91 lines
2.6 KiB
Python
91 lines
2.6 KiB
Python
""" Standard "encodings" Package
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Standard Python encoding modules are stored in this package
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directory.
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Codec modules must have names corresponding to standard lower-case
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encoding names with hyphens mapped to underscores, e.g. 'utf-8' is
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implemented by the module 'utf_8.py'.
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Each codec module must export the following interface:
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* getregentry() -> (encoder, decoder, stream_reader, stream_writer)
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The getregentry() API must return callable objects which adhere to
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the Python Codec Interface Standard.
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In addition, a module may optionally also define the following
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APIs which are then used by the package's codec search function:
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* getaliases() -> sequence of encoding name strings to use as aliases
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Alias names returned by getaliases() must be standard encoding
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names as defined above (lower-case, hyphens converted to
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underscores).
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Written by Marc-Andre Lemburg (mal@lemburg.com).
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(c) Copyright CNRI, All Rights Reserved. NO WARRANTY.
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"""#"
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import codecs,aliases,exceptions
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_cache = {}
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_unknown = '--unknown--'
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class CodecRegistryError(exceptions.LookupError,
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exceptions.SystemError):
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pass
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def search_function(encoding):
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# Cache lookup
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entry = _cache.get(encoding,_unknown)
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if entry is not _unknown:
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return entry
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# Import the module
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modname = encoding.replace('-', '_')
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modname = aliases.aliases.get(modname,modname)
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try:
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mod = __import__(modname,globals(),locals(),'*')
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except ImportError,why:
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# cache misses
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_cache[encoding] = None
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return None
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# Now ask the module for the registry entry
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try:
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entry = tuple(mod.getregentry())
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except AttributeError:
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entry = ()
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if len(entry) != 4:
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raise CodecRegistryError,\
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'module "%s" (%s) failed to register' % \
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(mod.__name__, mod.__file__)
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for obj in entry:
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if not callable(obj):
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raise CodecRegistryError,\
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'incompatible codecs in module "%s" (%s)' % \
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(mod.__name__, mod.__file__)
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# Cache the codec registry entry
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_cache[encoding] = entry
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# Register its aliases (without overwriting previously registered
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# aliases)
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try:
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codecaliases = mod.getaliases()
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except AttributeError:
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pass
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else:
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for alias in codecaliases:
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if not aliases.aliases.has_key(alias):
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aliases.aliases[alias] = modname
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# Return the registry entry
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return entry
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# Register the search_function in the Python codec registry
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codecs.register(search_function)
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