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+""" Standard "encodings" Package
+
+ Standard Python encoding modules are stored in this package
+ directory.
+
+ Codec modules must have names corresponding to normalized encoding
+ names as defined in the normalize_encoding() function below, e.g.
+ 'utf-8' must be implemented by the module 'utf_8.py'.
+
+ Each codec module must export the following interface:
+
+ * getregentry() -> codecs.CodecInfo object
+ The getregentry() API must a CodecInfo object with encoder, decoder,
+ incrementalencoder, incrementaldecoder, streamwriter and streamreader
+ atttributes which adhere to the Python Codec Interface Standard.
+
+ In addition, a module may optionally also define the following
+ APIs which are then used by the package's codec search function:
+
+ * getaliases() -> sequence of encoding name strings to use as aliases
+
+ Alias names returned by getaliases() must be normalized encoding
+ names as defined by normalize_encoding().
+
+Written by Marc-Andre Lemburg (mal@lemburg.com).
+
+(c) Copyright CNRI, All Rights Reserved. NO WARRANTY.
+
+"""#"
+
+import codecs
+from encodings import aliases
+import __builtin__
+
+_cache = {}
+_unknown = '--unknown--'
+_import_tail = ['*']
+_norm_encoding_map = (' . '
+ '0123456789 ABCDEFGHIJKLMNOPQRSTUVWXYZ '
+ ' abcdefghijklmnopqrstuvwxyz '
+ ' '
+ ' '
+ ' ')
+_aliases = aliases.aliases
+
+class CodecRegistryError(LookupError, SystemError):
+ pass
+
+def normalize_encoding(encoding):
+
+ """ Normalize an encoding name.
+
+ Normalization works as follows: all non-alphanumeric
+ characters except the dot used for Python package names are
+ collapsed and replaced with a single underscore, e.g. ' -;#'
+ becomes '_'. Leading and trailing underscores are removed.
+
+ Note that encoding names should be ASCII only; if they do use
+ non-ASCII characters, these must be Latin-1 compatible.
+
+ """
+ # Make sure we have an 8-bit string, because .translate() works
+ # differently for Unicode strings.
+ if hasattr(__builtin__, "unicode") and isinstance(encoding, unicode):
+ # Note that .encode('latin-1') does *not* use the codec
+ # registry, so this call doesn't recurse. (See unicodeobject.c
+ # PyUnicode_AsEncodedString() for details)
+ encoding = encoding.encode('latin-1')
+ return '_'.join(encoding.translate(_norm_encoding_map).split())
+
+def search_function(encoding):
+
+ # Cache lookup
+ entry = _cache.get(encoding, _unknown)
+ if entry is not _unknown:
+ return entry
+
+ # Import the module:
+ #
+ # First try to find an alias for the normalized encoding
+ # name and lookup the module using the aliased name, then try to
+ # lookup the module using the standard import scheme, i.e. first
+ # try in the encodings package, then at top-level.
+ #
+ norm_encoding = normalize_encoding(encoding)
+ aliased_encoding = _aliases.get(norm_encoding) or \
+ _aliases.get(norm_encoding.replace('.', '_'))
+ if aliased_encoding is not None:
+ modnames = [aliased_encoding,
+ norm_encoding]
+ else:
+ modnames = [norm_encoding]
+ for modname in modnames:
+ if not modname or '.' in modname:
+ continue
+ try:
+ # Import is absolute to prevent the possibly malicious import of a
+ # module with side-effects that is not in the 'encodings' package.
+ mod = __import__('encodings.' + modname, fromlist=_import_tail,
+ level=0)
+ except ImportError:
+ pass
+ else:
+ break
+ else:
+ mod = None
+
+ try:
+ getregentry = mod.getregentry
+ except AttributeError:
+ # Not a codec module
+ mod = None
+
+ if mod is None:
+ # Cache misses
+ _cache[encoding] = None
+ return None
+
+ # Now ask the module for the registry entry
+ entry = getregentry()
+ if not isinstance(entry, codecs.CodecInfo):
+ if not 4 <= len(entry) <= 7:
+ raise CodecRegistryError,\
+ 'module "%s" (%s) failed to register' % \
+ (mod.__name__, mod.__file__)
+ if not hasattr(entry[0], '__call__') or \
+ not hasattr(entry[1], '__call__') or \
+ (entry[2] is not None and not hasattr(entry[2], '__call__')) or \
+ (entry[3] is not None and not hasattr(entry[3], '__call__')) or \
+ (len(entry) > 4 and entry[4] is not None and not hasattr(entry[4], '__call__')) or \
+ (len(entry) > 5 and entry[5] is not None and not hasattr(entry[5], '__call__')):
+ raise CodecRegistryError,\
+ 'incompatible codecs in module "%s" (%s)' % \
+ (mod.__name__, mod.__file__)
+ if len(entry)<7 or entry[6] is None:
+ entry += (None,)*(6-len(entry)) + (mod.__name__.split(".", 1)[1],)
+ entry = codecs.CodecInfo(*entry)
+
+ # Cache the codec registry entry
+ _cache[encoding] = entry
+
+ # Register its aliases (without overwriting previously registered
+ # aliases)
+ try:
+ codecaliases = mod.getaliases()
+ except AttributeError:
+ pass
+ else:
+ for alias in codecaliases:
+ if alias not in _aliases:
+ _aliases[alias] = modname
+
+ # Return the registry entry
+ return entry
+
+# Register the search_function in the Python codec registry
+codecs.register(search_function)