bazarr/libs/webencodings/__init__.py

343 lines
10 KiB
Python
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

# coding: utf-8
"""
webencodings
~~~~~~~~~~~~
This is a Python implementation of the `WHATWG Encoding standard
<http://encoding.spec.whatwg.org/>`. See README for details.
:copyright: Copyright 2012 by Simon Sapin
:license: BSD, see LICENSE for details.
"""
from __future__ import unicode_literals
import codecs
from .labels import LABELS
VERSION = '0.5.1'
# Some names in Encoding are not valid Python aliases. Remap these.
PYTHON_NAMES = {
'iso-8859-8-i': 'iso-8859-8',
'x-mac-cyrillic': 'mac-cyrillic',
'macintosh': 'mac-roman',
'windows-874': 'cp874'}
CACHE = {}
def ascii_lower(string):
r"""Transform (only) ASCII letters to lower case: A-Z is mapped to a-z.
:param string: An Unicode string.
:returns: A new Unicode string.
This is used for `ASCII case-insensitive
<http://encoding.spec.whatwg.org/#ascii-case-insensitive>`_
matching of encoding labels.
The same matching is also used, among other things,
for `CSS keywords <http://dev.w3.org/csswg/css-values/#keywords>`_.
This is different from the :meth:`~py:str.lower` method of Unicode strings
which also affect non-ASCII characters,
sometimes mapping them into the ASCII range:
>>> keyword = u'Bac\N{KELVIN SIGN}ground'
>>> assert keyword.lower() == u'background'
>>> assert ascii_lower(keyword) != keyword.lower()
>>> assert ascii_lower(keyword) == u'bac\N{KELVIN SIGN}ground'
"""
# This turns out to be faster than unicode.translate()
return string.encode('utf8').lower().decode('utf8')
def lookup(label):
"""
Look for an encoding by its label.
This is the specs `get an encoding
<http://encoding.spec.whatwg.org/#concept-encoding-get>`_ algorithm.
Supported labels are listed there.
:param label: A string.
:returns:
An :class:`Encoding` object, or :obj:`None` for an unknown label.
"""
# Only strip ASCII whitespace: U+0009, U+000A, U+000C, U+000D, and U+0020.
label = ascii_lower(label.strip('\t\n\f\r '))
name = LABELS.get(label)
if name is None:
return None
encoding = CACHE.get(name)
if encoding is None:
if name == 'x-user-defined':
from .x_user_defined import codec_info
else:
python_name = PYTHON_NAMES.get(name, name)
# Any python_name value that gets to here should be valid.
codec_info = codecs.lookup(python_name)
encoding = Encoding(name, codec_info)
CACHE[name] = encoding
return encoding
def _get_encoding(encoding_or_label):
"""
Accept either an encoding object or label.
:param encoding: An :class:`Encoding` object or a label string.
:returns: An :class:`Encoding` object.
:raises: :exc:`~exceptions.LookupError` for an unknown label.
"""
if hasattr(encoding_or_label, 'codec_info'):
return encoding_or_label
encoding = lookup(encoding_or_label)
if encoding is None:
raise LookupError('Unknown encoding label: %r' % encoding_or_label)
return encoding
class Encoding(object):
"""Reresents a character encoding such as UTF-8,
that can be used for decoding or encoding.
.. attribute:: name
Canonical name of the encoding
.. attribute:: codec_info
The actual implementation of the encoding,
a stdlib :class:`~codecs.CodecInfo` object.
See :func:`codecs.register`.
"""
def __init__(self, name, codec_info):
self.name = name
self.codec_info = codec_info
def __repr__(self):
return '<Encoding %s>' % self.name
#: The UTF-8 encoding. Should be used for new content and formats.
UTF8 = lookup('utf-8')
_UTF16LE = lookup('utf-16le')
_UTF16BE = lookup('utf-16be')
def decode(input, fallback_encoding, errors='replace'):
"""
Decode a single string.
:param input: A byte string
:param fallback_encoding:
An :class:`Encoding` object or a label string.
The encoding to use if :obj:`input` does note have a BOM.
:param errors: Type of error handling. See :func:`codecs.register`.
:raises: :exc:`~exceptions.LookupError` for an unknown encoding label.
:return:
A ``(output, encoding)`` tuple of an Unicode string
and an :obj:`Encoding`.
"""
# Fail early if `encoding` is an invalid label.
fallback_encoding = _get_encoding(fallback_encoding)
bom_encoding, input = _detect_bom(input)
encoding = bom_encoding or fallback_encoding
return encoding.codec_info.decode(input, errors)[0], encoding
def _detect_bom(input):
"""Return (bom_encoding, input), with any BOM removed from the input."""
if input.startswith(b'\xFF\xFE'):
return _UTF16LE, input[2:]
if input.startswith(b'\xFE\xFF'):
return _UTF16BE, input[2:]
if input.startswith(b'\xEF\xBB\xBF'):
return UTF8, input[3:]
return None, input
def encode(input, encoding=UTF8, errors='strict'):
"""
Encode a single string.
:param input: An Unicode string.
:param encoding: An :class:`Encoding` object or a label string.
:param errors: Type of error handling. See :func:`codecs.register`.
:raises: :exc:`~exceptions.LookupError` for an unknown encoding label.
:return: A byte string.
"""
return _get_encoding(encoding).codec_info.encode(input, errors)[0]
def iter_decode(input, fallback_encoding, errors='replace'):
"""
"Pull"-based decoder.
:param input:
An iterable of byte strings.
The input is first consumed just enough to determine the encoding
based on the precense of a BOM,
then consumed on demand when the return value is.
:param fallback_encoding:
An :class:`Encoding` object or a label string.
The encoding to use if :obj:`input` does note have a BOM.
:param errors: Type of error handling. See :func:`codecs.register`.
:raises: :exc:`~exceptions.LookupError` for an unknown encoding label.
:returns:
An ``(output, encoding)`` tuple.
:obj:`output` is an iterable of Unicode strings,
:obj:`encoding` is the :obj:`Encoding` that is being used.
"""
decoder = IncrementalDecoder(fallback_encoding, errors)
generator = _iter_decode_generator(input, decoder)
encoding = next(generator)
return generator, encoding
def _iter_decode_generator(input, decoder):
"""Return a generator that first yields the :obj:`Encoding`,
then yields output chukns as Unicode strings.
"""
decode = decoder.decode
input = iter(input)
for chunck in input:
output = decode(chunck)
if output:
assert decoder.encoding is not None
yield decoder.encoding
yield output
break
else:
# Input exhausted without determining the encoding
output = decode(b'', final=True)
assert decoder.encoding is not None
yield decoder.encoding
if output:
yield output
return
for chunck in input:
output = decode(chunck)
if output:
yield output
output = decode(b'', final=True)
if output:
yield output
def iter_encode(input, encoding=UTF8, errors='strict'):
"""
“Pull”-based encoder.
:param input: An iterable of Unicode strings.
:param encoding: An :class:`Encoding` object or a label string.
:param errors: Type of error handling. See :func:`codecs.register`.
:raises: :exc:`~exceptions.LookupError` for an unknown encoding label.
:returns: An iterable of byte strings.
"""
# Fail early if `encoding` is an invalid label.
encode = IncrementalEncoder(encoding, errors).encode
return _iter_encode_generator(input, encode)
def _iter_encode_generator(input, encode):
for chunck in input:
output = encode(chunck)
if output:
yield output
output = encode('', final=True)
if output:
yield output
class IncrementalDecoder(object):
"""
“Push”-based decoder.
:param fallback_encoding:
An :class:`Encoding` object or a label string.
The encoding to use if :obj:`input` does note have a BOM.
:param errors: Type of error handling. See :func:`codecs.register`.
:raises: :exc:`~exceptions.LookupError` for an unknown encoding label.
"""
def __init__(self, fallback_encoding, errors='replace'):
# Fail early if `encoding` is an invalid label.
self._fallback_encoding = _get_encoding(fallback_encoding)
self._errors = errors
self._buffer = b''
self._decoder = None
#: The actual :class:`Encoding` that is being used,
#: or :obj:`None` if that is not determined yet.
#: (Ie. if there is not enough input yet to determine
#: if there is a BOM.)
self.encoding = None # Not known yet.
def decode(self, input, final=False):
"""Decode one chunk of the input.
:param input: A byte string.
:param final:
Indicate that no more input is available.
Must be :obj:`True` if this is the last call.
:returns: An Unicode string.
"""
decoder = self._decoder
if decoder is not None:
return decoder(input, final)
input = self._buffer + input
encoding, input = _detect_bom(input)
if encoding is None:
if len(input) < 3 and not final: # Not enough data yet.
self._buffer = input
return ''
else: # No BOM
encoding = self._fallback_encoding
decoder = encoding.codec_info.incrementaldecoder(self._errors).decode
self._decoder = decoder
self.encoding = encoding
return decoder(input, final)
class IncrementalEncoder(object):
"""
“Push”-based encoder.
:param encoding: An :class:`Encoding` object or a label string.
:param errors: Type of error handling. See :func:`codecs.register`.
:raises: :exc:`~exceptions.LookupError` for an unknown encoding label.
.. method:: encode(input, final=False)
:param input: An Unicode string.
:param final:
Indicate that no more input is available.
Must be :obj:`True` if this is the last call.
:returns: A byte string.
"""
def __init__(self, encoding=UTF8, errors='strict'):
encoding = _get_encoding(encoding)
self.encode = encoding.codec_info.incrementalencoder(errors).encode