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""" Standard "encodings" Package
Standard Python encoding modules are stored in this package
directory.
Codec modules must have names corresponding to standard lower-case
encoding names. Hyphens are automatically converted to
underscores, e.g. 'utf-8' is looked up as module utf_8.
Each codec module must export the following interface:
* getregentry() -> (encoder, decoder, stream_reader, stream_writer)
The getregentry() API must return callable objects 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 lower-case.
Written by Marc-Andre Lemburg (mal@lemburg.com).
(c) Copyright CNRI, All Rights Reserved. NO WARRANTY.
"""#"
import string,codecs,aliases
_cache = {}
_unkown = '--unkown--'
def search_function(encoding):
# Cache lookup
entry = _cache.get(encoding,_unkown)
if entry is not _unkown:
return entry
# Import the module
modname = string.replace(encoding,'-','_')
modname = aliases.aliases.get(modname,modname)
try:
mod = __import__(modname,globals(),locals(),'*')
except ImportError,why:
_cache[encoding] = None
return None
# Now ask the module for the registry entry
try:
entry = tuple(mod.getregentry())
except AttributeError:
entry = ()
if len(entry) != 4:
raise SystemError,\
'module "%s.%s" failed to register' % \
(__name__,modname)
for obj in entry:
if not callable(obj):
raise SystemError,\
'incompatible codecs in module "%s.%s"' % \
(__name__,modname)
# Cache the encoding and its aliases
_cache[encoding] = entry
try:
codecaliases = mod.getaliases()
except AttributeError:
pass
else:
for alias in codecaliases:
_cache[alias] = entry
return entry
# Register the search_function in the Python codec registry
codecs.register(search_function)
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