annotate mercurial/py3kcompat.py @ 26644:74de1c59f71c

clonebundles: filter on bundle specification

Not all clients are capable of reading every bundle. Currently, content
negotiation to ensure a server sends a client a compatible bundle
format is performed at request time. The response bundle is dynamically
generated at request time, so this works fine.

Clone bundles are statically generated *before* the request. This means
that a modern server could produce bundles that a legacy client isn't
capable of reading. Without some kind of "type hint" in the clone
bundles manifest, a client may attempt to download an incompatible
bundle. Furthermore, a client may not realize a bundle is incompatible
until it has processed part of the bundle (imagine consuming a 1 GB
changegroup bundle2 part only to discover the bundle2 part afterwards is
incompatibl). This would waste time and resources. And it isn't very
user friendly.

Clone bundle manifests thus need to advertise the *exact* format of the
hosted bundles so clients may filter out entries that they don't know
how to read. This patch introduces that mechanism.

We introduce the BUNDLESPEC attribute to declare the "bundle
specification" of the entry. Bundle specifications are parsed using
exchange.parsebundlespecification, which uses the same strings as the
"--type" argument to `hg bundle`. The supported bundle specifications
are well defined and backwards compatible.

When a client encounters a BUNDLESPEC that is invalid or unsupported, it
silently ignores the entry.

# 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.

import builtins

from numbers import 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()