Bit of code to make a stream look like a buffer

streambuffer.py

from __future__ import absolute_import, division, print_function, unicode_literals
import six

if six.PY2:
    __metaclass__ = type

class StreamBuffer:
    """
    Makes a buffer look like a stream. Assumes infinite stream.
    """
    def __init__(self, stream):
        self._stream = stream
        self._buffer = ""  # XXX: Is there a mutable string type in Python 2?
        self._chunksize = 1  # Used for iteration

    def _readtosize(self, size):
        while len(self._buffer) < size:
            self._buffer += self._stream.read(size-len(self._buffer))

    def __iter__(self):
        for c in self._buffer:
            yield c
        while True:
            l = len(self._buffer)
            self._readtosize(l+self._chunksize)
            for c in self._buffer[l:]:
                yield c

    def __getitem__(self, index):
        if isinstance(index, slice):
            if index.stop is None or index.stop < 0:
                raise IndexError("Slices must have a stop")
            self._readtosize(index.stop)
            return self._buffer[index]
        elif index < 0:
            raise IndexError("Infinite buffers don't support ")
        else:
            return self._buffer[index]

    def __delitem__(self, index):
        """del sb[int|slice]
        Removes part of the buffer, freeing memory.

        Only contiguous chunks at the begining of the buffer will be removed.
        """
        # Frees buffer
        if isinstance(index, slice):
            if index.stop is None or index.stop < 0:
                raise IndexError("Slices must have a stop")
            if index.start not in (None, 0):
                raise IndexError("Slices must be at the start")
            if index.step not in (None, 1):
                raise IndexError("Will only delete contiguous blocks")
            self._readtosize(index.stop)
            self._buffer = self._buffer[index.stop:]  # Can't use del because immutable
        else:
            if index != 0:
                raise IndexError("Will only delete at the begining")
            self._buffer = self._buffer[index+1:]  # Can't use del because immutable