Issue #5863: Rewrite BZ2File in pure Python, and allow it to accept
file-like objects using a new `fileobj` constructor argument. Patch by
Nadeem Vawda.
diff --git a/Lib/bz2.py b/Lib/bz2.py
new file mode 100644
index 0000000..667fffd
--- /dev/null
+++ b/Lib/bz2.py
@@ -0,0 +1,392 @@
+"""Interface to the libbzip2 compression library.
+
+This module provides a file interface, classes for incremental
+(de)compression, and functions for one-shot (de)compression.
+"""
+
+__all__ = ["BZ2File", "BZ2Compressor", "BZ2Decompressor", "compress",
+ "decompress"]
+
+__author__ = "Nadeem Vawda <nadeem.vawda@gmail.com>"
+
+import io
+import threading
+import warnings
+
+from _bz2 import BZ2Compressor, BZ2Decompressor
+
+
+_MODE_CLOSED = 0
+_MODE_READ = 1
+_MODE_READ_EOF = 2
+_MODE_WRITE = 3
+
+_BUFFER_SIZE = 8192
+
+
+class BZ2File(io.BufferedIOBase):
+
+ """A file object providing transparent bzip2 (de)compression.
+
+ A BZ2File can act as a wrapper for an existing file object, or refer
+ directly to a named file on disk.
+
+ Note that BZ2File provides a *binary* file interface - data read is
+ returned as bytes, and data to be written should be given as bytes.
+ """
+
+ def __init__(self, filename=None, mode="r", buffering=None,
+ compresslevel=9, fileobj=None):
+ """Open a bzip2-compressed file.
+
+ If filename is given, open the named file. Otherwise, operate on
+ the file object given by fileobj. Exactly one of these two
+ parameters should be provided.
+
+ mode can be 'r' for reading (default), or 'w' for writing.
+
+ buffering is ignored. Its use is deprecated.
+
+ If mode is 'w', compresslevel can be a number between 1 and 9
+ specifying the level of compression: 1 produces the least
+ compression, and 9 (default) produces the most compression.
+ """
+ # This lock must be recursive, so that BufferedIOBase's
+ # readline(), readlines() and writelines() don't deadlock.
+ self._lock = threading.RLock()
+ self._fp = None
+ self._closefp = False
+ self._mode = _MODE_CLOSED
+ self._pos = 0
+ self._size = -1
+
+ if buffering is not None:
+ warnings.warn("Use of 'buffering' argument is deprecated",
+ DeprecationWarning)
+
+ if not (1 <= compresslevel <= 9):
+ raise ValueError("compresslevel must be between 1 and 9")
+
+ if mode in ("", "r", "rb"):
+ mode = "rb"
+ mode_code = _MODE_READ
+ self._decompressor = BZ2Decompressor()
+ self._buffer = None
+ elif mode in ("w", "wb"):
+ mode = "wb"
+ mode_code = _MODE_WRITE
+ self._compressor = BZ2Compressor()
+ else:
+ raise ValueError("Invalid mode: {!r}".format(mode))
+
+ if filename is not None and fileobj is None:
+ self._fp = open(filename, mode)
+ self._closefp = True
+ self._mode = mode_code
+ elif fileobj is not None and filename is None:
+ self._fp = fileobj
+ self._mode = mode_code
+ else:
+ raise ValueError("Must give exactly one of filename and fileobj")
+
+ def close(self):
+ """Flush and close the file.
+
+ May be called more than once without error. Once the file is
+ closed, any other operation on it will raise a ValueError.
+ """
+ with self._lock:
+ if self._mode == _MODE_CLOSED:
+ return
+ try:
+ if self._mode in (_MODE_READ, _MODE_READ_EOF):
+ self._decompressor = None
+ elif self._mode == _MODE_WRITE:
+ self._fp.write(self._compressor.flush())
+ self._compressor = None
+ finally:
+ try:
+ if self._closefp:
+ self._fp.close()
+ finally:
+ self._fp = None
+ self._closefp = False
+ self._mode = _MODE_CLOSED
+ self._buffer = None
+
+ @property
+ def closed(self):
+ """True if this file is closed."""
+ return self._mode == _MODE_CLOSED
+
+ def fileno(self):
+ """Return the file descriptor for the underlying file."""
+ return self._fp.fileno()
+
+ def seekable(self):
+ """Return whether the file supports seeking."""
+ return self.readable()
+
+ def readable(self):
+ """Return whether the file was opened for reading."""
+ return self._mode in (_MODE_READ, _MODE_READ_EOF)
+
+ def writable(self):
+ """Return whether the file was opened for writing."""
+ return self._mode == _MODE_WRITE
+
+ # Mode-checking helper functions.
+
+ def _check_not_closed(self):
+ if self.closed:
+ raise ValueError("I/O operation on closed file")
+
+ def _check_can_read(self):
+ if not self.readable():
+ self._check_not_closed()
+ raise io.UnsupportedOperation("File not open for reading")
+
+ def _check_can_write(self):
+ if not self.writable():
+ self._check_not_closed()
+ raise io.UnsupportedOperation("File not open for writing")
+
+ def _check_can_seek(self):
+ if not self.seekable():
+ self._check_not_closed()
+ raise io.UnsupportedOperation("Seeking is only supported "
+ "on files opening for reading")
+
+ # Fill the readahead buffer if it is empty. Returns False on EOF.
+ def _fill_buffer(self):
+ if self._buffer:
+ return True
+ if self._decompressor.eof:
+ self._mode = _MODE_READ_EOF
+ self._size = self._pos
+ return False
+ rawblock = self._fp.read(_BUFFER_SIZE)
+ if not rawblock:
+ raise EOFError("Compressed file ended before the "
+ "end-of-stream marker was reached")
+ self._buffer = self._decompressor.decompress(rawblock)
+ return True
+
+ # Read data until EOF.
+ # If return_data is false, consume the data without returning it.
+ def _read_all(self, return_data=True):
+ blocks = []
+ while self._fill_buffer():
+ if return_data:
+ blocks.append(self._buffer)
+ self._pos += len(self._buffer)
+ self._buffer = None
+ if return_data:
+ return b"".join(blocks)
+
+ # Read a block of up to n bytes.
+ # If return_data is false, consume the data without returning it.
+ def _read_block(self, n, return_data=True):
+ blocks = []
+ while n > 0 and self._fill_buffer():
+ if n < len(self._buffer):
+ data = self._buffer[:n]
+ self._buffer = self._buffer[n:]
+ else:
+ data = self._buffer
+ self._buffer = None
+ if return_data:
+ blocks.append(data)
+ self._pos += len(data)
+ n -= len(data)
+ if return_data:
+ return b"".join(blocks)
+
+ def peek(self, n=0):
+ """Return buffered data without advancing the file position.
+
+ Always returns at least one byte of data, unless at EOF.
+ The exact number of bytes returned is unspecified.
+ """
+ with self._lock:
+ self._check_can_read()
+ if self._mode == _MODE_READ_EOF or not self._fill_buffer():
+ return b""
+ return self._buffer
+
+ def read(self, size=-1):
+ """Read up to size uncompressed bytes from the file.
+
+ If size is negative or omitted, read until EOF is reached.
+ Returns b'' if the file is already at EOF.
+ """
+ with self._lock:
+ self._check_can_read()
+ if self._mode == _MODE_READ_EOF or size == 0:
+ return b""
+ elif size < 0:
+ return self._read_all()
+ else:
+ return self._read_block(size)
+
+ def read1(self, size=-1):
+ """Read up to size uncompressed bytes with at most one read
+ from the underlying stream.
+
+ Returns b'' if the file is at EOF.
+ """
+ with self._lock:
+ self._check_can_read()
+ if (size == 0 or self._mode == _MODE_READ_EOF or
+ not self._fill_buffer()):
+ return b""
+ if 0 < size < len(self._buffer):
+ data = self._buffer[:size]
+ self._buffer = self._buffer[size:]
+ else:
+ data = self._buffer
+ self._buffer = None
+ self._pos += len(data)
+ return data
+
+ def readinto(self, b):
+ """Read up to len(b) bytes into b.
+
+ Returns the number of bytes read (0 for EOF).
+ """
+ with self._lock:
+ return io.BufferedIOBase.readinto(self, b)
+
+ def readline(self, size=-1):
+ """Read a line of uncompressed bytes from the file.
+
+ The terminating newline (if present) is retained. If size is
+ non-negative, no more than size bytes will be read (in which
+ case the line may be incomplete). Returns b'' if already at EOF.
+ """
+ if not hasattr(size, "__index__"):
+ raise TypeError("Integer argument expected")
+ size = size.__index__()
+ with self._lock:
+ return io.BufferedIOBase.readline(self, size)
+
+ def readlines(self, size=-1):
+ """Read a list of lines of uncompressed bytes from the file.
+
+ size can be specified to control the number of lines read: no
+ further lines will be read once the total size of the lines read
+ so far equals or exceeds size.
+ """
+ if not hasattr(size, "__index__"):
+ raise TypeError("Integer argument expected")
+ size = size.__index__()
+ with self._lock:
+ return io.BufferedIOBase.readlines(self, size)
+
+ def write(self, data):
+ """Write a byte string to the file.
+
+ Returns the number of uncompressed bytes written, which is
+ always len(data). Note that due to buffering, the file on disk
+ may not reflect the data written until close() is called.
+ """
+ with self._lock:
+ self._check_can_write()
+ compressed = self._compressor.compress(data)
+ self._fp.write(compressed)
+ self._pos += len(data)
+ return len(data)
+
+ def writelines(self, seq):
+ """Write a sequence of byte strings to the file.
+
+ Returns the number of uncompressed bytes written.
+ seq can be any iterable yielding byte strings.
+
+ Line separators are not added between the written byte strings.
+ """
+ with self._lock:
+ return io.BufferedIOBase.writelines(self, seq)
+
+ # Rewind the file to the beginning of the data stream.
+ def _rewind(self):
+ self._fp.seek(0, 0)
+ self._mode = _MODE_READ
+ self._pos = 0
+ self._decompressor = BZ2Decompressor()
+ self._buffer = None
+
+ def seek(self, offset, whence=0):
+ """Change the file position.
+
+ The new position is specified by offset, relative to the
+ position indicated by whence. Values for whence are:
+
+ 0: start of stream (default); offset must not be negative
+ 1: current stream position
+ 2: end of stream; offset must not be positive
+
+ Returns the new file position.
+
+ Note that seeking is emulated, so depending on the parameters,
+ this operation may be extremely slow.
+ """
+ with self._lock:
+ self._check_can_seek()
+
+ # Recalculate offset as an absolute file position.
+ if whence == 0:
+ pass
+ elif whence == 1:
+ offset = self._pos + offset
+ elif whence == 2:
+ # Seeking relative to EOF - we need to know the file's size.
+ if self._size < 0:
+ self._read_all(return_data=False)
+ offset = self._size + offset
+ else:
+ raise ValueError("Invalid value for whence: {}".format(whence))
+
+ # Make it so that offset is the number of bytes to skip forward.
+ if offset < self._pos:
+ self._rewind()
+ else:
+ offset -= self._pos
+
+ # Read and discard data until we reach the desired position.
+ if self._mode != _MODE_READ_EOF:
+ self._read_block(offset, return_data=False)
+
+ return self._pos
+
+ def tell(self):
+ """Return the current file position."""
+ with self._lock:
+ self._check_not_closed()
+ return self._pos
+
+
+def compress(data, compresslevel=9):
+ """Compress a block of data.
+
+ compresslevel, if given, must be a number between 1 and 9.
+
+ For incremental compression, use a BZ2Compressor object instead.
+ """
+ comp = BZ2Compressor(compresslevel)
+ return comp.compress(data) + comp.flush()
+
+
+def decompress(data):
+ """Decompress a block of data.
+
+ For incremental decompression, use a BZ2Decompressor object instead.
+ """
+ if len(data) == 0:
+ return b""
+ decomp = BZ2Decompressor()
+ result = decomp.decompress(data)
+ if not decomp.eof:
+ raise ValueError("Compressed data ended before the "
+ "end-of-stream marker was reached")
+ return result