source: trunk/essentials/dev-lang/python/Lib/gettext.py@ 3317

"""Internationalization and localization support.

This module provides internationalization (I18N) and localization (L10N)
support for your Python programs by providing an interface to the GNU gettext
message catalog library.

I18N refers to the operation by which a program is made aware of multiple
languages.  L10N refers to the adaptation of your program, once
internationalized, to the local language and cultural habits.

"""

# This module represents the integration of work, contributions, feedback, and
# suggestions from the following people:
#
# Martin von Loewis, who wrote the initial implementation of the underlying
# C-based libintlmodule (later renamed _gettext), along with a skeletal
# gettext.py implementation.
#
# Peter Funk, who wrote fintl.py, a fairly complete wrapper around intlmodule,
# which also included a pure-Python implementation to read .mo files if
# intlmodule wasn't available.
#
# James Henstridge, who also wrote a gettext.py module, which has some
# interesting, but currently unsupported experimental features: the notion of
# a Catalog class and instances, and the ability to add to a catalog file via
# a Python API.
#
# Barry Warsaw integrated these modules, wrote the .install() API and code,
# and conformed all C and Python code to Python's coding standards.
#
# Francois Pinard and Marc-Andre Lemburg also contributed valuably to this
# module.
#
# J. David Ibanez implemented plural forms. Bruno Haible fixed some bugs.
#
# TODO:
# - Lazy loading of .mo files.  Currently the entire catalog is loaded into
#   memory, but that's probably bad for large translated programs.  Instead,
#   the lexical sort of original strings in GNU .mo files should be exploited
#   to do binary searches and lazy initializations.  Or you might want to use
#   the undocumented double-hash algorithm for .mo files with hash tables, but
#   you'll need to study the GNU gettext code to do this.
#
# - Support Solaris .mo file formats.  Unfortunately, we've been unable to
#   find this format documented anywhere.


import locale, copy, os, re, struct, sys
from errno import ENOENT


__all__ = ['NullTranslations', 'GNUTranslations', 'Catalog',
           'find', 'translation', 'install', 'textdomain', 'bindtextdomain',
           'dgettext', 'dngettext', 'gettext', 'ngettext',
           ]

_default_localedir = os.path.join(sys.prefix, 'share', 'locale')


def test(condition, true, false):
    """
    Implements the C expression:

      condition ? true : false

    Required to correctly interpret plural forms.
    """
    if condition:
        return true
    else:
        return false


def c2py(plural):
    """Gets a C expression as used in PO files for plural forms and returns a
    Python lambda function that implements an equivalent expression.
    """
    # Security check, allow only the "n" identifier
    try:
        from cStringIO import StringIO
    except ImportError:
        from StringIO import StringIO
    import token, tokenize
    tokens = tokenize.generate_tokens(StringIO(plural).readline)
    try:
        danger = [x for x in tokens if x[0] == token.NAME and x[1] != 'n']
    except tokenize.TokenError:
        raise ValueError, \
              'plural forms expression error, maybe unbalanced parenthesis'
    else:
        if danger:
            raise ValueError, 'plural forms expression could be dangerous'

    # Replace some C operators by their Python equivalents
    plural = plural.replace('&&', ' and ')
    plural = plural.replace('||', ' or ')

    expr = re.compile(r'\!([^=])')
    plural = expr.sub(' not \\1', plural)

    # Regular expression and replacement function used to transform
    # "a?b:c" to "test(a,b,c)".
    expr = re.compile(r'(.*?)\?(.*?):(.*)')
    def repl(x):
        return "test(%s, %s, %s)" % (x.group(1), x.group(2),
                                     expr.sub(repl, x.group(3)))

    # Code to transform the plural expression, taking care of parentheses
    stack = ['']
    for c in plural:
        if c == '(':
            stack.append('')