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https://github.com/python/cpython
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79 lines
2.2 KiB
Python
79 lines
2.2 KiB
Python
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""" 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. Hyphens are automatically converted to
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underscores, e.g. 'utf-8' is looked up as module utf_8.
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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 lower-case.
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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 string,codecs,aliases
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_cache = {}
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_unkown = '--unkown--'
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def search_function(encoding):
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# Cache lookup
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entry = _cache.get(encoding,_unkown)
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if entry is not _unkown:
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return entry
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# Import the module
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modname = string.replace(encoding,'-','_')
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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[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 SystemError,\
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'module "%s.%s" failed to register' % \
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(__name__,modname)
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for obj in entry:
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if not callable(obj):
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raise SystemError,\
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'incompatible codecs in module "%s.%s"' % \
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(__name__,modname)
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# Cache the encoding and its aliases
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_cache[encoding] = entry
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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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_cache[alias] = 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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