view mercurial/i18n.py @ 18988:5bae936764bb

parsers: a C implementation of the new ancestors algorithm

The performance of both the old and new Python ancestor algorithms
depends on the number of revs they need to traverse.  Although the
new algorithm performs far better than the old when revs are
numerically and topologically close, both algorithms become slow
under other circumstances, taking up to 1.8 seconds to give answers
in a Linux kernel repo.

This C implementation of the new algorithm is a fairly straightforward
transliteration.  The only corner case of interest is that it raises
an OverflowError if the number of GCA candidates found during the
first pass is greater than 24, to avoid the dual perils of fixnum
overflow and trying to allocate too much memory.  (If this exception
is raised, the Python implementation is used instead.)

Performance numbers are good: in a Linux kernel repo, time for "hg
debugancestors" on two distant revs (24bf01de7537 and c2a8808f5943)
is as follows:

  Old Python: 0.36 sec
  New Python: 0.42 sec
  New C: 0.02 sec

For a case where the new algorithm should perform well:

  Old Python: 1.84 sec
  New Python: 0.07 sec
  New C: measures as zero when using --time

(This commit includes a paranoid cross-check to ensure that the
Python and C implementations give identical answers. The above
performance numbers were measured with that check disabled.)

# i18n.py - internationalization support for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[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 encoding
import gettext, sys, os

# modelled after templater.templatepath:
if getattr(sys, 'frozen', None) is not None:
    module = sys.executable
else:
    module = __file__

base = os.path.dirname(module)
for dir in ('.', '..'):
    localedir = os.path.join(base, dir, 'locale')
    if os.path.isdir(localedir):
        break

t = gettext.translation('hg', localedir, fallback=True)

def gettext(message):
    """Translate message.

    The message is looked up in the catalog to get a Unicode string,
    which is encoded in the local encoding before being returned.

    Important: message is restricted to characters in the encoding
    given by sys.getdefaultencoding() which is most likely 'ascii'.
    """
    # If message is None, t.ugettext will return u'None' as the
    # translation whereas our callers expect us to return None.
    if message is None:
        return message

    paragraphs = message.split('\n\n')
    # Be careful not to translate the empty string -- it holds the
    # meta data of the .po file.
    u = u'\n\n'.join([p and t.ugettext(p) or '' for p in paragraphs])
    try:
        # encoding.tolocal cannot be used since it will first try to
        # decode the Unicode string. Calling u.decode(enc) really
        # means u.encode(sys.getdefaultencoding()).decode(enc). Since
        # the Python encoding defaults to 'ascii', this fails if the
        # translated string use non-ASCII characters.
        return u.encode(encoding.encoding, "replace")
    except LookupError:
        # An unknown encoding results in a LookupError.
        return message

def _plain():
    if 'HGPLAIN' not in os.environ and 'HGPLAINEXCEPT' not in os.environ:
        return False
    exceptions = os.environ.get('HGPLAINEXCEPT', '').strip().split(',')
    return 'i18n' not in exceptions

if _plain():
    _ = lambda message: message
else:
    _ = gettext