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988ad2bdff
encodings package aliases mapping dictionary rather than in the internal cache used by the search function. This enables aliases to take advantage of the full normalization process applied to encoding names which was previously not available. The patch restricts alias registration to new aliases. Existing aliases cannot be overridden anymore.
86 lines
2.5 KiB
Python
86 lines
2.5 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
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_cache = {}
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_unknown = '--unknown--'
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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 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 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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