mercurial/py3kcompat.py

httppeer: use compression engine API for decompressing responses

In preparation for supporting multiple compression formats on the
wire protocol, we need all users of the wire protocol to use
compression engine APIs.

This commit ports the HTTP wire protocol client to use the
compression engine API.

The code for handling the HTTPException is a bit hacky. Essentially,
HTTPException could be thrown by any read() from the socket. However,
as part of porting the API, we no longer have a generator wrapping
the socket and we don't have a single place where we can trap the
exception. We solve this by introducing a proxy class that intercepts
read() and converts the exception appropriately.

In the future, we could introduce a new compression engine API that
supports emitting a generator of decompressed chunks. This would
eliminate the need for the proxy class. As I said when I introduced
the decompressorreader() API, I'm not fond of it and would support
transitioning to something better. This can be done as a follow-up,
preferably once all the code is using the compression engine API and
we have a better idea of the API needs of all the consumers.

# py3kcompat.py - compatibility definitions for running hg in py3k
#
# Copyright 2010 Renato Cunha <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import builtins
import numbers

Number = numbers.Number

def bytesformatter(format, args):
    '''Custom implementation of a formatter for bytestrings.

    This function currently relies on the string formatter to do the
    formatting and always returns bytes objects.

    >>> bytesformatter(20, 10)
    0
    >>> bytesformatter('unicode %s, %s!', ('string', 'foo'))
    b'unicode string, foo!'
    >>> bytesformatter(b'test %s', 'me')
    b'test me'
    >>> bytesformatter('test %s', 'me')
    b'test me'
    >>> bytesformatter(b'test %s', b'me')
    b'test me'
    >>> bytesformatter('test %s', b'me')
    b'test me'
    >>> bytesformatter('test %d: %s', (1, b'result'))
    b'test 1: result'
    '''
    # The current implementation just converts from bytes to unicode, do
    # what's needed and then convert the results back to bytes.
    # Another alternative is to use the Python C API implementation.
    if isinstance(format, Number):
        # If the fixer erroneously passes a number remainder operation to
        # bytesformatter, we just return the correct operation
        return format % args
    if isinstance(format, bytes):
        format = format.decode('utf-8', 'surrogateescape')
    if isinstance(args, bytes):
        args = args.decode('utf-8', 'surrogateescape')
    if isinstance(args, tuple):
        newargs = []
        for arg in args:
            if isinstance(arg, bytes):
                arg = arg.decode('utf-8', 'surrogateescape')
            newargs.append(arg)
        args = tuple(newargs)
    ret = format % args
    return ret.encode('utf-8', 'surrogateescape')
builtins.bytesformatter = bytesformatter

origord = builtins.ord
def fakeord(char):
    if isinstance(char, int):
        return char
    return origord(char)
builtins.ord = fakeord

if __name__ == '__main__':
    import doctest
    doctest.testmod()