not strictly necessary. However, it avoids us to
@@ -82,11 +143,11 @@
     if (self->pos > PY_SSIZE_T_MAX - len) {
         PyErr_SetString(PyExc_OverflowError,
                         "new position too large");
-        return -1;
+        goto fail;
     }
     if (self->pos + len > self->string_size) {
         if (resize_buffer(self, self->pos + len) < 0)
-            return -1;
+            goto fail;
     }
 
     if (self->pos > self->string_size) {
@@ -108,26 +169,47 @@
     memcpy(self->buf + self->pos, str, len * sizeof(Py_UNICODE));
     self->pos += len;
 
-    /* Set the new length of the internal string if it has changed */
+    /* Set the new length of the internal string if it has changed. */
     if (self->string_size < self->pos) {
         self->string_size = self->pos;
     }
 
-    return len;
+    Py_DECREF(decoded);
+    return 0;
+
+fail:
+    Py_XDECREF(decoded);
+    return -1;
 }
 
+PyDoc_STRVAR(stringio_getvalue_doc,
+    "Retrieve the entire contents of the object.");
+
 static PyObject *
 stringio_getvalue(StringIOObject *self)
 {
+    CHECK_INITIALIZED(self);
+    CHECK_CLOSED(self);
     return PyUnicode_FromUnicode(self->buf, self->string_size);
 }
 
+PyDoc_STRVAR(stringio_tell_doc,
+    "Tell the current file position.");
+
 static PyObject *
 stringio_tell(StringIOObject *self)
 {
+    CHECK_INITIALIZED(self);
+    CHECK_CLOSED(self);
     return PyLong_FromSsize_t(self->pos);
 }
 
+PyDoc_STRVAR(stringio_read_doc,
+    "Read at most n characters, returned as a string.\n"
+    "\n"
+    "If the argument is negative or omitted, read until EOF\n"
+    "is reached. Return an empty string at EOF.\n");
+
 static PyObject *
 stringio_read(StringIOObject *self, PyObject *args)
 {
@@ -135,11 +217,13 @@
     Py_UNICODE *output;
     PyObject *arg = Py_None;
 
+    CHECK_INITIALIZED(self);
     if (!PyArg_ParseTuple(args, "|O:read", &arg))
         return NULL;
+    CHECK_CLOSED(self);
 
-    if (PyLong_Check(arg)) {
-        size = PyLong_AsSsize_t(arg);
+    if (PyNumber_Check(arg)) {
+        size = PyNumber_AsSsize_t(arg, PyExc_OverflowError);
         if (size == -1 && PyErr_Occurred())
             return NULL;
     }
@@ -161,24 +245,127 @@
             size = 0;
     }
 
-    assert(self->buf != NULL);
     output = self->buf + self->pos;
     self->pos += size;
-
     return PyUnicode_FromUnicode(output, size);
 }
 
+/* Internal helper, used by stringio_readline and stringio_iternext */
+static PyObject *
+_stringio_readline(StringIOObject *self, Py_ssize_t limit)
+{
+    Py_UNICODE *start, *end, old_char;
+    Py_ssize_t len, consumed;
+
+    /* In case of overseek, return the empty string */
+    if (self->pos >= self->string_size)
+        return PyUnicode_FromString("");
+
+    start = self->buf + self->pos;
+    if (limit < 0 || limit > self->string_size - self->pos)
+        limit = self->string_size - self->pos;
+
+    end = start + limit;
+    old_char = *end;
+    *end = '\0';
+    len = _PyIO_find_line_ending(
+        self->readtranslate, self->readuniversal, self->readnl,
+        start, end, &consumed);
+    *end = old_char;
+    /* If we haven't found any line ending, we just return everything
+       (`consumed` is ignored). */
+    if (len < 0)
+        len = limit;
+    self->pos += len;
+    return PyUnicode_FromUnicode(start, len);
+}
+
+PyDoc_STRVAR(stringio_readline_doc,
+    "Read until newline or EOF.\n"
+    "\n"
+    "Returns an empty string if EOF is hit immediately.\n");
+
+static PyObject *
+stringio_readline(StringIOObject *self, PyObject *args)
+{
+    PyObject *arg = Py_None;
+    Py_ssize_t limit = -1;
+
+    CHECK_INITIALIZED(self);
+    if (!PyArg_ParseTuple(args, "|O:readline", &arg))
+        return NULL;
+    CHECK_CLOSED(self);
+
+    if (PyNumber_Check(arg)) {
+        limit = PyNumber_AsSsize_t(arg, PyExc_OverflowError);
+        if (limit == -1 && PyErr_Occurred())
+            return NULL;
+    }
+    else if (arg != Py_None) {
+        PyErr_Format(PyExc_TypeError, "integer argument expected, got '%s'",
+                     Py_TYPE(arg)->tp_name);
+        return NULL;
+    }
+    return _stringio_readline(self, limit);
+}
+
+static PyObject *
+stringio_iternext(StringIOObject *self)
+{
+    PyObject *line;
+
+    CHECK_INITIALIZED(self);
+    CHECK_CLOSED(self);
+
+    if (Py_TYPE(self) == &PyStringIO_Type) {
+        /* Skip method call overhead for speed */
+        line = _stringio_readline(self, -1);
+    }
+    else {
+        /* XXX is subclassing StringIO really supported? */
+        line = PyObject_CallMethodObjArgs((PyObject *)self,
+                                           _PyIO_str_readline, NULL);
+        if (line && !PyUnicode_Check(line)) {
+            PyErr_Format(PyExc_IOError,
+                         "readline() should have returned an str object, "
+                         "not '%.200s'", Py_TYPE(line)->tp_name);
+            Py_DECREF(line);
+            return NULL;
+        }
+    }
+
+    if (line == NULL)
+        return NULL;
+
+    if (PyUnicode_GET_SIZE(line) == 0) {
+        /* Reached EOF */
+        Py_DECREF(line);
+        return NULL;
+    }
+
+    return line;
+}
+
+PyDoc_STRVAR(stringio_truncate_doc,
+    "Truncate size to pos.\n"
+    "\n"
+    "The pos argument defaults to the current file position, as\n"
+    "returned by tell().  Imply an absolute seek to pos.\n"
+    "Returns the new absolute position.\n");
+
 static PyObject *
 stringio_truncate(StringIOObject *self, PyObject *args)
 {
     Py_ssize_t size;
     PyObject *arg = Py_None;
 
+    CHECK_INITIALIZED(self);
     if (!PyArg_ParseTuple(args, "|O:truncate", &arg))
         return NULL;
+    CHECK_CLOSED(self);
 
-    if (PyLong_Check(arg)) {
-        size = PyLong_AsSsize_t(arg);
+    if (PyNumber_Check(arg)) {
+        size = PyNumber_AsSsize_t(arg, PyExc_OverflowError);
         if (size == -1 && PyErr_Occurred())
             return NULL;
     }
@@ -199,23 +386,34 @@
     }
 
     if (size < self->string_size) {
-        self->string_size = size;
         if (resize_buffer(self, size) < 0)
             return NULL;
+        self->string_size = size;
     }
     self->pos = size;
 
     return PyLong_FromSsize_t(size);
 }
 
+PyDoc_STRVAR(stringio_seek_doc,
+    "Change stream position.\n"
+    "\n"
+    "Seek to character offset pos relative to position indicated by whence:\n"
+    "    0  Start of stream (the default).  pos should be >= 0;\n"
+    "    1  Current position - pos must be 0;\n"
+    "    2  End of stream - pos must be 0.\n"
+    "Returns the new absolute position.\n");
+
 static PyObject *
 stringio_seek(StringIOObject *self, PyObject *args)
 {
     Py_ssize_t pos;
     int mode = 0;
 
+    CHECK_INITIALIZED(self);
     if (!PyArg_ParseTuple(args, "n|i:seek", &pos, &mode))
         return NULL;
+    CHECK_CLOSED(self);
 
     if (mode != 0 && mode != 1 && mode != 2) {
         PyErr_Format(PyExc_ValueError,
@@ -248,36 +446,76 @@
     return PyLong_FromSsize_t(self->pos);
 }
 
+PyDoc_STRVAR(stringio_write_doc,
+    "Write string to file.\n"
+    "\n"
+    "Returns the number of characters written, which is always equal to\n"
+    "the length of the string.\n");
+
 static PyObject *
 stringio_write(StringIOObject *self, PyObject *obj)
 {
-    const Py_UNICODE *str;
     Py_ssize_t size;
-    Py_ssize_t n = 0;
 
-    if (PyUnicode_Check(obj)) {
-        str = PyUnicode_AsUnicode(obj);
-        size = PyUnicode_GetSize(obj);
-    }
-    else {
+    CHECK_INITIALIZED(self);
+    if (!PyUnicode_Check(obj)) {
         PyErr_Format(PyExc_TypeError, "string argument expected, got '%s'",
                      Py_TYPE(obj)->tp_name);
         return NULL;
     }
+    CHECK_CLOSED(self);
+    size = PyUnicode_GET_SIZE(obj);
 
-    if (size != 0) {
-        n = write_str(self, str, size);
-        if (n < 0)
-            return NULL;
-    }
+    if (size > 0 && write_str(self, obj) < 0)
+        return NULL;
 
-    return PyLong_FromSsize_t(n);
+    return PyLong_FromSsize_t(size);
+}
+
+PyDoc_STRVAR(stringio_close_doc,
+    "Close the IO object. Attempting any further operation after the\n"
+    "object is closed will raise a ValueError.\n"
+    "\n"
+    "This method has no effect if the file is already closed.\n");
+
+static PyObject *
+stringio_close(StringIOObject *self)
+{
+    self->closed = 1;
+    /* Free up some memory */
+    if (resize_buffer(self, 0) < 0)
+        return NULL;
+    Py_CLEAR(self->readnl);
+    Py_CLEAR(self->writenl);
+    Py_CLEAR(self->decoder);
+    Py_RETURN_NONE;
+}
+
+static int
+stringio_traverse(StringIOObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->dict);
+    return 0;
+}
+
+static int
+stringio_clear(StringIOObject *self)
+{
+    Py_CLEAR(self->dict);
+    return 0;
 }
 
 static void
 stringio_dealloc(StringIOObject *self)
 {
-    PyMem_Free(self->buf);
+    _PyObject_GC_UNTRACK(self);
+    Py_CLEAR(self->readnl);
+    Py_CLEAR(self->writenl);
+    Py_CLEAR(self->decoder);
+    if (self->buf)
+        PyMem_Free(self->buf);
+    if (self->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *) self);
     Py_TYPE(self)->tp_free(self);
 }
 
@@ -303,19 +541,194 @@
     return (PyObject *)self;
 }
 
+static int
+stringio_init(StringIOObject *self, PyObject *args, PyObject *kwds)
+{
+    char *kwlist[] = {"initial_value", "newline", NULL};
+    PyObject *value = NULL;
+    char *newline = "\n";
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|Oz:__init__", kwlist,
+                                     &value, &newline))
+        return -1;
+
+    if (newline && newline[0] != '\0'
+        && !(newline[0] == '\n' && newline[1] == '\0')
+        && !(newline[0] == '\r' && newline[1] == '\0')
+        && !(newline[0] == '\r' && newline[1] == '\n' && newline[2] == '\0')) {
+        PyErr_Format(PyExc_ValueError,
+                     "illegal newline value: %s", newline);
+        return -1;
+    }
+    if (value && value != Py_None && !PyUnicode_Check(value)) {
+        PyErr_Format(PyExc_ValueError,
+                     "initial_value must be str or None, not %.200s",
+                     Py_TYPE(value)->tp_name);
+        return -1;
+    }
+
+    self->ok = 0;
+
+    Py_CLEAR(self->readnl);
+    Py_CLEAR(self->writenl);
+    Py_CLEAR(self->decoder);
+
+    if (newline) {
+        self->readnl = PyUnicode_FromString(newline);
+        if (self->readnl == NULL)
+            return -1;
+    }
+    self->readuniversal = (newline == NULL || newline[0] == '\0');
+    self->readtranslate = (newline == NULL);
+    /* If newline == "", we don't translate anything.
+       If newline == "\n" or newline == None, we translate to "\n", which is
+       a no-op.
+       (for newline == None, TextIOWrapper translates to os.sepline, but it
+       is pointless for StringIO)
+    */
+    if (newline != NULL && newline[0] == '\r') {
+        self->writenl = self->readnl;
+        Py_INCREF(self->writenl);
+    }
+
+    if (self->readuniversal) {
+        self->decoder = PyObject_CallFunction(
+            (PyObject *)&PyIncrementalNewlineDecoder_Type,
+            "Oi", Py_None, (int) self->readtranslate);
+        if (self->decoder == NULL)
+            return -1;
+    }
+
+    /* Now everything is set up, resize buffer to size of initial value,
+       and copy it */
+    self->string_size = 0;
+    if (value && value != Py_None) {
+        Py_ssize_t len = PyUnicode_GetSize(value);
+        /* This is a heuristic, for newline translation might change
+           the string length. */
+        if (resize_buffer(self, len) < 0)
+            return -1;
+        self->pos = 0;
+        if (write_str(self, value) < 0)
+            return -1;
+    }
+    else {
+        if (resize_buffer(self, 0) < 0)
+            return -1;
+    }
+    self->pos = 0;
+
+    self->closed = 0;
+    self->ok = 1;
+    return 0;
+}
+
+/* Properties and pseudo-properties */
+static PyObject *
+stringio_seekable(StringIOObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self);
+    Py_RETURN_TRUE;
+}
+
+static PyObject *
+stringio_readable(StringIOObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self);
+    Py_RETURN_TRUE;
+}
+
+static PyObject *
+stringio_writable(StringIOObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self);
+    Py_RETURN_TRUE;
+}
+
+static PyObject *
+stringio_buffer(StringIOObject *self, void *context)
+{
+    PyErr_SetString(IO_STATE->unsupported_operation,
+                    "buffer attribute is unsupported on type StringIO");
+    return NULL;
+}
+
+static PyObject *
+stringio_closed(StringIOObject *self, void *context)
+{
+    CHECK_INITIALIZED(self);
+    return PyBool_FromLong(self->closed);
+}
+
+static PyObject *
+stringio_encoding(StringIOObject *self, void *context)
+{
+    CHECK_INITIALIZED(self);
+    CHECK_CLOSED(self);
+    return PyUnicode_FromString("utf-8");
+}
+
+static PyObject *
+stringio_errors(StringIOObject *self, void *context)
+{
+    CHECK_INITIALIZED(self);
+    CHECK_CLOSED(self);
+    return PyUnicode_FromString("strict");
+}
+
+static PyObject *
+stringio_line_buffering(StringIOObject *self, void *context)
+{
+    CHECK_INITIALIZED(self);
+    CHECK_CLOSED(self);
+    Py_RETURN_FALSE;
+}
+
+static PyObject *
+stringio_newlines(StringIOObject *self, void *context)
+{
+    CHECK_INITIALIZED(self);
+    CHECK_CLOSED(self);
+    if (self->decoder == NULL)
+        Py_RETURN_NONE;
+    return PyObject_GetAttr(self->decoder, _PyIO_str_newlines);
+}
+
 static struct PyMethodDef stringio_methods[] = {
-    {"getvalue",   (PyCFunction)stringio_getvalue, METH_VARARGS, NULL},
-    {"read",       (PyCFunction)stringio_read,     METH_VARARGS, NULL},
-    {"tell",       (PyCFunction)stringio_tell,     METH_NOARGS,  NULL},
-    {"truncate",   (PyCFunction)stringio_truncate, METH_VARARGS, NULL},
-    {"seek",       (PyCFunction)stringio_seek,     METH_VARARGS, NULL},
-    {"write",      (PyCFunction)stringio_write,    METH_O,       NULL},
+    {"close",    (PyCFunction)stringio_close,    METH_NOARGS,  stringio_close_doc},
+    {"getvalue", (PyCFunction)stringio_getvalue, METH_VARARGS, stringio_getvalue_doc},
+    {"read",     (PyCFunction)stringio_read,     METH_VARARGS, stringio_read_doc},
+    {"readline", (PyCFunction)stringio_readline, METH_VARARGS, stringio_readline_doc},
+    {"tell",     (PyCFunction)stringio_tell,     METH_NOARGS,  stringio_tell_doc},
+    {"truncate", (PyCFunction)stringio_truncate, METH_VARARGS, stringio_truncate_doc},
+    {"seek",     (PyCFunction)stringio_seek,     METH_VARARGS, stringio_seek_doc},
+    {"write",    (PyCFunction)stringio_write,    METH_O,       stringio_write_doc},
+    
+    {"seekable", (PyCFunction)stringio_seekable, METH_NOARGS},
+    {"readable", (PyCFunction)stringio_readable, METH_NOARGS},
+    {"writable", (PyCFunction)stringio_writable, METH_NOARGS},
     {NULL, NULL}        /* sentinel */
 };
 
-static PyTypeObject StringIO_Type = {
+static PyGetSetDef stringio_getset[] = {
+    {"closed",         (getter)stringio_closed,         NULL, NULL},
+    {"newlines",       (getter)stringio_newlines,       NULL, NULL},
+    /*  (following comments straight off of the original Python wrapper:)
+        XXX Cruft to support the TextIOWrapper API. This would only
+        be meaningful if StringIO supported the buffer attribute.
+        Hopefully, a better solution, than adding these pseudo-attributes,
+        will be found.
+    */
+    {"buffer",         (getter)stringio_buffer,         NULL, NULL},
+    {"encoding",       (getter)stringio_encoding,       NULL, NULL},
+    {"errors",         (getter)stringio_errors,         NULL, NULL},
+    {"line_buffering", (getter)stringio_line_buffering, NULL, NULL},
+    {0}
+};
+
+PyTypeObject PyStringIO_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
-    "_stringio._StringIO",                     /*tp_name*/
+    "_io.StringIO",                            /*tp_name*/
     sizeof(StringIOObject),                    /*tp_basicsize*/
     0,                                         /*tp_itemsize*/
     (destructor)stringio_dealloc,              /*tp_dealloc*/
@@ -333,51 +746,24 @@
     0,                                         /*tp_getattro*/
     0,                                         /*tp_setattro*/
     0,                                         /*tp_as_buffer*/
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
-    0,                                         /*tp_doc*/
-    0,                                         /*tp_traverse*/
-    0,                                         /*tp_clear*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+                       | Py_TPFLAGS_HAVE_GC,   /*tp_flags*/
+    stringio_doc,                              /*tp_doc*/
+    (traverseproc)stringio_traverse,           /*tp_traverse*/
+    (inquiry)stringio_clear,                   /*tp_clear*/
     0,                                         /*tp_richcompare*/
-    0,                                         /*tp_weaklistoffset*/
+    offsetof(StringIOObject, weakreflist),     /*tp_weaklistoffset*/
     0,                                         /*tp_iter*/
-    0,                                         /*tp_iternext*/
+    (iternextfunc)stringio_iternext,           /*tp_iternext*/
     stringio_methods,                          /*tp_methods*/
     0,                                         /*tp_members*/
-    0,                                         /*tp_getset*/
+    stringio_getset,                           /*tp_getset*/
     0,                                         /*tp_base*/
     0,                                         /*tp_dict*/
     0,                                         /*tp_descr_get*/
     0,                                         /*tp_descr_set*/
-    0,                                         /*tp_dictoffset*/
-    0,                                         /*tp_init*/
+    offsetof(StringIOObject, dict),            /*tp_dictoffset*/
+    (initproc)stringio_init,                   /*tp_init*/
     0,                                         /*tp_alloc*/
     stringio_new,                              /*tp_new*/
 };
-
-static struct PyModuleDef _stringiomodule = {
-	PyModuleDef_HEAD_INIT,
-	"_stringio",
-	NULL,
-	-1,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL
-};
-
-PyMODINIT_FUNC
-PyInit__stringio(void)
-{
-    PyObject *m;
-
-    if (PyType_Ready(&StringIO_Type) < 0)
-        return NULL;
-    m = PyModule_Create(&_stringiomodule);
-    if (m == NULL)
-        return NULL;
-    Py_INCREF(&StringIO_Type);
-    if (PyModule_AddObject(m, "_StringIO", (PyObject *)&StringIO_Type) < 0)
-        return NULL;
-    return m;
-}
diff --git a/Modules/_textio.c b/Modules/_textio.c
new file mode 100644
index 0000000..54bf055
--- /dev/null
+++ b/Modules/_textio.c
@@ -0,0 +1,2389 @@
+/*
+    An implementation of Text I/O as defined by PEP 3116 - "New I/O"
+    
+    Classes defined here: TextIOBase, IncrementalNewlineDecoder, TextIOWrapper.
+    
+    Written by Amaury Forgeot d'Arc and Antoine Pitrou
+*/
+
+#define PY_SSIZE_T_CLEAN
+#include "Python.h"
+#include "structmember.h"
+#include "_iomodule.h"
+
+/* TextIOBase */
+
+PyDoc_STRVAR(TextIOBase_doc,
+    "Base class for text I/O.\n"
+    "\n"
+    "This class provides a character and line based interface to stream\n"
+    "I/O. There is no readinto method because Python's character strings\n"
+    "are immutable. There is no public constructor.\n"
+    );
+
+static PyObject *
+_unsupported(const char *message)
+{
+    PyErr_SetString(IO_STATE->unsupported_operation, message);
+    return NULL;
+}
+
+PyDoc_STRVAR(TextIOBase_read_doc,
+    "Read at most n characters from stream.\n"
+    "\n"
+    "Read from underlying buffer until we have n characters or we hit EOF.\n"
+    "If n is negative or omitted, read until EOF.\n"
+    );
+
+static PyObject *
+TextIOBase_read(PyObject *self, PyObject *args)
+{
+    return _unsupported("read");
+}
+
+PyDoc_STRVAR(TextIOBase_readline_doc,
+    "Read until newline or EOF.\n"
+    "\n"
+    "Returns an empty string if EOF is hit immediately.\n"
+    );
+
+static PyObject *
+TextIOBase_readline(PyObject *self, PyObject *args)
+{
+    return _unsupported("readline");
+}
+
+PyDoc_STRVAR(TextIOBase_write_doc,
+    "Write string to stream.\n"
+    "Returns the number of characters written (which is always equal to\n"
+    "the length of the string).\n"
+    );
+
+static PyObject *
+TextIOBase_write(PyObject *self, PyObject *args)
+{
+    return _unsupported("write");
+}
+
+PyDoc_STRVAR(TextIOBase_encoding_doc,
+    "Encoding of the text stream.\n"
+    "\n"
+    "Subclasses should override.\n"
+    );
+
+static PyObject *
+TextIOBase_encoding_get(PyObject *self, void *context)
+{
+    Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(TextIOBase_newlines_doc,
+    "Line endings translated so far.\n"
+    "\n"
+    "Only line endings translated during reading are considered.\n"
+    "\n"
+    "Subclasses should override.\n"
+    );
+
+static PyObject *
+TextIOBase_newlines_get(PyObject *self, void *context)
+{
+    Py_RETURN_NONE;
+}
+
+
+static PyMethodDef TextIOBase_methods[] = {
+    {"read", TextIOBase_read, METH_VARARGS, TextIOBase_read_doc},
+    {"readline", TextIOBase_readline, METH_VARARGS, TextIOBase_readline_doc},
+    {"write", TextIOBase_write, METH_VARARGS, TextIOBase_write_doc},
+    {NULL, NULL}
+};
+
+static PyGetSetDef TextIOBase_getset[] = {
+    {"encoding", (getter)TextIOBase_encoding_get, NULL, TextIOBase_encoding_doc},
+    {"newlines", (getter)TextIOBase_newlines_get, NULL, TextIOBase_newlines_doc},
+    {0}
+};
+
+PyTypeObject PyTextIOBase_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io._TextIOBase",          /*tp_name*/
+    0,                          /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    0,                          /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
+    TextIOBase_doc,             /* tp_doc */
+    0,                          /* tp_traverse */
+    0,                          /* tp_clear */
+    0,                          /* tp_richcompare */
+    0,                          /* tp_weaklistoffset */
+    0,                          /* tp_iter */
+    0,                          /* tp_iternext */
+    TextIOBase_methods,         /* tp_methods */
+    0,                          /* tp_members */
+    TextIOBase_getset,          /* tp_getset */
+    &PyIOBase_Type,             /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    0,                          /* tp_dictoffset */
+    0,                          /* tp_init */
+    0,                          /* tp_alloc */
+    0,                          /* tp_new */
+};
+
+
+/* IncrementalNewlineDecoder */
+
+PyDoc_STRVAR(IncrementalNewlineDecoder_doc,
+    "Codec used when reading a file in universal newlines mode.  It wraps\n"
+    "another incremental decoder, translating \\r\\n and \\r into \\n.  It also\n"
+    "records the types of newlines encountered.  When used with\n"
+    "translate=False, it ensures that the newline sequence is returned in\n"
+    "one piece. When used with decoder=None, it expects unicode strings as\n"
+    "decode input and translates newlines without first invoking an external\n"
+    "decoder.\n"
+    );
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *decoder;
+    PyObject *errors;
+    int pendingcr:1;
+    int translate:1;
+    unsigned int seennl:3;
+} PyNewLineDecoderObject;
+
+static int
+IncrementalNewlineDecoder_init(PyNewLineDecoderObject *self, 
+                               PyObject *args, PyObject *kwds)
+{
+    PyObject *decoder;
+    int translate;
+    PyObject *errors = NULL;
+    char *kwlist[] = {"decoder", "translate", "errors", NULL};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "Oi|O:IncrementalNewlineDecoder",
+                                     kwlist, &decoder, &translate, &errors))
+        return -1;
+
+    self->decoder = decoder;
+    Py_INCREF(decoder);
+
+    if (errors == NULL) {
+        self->errors = PyUnicode_FromString("strict");
+        if (self->errors == NULL)
+            return -1;
+    }
+    else {
+        Py_INCREF(errors);
+        self->errors = errors;
+    }
+
+    self->translate = translate;
+    self->seennl = 0;
+    self->pendingcr = 0;
+
+    return 0;
+}
+
+static void
+IncrementalNewlineDecoder_dealloc(PyNewLineDecoderObject *self)
+{
+    Py_CLEAR(self->decoder);
+    Py_CLEAR(self->errors);
+    Py_TYPE(self)->tp_free((PyObject *)self);
+}
+
+#define SEEN_CR   1
+#define SEEN_LF   2
+#define SEEN_CRLF 4
+#define SEEN_ALL (SEEN_CR | SEEN_LF | SEEN_CRLF)
+
+PyObject *
+_PyIncrementalNewlineDecoder_decode(PyObject *_self, 
+                                    PyObject *input, int final)
+{
+    PyObject *output;
+    Py_ssize_t output_len;
+    PyNewLineDecoderObject *self = (PyNewLineDecoderObject *) _self;
+
+    if (self->decoder == NULL) {
+        PyErr_SetString(PyExc_ValueError,
+                        "IncrementalNewlineDecoder.__init__ not called");
+        return NULL;
+    }
+
+    /* decode input (with the eventual \r from a previous pass) */
+    if (self->decoder != Py_None) {
+        output = PyObject_CallMethodObjArgs(self->decoder,
+            _PyIO_str_decode, input, final ? Py_True : Py_False, NULL);
+    }
+    else {
+        output = input;
+        Py_INCREF(output);
+    }
+
+    if (output == NULL)
+        return NULL;
+
+    if (!PyUnicode_Check(output)) {
+        PyErr_SetString(PyExc_TypeError,
+                        "decoder should return a string result");
+        goto error;
+    }
+
+    output_len = PyUnicode_GET_SIZE(output);
+    if (self->pendingcr && (final || output_len > 0)) {
+        Py_UNICODE *out;
+        PyObject *modified = PyUnicode_FromUnicode(NULL, output_len + 1);
+        if (modified == NULL)
+            goto error;
+        out = PyUnicode_AS_UNICODE(modified);
+        out[0] = '\r';
+        memcpy(out + 1, PyUnicode_AS_UNICODE(output),
+               output_len * sizeof(Py_UNICODE));
+        Py_DECREF(output);
+        output = modified;
+        self->pendingcr = 0;
+        output_len++;
+    }
+
+    /* retain last \r even when not translating data:
+     * then readline() is sure to get \r\n in one pass
+     */
+    if (!final) {
+        if (output_len > 0 
+            && PyUnicode_AS_UNICODE(output)[output_len - 1] == '\r') {
+
+            if (Py_REFCNT(output) == 1) {
+                if (PyUnicode_Resize(&output, output_len - 1) < 0)
+                    goto error;
+            }
+            else {
+                PyObject *modified = PyUnicode_FromUnicode(
+                    PyUnicode_AS_UNICODE(output),
+                    output_len - 1);
+                if (modified == NULL)
+                    goto error;
+                Py_DECREF(output);
+                output = modified;
+            }
+            self->pendingcr = 1;
+        }
+    }
+
+    /* Record which newlines are read and do newline translation if desired,
+       all in one pass. */
+    {
+        Py_UNICODE *in_str;
+        Py_ssize_t len;
+        int seennl = self->seennl;
+        int only_lf = 0;
+
+        in_str = PyUnicode_AS_UNICODE(output);
+        len = PyUnicode_GET_SIZE(output);
+
+        if (len == 0)
+            return output;
+
+        /* If, up to now, newlines are consistently \n, do a quick check
+           for the \r *byte* with the libc's optimized memchr.
+           */
+        if (seennl == SEEN_LF || seennl == 0) {
+            int has_cr, has_lf;
+            has_lf = (seennl == SEEN_LF) ||
+                    (memchr(in_str, '\n', len * sizeof(Py_UNICODE)) != NULL);
+            has_cr = (memchr(in_str, '\r', len * sizeof(Py_UNICODE)) != NULL);
+            if (has_lf && !has_cr) {
+                only_lf = 1;
+                seennl = SEEN_LF;
+            }
+        }
+
+        if (!self->translate) {
+            Py_UNICODE *s, *end;
+            if (seennl == SEEN_ALL)
+                goto endscan;
+            if (only_lf)
+                goto endscan;
+            s = in_str;
+            end = in_str + len;
+            for (;;) {
+                Py_UNICODE c;
+                /* Fast loop for non-control characters */
+                while (*s > '\r')
+                    s++;
+                c = *s++;
+                if (c == '\n')
+                    seennl |= SEEN_LF;
+                else if (c == '\r') {
+                    if (*s == '\n') {
+                        seennl |= SEEN_CRLF;
+                        s++;
+                    }
+                    else
+                        seennl |= SEEN_CR;
+                }
+                if (s > end)
+                    break;
+                if (seennl == SEEN_ALL)
+                    break;
+            }
+        endscan:
+            ;
+        }
+        else if (!only_lf) {
+            PyObject *translated = NULL;
+            Py_UNICODE *out_str;
+            Py_UNICODE *in, *out, *end;
+            if (Py_REFCNT(output) != 1) {
+                /* We could try to optimize this so that we only do a copy
+                   when there is something to translate. On the other hand,
+                   most decoders should only output non-shared strings, i.e.
+                   translation is done in place. */
+                translated = PyUnicode_FromUnicode(NULL, len);
+                if (translated == NULL)
+                    goto error;
+                assert(Py_REFCNT(translated) == 1);
+                memcpy(PyUnicode_AS_UNICODE(translated),
+                       PyUnicode_AS_UNICODE(output),
+                       len * sizeof(Py_UNICODE));
+            }
+            else {
+                translated = output;
+            }
+            out_str = PyUnicode_AS_UNICODE(translated);
+            in = in_str;
+            out = out_str;
+            end = in_str + len;
+            for (;;) {
+                Py_UNICODE c;
+                /* Fast loop for non-control characters */
+                while ((c = *in++) > '\r')
+                    *out++ = c;
+                if (c == '\n') {
+                    *out++ = c;
+                    seennl |= SEEN_LF;
+                    continue;
+                }
+                if (c == '\r') {
+                    if (*in == '\n') {
+                        in++;
+                        seennl |= SEEN_CRLF;
+                    }
+                    else
+                        seennl |= SEEN_CR;
+                    *out++ = '\n';
+                    continue;
+                }
+                if (in > end)
+                    break;
+                *out++ = c;
+            }
+            if (translated != output) {
+                Py_DECREF(output);
+                output = translated;
+            }
+            if (out - out_str != len) {
+                if (PyUnicode_Resize(&output, out - out_str) < 0)
+                    goto error;
+            }
+        }
+        self->seennl |= seennl;
+    }
+
+    return output;
+
+  error:
+    Py_DECREF(output);
+    return NULL;
+}
+
+static PyObject *
+IncrementalNewlineDecoder_decode(PyNewLineDecoderObject *self, 
+                                 PyObject *args, PyObject *kwds)
+{
+    char *kwlist[] = {"input", "final", NULL};
+    PyObject *input;
+    int final = 0;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|i:IncrementalNewlineDecoder",
+                                     kwlist, &input, &final))
+        return NULL;
+    return _PyIncrementalNewlineDecoder_decode((PyObject *) self, input, final);
+}
+
+static PyObject *
+IncrementalNewlineDecoder_getstate(PyNewLineDecoderObject *self, PyObject *args)
+{
+    PyObject *buffer;
+    unsigned PY_LONG_LONG flag;
+
+    if (self->decoder != Py_None) {
+        PyObject *state = PyObject_CallMethodObjArgs(self->decoder,
+           _PyIO_str_getstate, NULL);
+        if (state == NULL)
+            return NULL;
+        if (!PyArg_Parse(state, "(OK)", &buffer, &flag)) {
+            Py_DECREF(state);
+            return NULL;
+        }
+        Py_INCREF(buffer);
+        Py_DECREF(state);
+    }
+    else {
+        buffer = PyBytes_FromString("");
+        flag = 0;
+    }
+    flag <<= 1;
+    if (self->pendingcr)
+        flag |= 1;
+    return Py_BuildValue("NK", buffer, flag);
+}
+
+static PyObject *
+IncrementalNewlineDecoder_setstate(PyNewLineDecoderObject *self, PyObject *state)
+{
+    PyObject *buffer;
+    unsigned PY_LONG_LONG flag;
+
+    if (!PyArg_Parse(state, "(OK)", &buffer, &flag))
+        return NULL;
+
+    self->pendingcr = (int) flag & 1;
+    flag >>= 1;
+
+    if (self->decoder != Py_None)
+        return PyObject_CallMethod(self->decoder,
+                                   "setstate", "((OK))", buffer, flag);
+    else
+        Py_RETURN_NONE;
+}
+
+static PyObject *
+IncrementalNewlineDecoder_reset(PyNewLineDecoderObject *self, PyObject *args)
+{
+    self->seennl = 0;
+    self->pendingcr = 0;
+    if (self->decoder != Py_None)
+        return PyObject_CallMethodObjArgs(self->decoder, _PyIO_str_reset, NULL);
+    else
+        Py_RETURN_NONE;
+}
+
+static PyObject *
+IncrementalNewlineDecoder_newlines_get(PyNewLineDecoderObject *self, void *context)
+{
+    switch (self->seennl) {
+    case SEEN_CR:
+        return PyUnicode_FromString("\r");
+    case SEEN_LF:
+        return PyUnicode_FromString("\n");
+    case SEEN_CRLF:
+        return PyUnicode_FromString("\r\n");
+    case SEEN_CR | SEEN_LF:
+        return Py_BuildValue("ss", "\r", "\n");
+    case SEEN_CR | SEEN_CRLF:
+        return Py_BuildValue("ss", "\r", "\r\n");
+    case SEEN_LF | SEEN_CRLF:
+        return Py_BuildValue("ss", "\n", "\r\n");
+    case SEEN_CR | SEEN_LF | SEEN_CRLF:
+        return Py_BuildValue("sss", "\r", "\n", "\r\n");
+    default:
+        Py_RETURN_NONE;
+   }
+
+}
+
+
+static PyMethodDef IncrementalNewlineDecoder_methods[] = {
+    {"decode", (PyCFunction)IncrementalNewlineDecoder_decode, METH_VARARGS|METH_KEYWORDS},
+    {"getstate", (PyCFunction)IncrementalNewlineDecoder_getstate, METH_NOARGS},
+    {"setstate", (PyCFunction)IncrementalNewlineDecoder_setstate, METH_O},
+    {"reset", (PyCFunction)IncrementalNewlineDecoder_reset, METH_NOARGS},
+    {0}
+};
+
+static PyGetSetDef IncrementalNewlineDecoder_getset[] = {
+    {"newlines", (getter)IncrementalNewlineDecoder_newlines_get, NULL, NULL},
+    {0}
+};
+
+PyTypeObject PyIncrementalNewlineDecoder_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io.IncrementalNewlineDecoder", /*tp_name*/
+    sizeof(PyNewLineDecoderObject), /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    (destructor)IncrementalNewlineDecoder_dealloc, /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
+    IncrementalNewlineDecoder_doc,          /* tp_doc */
+    0,                          /* tp_traverse */
+    0,                          /* tp_clear */
+    0,                          /* tp_richcompare */
+    0,                          /*tp_weaklistoffset*/
+    0,                          /* tp_iter */
+    0,                          /* tp_iternext */
+    IncrementalNewlineDecoder_methods, /* tp_methods */
+    0,                          /* tp_members */
+    IncrementalNewlineDecoder_getset, /* tp_getset */
+    0,                          /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    0,                          /* tp_dictoffset */
+    (initproc)IncrementalNewlineDecoder_init, /* tp_init */
+    0,                          /* tp_alloc */
+    PyType_GenericNew,          /* tp_new */
+};
+
+
+/* TextIOWrapper */
+
+PyDoc_STRVAR(TextIOWrapper_doc,
+    "Character and line based layer over a BufferedIOBase object, buffer.\n"
+    "\n"
+    "encoding gives the name of the encoding that the stream will be\n"
+    "decoded or encoded with. It defaults to locale.getpreferredencoding.\n"
+    "\n"
+    "errors determines the strictness of encoding and decoding (see the\n"
+    "codecs.register) and defaults to \"strict\".\n"
+    "\n"
+    "newline can be None, '', '\\n', '\\r', or '\\r\\n'.  It controls the\n"
+    "handling of line endings. If it is None, universal newlines is\n"
+    "enabled.  With this enabled, on input, the lines endings '\\n', '\\r',\n"
+    "or '\\r\\n' are translated to '\\n' before being returned to the\n"
+    "caller. Conversely, on output, '\\n' is translated to the system\n"
+    "default line seperator, os.linesep. If newline is any other of its\n"
+    "legal values, that newline becomes the newline when the file is read\n"
+    "and it is returned untranslated. On output, '\\n' is converted to the\n"
+    "newline.\n"
+    "\n"
+    "If line_buffering is True, a call to flush is implied when a call to\n"
+    "write contains a newline character."
+    );
+
+typedef PyObject *
+        (*encodefunc_t)(PyObject *, PyObject *);
+
+typedef struct
+{
+    PyObject_HEAD
+    int ok; /* initialized? */
+    Py_ssize_t chunk_size;
+    PyObject *buffer;
+    PyObject *encoding;
+    PyObject *encoder;
+    PyObject *decoder;
+    PyObject *readnl;
+    PyObject *errors;
+    const char *writenl; /* utf-8 encoded, NULL stands for \n */
+    char line_buffering;
+    char readuniversal;
+    char readtranslate;
+    char writetranslate;
+    char seekable;
+    char telling;
+    /* Specialized encoding func (see below) */
+    encodefunc_t encodefunc;
+
+    /* Reads and writes are internally buffered in order to speed things up.
+       However, any read will first flush the write buffer if itsn't empty.
+    
+       Please also note that text to be written is first encoded before being
+       buffered. This is necessary so that encoding errors are immediately
+       reported to the caller, but it unfortunately means that the
+       IncrementalEncoder (whose encode() method is always written in Python)
+       becomes a bottleneck for small writes.
+    */
+    PyObject *decoded_chars;       /* buffer for text returned from decoder */
+    Py_ssize_t decoded_chars_used; /* offset into _decoded_chars for read() */
+    PyObject *pending_bytes;       /* list of bytes objects waiting to be
+                                      written, or NULL */
+    Py_ssize_t pending_bytes_count;
+    PyObject *snapshot;
+    /* snapshot is either None, or a tuple (dec_flags, next_input) where
+     * dec_flags is the second (integer) item of the decoder state and
+     * next_input is the chunk of input bytes that comes next after the
+     * snapshot point.  We use this to reconstruct decoder states in tell().
+     */
+
+    /* Cache raw object if it's a FileIO object */
+    PyObject *raw;
+
+    PyObject *weakreflist;
+    PyObject *dict;
+} PyTextIOWrapperObject;
+
+
+/* A couple of specialized cases in order to bypass the slow incremental
+   encoding methods for the most popular encodings. */
+
+static PyObject *
+ascii_encode(PyTextIOWrapperObject *self, PyObject *text)
+{
+    return PyUnicode_EncodeASCII(PyUnicode_AS_UNICODE(text),
+                                 PyUnicode_GET_SIZE(text),
+                                 PyBytes_AS_STRING(self->errors));
+}
+
+static PyObject *
+utf16be_encode(PyTextIOWrapperObject *self, PyObject *text)
+{
+    return PyUnicode_EncodeUTF16(PyUnicode_AS_UNICODE(text),
+                                 PyUnicode_GET_SIZE(text),
+                                 PyBytes_AS_STRING(self->errors), 1);
+}
+
+static PyObject *
+utf16le_encode(PyTextIOWrapperObject *self, PyObject *text)
+{
+    return PyUnicode_EncodeUTF16(PyUnicode_AS_UNICODE(text),
+                                 PyUnicode_GET_SIZE(text),
+                                 PyBytes_AS_STRING(self->errors), -1);
+}
+
+static PyObject *
+utf16_encode(PyTextIOWrapperObject *self, PyObject *text)
+{
+    PyObject *res;
+    res = PyUnicode_EncodeUTF16(PyUnicode_AS_UNICODE(text),
+                                PyUnicode_GET_SIZE(text),
+                                PyBytes_AS_STRING(self->errors), 0);
+    if (res == NULL)
+        return NULL;
+    /* Next writes will skip the BOM and use native byte ordering */
+#if defined(WORDS_BIGENDIAN)
+    self->encodefunc = (encodefunc_t) utf16be_encode;
+#else
+    self->encodefunc = (encodefunc_t) utf16le_encode;
+#endif
+    return res;
+}
+
+
+static PyObject *
+utf8_encode(PyTextIOWrapperObject *self, PyObject *text)
+{
+    return PyUnicode_EncodeUTF8(PyUnicode_AS_UNICODE(text),
+                                PyUnicode_GET_SIZE(text),
+                                PyBytes_AS_STRING(self->errors));
+}
+
+static PyObject *
+latin1_encode(PyTextIOWrapperObject *self, PyObject *text)
+{
+    return PyUnicode_EncodeLatin1(PyUnicode_AS_UNICODE(text),
+                                  PyUnicode_GET_SIZE(text),
+                                  PyBytes_AS_STRING(self->errors));
+}
+
+/* Map normalized encoding names onto the specialized encoding funcs */
+
+typedef struct {
+    const char *name;
+    encodefunc_t encodefunc;
+} encodefuncentry;
+
+encodefuncentry encodefuncs[] = {
+    {"ascii",       (encodefunc_t) ascii_encode},
+    {"iso8859-1",   (encodefunc_t) latin1_encode},
+    {"utf-16-be",   (encodefunc_t) utf16be_encode},
+    {"utf-16-le",   (encodefunc_t) utf16le_encode},
+    {"utf-16",      (encodefunc_t) utf16_encode},
+    {"utf-8",       (encodefunc_t) utf8_encode},
+    {NULL, NULL}
+};
+
+
+static int
+TextIOWrapper_init(PyTextIOWrapperObject *self, PyObject *args, PyObject *kwds)
+{
+    char *kwlist[] = {"buffer", "encoding", "errors",
+                      "newline", "line_buffering",
+                      NULL};
+    PyObject *buffer, *raw;
+    char *encoding = NULL;
+    char *errors = NULL;
+    char *newline = NULL;
+    int line_buffering = 0;
+    _PyIO_State *state = IO_STATE;
+
+    PyObject *res;
+    int r;
+
+    self->ok = 0;
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|zzzi:fileio",
+                                     kwlist, &buffer, &encoding, &errors,
+                                     &newline, &line_buffering))
+        return -1;
+
+    if (newline && newline[0] != '\0'
+        && !(newline[0] == '\n' && newline[1] == '\0')
+        && !(newline[0] == '\r' && newline[1] == '\0')
+        && !(newline[0] == '\r' && newline[1] == '\n' && newline[2] == '\0')) {
+        PyErr_Format(PyExc_ValueError,
+                     "illegal newline value: %s", newline);
+        return -1;
+    }
+
+    Py_CLEAR(self->buffer);
+    Py_CLEAR(self->encoding);
+    Py_CLEAR(self->encoder);
+    Py_CLEAR(self->decoder);
+    Py_CLEAR(self->readnl);
+    Py_CLEAR(self->decoded_chars);
+    Py_CLEAR(self->pending_bytes);
+    Py_CLEAR(self->snapshot);
+    Py_CLEAR(self->errors);
+    Py_CLEAR(self->raw);
+    self->decoded_chars_used = 0;
+    self->pending_bytes_count = 0;
+    self->encodefunc = NULL;
+
+    if (encoding == NULL) {
+        /* Try os.device_encoding(fileno) */
+        PyObject *fileno;
+        fileno = PyObject_CallMethod(buffer, "fileno", NULL);
+        /* Ignore only AttributeError and UnsupportedOperation */
+        if (fileno == NULL) {
+            if (PyErr_ExceptionMatches(PyExc_AttributeError) ||
+                PyErr_ExceptionMatches(state->unsupported_operation)) {
+                PyErr_Clear();
+            }
+            else {
+                goto error;
+            }
+        }
+        else {
+            self->encoding = PyObject_CallMethod(state->os_module,
+                                                 "device_encoding",
+                                                 "N", fileno);
+            if (self->encoding == NULL)
+                goto error;
+            else if (!PyUnicode_Check(self->encoding))
+                Py_CLEAR(self->encoding);
+        }
+    }
+    if (encoding == NULL && self->encoding == NULL) {
+        if (state->locale_module == NULL) {
+            state->locale_module = PyImport_ImportModule("locale");
+            if (state->locale_module == NULL)
+                goto catch_ImportError;
+            else
+                goto use_locale;
+        }
+        else {
+          use_locale:
+            self->encoding = PyObject_CallMethod(
+                state->locale_module, "getpreferredencoding", NULL);
+            if (self->encoding == NULL) {
+              catch_ImportError:
+                /*
+                 Importing locale can raise a ImportError because of
+                 _functools, and locale.getpreferredencoding can raise a
+                 ImportError if _locale is not available.  These will happen
+                 during module building.
+                */
+                if (PyErr_ExceptionMatches(PyExc_ImportError)) {
+                    PyErr_Clear();
+                    self->encoding = PyUnicode_FromString("ascii");
+                }
+                else
+                    goto error;
+            }
+            else if (!PyUnicode_Check(self->encoding))
+                Py_CLEAR(self->encoding);
+        }
+    }
+    if (self->encoding != NULL)
+        encoding = _PyUnicode_AsString(self->encoding);
+    else if (encoding != NULL) {
+        self->encoding = PyUnicode_FromString(encoding);
+        if (self->encoding == NULL)
+            goto error;
+    }
+    else {
+        PyErr_SetString(PyExc_IOError,
+                        "could not determine default encoding");
+    }
+
+    if (errors == NULL)
+        errors = "strict";
+    self->errors = PyBytes_FromString(errors);
+    if (self->errors == NULL)
+        goto error;
+
+    self->chunk_size = 8192;
+    self->readuniversal = (newline == NULL || newline[0] == '\0');
+    self->line_buffering = line_buffering;
+    self->readtranslate = (newline == NULL);
+    if (newline) {
+        self->readnl = PyUnicode_FromString(newline);
+        if (self->readnl == NULL)
+            return -1;
+    }
+    self->writetranslate = (newline == NULL || newline[0] != '\0');
+    if (!self->readuniversal && self->readnl) {
+        self->writenl = _PyUnicode_AsString(self->readnl);
+        if (!strcmp(self->writenl, "\n"))
+            self->writenl = NULL;
+    }
+#ifdef MS_WINDOWS
+    else
+        self->writenl = "\r\n";
+#endif
+
+    /* Build the decoder object */
+    res = PyObject_CallMethod(buffer, "readable", NULL);
+    if (res == NULL)
+        goto error;
+    r = PyObject_IsTrue(res);
+    Py_DECREF(res);
+    if (r == -1)
+        goto error;
+    if (r == 1) {
+        self->decoder = PyCodec_IncrementalDecoder(
+            encoding, errors);
+        if (self->decoder == NULL)
+            goto error;
+
+        if (self->readuniversal) {
+            PyObject *incrementalDecoder = PyObject_CallFunction(
+                (PyObject *)&PyIncrementalNewlineDecoder_Type,
+                "Oi", self->decoder, (int)self->readtranslate);
+            if (incrementalDecoder == NULL)
+                goto error;
+            Py_CLEAR(self->decoder);
+            self->decoder = incrementalDecoder;
+        }
+    }
+
+    /* Build the encoder object */
+    res = PyObject_CallMethod(buffer, "writable", NULL);
+    if (res == NULL)
+        goto error;
+    r = PyObject_IsTrue(res);
+    Py_DECREF(res);
+    if (r == -1)
+        goto error;
+    if (r == 1) {
+        PyObject *ci;
+        self->encoder = PyCodec_IncrementalEncoder(
+            encoding, errors);
+        if (self->encoder == NULL)
+            goto error;
+        /* Get the normalized named of the codec */
+        ci = _PyCodec_Lookup(encoding);
+        if (ci == NULL)
+            goto error;
+        res = PyObject_GetAttrString(ci, "name");
+        Py_DECREF(ci);
+        if (res == NULL)
+            PyErr_Clear();
+        else if (PyUnicode_Check(res)) {
+            encodefuncentry *e = encodefuncs;
+            while (e->name != NULL) {
+                if (!PyUnicode_CompareWithASCIIString(res, e->name)) {
+                    self->encodefunc = e->encodefunc;
+                    break;
+                }
+                e++;
+            }
+        }
+        Py_XDECREF(res);
+    }
+
+    self->buffer = buffer;
+    Py_INCREF(buffer);
+    
+    if (Py_TYPE(buffer) == &PyBufferedReader_Type ||
+        Py_TYPE(buffer) == &PyBufferedWriter_Type ||
+        Py_TYPE(buffer) == &PyBufferedRandom_Type) {
+        raw = PyObject_GetAttrString(buffer, "raw");
+        /* Cache the raw FileIO object to speed up 'closed' checks */
+        if (raw == NULL)
+            PyErr_Clear();
+        else if (Py_TYPE(raw) == &PyFileIO_Type)
+            self->raw = raw;
+        else
+            Py_DECREF(raw);
+    }
+
+    res = PyObject_CallMethod(buffer, "seekable", NULL);
+    if (res == NULL)
+        goto error;
+    self->seekable = self->telling = PyObject_IsTrue(res);
+    Py_DECREF(res);
+
+    self->ok = 1;
+    return 0;
+
+  error:
+    return -1;
+}
+
+static int
+_TextIOWrapper_clear(PyTextIOWrapperObject *self)
+{
+    if (self->ok && _PyIOBase_finalize((PyObject *) self) < 0)
+        return -1;
+    self->ok = 0;
+    Py_CLEAR(self->buffer);
+    Py_CLEAR(self->encoding);
+    Py_CLEAR(self->encoder);
+    Py_CLEAR(self->decoder);
+    Py_CLEAR(self->readnl);
+    Py_CLEAR(self->decoded_chars);
+    Py_CLEAR(self->pending_bytes);
+    Py_CLEAR(self->snapshot);
+    Py_CLEAR(self->errors);
+    Py_CLEAR(self->raw);
+    return 0;
+}
+
+static void
+TextIOWrapper_dealloc(PyTextIOWrapperObject *self)
+{
+    if (_TextIOWrapper_clear(self) < 0)
+        return;
+    _PyObject_GC_UNTRACK(self);
+    if (self->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *)self);
+    Py_CLEAR(self->dict);
+    Py_TYPE(self)->tp_free((PyObject *)self);
+}
+
+static int
+TextIOWrapper_traverse(PyTextIOWrapperObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->buffer);
+    Py_VISIT(self->encoding);
+    Py_VISIT(self->encoder);
+    Py_VISIT(self->decoder);
+    Py_VISIT(self->readnl);
+    Py_VISIT(self->decoded_chars);
+    Py_VISIT(self->pending_bytes);
+    Py_VISIT(self->snapshot);
+    Py_VISIT(self->errors);
+    Py_VISIT(self->raw);
+
+    Py_VISIT(self->dict);
+    return 0;
+}
+
+static int
+TextIOWrapper_clear(PyTextIOWrapperObject *self)
+{
+    if (_TextIOWrapper_clear(self) < 0)
+        return -1;
+    Py_CLEAR(self->dict);
+    return 0;
+}
+
+static PyObject *
+TextIOWrapper_closed_get(PyTextIOWrapperObject *self, void *context);
+
+/* This macro takes some shortcuts to make the common case faster. */
+#define CHECK_CLOSED(self) \
+    do { \
+        int r; \
+        PyObject *_res; \
+        if (Py_TYPE(self) == &PyTextIOWrapper_Type) { \
+            if (self->raw != NULL) \
+                r = _PyFileIO_closed(self->raw); \
+            else { \
+                _res = TextIOWrapper_closed_get(self, NULL); \
+                if (_res == NULL) \
+                    return NULL; \
+                r = PyObject_IsTrue(_res); \
+                Py_DECREF(_res); \
+                if (r < 0) \
+                    return NULL; \
+            } \
+            if (r > 0) { \
+                PyErr_SetString(PyExc_ValueError, \
+                                "I/O operation on closed file."); \
+                return NULL; \
+            } \
+        } \
+        else if (_PyIOBase_checkClosed((PyObject *)self, Py_True) == NULL) \
+            return NULL; \
+    } while (0)
+
+#define CHECK_INITIALIZED(self) \
+    if (self->ok <= 0) { \
+        PyErr_SetString(PyExc_ValueError, \
+            "I/O operation on uninitialized object"); \
+        return NULL; \
+    }
+
+#define CHECK_INITIALIZED_INT(self) \
+    if (self->ok <= 0) { \
+        PyErr_SetString(PyExc_ValueError, \
+            "I/O operation on uninitialized object"); \
+        return -1; \
+    }
+
+
+Py_LOCAL_INLINE(const Py_UNICODE *)
+findchar(const Py_UNICODE *s, Py_ssize_t size, Py_UNICODE ch)
+{
+    /* like wcschr, but doesn't stop at NULL characters */
+    while (size-- > 0) {
+        if (*s == ch)
+            return s;
+        s++;
+    }
+    return NULL;
+}
+
+/* Flush the internal write buffer. This doesn't explicitly flush the 
+   underlying buffered object, though. */
+static int
+_TextIOWrapper_writeflush(PyTextIOWrapperObject *self)
+{
+    PyObject *b, *ret;
+
+    if (self->pending_bytes == NULL)
+        return 0;
+    b = _PyBytes_Join(_PyIO_empty_bytes, self->pending_bytes);
+    if (b == NULL)
+        return -1;
+    ret = PyObject_CallMethodObjArgs(self->buffer,
+                                     _PyIO_str_write, b, NULL);
+    Py_DECREF(b);
+    if (ret == NULL)
+        return -1;
+    Py_DECREF(ret);
+    Py_CLEAR(self->pending_bytes);
+    self->pending_bytes_count = 0;
+    return 0;
+}
+
+static PyObject *
+TextIOWrapper_write(PyTextIOWrapperObject *self, PyObject *args)
+{
+    PyObject *ret;
+    PyObject *text; /* owned reference */
+    PyObject *b;
+    Py_ssize_t textlen;
+    int haslf = 0;
+    int needflush = 0;
+
+    CHECK_INITIALIZED(self);
+
+    if (!PyArg_ParseTuple(args, "U:write", &text)) {
+        return NULL;
+    }
+
+    CHECK_CLOSED(self);
+
+    Py_INCREF(text);
+
+    textlen = PyUnicode_GetSize(text);
+
+    if ((self->writetranslate && self->writenl != NULL) || self->line_buffering)
+        if (findchar(PyUnicode_AS_UNICODE(text),
+                     PyUnicode_GET_SIZE(text), '\n'))
+            haslf = 1;
+
+    if (haslf && self->writetranslate && self->writenl != NULL) {
+        PyObject *newtext = PyObject_CallMethod(
+            text, "replace", "ss", "\n", self->writenl);
+        Py_DECREF(text);
+        if (newtext == NULL)
+            return NULL;
+        text = newtext;
+    }
+
+    if (self->line_buffering &&
+        (haslf ||
+         findchar(PyUnicode_AS_UNICODE(text),
+                  PyUnicode_GET_SIZE(text), '\r')))
+        needflush = 1;
+
+    /* XXX What if we were just reading? */
+    if (self->encodefunc != NULL)
+        b = (*self->encodefunc)((PyObject *) self, text);
+    else
+        b = PyObject_CallMethodObjArgs(self->encoder,
+                                       _PyIO_str_encode, text, NULL);
+    Py_DECREF(text);
+    if (b == NULL)
+        return NULL;
+
+    if (self->pending_bytes == NULL) {
+        self->pending_bytes = PyList_New(0);
+        if (self->pending_bytes == NULL) {
+            Py_DECREF(b);
+            return NULL;
+        }
+        self->pending_bytes_count = 0;
+    }
+    if (PyList_Append(self->pending_bytes, b) < 0) {
+        Py_DECREF(b);
+        return NULL;
+    }
+    self->pending_bytes_count += PyBytes_GET_SIZE(b);
+    Py_DECREF(b);
+    if (self->pending_bytes_count > self->chunk_size || needflush) {
+        if (_TextIOWrapper_writeflush(self) < 0)
+            return NULL;
+    }
+    
+    if (needflush) {
+        ret = PyObject_CallMethodObjArgs(self->buffer, _PyIO_str_flush, NULL);
+        if (ret == NULL)
+            return NULL;
+        Py_DECREF(ret);
+    }
+
+    Py_CLEAR(self->snapshot);
+
+    if (self->decoder) {
+        ret = PyObject_CallMethod(self->decoder, "reset", NULL);
+        if (ret == NULL)
+            return NULL;
+        Py_DECREF(ret);
+    }
+
+    return PyLong_FromSsize_t(textlen);
+}
+
+/* Steal a reference to chars and store it in the decoded_char buffer;
+ */
+static void
+TextIOWrapper_set_decoded_chars(PyTextIOWrapperObject *self, PyObject *chars)
+{
+    Py_CLEAR(self->decoded_chars);
+    self->decoded_chars = chars;
+    self->decoded_chars_used = 0;
+}
+
+static PyObject *
+TextIOWrapper_get_decoded_chars(PyTextIOWrapperObject *self, Py_ssize_t n)
+{
+    PyObject *chars;
+    Py_ssize_t avail;
+
+    if (self->decoded_chars == NULL)
+        return PyUnicode_FromStringAndSize(NULL, 0);
+
+    avail = (PyUnicode_GET_SIZE(self->decoded_chars)
+             - self->decoded_chars_used);
+
+    assert(avail >= 0);
+
+    if (n < 0 || n > avail)
+        n = avail;
+
+    if (self->decoded_chars_used > 0 || n < avail) {
+        chars = PyUnicode_FromUnicode(
+            PyUnicode_AS_UNICODE(self->decoded_chars)
+            + self->decoded_chars_used, n);
+        if (chars == NULL)
+            return NULL;
+    }
+    else {
+        chars = self->decoded_chars;
+        Py_INCREF(chars);
+    }
+
+    self->decoded_chars_used += n;
+    return chars;
+}
+
+/* Read and decode the next chunk of data from the BufferedReader.
+ */
+static int
+TextIOWrapper_read_chunk(PyTextIOWrapperObject *self)
+{
+    PyObject *dec_buffer = NULL;
+    PyObject *dec_flags = NULL;
+    PyObject *input_chunk = NULL;
+    PyObject *decoded_chars, *chunk_size;
+    int eof;
+
+    /* The return value is True unless EOF was reached.  The decoded string is
+     * placed in self._decoded_chars (replacing its previous value).  The
+     * entire input chunk is sent to the decoder, though some of it may remain
+     * buffered in the decoder, yet to be converted.
+     */
+
+    if (self->decoder == NULL) {
+        PyErr_SetString(PyExc_ValueError, "no decoder");
+        return -1;
+    }
+
+    if (self->telling) {
+        /* To prepare for tell(), we need to snapshot a point in the file
+         * where the decoder's input buffer is empty.
+         */
+
+        PyObject *state = PyObject_CallMethodObjArgs(self->decoder,
+                                                     _PyIO_str_getstate, NULL);
+        if (state == NULL)
+            return -1;
+        /* Given this, we know there was a valid snapshot point
+         * len(dec_buffer) bytes ago with decoder state (b'', dec_flags).
+         */
+        if (PyArg_Parse(state, "(OO)", &dec_buffer, &dec_flags) < 0) {
+            Py_DECREF(state);
+            return -1;
+        }
+        Py_INCREF(dec_buffer);
+        Py_INCREF(dec_flags);
+        Py_DECREF(state);
+    }
+
+    /* Read a chunk, decode it, and put the result in self._decoded_chars. */
+    chunk_size = PyLong_FromSsize_t(self->chunk_size);
+    if (chunk_size == NULL)
+        goto fail;
+    input_chunk = PyObject_CallMethodObjArgs(self->buffer,
+        _PyIO_str_read1, chunk_size, NULL);
+    Py_DECREF(chunk_size);
+    if (input_chunk == NULL)
+        goto fail;
+    assert(PyBytes_Check(input_chunk));
+
+    eof = (PyBytes_Size(input_chunk) == 0);
+
+    if (Py_TYPE(self->decoder) == &PyIncrementalNewlineDecoder_Type) {
+        decoded_chars = _PyIncrementalNewlineDecoder_decode(
+            self->decoder, input_chunk, eof);
+    }
+    else {
+        decoded_chars = PyObject_CallMethodObjArgs(self->decoder,
+            _PyIO_str_decode, input_chunk, eof ? Py_True : Py_False, NULL);
+    }
+
+    /* TODO sanity check: isinstance(decoded_chars, unicode) */
+    if (decoded_chars == NULL)
+        goto fail;
+    TextIOWrapper_set_decoded_chars(self, decoded_chars);
+    if (PyUnicode_GET_SIZE(decoded_chars) > 0)
+        eof = 0;
+
+    if (self->telling) {
+        /* At the snapshot point, len(dec_buffer) bytes before the read, the
+         * next input to be decoded is dec_buffer + input_chunk.
+         */
+        PyObject *next_input = PyNumber_Add(dec_buffer, input_chunk);
+        if (next_input == NULL)
+            goto fail;
+        assert (PyBytes_Check(next_input));
+        Py_DECREF(dec_buffer);
+        Py_CLEAR(self->snapshot);
+        self->snapshot = Py_BuildValue("NN", dec_flags, next_input);
+    }
+    Py_DECREF(input_chunk);
+
+    return (eof == 0);
+
+  fail:
+    Py_XDECREF(dec_buffer);
+    Py_XDECREF(dec_flags);
+    Py_XDECREF(input_chunk);
+    return -1;
+}
+
+static PyObject *
+TextIOWrapper_read(PyTextIOWrapperObject *self, PyObject *args)
+{
+    Py_ssize_t n = -1;
+    PyObject *result = NULL, *chunks = NULL;
+
+    CHECK_INITIALIZED(self);
+
+    if (!PyArg_ParseTuple(args, "|n:read", &n))
+        return NULL;
+
+    CHECK_CLOSED(self);
+
+    if (_TextIOWrapper_writeflush(self) < 0)
+        return NULL;
+
+    if (n < 0) {
+        /* Read everything */
+        PyObject *bytes = PyObject_CallMethod(self->buffer, "read", NULL);
+        PyObject *decoded;
+        if (bytes == NULL)
+            goto fail;
+        decoded = PyObject_CallMethodObjArgs(self->decoder, _PyIO_str_decode,
+                                             bytes, Py_True, NULL);
+        Py_DECREF(bytes);
+        if (decoded == NULL)
+            goto fail;
+
+        result = TextIOWrapper_get_decoded_chars(self, -1);
+
+        if (result == NULL) {
+            Py_DECREF(decoded);
+            return NULL;
+        }
+
+        PyUnicode_AppendAndDel(&result, decoded);
+        if (result == NULL)
+            goto fail;
+
+        Py_CLEAR(self->snapshot);
+        return result;
+    }
+    else {
+        int res = 1;
+        Py_ssize_t remaining = n;
+
+        result = TextIOWrapper_get_decoded_chars(self, n);
+        if (result == NULL)
+            goto fail;
+        remaining -= PyUnicode_GET_SIZE(result);
+
+        /* Keep reading chunks until we have n characters to return */
+        while (remaining > 0) {
+            res = TextIOWrapper_read_chunk(self);
+            if (res < 0)
+                goto fail;
+            if (res == 0)  /* EOF */
+                break;
+            if (chunks == NULL) {
+                chunks = PyList_New(0);
+                if (chunks == NULL)
+                    goto fail;
+            }
+            if (PyList_Append(chunks, result) < 0)
+                goto fail;
+            Py_DECREF(result);
+            result = TextIOWrapper_get_decoded_chars(self, remaining);
+            if (result == NULL)
+                goto fail;
+            remaining -= PyUnicode_GET_SIZE(result);
+        }
+        if (chunks != NULL) {
+            if (result != NULL && PyList_Append(chunks, result) < 0)
+                goto fail;
+            Py_CLEAR(result);
+            result = PyUnicode_Join(_PyIO_empty_str, chunks);
+            if (result == NULL)
+                goto fail;
+            Py_CLEAR(chunks);
+        }
+        return result;
+    }
+  fail:
+    Py_XDECREF(result);
+    Py_XDECREF(chunks);
+    return NULL;
+}
+
+
+/* NOTE: `end` must point to the real end of the Py_UNICODE storage,
+   that is to the NUL character. Otherwise the function will produce
+   incorrect results. */
+static Py_UNICODE *
+find_control_char(Py_UNICODE *start, Py_UNICODE *end, Py_UNICODE ch)
+{
+    Py_UNICODE *s = start;
+    for (;;) {
+        while (*s > ch)
+            s++;
+        if (*s == ch)
+            return s;
+        if (s == end)
+            return NULL;
+        s++;
+    }
+}
+
+Py_ssize_t
+_PyIO_find_line_ending(
+    int translated, int universal, PyObject *readnl,
+    Py_UNICODE *start, Py_UNICODE *end, Py_ssize_t *consumed)
+{
+    Py_ssize_t len = end - start;
+
+    if (translated) {
+        /* Newlines are already translated, only search for \n */
+        Py_UNICODE *pos = find_control_char(start, end, '\n');
+        if (pos != NULL)
+            return pos - start + 1;
+        else {
+            *consumed = len;
+            return -1;
+        }
+    }
+    else if (universal) {
+        /* Universal newline search. Find any of \r, \r\n, \n
+         * The decoder ensures that \r\n are not split in two pieces
+         */
+        Py_UNICODE *s = start;
+        for (;;) {
+            Py_UNICODE ch;
+            /* Fast path for non-control chars. The loop always ends
+               since the Py_UNICODE storage is NUL-terminated. */
+            while (*s > '\r')
+                s++;
+            if (s >= end) {
+                *consumed = len;
+                return -1;
+            }
+            ch = *s++;
+            if (ch == '\n')
+                return s - start;
+            if (ch == '\r') {
+                if (*s == '\n')
+                    return s - start + 1;
+                else
+                    return s - start;
+            }
+        }
+    }
+    else {
+        /* Non-universal mode. */
+        Py_ssize_t readnl_len = PyUnicode_GET_SIZE(readnl);
+        Py_UNICODE *nl = PyUnicode_AS_UNICODE(readnl);
+        if (readnl_len == 1) {
+            Py_UNICODE *pos = find_control_char(start, end, nl[0]);
+            if (pos != NULL)
+                return pos - start + 1;
+            *consumed = len;
+            return -1;
+        }
+        else {
+            Py_UNICODE *s = start;
+            Py_UNICODE *e = end - readnl_len + 1;
+            Py_UNICODE *pos;
+            if (e < s)
+                e = s;
+            while (s < e) {
+                Py_ssize_t i;
+                Py_UNICODE *pos = find_control_char(s, end, nl[0]);
+                if (pos == NULL || pos >= e)
+                    break;
+                for (i = 1; i < readnl_len; i++) {
+                    if (pos[i] != nl[i])
+                        break;
+                }
+                if (i == readnl_len)
+                    return pos - start + readnl_len;
+                s = pos + 1;
+            }
+            pos = find_control_char(e, end, nl[0]);
+            if (pos == NULL)
+                *consumed = len;
+            else
+                *consumed = pos - start;
+            return -1;
+        }
+    }
+}
+
+static PyObject *
+_TextIOWrapper_readline(PyTextIOWrapperObject *self, Py_ssize_t limit)
+{
+    PyObject *line = NULL, *chunks = NULL, *remaining = NULL;
+    Py_ssize_t start, endpos, chunked, offset_to_buffer;
+    int res;
+
+    CHECK_CLOSED(self);
+
+    if (_TextIOWrapper_writeflush(self) < 0)
+        return NULL;
+
+    chunked = 0;
+
+    while (1) {
+        Py_UNICODE *ptr;
+        Py_ssize_t line_len;
+        Py_ssize_t consumed = 0;
+
+        /* First, get some data if necessary */
+        res = 1;
+        while (!self->decoded_chars ||
+               !PyUnicode_GET_SIZE(self->decoded_chars)) {
+            res = TextIOWrapper_read_chunk(self);
+            if (res < 0)
+                goto error;
+            if (res == 0)
+                break;
+        }
+        if (res == 0) {
+            /* end of file */
+            TextIOWrapper_set_decoded_chars(self, NULL);
+            Py_CLEAR(self->snapshot);
+            start = endpos = offset_to_buffer = 0;
+            break;
+        }
+
+        if (remaining == NULL) {
+            line = self->decoded_chars;
+            start = self->decoded_chars_used;
+            offset_to_buffer = 0;
+            Py_INCREF(line);
+        }
+        else {
+            assert(self->decoded_chars_used == 0);
+            line = PyUnicode_Concat(remaining, self->decoded_chars);
+            start = 0;
+            offset_to_buffer = PyUnicode_GET_SIZE(remaining);
+            Py_CLEAR(remaining);
+            if (line == NULL)
+                goto error;
+        }
+
+        ptr = PyUnicode_AS_UNICODE(line);
+        line_len = PyUnicode_GET_SIZE(line);
+
+        endpos = _PyIO_find_line_ending(
+            self->readtranslate, self->readuniversal, self->readnl,
+            ptr + start, ptr + line_len, &consumed);
+        if (endpos >= 0) {
+            endpos += start;
+            if (limit >= 0 && (endpos - start) + chunked >= limit)
+                endpos = start + limit - chunked;
+            break;
+        }
+
+        /* We can put aside up to `endpos` */
+        endpos = consumed + start;
+        if (limit >= 0 && (endpos - start) + chunked >= limit) {
+            /* Didn't find line ending, but reached length limit */
+            endpos = start + limit - chunked;
+            break;
+        }
+
+        if (endpos > start) {
+            /* No line ending seen yet - put aside current data */
+            PyObject *s;
+            if (chunks == NULL) {
+                chunks = PyList_New(0);
+                if (chunks == NULL)
+                    goto error;
+            }
+            s = PyUnicode_FromUnicode(ptr + start, endpos - start);
+            if (s == NULL)
+                goto error;
+            if (PyList_Append(chunks, s) < 0) {
+                Py_DECREF(s);
+                goto error;
+            }
+            chunked += PyUnicode_GET_SIZE(s);
+            Py_DECREF(s);
+        }
+        /* There may be some remaining bytes we'll have to prepend to the
+           next chunk of data */
+        if (endpos < line_len) {
+            remaining = PyUnicode_FromUnicode(
+                    ptr + endpos, line_len - endpos);
+            if (remaining == NULL)
+                goto error;
+        }
+        Py_CLEAR(line);
+        /* We have consumed the buffer */
+        TextIOWrapper_set_decoded_chars(self, NULL);
+    }
+
+    if (line != NULL) {
+        /* Our line ends in the current buffer */
+        self->decoded_chars_used = endpos - offset_to_buffer;
+        if (start > 0 || endpos < PyUnicode_GET_SIZE(line)) {
+            if (start == 0 && Py_REFCNT(line) == 1) {
+                if (PyUnicode_Resize(&line, endpos) < 0)
+                    goto error;
+            }
+            else {
+                PyObject *s = PyUnicode_FromUnicode(
+                        PyUnicode_AS_UNICODE(line) + start, endpos - start);
+                Py_CLEAR(line);
+                if (s == NULL)
+                    goto error;
+                line = s;
+            }
+        }
+    }
+    if (remaining != NULL) {
+        if (chunks == NULL) {
+            chunks = PyList_New(0);
+            if (chunks == NULL)
+                goto error;
+        }
+        if (PyList_Append(chunks, remaining) < 0)
+            goto error;
+        Py_CLEAR(remaining);
+    }
+    if (chunks != NULL) {
+        if (line != NULL && PyList_Append(chunks, line) < 0)
+            goto error;
+        Py_CLEAR(line);
+        line = PyUnicode_Join(_PyIO_empty_str, chunks);
+        if (line == NULL)
+            goto error;
+        Py_DECREF(chunks);
+    }
+    if (line == NULL)
+        line = PyUnicode_FromStringAndSize(NULL, 0);
+
+    return line;
+
+  error:
+    Py_XDECREF(chunks);
+    Py_XDECREF(remaining);
+    Py_XDECREF(line);
+    return NULL;
+}
+
+static PyObject *
+TextIOWrapper_readline(PyTextIOWrapperObject *self, PyObject *args)
+{
+    Py_ssize_t limit = -1;
+
+    CHECK_INITIALIZED(self);
+    if (!PyArg_ParseTuple(args, "|n:readline", &limit)) {
+        return NULL;
+    }
+    return _TextIOWrapper_readline(self, limit);
+}
+
+/* Seek and Tell */
+
+typedef struct {
+    Py_off_t start_pos;
+    int dec_flags;
+    int bytes_to_feed;
+    int chars_to_skip;
+    char need_eof;
+} CookieStruct;
+
+/*
+   To speed up cookie packing/unpacking, we store the fields in a temporary
+   string and call _PyLong_FromByteArray() or _PyLong_AsByteArray (resp.).
+   The following macros define at which offsets in the intermediary byte
+   string the various CookieStruct fields will be stored.
+ */
+
+#define COOKIE_BUF_LEN      (sizeof(Py_off_t) + 3 * sizeof(int) + sizeof(char))
+
+#if defined(WORDS_BIGENDIAN)
+
+# define IS_LITTLE_ENDIAN   0
+
+/* We want the least significant byte of start_pos to also be the least
+   significant byte of the cookie, which means that in big-endian mode we
+   must copy the fields in reverse order. */
+
+# define OFF_START_POS      (sizeof(char) + 3 * sizeof(int))
+# define OFF_DEC_FLAGS      (sizeof(char) + 2 * sizeof(int))
+# define OFF_BYTES_TO_FEED  (sizeof(char) + sizeof(int))
+# define OFF_CHARS_TO_SKIP  (sizeof(char))
+# define OFF_NEED_EOF       0
+
+#else
+
+# define IS_LITTLE_ENDIAN   1
+
+/* Little-endian mode: the least significant byte of start_pos will
+   naturally end up the least significant byte of the cookie. */
+
+# define OFF_START_POS      0
+# define OFF_DEC_FLAGS      (sizeof(Py_off_t))
+# define OFF_BYTES_TO_FEED  (sizeof(Py_off_t) + sizeof(int))
+# define OFF_CHARS_TO_SKIP  (sizeof(Py_off_t) + 2 * sizeof(int))
+# define OFF_NEED_EOF       (sizeof(Py_off_t) + 3 * sizeof(int))
+
+#endif
+
+static int
+TextIOWrapper_parseCookie(CookieStruct *cookie, PyObject *cookieObj)
+{
+    unsigned char buffer[COOKIE_BUF_LEN];
+    PyLongObject *cookieLong = (PyLongObject *)PyNumber_Long(cookieObj);
+    if (cookieLong == NULL)
+        return -1;
+
+    if (_PyLong_AsByteArray(cookieLong, buffer, sizeof(buffer),
+                            IS_LITTLE_ENDIAN, 0) < 0) {
+        Py_DECREF(cookieLong);
+        return -1;
+    }
+    Py_DECREF(cookieLong);
+
+    cookie->start_pos     = * (Py_off_t *)(buffer + OFF_START_POS);
+    cookie->dec_flags     = * (int *)     (buffer + OFF_DEC_FLAGS);
+    cookie->bytes_to_feed = * (int *)     (buffer + OFF_BYTES_TO_FEED);
+    cookie->chars_to_skip = * (int *)     (buffer + OFF_CHARS_TO_SKIP);
+    cookie->need_eof      = * (char *)    (buffer + OFF_NEED_EOF);
+
+    return 0;
+}
+
+static PyObject *
+TextIOWrapper_buildCookie(CookieStruct *cookie)
+{
+    unsigned char buffer[COOKIE_BUF_LEN];
+
+    * (Py_off_t *)(buffer + OFF_START_POS)     = cookie->start_pos;
+    * (int *)     (buffer + OFF_DEC_FLAGS)     = cookie->dec_flags;
+    * (int *)     (buffer + OFF_BYTES_TO_FEED) = cookie->bytes_to_feed;
+    * (int *)     (buffer + OFF_CHARS_TO_SKIP) = cookie->chars_to_skip;
+    * (char *)    (buffer + OFF_NEED_EOF)      = cookie->need_eof;
+
+    return _PyLong_FromByteArray(buffer, sizeof(buffer), IS_LITTLE_ENDIAN, 0);
+}
+#undef IS_LITTLE_ENDIAN
+
+static int
+_TextIOWrapper_decoder_setstate(PyTextIOWrapperObject *self,
+                                CookieStruct *cookie)
+{
+    PyObject *res;
+    /* When seeking to the start of the stream, we call decoder.reset()
+       rather than decoder.getstate().
+       This is for a few decoders such as utf-16 for which the state value
+       at start is not (b"", 0) but e.g. (b"", 2) (meaning, in the case of
+       utf-16, that we are expecting a BOM).
+    */
+    if (cookie->start_pos == 0 && cookie->dec_flags == 0)
+        res = PyObject_CallMethodObjArgs(self->decoder, _PyIO_str_reset, NULL);
+    else
+        res = PyObject_CallMethod(self->decoder, "setstate",
+                                  "((yi))", "", cookie->dec_flags);
+    if (res == NULL)
+        return -1;
+    Py_DECREF(res);
+    return 0;
+}
+
+static PyObject *
+TextIOWrapper_seek(PyTextIOWrapperObject *self, PyObject *args)
+{
+    PyObject *cookieObj, *posobj;
+    CookieStruct cookie;
+    int whence = 0;
+    static PyObject *zero = NULL;
+    PyObject *res;
+    int cmp;
+
+    CHECK_INITIALIZED(self);
+
+    if (zero == NULL) {
+        zero = PyLong_FromLong(0L);
+        if (zero == NULL)
+            return NULL;
+    }
+
+    if (!PyArg_ParseTuple(args, "O|i:seek", &cookieObj, &whence))
+        return NULL;
+    CHECK_CLOSED(self);
+
+    Py_INCREF(cookieObj);
+
+    if (!self->seekable) {
+        PyErr_SetString(PyExc_IOError,
+                        "underlying stream is not seekable");
+        goto fail;
+    }
+
+    if (whence == 1) {
+        /* seek relative to current position */
+        cmp = PyObject_RichCompareBool(cookieObj, zero, Py_EQ);
+        if (cmp < 0)
+            goto fail;
+
+        if (cmp == 0) {
+            PyErr_SetString(PyExc_IOError,
+                            "can't do nonzero cur-relative seeks");
+            goto fail;
+        }
+
+        /* Seeking to the current position should attempt to
+         * sync the underlying buffer with the current position.
+         */
+        Py_DECREF(cookieObj);
+        cookieObj = PyObject_CallMethod((PyObject *)self, "tell", NULL);
+        if (cookieObj == NULL)
+            goto fail;
+    }
+    else if (whence == 2) {
+        /* seek relative to end of file */
+
+        cmp = PyObject_RichCompareBool(cookieObj, zero, Py_EQ);
+        if (cmp < 0)
+            goto fail;
+
+        if (cmp == 0) {
+            PyErr_SetString(PyExc_IOError,
+                            "can't do nonzero end-relative seeks");
+            goto fail;
+        }
+
+        res = PyObject_CallMethod((PyObject *)self, "flush", NULL);
+        if (res == NULL)
+            goto fail;
+        Py_DECREF(res);
+
+        TextIOWrapper_set_decoded_chars(self, NULL);
+        Py_CLEAR(self->snapshot);
+        if (self->decoder) {
+            res = PyObject_CallMethod(self->decoder, "reset", NULL);
+            if (res == NULL)
+                goto fail;
+            Py_DECREF(res);
+        }
+
+        res = PyObject_CallMethod(self->buffer, "seek", "ii", 0, 2);
+        Py_XDECREF(cookieObj);
+        return res;
+    }
+    else if (whence != 0) {
+        PyErr_Format(PyExc_ValueError,
+                     "invalid whence (%d, should be 0, 1 or 2)", whence);
+        goto fail;
+    }
+
+    cmp = PyObject_RichCompareBool(cookieObj, zero, Py_LT);
+    if (cmp < 0)
+        goto fail;
+
+    if (cmp == 1) {
+        PyErr_Format(PyExc_ValueError,
+                     "negative seek position %R", cookieObj);
+        goto fail;
+    }
+
+    res = PyObject_CallMethodObjArgs((PyObject *)self, _PyIO_str_flush, NULL);
+    if (res == NULL)
+        goto fail;
+    Py_DECREF(res);
+
+    /* The strategy of seek() is to go back to the safe start point
+     * and replay the effect of read(chars_to_skip) from there.
+     */
+    if (TextIOWrapper_parseCookie(&cookie, cookieObj) < 0)
+        goto fail;
+
+    /* Seek back to the safe start point. */
+    posobj = PyLong_FromOff_t(cookie.start_pos);
+    if (posobj == NULL)
+        goto fail;
+    res = PyObject_CallMethodObjArgs(self->buffer,
+                                     _PyIO_str_seek, posobj, NULL);
+    Py_DECREF(posobj);
+    if (res == NULL)
+        goto fail;
+    Py_DECREF(res);
+
+    TextIOWrapper_set_decoded_chars(self, NULL);
+    Py_CLEAR(self->snapshot);
+
+    /* Restore the decoder to its state from the safe start point. */
+    if (self->decoder) {
+        if (_TextIOWrapper_decoder_setstate(self, &cookie) < 0)
+            goto fail;
+    }
+
+    if (cookie.chars_to_skip) {
+        /* Just like _read_chunk, feed the decoder and save a snapshot. */
+        PyObject *input_chunk = PyObject_CallMethod(
+            self->buffer, "read", "i", cookie.bytes_to_feed);
+        PyObject *decoded;
+
+        if (input_chunk == NULL)
+            goto fail;
+
+        assert (PyBytes_Check(input_chunk));
+
+        self->snapshot = Py_BuildValue("iN", cookie.dec_flags, input_chunk);
+        if (self->snapshot == NULL) {
+            Py_DECREF(input_chunk);
+            goto fail;
+        }
+
+        decoded = PyObject_CallMethod(self->decoder, "decode",
+                                      "Oi", input_chunk, (int)cookie.need_eof);
+
+        if (decoded == NULL)
+            goto fail;
+
+        TextIOWrapper_set_decoded_chars(self, decoded);
+
+        /* Skip chars_to_skip of the decoded characters. */
+        if (PyUnicode_GetSize(self->decoded_chars) < cookie.chars_to_skip) {
+            PyErr_SetString(PyExc_IOError, "can't restore logical file position");
+            goto fail;
+        }
+        self->decoded_chars_used = cookie.chars_to_skip;
+    }
+    else {
+        self->snapshot = Py_BuildValue("iy", cookie.dec_flags, "");
+        if (self->snapshot == NULL)
+            goto fail;
+    }
+
+    return cookieObj;
+  fail:
+    Py_XDECREF(cookieObj);
+    return NULL;
+
+}
+
+static PyObject *
+TextIOWrapper_tell(PyTextIOWrapperObject *self, PyObject *args)
+{
+    PyObject *res;
+    PyObject *posobj = NULL;
+    CookieStruct cookie = {0,0,0,0,0};
+    PyObject *next_input;
+    Py_ssize_t chars_to_skip, chars_decoded;
+    PyObject *saved_state = NULL;
+    char *input, *input_end;
+
+    CHECK_INITIALIZED(self);
+    CHECK_CLOSED(self);
+
+    if (!self->seekable) {
+        PyErr_SetString(PyExc_IOError,
+                        "underlying stream is not seekable");
+        goto fail;
+    }
+    if (!self->telling) {
+        PyErr_SetString(PyExc_IOError,
+                        "telling position disabled by next() call");
+        goto fail;
+    }
+
+    if (_TextIOWrapper_writeflush(self) < 0)
+        return NULL;
+    res = PyObject_CallMethod((PyObject *)self, "flush", NULL);
+    if (res == NULL)
+        goto fail;
+    Py_DECREF(res);
+
+    posobj = PyObject_CallMethod(self->buffer, "tell", NULL);
+    if (posobj == NULL)
+        goto fail;
+
+    if (self->decoder == NULL || self->snapshot == NULL) {
+        assert (self->decoded_chars == NULL || PyUnicode_GetSize(self->decoded_chars) == 0);
+        return posobj;
+    }
+
+#if defined(HAVE_LARGEFILE_SUPPORT)
+    cookie.start_pos = PyLong_AsLongLong(posobj);
+#else
+    cookie.start_pos = PyLong_AsLong(posobj);
+#endif
+    if (PyErr_Occurred())
+        goto fail;
+
+    /* Skip backward to the snapshot point (see _read_chunk). */
+    if (!PyArg_Parse(self->snapshot, "(iO)", &cookie.dec_flags, &next_input))
+        goto fail;
+
+    assert (PyBytes_Check(next_input));
+
+    cookie.start_pos -= PyBytes_GET_SIZE(next_input);
+
+    /* How many decoded characters have been used up since the snapshot? */
+    if (self->decoded_chars_used == 0)  {
+        /* We haven't moved from the snapshot point. */
+        Py_DECREF(posobj);
+        return TextIOWrapper_buildCookie(&cookie);
+    }
+
+    chars_to_skip = self->decoded_chars_used;
+
+    /* Starting from the snapshot position, we will walk the decoder
+     * forward until it gives us enough decoded characters.
+     */
+    saved_state = PyObject_CallMethodObjArgs(self->decoder,
+                                             _PyIO_str_getstate, NULL);
+    if (saved_state == NULL)
+        goto fail;
+
+    /* Note our initial start point. */
+    if (_TextIOWrapper_decoder_setstate(self, &cookie) < 0)
+        goto fail;
+
+    /* Feed the decoder one byte at a time.  As we go, note the
+     * nearest "safe start point" before the current location
+     * (a point where the decoder has nothing buffered, so seek()
+     * can safely start from there and advance to this location).
+     */
+    chars_decoded = 0;
+    input = PyBytes_AS_STRING(next_input);
+    input_end = input + PyBytes_GET_SIZE(next_input);
+    while (input < input_end) {
+        PyObject *state;
+        char *dec_buffer;
+        Py_ssize_t dec_buffer_len;
+        int dec_flags;
+
+        PyObject *decoded = PyObject_CallMethod(
+            self->decoder, "decode", "y#", input, 1);
+        if (decoded == NULL)
+            goto fail;
+        assert (PyUnicode_Check(decoded));
+        chars_decoded += PyUnicode_GET_SIZE(decoded);
+        Py_DECREF(decoded);
+
+        cookie.bytes_to_feed += 1;
+
+        state = PyObject_CallMethodObjArgs(self->decoder,
+                                           _PyIO_str_getstate, NULL);
+        if (state == NULL)
+            goto fail;
+        if (!PyArg_Parse(state, "(y#i)", &dec_buffer, &dec_buffer_len, &dec_flags)) {
+            Py_DECREF(state);
+            goto fail;
+        }
+        Py_DECREF(state);
+
+        if (dec_buffer_len == 0 && chars_decoded <= chars_to_skip) {
+            /* Decoder buffer is empty, so this is a safe start point. */
+            cookie.start_pos += cookie.bytes_to_feed;
+            chars_to_skip -= chars_decoded;
+            cookie.dec_flags = dec_flags;
+            cookie.bytes_to_feed = 0;
+            chars_decoded = 0;
+        }
+        if (chars_decoded >= chars_to_skip)
+            break;
+        input++;
+    }
+    if (input == input_end) {
+        /* We didn't get enough decoded data; signal EOF to get more. */
+        PyObject *decoded = PyObject_CallMethod(
+            self->decoder, "decode", "yi", "", /* final = */ 1);
+        if (decoded == NULL)
+            goto fail;
+        assert (PyUnicode_Check(decoded));
+        chars_decoded += PyUnicode_GET_SIZE(decoded);
+        Py_DECREF(decoded);
+        cookie.need_eof = 1;
+
+        if (chars_decoded < chars_to_skip) {
+            PyErr_SetString(PyExc_IOError,
+                            "can't reconstruct logical file position");
+            goto fail;
+        }
+    }
+
+    /* finally */
+    Py_XDECREF(posobj);
+    res = PyObject_CallMethod(self->decoder, "setstate", "(O)", saved_state);
+    Py_DECREF(saved_state);
+    if (res == NULL)
+        return NULL;
+    Py_DECREF(res);
+
+    /* The returned cookie corresponds to the last safe start point. */
+    cookie.chars_to_skip = Py_SAFE_DOWNCAST(chars_to_skip, Py_ssize_t, int);
+    return TextIOWrapper_buildCookie(&cookie);
+
+  fail:
+    Py_XDECREF(posobj);
+    if (saved_state) {
+        PyObject *type, *value, *traceback;
+        PyErr_Fetch(&type, &value, &traceback);
+
+        res = PyObject_CallMethod(self->decoder, "setstate", "(O)", saved_state);
+        Py_DECREF(saved_state);
+        if (res == NULL)
+            return NULL;
+        Py_DECREF(res);
+
+        PyErr_Restore(type, value, traceback);
+    }
+    return NULL;
+}
+
+static PyObject *
+TextIOWrapper_truncate(PyTextIOWrapperObject *self, PyObject *args)
+{
+    PyObject *pos = Py_None;
+    PyObject *res;
+
+    CHECK_INITIALIZED(self)
+    if (!PyArg_ParseTuple(args, "|O:truncate", &pos)) {
+        return NULL;
+    }
+
+    res = PyObject_CallMethodObjArgs((PyObject *) self, _PyIO_str_flush, NULL);
+    if (res == NULL)
+        return NULL;
+    Py_DECREF(res);
+
+    if (pos != Py_None) {
+        res = PyObject_CallMethodObjArgs((PyObject *) self,
+                                          _PyIO_str_seek, pos, NULL);
+        if (res == NULL)
+            return NULL;
+        Py_DECREF(res);
+    }
+
+    return PyObject_CallMethodObjArgs(self->buffer, _PyIO_str_truncate, NULL);
+}
+
+/* Inquiries */
+
+static PyObject *
+TextIOWrapper_fileno(PyTextIOWrapperObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self);
+    return PyObject_CallMethod(self->buffer, "fileno", NULL);
+}
+
+static PyObject *
+TextIOWrapper_seekable(PyTextIOWrapperObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self);
+    return PyObject_CallMethod(self->buffer, "seekable", NULL);
+}
+
+static PyObject *
+TextIOWrapper_readable(PyTextIOWrapperObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self);
+    return PyObject_CallMethod(self->buffer, "readable", NULL);
+}
+
+static PyObject *
+TextIOWrapper_writable(PyTextIOWrapperObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self);
+    return PyObject_CallMethod(self->buffer, "writable", NULL);
+}
+
+static PyObject *
+TextIOWrapper_isatty(PyTextIOWrapperObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self);
+    return PyObject_CallMethod(self->buffer, "isatty", NULL);
+}
+
+static PyObject *
+TextIOWrapper_flush(PyTextIOWrapperObject *self, PyObject *args)
+{
+    CHECK_INITIALIZED(self);
+    CHECK_CLOSED(self);
+    self->telling = self->seekable;
+    if (_TextIOWrapper_writeflush(self) < 0)
+        return NULL;
+    return PyObject_CallMethod(self->buffer, "flush", NULL);
+}
+
+static PyObject *
+TextIOWrapper_close(PyTextIOWrapperObject *self, PyObject *args)
+{
+    PyObject *res;
+    CHECK_INITIALIZED(self);
+    res = PyObject_CallMethod((PyObject *)self, "flush", NULL);
+    if (res == NULL) {
+        /* If flush() fails, just give up */
+        PyErr_Clear();
+    }
+    else
+        Py_DECREF(res);
+
+    return PyObject_CallMethod(self->buffer, "close", NULL);
+}
+
+static PyObject *
+TextIOWrapper_iternext(PyTextIOWrapperObject *self)
+{
+    PyObject *line;
+
+    CHECK_INITIALIZED(self);
+
+    self->telling = 0;
+    if (Py_TYPE(self) == &PyTextIOWrapper_Type) {
+        /* Skip method call overhead for speed */
+        line = _TextIOWrapper_readline(self, -1);
+    }
+    else {
+        line = PyObject_CallMethodObjArgs((PyObject *)self,
+                                           _PyIO_str_readline, NULL);
+        if (line && !PyUnicode_Check(line)) {
+            PyErr_Format(PyExc_IOError,
+                         "readline() should have returned an str object, "
+                         "not '%.200s'", Py_TYPE(line)->tp_name);
+            Py_DECREF(line);
+            return NULL;
+        }
+    }
+
+    if (line == NULL)
+        return NULL;
+
+    if (PyUnicode_GET_SIZE(line) == 0) {
+        /* Reached EOF or would have blocked */
+        Py_DECREF(line);
+        Py_CLEAR(self->snapshot);
+        self->telling = self->seekable;
+        return NULL;
+    }
+
+    return line;
+}
+
+static PyObject *
+TextIOWrapper_name_get(PyTextIOWrapperObject *self, void *context)
+{
+    CHECK_INITIALIZED(self);
+    return PyObject_GetAttrString(self->buffer, "name");
+}
+
+static PyObject *
+TextIOWrapper_closed_get(PyTextIOWrapperObject *self, void *context)
+{
+    CHECK_INITIALIZED(self);
+    return PyObject_GetAttr(self->buffer, _PyIO_str_closed);
+}
+
+static PyObject *
+TextIOWrapper_newlines_get(PyTextIOWrapperObject *self, void *context)
+{
+    PyObject *res;
+    CHECK_INITIALIZED(self);
+    if (self->decoder == NULL)
+        Py_RETURN_NONE;
+    res = PyObject_GetAttr(self->decoder, _PyIO_str_newlines);
+    if (res == NULL) {
+        PyErr_Clear();
+        Py_RETURN_NONE;
+    }
+    return res;
+}
+
+static PyObject *
+TextIOWrapper_chunk_size_get(PyTextIOWrapperObject *self, void *context)
+{
+    CHECK_INITIALIZED(self);
+    return PyLong_FromSsize_t(self->chunk_size);
+}
+
+static int
+TextIOWrapper_chunk_size_set(PyTextIOWrapperObject *self,
+                             PyObject *arg, void *context)
+{
+    Py_ssize_t n;
+    CHECK_INITIALIZED_INT(self);
+    n = PyNumber_AsSsize_t(arg, PyExc_TypeError);
+    if (n == -1 && PyErr_Occurred())
+        return -1;
+    if (n <= 0) {
+        PyErr_SetString(PyExc_ValueError,
+                        "a strictly positive integer is required");
+        return -1;
+    }
+    self->chunk_size = n;
+    return 0;
+}
+
+static PyMethodDef TextIOWrapper_methods[] = {
+    {"write", (PyCFunction)TextIOWrapper_write, METH_VARARGS},
+    {"read", (PyCFunction)TextIOWrapper_read, METH_VARARGS},
+    {"readline", (PyCFunction)TextIOWrapper_readline, METH_VARARGS},
+    {"flush", (PyCFunction)TextIOWrapper_flush, METH_NOARGS},
+    {"close", (PyCFunction)TextIOWrapper_close, METH_NOARGS},
+
+    {"fileno", (PyCFunction)TextIOWrapper_fileno, METH_NOARGS},
+    {"seekable", (PyCFunction)TextIOWrapper_seekable, METH_NOARGS},
+    {"readable", (PyCFunction)TextIOWrapper_readable, METH_NOARGS},
+    {"writable", (PyCFunction)TextIOWrapper_writable, METH_NOARGS},
+    {"isatty", (PyCFunction)TextIOWrapper_isatty, METH_NOARGS},
+
+    {"seek", (PyCFunction)TextIOWrapper_seek, METH_VARARGS},
+    {"tell", (PyCFunction)TextIOWrapper_tell, METH_NOARGS},
+    {"truncate", (PyCFunction)TextIOWrapper_truncate, METH_VARARGS},
+    {NULL, NULL}
+};
+
+static PyMemberDef TextIOWrapper_members[] = {
+    {"encoding", T_OBJECT, offsetof(PyTextIOWrapperObject, encoding), READONLY},
+    {"buffer", T_OBJECT, offsetof(PyTextIOWrapperObject, buffer), READONLY},
+    {"line_buffering", T_BOOL, offsetof(PyTextIOWrapperObject, line_buffering), READONLY},
+    {NULL}
+};
+
+static PyGetSetDef TextIOWrapper_getset[] = {
+    {"name", (getter)TextIOWrapper_name_get, NULL, NULL},
+    {"closed", (getter)TextIOWrapper_closed_get, NULL, NULL},
+/*    {"mode", (getter)TextIOWrapper_mode_get, NULL, NULL},
+*/
+    {"newlines", (getter)TextIOWrapper_newlines_get, NULL, NULL},
+    {"_CHUNK_SIZE", (getter)TextIOWrapper_chunk_size_get,
+                    (setter)TextIOWrapper_chunk_size_set, NULL},
+    {0}
+};
+
+PyTypeObject PyTextIOWrapper_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "_io.TextIOWrapper",        /*tp_name*/
+    sizeof(PyTextIOWrapperObject), /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    (destructor)TextIOWrapper_dealloc, /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+            | Py_TPFLAGS_HAVE_GC, /*tp_flags*/
+    TextIOWrapper_doc,          /* tp_doc */
+    (traverseproc)TextIOWrapper_traverse, /* tp_traverse */
+    (inquiry)TextIOWrapper_clear, /* tp_clear */
+    0,                          /* tp_richcompare */
+    offsetof(PyTextIOWrapperObject, weakreflist), /*tp_weaklistoffset*/
+    0,                          /* tp_iter */
+    (iternextfunc)TextIOWrapper_iternext, /* tp_iternext */
+    TextIOWrapper_methods,      /* tp_methods */
+    TextIOWrapper_members,      /* tp_members */
+    TextIOWrapper_getset,       /* tp_getset */
+    0,                          /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    offsetof(PyTextIOWrapperObject, dict), /*tp_dictoffset*/
+    (initproc)TextIOWrapper_init, /* tp_init */
+    0,                          /* tp_alloc */
+    PyType_GenericNew,          /* tp_new */
+};
diff --git a/Modules/io.c b/Modules/io.c
new file mode 100644
index 0000000..58b5798
--- /dev/null
+++ b/Modules/io.c
@@ -0,0 +1,760 @@
+/*
+    An implementation of the new I/O lib as defined by PEP 3116 - "New I/O"
+    
+    Classes defined here: UnsupportedOperation, BlockingIOError.
+    Functions defined here: open().
+    
+    Mostly written by Amaury Forgeot d'Arc
+*/
+
+#define PY_SSIZE_T_CLEAN
+#include "Python.h"
+#include "structmember.h"
+#include "_iomodule.h"
+
+#ifdef HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif /* HAVE_SYS_TYPES_H */
+
+#ifdef HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif /* HAVE_SYS_STAT_H */
+
+
+/* Various interned strings */
+
+PyObject *_PyIO_str_close;
+PyObject *_PyIO_str_closed;
+PyObject *_PyIO_str_decode;
+PyObject *_PyIO_str_encode;
+PyObject *_PyIO_str_fileno;
+PyObject *_PyIO_str_flush;
+PyObject *_PyIO_str_getstate;
+PyObject *_PyIO_str_isatty;
+PyObject *_PyIO_str_newlines;
+PyObject *_PyIO_str_nl;
+PyObject *_PyIO_str_read;
+PyObject *_PyIO_str_read1;
+PyObject *_PyIO_str_readable;
+PyObject *_PyIO_str_readinto;
+PyObject *_PyIO_str_readline;
+PyObject *_PyIO_str_reset;
+PyObject *_PyIO_str_seek;
+PyObject *_PyIO_str_seekable;
+PyObject *_PyIO_str_tell;
+PyObject *_PyIO_str_truncate;
+PyObject *_PyIO_str_writable;
+PyObject *_PyIO_str_write;
+
+PyObject *_PyIO_empty_str;
+PyObject *_PyIO_empty_bytes;
+
+
+PyDoc_STRVAR(module_doc,
+"The io module provides the Python interfaces to stream handling. The\n"
+"builtin open function is defined in this module.\n"
+"\n"
+"At the top of the I/O hierarchy is the abstract base class IOBase. It\n"
+"defines the basic interface to a stream. Note, however, that there is no\n"
+"seperation between reading and writing to streams; implementations are\n"
+"allowed to throw an IOError if they do not support a given operation.\n"
+"\n"
+"Extending IOBase is RawIOBase which deals simply with the reading and\n"
+"writing of raw bytes to a stream. FileIO subc lasses RawIOBase to provide\n"
+"an interface to OS files.\n"
+"\n"
+"BufferedIOBase deals with buffering on a raw byte stream (RawIOBase). Its\n"
+"subclasses, BufferedWriter, BufferedReader, and BufferedRWPair buffer\n"
+"streams that are readable, writable, and both respectively.\n"
+"BufferedRandom provides a buffered interface to random access\n"
+"streams. BytesIO is a simple stream of in-memory bytes.\n"
+"\n"
+"Another IOBase subclass, TextIOBase, deals with the encoding and decoding\n"
+"of streams into text. TextIOWrapper, which extends it, is a buffered text\n"
+"interface to a buffered raw stream (`BufferedIOBase`). Finally, StringIO\n"
+"is a in-memory stream for text.\n"
+"\n"
+"Argument names are not part of the specification, and only the arguments\n"
+"of open() are intended to be used as keyword arguments.\n"
+"\n"
+"data:\n"
+"\n"
+"DEFAULT_BUFFER_SIZE\n"
+"\n"
+"   An int containing the default buffer size used by the module's buffered\n"
+"   I/O classes. open() uses the file's blksize (as obtained by os.stat) if\n"
+"   possible.\n"
+    );
+
+
+/*
+ * BlockingIOError extends IOError
+ */
+
+static int
+BlockingIOError_init(PyBlockingIOErrorObject *self, PyObject *args,
+                     PyObject *kwds)
+{
+    PyObject *myerrno = NULL, *strerror = NULL;
+    PyObject *baseargs = NULL;
+    Py_ssize_t written = 0;
+
+    assert(PyTuple_Check(args));
+
+    self->written = 0;
+    if (!PyArg_ParseTuple(args, "OO|n:BlockingIOError",
+                          &myerrno, &strerror, &written))
+        return -1;
+
+    baseargs = PyTuple_Pack(2, myerrno, strerror);
+    if (baseargs == NULL)
+        return -1;
+    /* This will take care of initializing of myerrno and strerror members */
+    if (((PyTypeObject *)PyExc_IOError)->tp_init(
+                (PyObject *)self, baseargs, kwds) == -1) {
+        Py_DECREF(baseargs);
+        return -1;
+    }
+    Py_DECREF(baseargs);
+
+    self->written = written;
+    return 0;
+}
+
+static PyMemberDef BlockingIOError_members[] = {
+    {"characters_written", T_PYSSIZET, offsetof(PyBlockingIOErrorObject, written), 0},
+    {NULL}  /* Sentinel */
+};
+
+static PyTypeObject _PyExc_BlockingIOError = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "BlockingIOError", /*tp_name*/
+    sizeof(PyBlockingIOErrorObject), /*tp_basicsize*/
+    0,                          /*tp_itemsize*/
+    0,                          /*tp_dealloc*/
+    0,                          /*tp_print*/
+    0,                          /*tp_getattr*/
+    0,                          /*tp_setattr*/
+    0,                          /*tp_compare */
+    0,                          /*tp_repr*/
+    0,                          /*tp_as_number*/
+    0,                          /*tp_as_sequence*/
+    0,                          /*tp_as_mapping*/
+    0,                          /*tp_hash */
+    0,                          /*tp_call*/
+    0,                          /*tp_str*/
+    0,                          /*tp_getattro*/
+    0,                          /*tp_setattro*/
+    0,                          /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
+    PyDoc_STR("Exception raised when I/O would block "
+              "on a non-blocking I/O stream"), /* tp_doc */
+    0,                          /* tp_traverse */
+    0,                          /* tp_clear */
+    0,                          /* tp_richcompare */
+    0,                          /* tp_weaklistoffset */
+    0,                          /* tp_iter */
+    0,                          /* tp_iternext */
+    0,                          /* tp_methods */
+    BlockingIOError_members,    /* tp_members */
+    0,                          /* tp_getset */
+    0,                          /* tp_base */
+    0,                          /* tp_dict */
+    0,                          /* tp_descr_get */
+    0,                          /* tp_descr_set */
+    0,                          /* tp_dictoffset */
+    (initproc)BlockingIOError_init, /* tp_init */
+    0,                          /* tp_alloc */
+    0,                          /* tp_new */
+};
+PyObject *PyExc_BlockingIOError = (PyObject *)&_PyExc_BlockingIOError;
+
+
+/*
+ * The main open() function
+ */
+PyDoc_STRVAR(open_doc,
+"Open file and return a stream.  Raise IOError upon failure.\n"
+"\n"
+"file is either a text or byte string giving the name (and the path\n"
+"if the file isn't in the current working directory) of the file to\n"
+"be opened or an integer file descriptor of the file to be\n"
+"wrapped. (If a file descriptor is given, it is closed when the\n"
+"returned I/O object is closed, unless closefd is set to False.)\n"
+"\n"
+"mode is an optional string that specifies the mode in which the file\n"
+"is opened. It defaults to 'r' which means open for reading in text\n"
+"mode.  Other common values are 'w' for writing (truncating the file if\n"
+"it already exists), and 'a' for appending (which on some Unix systems,\n"
+"means that all writes append to the end of the file regardless of the\n"
+"current seek position). In text mode, if encoding is not specified the\n"
+"encoding used is platform dependent. (For reading and writing raw\n"
+"bytes use binary mode and leave encoding unspecified.) The available\n"
+"modes are:\n"
+"\n"
+"========= ===============================================================\n"
+"Character Meaning\n"
+"--------- ---------------------------------------------------------------\n"
+"'r'       open for reading (default)\n"
+"'w'       open for writing, truncating the file first\n"
+"'a'       open for writing, appending to the end of the file if it exists\n"
+"'b'       binary mode\n"
+"'t'       text mode (default)\n"
+"'+'       open a disk file for updating (reading and writing)\n"
+"'U'       universal newline mode (for backwards compatibility; unneeded\n"
+"          for new code)\n"
+"========= ===============================================================\n"
+"\n"
+"The default mode is 'rt' (open for reading text). For binary random\n"
+"access, the mode 'w+b' opens and truncates the file to 0 bytes, while\n"
+"'r+b' opens the file without truncation.\n"
+"\n"
+"Python distinguishes between files opened in binary and text modes,\n"
+"even when the underlying operating system doesn't. Files opened in\n"
+"binary mode (appending 'b' to the mode argument) return contents as\n"
+"bytes objects without any decoding. In text mode (the default, or when\n"
+"'t' is appended to the mode argument), the contents of the file are\n"
+"returned as strings, the bytes having been first decoded using a\n"
+"platform-dependent encoding or using the specified encoding if given.\n"
+"\n"
+"buffering is an optional integer used to set the buffering policy. By\n"
+"default full buffering is on. Pass 0 to switch buffering off (only\n"
+"allowed in binary mode), 1 to set line buffering, and an integer > 1\n"
+"for full buffering.\n"
+"\n"
+"encoding is the name of the encoding used to decode or encode the\n"
+"file. This should only be used in text mode. The default encoding is\n"
+"platform dependent, but any encoding supported by Python can be\n"
+"passed.  See the codecs module for the list of supported encodings.\n"
+"\n"
+"errors is an optional string that specifies how encoding errors are to\n"
+"be handled---this argument should not be used in binary mode. Pass\n"
+"'strict' to raise a ValueError exception if there is an encoding error\n"
+"(the default of None has the same effect), or pass 'ignore' to ignore\n"
+"errors. (Note that ignoring encoding errors can lead to data loss.)\n"
+"See the documentation for codecs.register for a list of the permitted\n"
+"encoding error strings.\n"
+"\n"
+"newline controls how universal newlines works (it only applies to text\n"
+"mode). It can be None, '', '\\n', '\\r', and '\\r\\n'.  It works as\n"
+"follows:\n"
+"\n"
+"* On input, if newline is None, universal newlines mode is\n"
+"  enabled. Lines in the input can end in '\\n', '\\r', or '\\r\\n', and\n"
+"  these are translated into '\\n' before being returned to the\n"
+"  caller. If it is '', universal newline mode is enabled, but line\n"
+"  endings are returned to the caller untranslated. If it has any of\n"
+"  the other legal values, input lines are only terminated by the given\n"
+"  string, and the line ending is returned to the caller untranslated.\n"
+"\n"
+"* On output, if newline is None, any '\\n' characters written are\n"
+"  translated to the system default line separator, os.linesep. If\n"
+"  newline is '', no translation takes place. If newline is any of the\n"
+"  other legal values, any '\\n' characters written are translated to\n"
+"  the given string.\n"
+"\n"
+"If closefd is False, the underlying file descriptor will be kept open\n"
+"when the file is closed. This does not work when a file name is given\n"
+"and must be True in that case.\n"
+"\n"
+"open() returns a file object whose type depends on the mode, and\n"
+"through which the standard file operations such as reading and writing\n"
+"are performed. When open() is used to open a file in a text mode ('w',\n"
+"'r', 'wt', 'rt', etc.), it returns a TextIOWrapper. When used to open\n"
+"a file in a binary mode, the returned class varies: in read binary\n"
+"mode, it returns a BufferedReader; in write binary and append binary\n"
+"modes, it returns a BufferedWriter, and in read/write mode, it returns\n"
+"a BufferedRandom.\n"
+"\n"
+"It is also possible to use a string or bytearray as a file for both\n"
+"reading and writing. For strings StringIO can be used like a file\n"
+"opened in a text mode, and for bytes a BytesIO can be used like a file\n"
+"opened in a binary mode.\n"
+    );
+
+static PyObject *
+io_open(PyObject *self, PyObject *args, PyObject *kwds)
+{
+    char *kwlist[] = {"file", "mode", "buffering",
+                      "encoding", "errors", "newline",
+                      "closefd", NULL};
+    PyObject *file;
+    char *mode = "r";
+    int buffering = -1, closefd = 1;
+    char *encoding = NULL, *errors = NULL, *newline = NULL;
+    unsigned i;
+
+    int reading = 0, writing = 0, appending = 0, updating = 0;
+    int text = 0, binary = 0, universal = 0;
+
+    char rawmode[5], *m;
+    int line_buffering, isatty;
+
+    PyObject *raw, *modeobj = NULL, *buffer = NULL, *wrapper = NULL;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|sizzzi:open", kwlist,
+                                     &file, &mode, &buffering,
+                                     &encoding, &errors, &newline,
+                                     &closefd)) {
+        return NULL;
+    }
+
+    if (!PyUnicode_Check(file) &&
+	!PyBytes_Check(file) &&
+	!PyNumber_Check(file)) {
+        PyErr_Format(PyExc_TypeError, "invalid file: %R", file);
+        return NULL;
+    }
+
+    /* Decode mode */
+    for (i = 0; i < strlen(mode); i++) {
+        char c = mode[i];
+
+        switch (c) {
+        case 'r':
+            reading = 1;
+            break;
+        case 'w':
+            writing = 1;
+            break;
+        case 'a':
+            appending = 1;
+            break;
+        case '+':
+            updating = 1;
+            break;
+        case 't':
+            text = 1;
+            break;
+        case 'b':
+            binary = 1;
+            break;
+        case 'U':
+            universal = 1;
+            reading = 1;
+            break;
+        default:
+            goto invalid_mode;
+        }
+
+        /* c must not be duplicated */
+        if (strchr(mode+i+1, c)) {
+          invalid_mode:
+            PyErr_Format(PyExc_ValueError, "invalid mode: '%s'", mode);
+            return NULL;
+        }
+
+    }
+
+    m = rawmode;
+    if (reading)   *(m++) = 'r';
+    if (writing)   *(m++) = 'w';
+    if (appending) *(m++) = 'a';
+    if (updating)  *(m++) = '+';
+    *m = '\0';
+
+    /* Parameters validation */
+    if (universal) {
+        if (writing || appending) {
+            PyErr_SetString(PyExc_ValueError,
+                            "can't use U and writing mode at once");
+            return NULL;
+        }
+        reading = 1;
+    }
+
+    if (text && binary) {
+        PyErr_SetString(PyExc_ValueError,
+                        "can't have text and binary mode at once");
+        return NULL;
+    }
+
+    if (reading + writing + appending > 1) {
+        PyErr_SetString(PyExc_ValueError,
+                        "must have exactly one of read/write/append mode");
+        return NULL;
+    }
+
+    if (binary && encoding != NULL) {
+        PyErr_SetString(PyExc_ValueError,
+                        "binary mode doesn't take an encoding argument");
+        return NULL;
+    }
+
+    if (binary && errors != NULL) {
+        PyErr_SetString(PyExc_ValueError,
+                        "binary mode doesn't take an errors argument");
+        return NULL;
+    }
+
+    if (binary && newline != NULL) {
+        PyErr_SetString(PyExc_ValueError,
+                        "binary mode doesn't take a newline argument");
+        return NULL;
+    }
+
+    /* Create the Raw file stream */
+    raw = PyObject_CallFunction((PyObject *)&PyFileIO_Type,
+				"Osi", file, rawmode, closefd);
+    if (raw == NULL)
+        return NULL;
+
+    modeobj = PyUnicode_FromString(mode);
+    if (modeobj == NULL)
+        goto error;
+
+    /* buffering */
+    {
+        PyObject *res = PyObject_CallMethod(raw, "isatty", NULL);
+        if (res == NULL)
+            goto error;
+        isatty = PyLong_AsLong(res);
+        Py_DECREF(res);
+        if (isatty == -1 && PyErr_Occurred())
+            goto error;
+    }
+
+    if (buffering == 1 || (buffering < 0 && isatty)) {
+        buffering = -1;
+        line_buffering = 1;
+    }
+    else
+        line_buffering = 0;
+
+    if (buffering < 0) {
+        buffering = DEFAULT_BUFFER_SIZE;
+#ifdef HAVE_STRUCT_STAT_ST_BLKSIZE
+        {
+            struct stat st;
+            long fileno;
+            PyObject *res = PyObject_CallMethod(raw, "fileno", NULL);
+            if (res == NULL)
+                goto error;
+
+            fileno = PyLong_AsLong(res);
+            Py_DECREF(res);
+            if (fileno == -1 && PyErr_Occurred())
+                goto error;
+
+            if (fstat(fileno, &st) >= 0)
+                buffering = st.st_blksize;
+        }
+#endif
+    }
+    if (buffering < 0) {
+        PyErr_SetString(PyExc_ValueError,
+                        "invalid buffering size");
+        goto error;
+    }
+
+    /* if not buffering, returns the raw file object */
+    if (buffering == 0) {
+        if (!binary) {
+            PyErr_SetString(PyExc_ValueError,
+                            "can't have unbuffered text I/O");
+            goto error;
+        }
+
+        Py_DECREF(modeobj);
+        return raw;
+    }
+
+    /* wraps into a buffered file */
+    {
+        PyObject *Buffered_class;
+
+        if (updating)
+            Buffered_class = (PyObject *)&PyBufferedRandom_Type;
+        else if (writing || appending)
+            Buffered_class = (PyObject *)&PyBufferedWriter_Type;
+        else if (reading)
+            Buffered_class = (PyObject *)&PyBufferedReader_Type;
+        else {
+            PyErr_Format(PyExc_ValueError,
+                         "unknown mode: '%s'", mode);
+            goto error;
+        }
+
+        buffer = PyObject_CallFunction(Buffered_class, "Oi", raw, buffering);
+    }
+    Py_CLEAR(raw);
+    if (buffer == NULL)
+        goto error;
+
+
+    /* if binary, returns the buffered file */
+    if (binary) {
+        Py_DECREF(modeobj);
+        return buffer;
+    }
+
+    /* wraps into a TextIOWrapper */
+    wrapper = PyObject_CallFunction((PyObject *)&PyTextIOWrapper_Type,
+				    "Osssi",
+				    buffer,
+				    encoding, errors, newline,
+				    line_buffering);
+    Py_CLEAR(buffer);
+    if (wrapper == NULL)
+        goto error;
+
+    if (PyObject_SetAttrString(wrapper, "mode", modeobj) < 0)
+        goto error;
+    Py_DECREF(modeobj);
+    return wrapper;
+
+  error:
+    Py_XDECREF(raw);
+    Py_XDECREF(modeobj);
+    Py_XDECREF(buffer);
+    Py_XDECREF(wrapper);
+    return NULL;
+}
+
+/*
+ * Private helpers for the io module.
+ */
+
+Py_off_t
+PyNumber_AsOff_t(PyObject *item, PyObject *err)
+{
+    Py_off_t result;
+    PyObject *runerr;
+    PyObject *value = PyNumber_Index(item);
+    if (value == NULL)
+        return -1;
+
+    /* We're done if PyLong_AsSsize_t() returns without error. */
+    result = PyLong_AsOff_t(value);
+    if (result != -1 || !(runerr = PyErr_Occurred()))
+        goto finish;
+
+    /* Error handling code -- only manage OverflowError differently */
+    if (!PyErr_GivenExceptionMatches(runerr, PyExc_OverflowError))
+        goto finish;
+
+    PyErr_Clear();
+    /* If no error-handling desired then the default clipping
+       is sufficient.
+     */
+    if (!err) {
+        assert(PyLong_Check(value));
+        /* Whether or not it is less than or equal to
+           zero is determined by the sign of ob_size
+        */
+        if (_PyLong_Sign(value) < 0)
+            result = PY_OFF_T_MIN;
+        else
+            result = PY_OFF_T_MAX;
+    }
+    else {
+        /* Otherwise replace the error with caller's error object. */
+        PyErr_Format(err,
+                     "cannot fit '%.200s' into an offset-sized integer",
+                     item->ob_type->tp_name);
+    }
+
+ finish:
+    Py_DECREF(value);
+    return result;
+}
+
+static int
+iomodule_traverse(PyObject *mod, visitproc visit, void *arg) {
+    _PyIO_State *state = IO_MOD_STATE(mod);
+    if (!state->initialized)
+        return 0;
+    Py_VISIT(state->os_module);
+    if (state->locale_module != NULL) {
+        Py_VISIT(state->locale_module);
+    }
+    Py_VISIT(state->unsupported_operation);
+    return 0;
+}
+
+static int
+iomodule_clear(PyObject *mod) {
+    _PyIO_State *state = IO_MOD_STATE(mod);
+    if (!state->initialized)
+        return 0;
+    Py_CLEAR(state->os_module);
+    if (state->locale_module != NULL)
+        Py_CLEAR(state->locale_module);
+    Py_CLEAR(state->unsupported_operation);
+    return 0;
+}
+
+static void
+iomodule_free(PyObject *mod) {
+    iomodule_clear(mod);
+}
+
+/*
+ * Module definition
+ */
+
+static PyMethodDef module_methods[] = {
+    {"open", (PyCFunction)io_open, METH_VARARGS|METH_KEYWORDS, open_doc},
+    {NULL, NULL}
+};
+
+struct PyModuleDef _PyIO_Module = {
+    PyModuleDef_HEAD_INIT,
+    "io",
+    module_doc,
+    sizeof(_PyIO_State),
+    module_methods,
+    NULL,
+    iomodule_traverse,
+    iomodule_clear,
+    (freefunc)iomodule_free,
+};
+
+PyMODINIT_FUNC
+PyInit__io(void)
+{
+    PyObject *m = PyModule_Create(&_PyIO_Module);
+    _PyIO_State *state = NULL;
+    if (m == NULL)
+        return NULL;
+    state = IO_MOD_STATE(m);
+    state->initialized = 0;
+
+    /* put os in the module state */
+    state->os_module = PyImport_ImportModule("os");
+    if (state->os_module == NULL)
+        goto fail;
+
+#define ADD_TYPE(type, name) \
+    if (PyType_Ready(type) < 0) \
+        goto fail; \
+    Py_INCREF(type); \
+    if (PyModule_AddObject(m, name, (PyObject *)type) < 0) {  \
+        Py_DECREF(type); \
+        goto fail; \
+    }
+
+    /* DEFAULT_BUFFER_SIZE */
+    if (PyModule_AddIntMacro(m, DEFAULT_BUFFER_SIZE) < 0)
+        goto fail;
+
+    /* UnsupportedOperation inherits from ValueError and IOError */
+    state->unsupported_operation = PyObject_CallFunction(
+        (PyObject *)&PyType_Type, "s(OO){}",
+        "UnsupportedOperation", PyExc_ValueError, PyExc_IOError);
+    if (state->unsupported_operation == NULL)
+        goto fail;
+    Py_INCREF(state->unsupported_operation);
+    if (PyModule_AddObject(m, "UnsupportedOperation",
+                           state->unsupported_operation) < 0)
+        goto fail;
+
+    /* BlockingIOError */
+    _PyExc_BlockingIOError.tp_base = (PyTypeObject *) PyExc_IOError;
+    ADD_TYPE(&_PyExc_BlockingIOError, "BlockingIOError");
+
+    /* Concrete base types of the IO ABCs.
+       (the ABCs themselves are declared through inheritance in io.py)
+    */
+    ADD_TYPE(&PyIOBase_Type, "_IOBase");
+    ADD_TYPE(&PyRawIOBase_Type, "_RawIOBase");
+    ADD_TYPE(&PyBufferedIOBase_Type, "_BufferedIOBase");
+    ADD_TYPE(&PyTextIOBase_Type, "_TextIOBase");
+
+    /* Implementation of concrete IO objects. */
+    /* FileIO */
+    PyFileIO_Type.tp_base = &PyRawIOBase_Type;
+    ADD_TYPE(&PyFileIO_Type, "FileIO");
+
+    /* BytesIO */
+    PyBytesIO_Type.tp_base = &PyBufferedIOBase_Type;
+    ADD_TYPE(&PyBytesIO_Type, "BytesIO");
+
+    /* StringIO */
+    PyStringIO_Type.tp_base = &PyTextIOBase_Type;
+    ADD_TYPE(&PyStringIO_Type, "StringIO");
+
+    /* BufferedReader */
+    PyBufferedReader_Type.tp_base = &PyBufferedIOBase_Type;
+    ADD_TYPE(&PyBufferedReader_Type, "BufferedReader");
+
+    /* BufferedWriter */
+    PyBufferedWriter_Type.tp_base = &PyBufferedIOBase_Type;
+    ADD_TYPE(&PyBufferedWriter_Type, "BufferedWriter");
+
+    /* BufferedRWPair */
+    PyBufferedRWPair_Type.tp_base = &PyBufferedIOBase_Type;
+    ADD_TYPE(&PyBufferedRWPair_Type, "BufferedRWPair");
+
+    /* BufferedRandom */
+    PyBufferedRandom_Type.tp_base = &PyBufferedIOBase_Type;
+    ADD_TYPE(&PyBufferedRandom_Type, "BufferedRandom");
+
+    /* TextIOWrapper */
+    PyTextIOWrapper_Type.tp_base = &PyTextIOBase_Type;
+    ADD_TYPE(&PyTextIOWrapper_Type, "TextIOWrapper");
+
+    /* IncrementalNewlineDecoder */
+    ADD_TYPE(&PyIncrementalNewlineDecoder_Type, "IncrementalNewlineDecoder");
+
+    /* Interned strings */
+    if (!(_PyIO_str_close = PyUnicode_InternFromString("close")))
+        goto fail;
+    if (!(_PyIO_str_closed = PyUnicode_InternFromString("closed")))
+        goto fail;
+    if (!(_PyIO_str_decode = PyUnicode_InternFromString("decode")))
+        goto fail;
+    if (!(_PyIO_str_encode = PyUnicode_InternFromString("encode")))
+        goto fail;
+    if (!(_PyIO_str_fileno = PyUnicode_InternFromString("fileno")))
+        goto fail;
+    if (!(_PyIO_str_flush = PyUnicode_InternFromString("flush")))
+        goto fail;
+    if (!(_PyIO_str_getstate = PyUnicode_InternFromString("getstate")))
+        goto fail;
+    if (!(_PyIO_str_isatty = PyUnicode_InternFromString("isatty")))
+        goto fail;
+    if (!(_PyIO_str_newlines = PyUnicode_InternFromString("newlines")))
+        goto fail;
+    if (!(_PyIO_str_nl = PyUnicode_InternFromString("\n")))
+        goto fail;
+    if (!(_PyIO_str_read = PyUnicode_InternFromString("read")))
+        goto fail;
+    if (!(_PyIO_str_read1 = PyUnicode_InternFromString("read1")))
+        goto fail;
+    if (!(_PyIO_str_readable = PyUnicode_InternFromString("readable")))
+        goto fail;
+    if (!(_PyIO_str_readinto = PyUnicode_InternFromString("readinto")))
+        goto fail;
+    if (!(_PyIO_str_readline = PyUnicode_InternFromString("readline")))
+        goto fail;
+    if (!(_PyIO_str_reset = PyUnicode_InternFromString("reset")))
+        goto fail;
+    if (!(_PyIO_str_seek = PyUnicode_InternFromString("seek")))
+        goto fail;
+    if (!(_PyIO_str_seekable = PyUnicode_InternFromString("seekable")))
+        goto fail;
+    if (!(_PyIO_str_tell = PyUnicode_InternFromString("tell")))
+        goto fail;
+    if (!(_PyIO_str_truncate = PyUnicode_InternFromString("truncate")))
+        goto fail;
+    if (!(_PyIO_str_write = PyUnicode_InternFromString("write")))
+        goto fail;
+    if (!(_PyIO_str_writable = PyUnicode_InternFromString("writable")))
+        goto fail;
+    
+    if (!(_PyIO_empty_str = PyUnicode_FromStringAndSize(NULL, 0)))
+        goto fail;
+    if (!(_PyIO_empty_bytes = PyBytes_FromStringAndSize(NULL, 0)))
+        goto fail;
+
+    state->initialized = 1;
+
+    return m;
+
+  fail:
+    Py_XDECREF(state->os_module);
+    Py_XDECREF(state->unsupported_operation);
+    Py_DECREF(m);
+    return NULL;
+}
diff --git a/PC/VC6/pythoncore.dsp b/PC/VC6/pythoncore.dsp
index 6f6abdb..3803c03 100644
--- a/PC/VC6/pythoncore.dsp
+++ b/PC/VC6/pythoncore.dsp
@@ -97,6 +97,10 @@
 # End Source File
 # Begin Source File
 
+SOURCE=..\..\Modules\_bufferedio.c
+# End Source File
+# Begin Source File
+
 SOURCE=..\..\Modules\_bytesio.c
 # End Source File
 # Begin Source File
@@ -149,6 +153,10 @@
 # End Source File
 # Begin Source File
 
+SOURCE=..\..\Modules\_iobase.c
+# End Source File
+# Begin Source File
+
 SOURCE=..\..\Modules\_json.c
 # End Source File
 # Begin Source File
@@ -185,6 +193,10 @@
 # End Source File
 # Begin Source File
 
+SOURCE=..\..\Modules\_textio.c
+# End Source File
+# Begin Source File
+
 SOURCE=..\..\Modules\_threadmodule.c
 # End Source File
 # Begin Source File
@@ -463,6 +475,10 @@
 # End Source File
 # Begin Source File
 
+SOURCE=..\..\Modules\io.c
+# End Source File
+# Begin Source File
+
 SOURCE=..\..\Objects\iterobject.c
 # End Source File
 # Begin Source File
diff --git a/PC/config.c b/PC/config.c
index f2bdfdb..5f58f20 100644
--- a/PC/config.c
+++ b/PC/config.c
@@ -58,9 +58,7 @@
 extern PyObject* PyInit__subprocess(void);
 extern PyObject* PyInit__lsprof(void);
 extern PyObject* PyInit__ast(void);
-extern PyObject* PyInit__fileio(void);
-extern PyObject* PyInit__bytesio(void);
-extern PyObject* PyInit__stringio(void);
+extern PyObject* PyInit__io(void);
 extern PyObject* PyInit__pickle(void);
 extern PyObject* PyInit_atexit(void);
 extern PyObject* _PyWarnings_Init(void);
@@ -150,9 +148,7 @@
         {"sys", NULL},
         {"_warnings", _PyWarnings_Init},
 
-        {"_fileio", PyInit__fileio},
-        {"_bytesio", PyInit__bytesio},
-        {"_stringio", PyInit__stringio},
+        {"_io", PyInit__io},
         {"_pickle", PyInit__pickle},
         {"atexit", PyInit_atexit},
 
diff --git a/PCbuild/pythoncore.vcproj b/PCbuild/pythoncore.vcproj
index 33fd07b..dc64bfa 100644
--- a/PCbuild/pythoncore.vcproj
+++ b/PCbuild/pythoncore.vcproj
@@ -975,6 +975,10 @@
 				>
 			</File>
 			<File
+				RelativePath="..\Modules\_bufferedio.c"
+				>
+			</File>
+			<File
 				RelativePath="..\Modules\_codecsmodule.c"
 				>
 			</File>
@@ -1003,6 +1007,14 @@
 				>
 			</File>
 			<File
+				RelativePath="..\Modules\_iobase.c"
+				>
+			</File>
+			<File
+				RelativePath="..\Modules\_iomodule.h"
+				>
+			</File>
+			<File
 				RelativePath="..\Modules\_json.c"
 				>
 			</File>
@@ -1035,6 +1047,10 @@
 				>
 			</File>
 			<File
+				RelativePath="..\Modules\_textio.c"
+				>
+			</File>
+			<File
 				RelativePath="..\Modules\_weakref.c"
 				>
 			</File>
@@ -1075,6 +1091,10 @@
 				>
 			</File>
 			<File
+				RelativePath="..\Modules\io.c"
+				>
+			</File>
+			<File
 				RelativePath="..\Modules\main.c"
 				>
 			</File>
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index dee18b6..7add832 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -769,7 +769,7 @@
 	}
 
 	text = PyUnicode_FromString(name);
-	if (text == NULL || PyObject_SetAttrString(raw, "_name", text) < 0)
+	if (text == NULL || PyObject_SetAttrString(raw, "name", text) < 0)
 		goto error;
 	res = PyObject_CallMethod(raw, "isatty", "");
 	if (res == NULL)
diff --git a/setup.py b/setup.py
index 58f7e8c..712f54c 100644
--- a/setup.py
+++ b/setup.py
@@ -982,8 +982,6 @@
         # Thomas Heller's _ctypes module
         self.detect_ctypes(inc_dirs, lib_dirs)
 
-        # _fileio -- supposedly cross platform
-        exts.append(Extension('_fileio', ['_fileio.c']))
         # Richard Oudkerk's multiprocessing module
         if platform == 'win32':             # Windows
             macros = dict()