diff --git a/Lib/io.py b/Lib/io.py
index 20821b6..5f503c2 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -415,8 +415,8 @@
     def read(self, n: int = -1) -> bytes:
         """read(n: int = -1) -> bytes.  Read and return up to n bytes.
 
-        If the argument is omitted, or negative, reads and returns all
-        data until EOF.
+        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
@@ -450,6 +450,20 @@
         b[:n] = data
         return n
 
+    def readline(self, sizehint: int = -1) -> bytes:
+        """For backwards compatibility, a (slow) readline()."""
+        if sizehint is None:
+            sizehint = -1
+        res = b""
+        while sizehint < 0 or len(res) < sizehint:
+            b = self.read(1)
+            if not b:
+                break
+            res += b
+            if b == b"\n":
+                break
+        return res
+
     def write(self, b: bytes) -> int:
         """write(b: bytes) -> int.  Write the given buffer to the IO stream.
 
@@ -518,19 +532,25 @@
         return self.raw.isatty()
 
 
-class _MemoryIOMixin(BufferedIOBase):
+class BytesIO(BufferedIOBase):
 
-    # XXX docstring
+    """Buffered I/O implementation using an in-memory bytes buffer."""
 
-    def __init__(self, buffer):
+    # XXX More docs
+
+    def __init__(self, initial_bytes=None):
+        buffer = b""
+        if initial_bytes is not None:
+            buffer += initial_bytes
         self._buffer = buffer
         self._pos = 0
 
     def getvalue(self):
         return self._buffer
 
-    def read(self, n=-1):
-        assert n is not None
+    def read(self, n=None):
+        if n is None:
+            n = -1
         if n < 0:
             n = len(self._buffer)
         newpos = min(len(self._buffer), self._pos + n)
@@ -538,6 +558,9 @@
         self._pos = newpos
         return b
 
+    def read1(self, n):
+        return self.read(n)
+
     def write(self, b):
         n = len(b)
         newpos = self._pos + n
@@ -575,65 +598,6 @@
         return True
 
 
-class BytesIO(_MemoryIOMixin):
-
-    """Buffered I/O implementation using a bytes buffer, like StringIO."""
-
-    # XXX More docs
-
-    def __init__(self, initial_bytes=None):
-        buffer = b""
-        if initial_bytes is not None:
-            buffer += initial_bytes
-        _MemoryIOMixin.__init__(self, buffer)
-
-
-# XXX This should inherit from TextIOBase
-class StringIO(_MemoryIOMixin):
-
-    """Buffered I/O implementation using a string buffer, like StringIO."""
-
-    # XXX More docs
-
-    # Reuses the same code as BytesIO, but encode strings on the way in
-    # and decode them on the way out.
-
-    charsize = len("!".encode("unicode-internal"))
-
-    def __init__(self, initial_string=None):
-        if initial_string is not None:
-            buffer = initial_string.encode("unicode-internal")
-        else:
-            buffer = b""
-        _MemoryIOMixin.__init__(self, buffer)
-
-    def getvalue(self):
-        return self._buffer.encode("unicode-internal")
-
-    def read(self, n=-1):
-        return super(StringIO, self).read(n*self.charsize) \
-                                    .decode("unicode-internal")
-
-    def write(self, s):
-        return super(StringIO, self).write(s.encode("unicode-internal")) \
-                                    //self.charsize
-
-    def seek(self, pos, whence=0):
-        return super(StringIO, self).seek(self.charsize*pos, whence) \
-                                    //self.charsize
-
-    def tell(self):
-        return super(StringIO, self).tell()//self.charsize
-
-    def truncate(self, pos=None):
-        if pos is not None:
-            pos *= self.charsize
-        return super(StringIO, self).truncate(pos)//self.charsize
-
-    def readinto(self, b: bytes) -> int:
-        self._unsupported("readinto")
-
-
 class BufferedReader(_BufferedIOMixin):
 
     """Buffer for a readable sequential RawIO object."""
@@ -646,7 +610,7 @@
         self._read_buf = b""
         self.buffer_size = buffer_size
 
-    def read(self, n=-1):
+    def read(self, n=None):
         """Read n bytes.
 
         Returns exactly n bytes of data unless the underlying raw IO
@@ -654,7 +618,8 @@
         mode. If n is negative, read until EOF or until read() would
         block.
         """
-        assert n is not None
+        if n is None:
+            n = -1
         nodata_val = b""
         while n < 0 or len(self._read_buf) < n:
             to_read = max(self.buffer_size,
@@ -801,7 +766,9 @@
         self.reader = BufferedReader(reader, buffer_size)
         self.writer = BufferedWriter(writer, buffer_size, max_buffer_size)
 
-    def read(self, n=-1):
+    def read(self, n=None):
+        if n is None:
+            n = -1
         return self.reader.read(n)
 
     def readinto(self, b):
@@ -861,7 +828,9 @@
         else:
             return self.raw.tell() - len(self._read_buf)
 
-    def read(self, n=-1):
+    def read(self, n=None):
+        if n is None:
+            n = -1
         self.flush()
         return BufferedReader.read(self, n)
 
@@ -1129,7 +1098,9 @@
         except UnicodeEncodeError:
             return u
 
-    def read(self, n: int = -1):
+    def read(self, n=None):
+        if n is None:
+            n = -1
         decoder = self._decoder or self._get_decoder()
         res = self._pending
         if n < 0:
@@ -1146,7 +1117,7 @@
             self._pending = res[n:]
             return self._simplify(res[:n])
 
-    def __next__(self) -> str:
+    def __next__(self):
         self._telling = False
         line = self.readline()
         if not line:
@@ -1218,3 +1189,17 @@
             return self._simplify(line[:endpos] + "\n")
         else:
             return self._simplify(line[:nextpos])
+
+
+class StringIO(TextIOWrapper):
+
+    # XXX This is really slow, but fully functional
+
+    def __init__(self, initial_value=""):
+        super(StringIO, self).__init__(BytesIO(), "utf-8")
+        if initial_value:
+            self.write(initial_value)
+            self.seek(0)
+
+    def getvalue(self):
+        return self.buffer.getvalue().decode("utf-8")