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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 . import aliases
_cache = {}
_unknown = '--unknown--'
_import_tail = ['*']
_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.
"""
if isinstance(encoding, bytes):
encoding = str(encoding, "ascii")
chars = []
punct = False
for c in encoding:
if c.isalnum() or c == '.':
if punct and chars:
chars.append('_')
chars.append(c)
punct = False
else:
punct = True
return ''.join(chars)
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)
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