mirror of https://github.com/python/cpython
129 lines
3.7 KiB
Python
129 lines
3.7 KiB
Python
""" 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() -> (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 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, exceptions, re
|
|
|
|
_cache = {}
|
|
_unknown = '--unknown--'
|
|
_import_tail = ['*']
|
|
_norm_encoding_RE = re.compile('[^a-zA-Z0-9.]')
|
|
|
|
class CodecRegistryError(exceptions.LookupError,
|
|
exceptions.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 '_'.
|
|
|
|
"""
|
|
return '_'.join(_norm_encoding_RE.split(encoding))
|
|
|
|
def search_function(encoding):
|
|
|
|
# Cache lookup
|
|
entry = _cache.get(encoding, _unknown)
|
|
if entry is not _unknown:
|
|
return entry
|
|
|
|
# Import the module:
|
|
#
|
|
# First look in the encodings package, then try to lookup the
|
|
# encoding in the aliases mapping and retry the import using the
|
|
# default import module lookup scheme with the alias name.
|
|
#
|
|
modname = normalize_encoding(encoding)
|
|
try:
|
|
mod = __import__('encodings.' + modname,
|
|
globals(), locals(), _import_tail)
|
|
except ImportError:
|
|
import aliases
|
|
modname = (aliases.aliases.get(modname) or
|
|
aliases.aliases.get(modname.replace('.', '_')) or
|
|
modname)
|
|
try:
|
|
mod = __import__(modname, globals(), locals(), _import_tail)
|
|
except ImportError:
|
|
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 = tuple(getregentry())
|
|
if len(entry) != 4:
|
|
raise CodecRegistryError,\
|
|
'module "%s" (%s) failed to register' % \
|
|
(mod.__name__, mod.__file__)
|
|
for obj in entry:
|
|
if not callable(obj):
|
|
raise CodecRegistryError,\
|
|
'incompatible codecs in module "%s" (%s)' % \
|
|
(mod.__name__, mod.__file__)
|
|
|
|
# Cache the codec registry entry
|
|
_cache[encoding] = entry
|
|
|
|
# Register its aliases (without overwriting previously registered
|
|
# aliases)
|
|
try:
|
|
codecaliases = mod.getaliases()
|
|
except AttributeError:
|
|
pass
|
|
else:
|
|
import aliases
|
|
for alias in codecaliases:
|
|
if not aliases.aliases.has_key(alias):
|
|
aliases.aliases[alias] = modname
|
|
|
|
# Return the registry entry
|
|
return entry
|
|
|
|
# Register the search_function in the Python codec registry
|
|
codecs.register(search_function)
|
|
|
|
# Register iconv_codec lookup function if available
|
|
try:
|
|
import iconv_codec
|
|
except (ImportError, RuntimeError):
|
|
pass
|