~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2006 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

# TODO: Some kind of command-line display of revision properties:

# perhaps show them in log -v and allow them as options to the commit command.

"""Some functions to enable caching the conversion between unicode to utf8"""

from __future__ import absolute_import

import codecs

_utf8_encode = codecs.utf_8_encode

_utf8_decode = codecs.utf_8_decode

def _utf8_decode_with_None(bytestring, _utf8_decode=_utf8_decode):

    """wrap _utf8_decode to support None->None for optional strings.

    Also, only return the Unicode portion, since we don't care about the second

    return value.

    """

    if bytestring is None:

        return None

    else:

        return _utf8_decode(bytestring)[0]

# Map revisions from and to utf8 encoding

# Whenever we do an encode/decode operation, we save the result, so that

# we don't have to do it again.

_unicode_to_utf8_map = {}

_utf8_to_unicode_map = {}

def encode(unicode_str,

           _uni_to_utf8=_unicode_to_utf8_map,

           _utf8_to_uni=_utf8_to_unicode_map,

           _utf8_encode=_utf8_encode):

    """Take this unicode revision id, and get a unicode version"""

    # If the key is in the cache try/KeyError is 50% faster than

    # val = dict.get(key), if val is None:

    # On jam's machine the difference is

    # try/KeyError:  900ms

    #      if None: 1250ms

    # Since these are primarily used when iterating over a knit entry

    # *most* of the time the key will already be in the cache, so use the

    # fast path

    try:

        return _uni_to_utf8[unicode_str]

    except KeyError:

        _uni_to_utf8[unicode_str] = utf8_str = _utf8_encode(unicode_str)[0]

        _utf8_to_uni[utf8_str] = unicode_str

        return utf8_str

def decode(utf8_str,

           _uni_to_utf8=_unicode_to_utf8_map,

           _utf8_to_uni=_utf8_to_unicode_map,

           _utf8_decode=_utf8_decode):

    """Take a utf8 revision id, and decode it, but cache the result"""

    try:

        return _utf8_to_uni[utf8_str]

    except KeyError:

        unicode_str = _utf8_decode(utf8_str)[0]

        _utf8_to_uni[utf8_str] = unicode_str

        _uni_to_utf8[unicode_str] = utf8_str

        return unicode_str

def get_cached_unicode(unicode_str):

    """Return a cached version of the unicode string.

    This has a similar idea to that of intern() in that it tries

    to return a singleton string. Only it works for unicode strings.

    """

    # This might return the same object, or it might return the cached one

    # the decode() should just be a hash lookup, because the encode() side

    # should add the entry to the maps

    return decode(encode(unicode_str))

def get_cached_utf8(utf8_str):

    """Return a cached version of the utf-8 string.

    Get a cached version of this string (similar to intern()).

    At present, this will be decoded to ensure it is a utf-8 string. In the

    future this might change to simply caching the string.

    """

    return encode(decode(utf8_str))

def get_cached_ascii(ascii_str,

                     _uni_to_utf8=_unicode_to_utf8_map,

                     _utf8_to_uni=_utf8_to_unicode_map):

    """This is a string which is identical in utf-8 and unicode."""

    # We don't need to do any encoding, but we want _utf8_to_uni to return a

    # real Unicode string. Unicode and plain strings of this type will have the

    # same hash, so we can just use it as the key in _uni_to_utf8, but we need

    # the return value to be different in _utf8_to_uni

    ascii_str = _uni_to_utf8.setdefault(ascii_str, ascii_str)

    _utf8_to_uni.setdefault(ascii_str, unicode(ascii_str))

    return ascii_str

def clear_encoding_cache():

    """Clear the encoding and decoding caches"""

    _unicode_to_utf8_map.clear()

    _utf8_to_unicode_map.clear()