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114 lines
4.7 KiB
Python
114 lines
4.7 KiB
Python
from webencodings import UTF8, decode, lookup
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from .parser import parse_stylesheet
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def decode_stylesheet_bytes(css_bytes, protocol_encoding=None,
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environment_encoding=None):
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"""Determine the character encoding of a CSS stylesheet and decode it.
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This is based on the presence of a :abbr:`BOM (Byte Order Mark)`,
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a ``@charset`` rule, and encoding meta-information.
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:type css_bytes: :obj:`bytes`
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:param css_bytes: A CSS byte string.
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:type protocol_encoding: :obj:`str`
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:param protocol_encoding:
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The encoding label, if any, defined by HTTP or equivalent protocol.
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(e.g. via the ``charset`` parameter of the ``Content-Type`` header.)
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:type environment_encoding: :class:`webencodings.Encoding`
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:param environment_encoding:
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The `environment encoding
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<https://www.w3.org/TR/css-syntax/#environment-encoding>`_, if any.
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:returns:
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A 2-tuple of a decoded Unicode string and the
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:class:`webencodings.Encoding` object that was used.
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"""
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# https://drafts.csswg.org/css-syntax/#the-input-byte-stream
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if protocol_encoding:
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fallback = lookup(protocol_encoding)
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if fallback:
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return decode(css_bytes, fallback)
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if css_bytes.startswith(b'@charset "'):
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# 10 is len(b'@charset "')
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# 100 is arbitrary so that no encoding label is more than 100-10 bytes.
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end_quote = css_bytes.find(b'"', 10, 100)
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if end_quote != -1 and css_bytes.startswith(b'";', end_quote):
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fallback = lookup(css_bytes[10:end_quote].decode('latin1'))
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if fallback:
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if fallback.name in ('utf-16be', 'utf-16le'):
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return decode(css_bytes, UTF8)
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return decode(css_bytes, fallback)
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if environment_encoding:
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return decode(css_bytes, environment_encoding)
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return decode(css_bytes, UTF8)
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def parse_stylesheet_bytes(css_bytes, protocol_encoding=None,
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environment_encoding=None,
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skip_comments=False, skip_whitespace=False):
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"""Parse :diagram:`stylesheet` from bytes,
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determining the character encoding as web browsers do.
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This is used when reading a file or fetching a URL.
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The character encoding is determined from the initial bytes
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(a :abbr:`BOM (Byte Order Mark)` or a ``@charset`` rule)
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as well as the parameters. The ultimate fallback is UTF-8.
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:type css_bytes: :obj:`bytes`
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:param css_bytes: A CSS byte string.
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:type protocol_encoding: :obj:`str`
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:param protocol_encoding:
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The encoding label, if any, defined by HTTP or equivalent protocol.
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(e.g. via the ``charset`` parameter of the ``Content-Type`` header.)
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:type environment_encoding: :class:`webencodings.Encoding`
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:param environment_encoding:
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The `environment encoding`_, if any.
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:type skip_comments: :obj:`bool`
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:param skip_comments:
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Ignore CSS comments at the top-level of the stylesheet.
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If the input is a string, ignore all comments.
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:type skip_whitespace: :obj:`bool`
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:param skip_whitespace:
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Ignore whitespace at the top-level of the stylesheet.
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Whitespace is still preserved
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in the :attr:`~tinycss2.ast.QualifiedRule.prelude`
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and the :attr:`~tinycss2.ast.QualifiedRule.content` of rules.
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:returns:
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A ``(rules, encoding)`` tuple.
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* ``rules`` is a list of
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:class:`~tinycss2.ast.QualifiedRule`,
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:class:`~tinycss2.ast.AtRule`,
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:class:`~tinycss2.ast.Comment` (if ``skip_comments`` is false),
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:class:`~tinycss2.ast.WhitespaceToken`
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(if ``skip_whitespace`` is false),
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and :class:`~tinycss2.ast.ParseError` objects.
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* ``encoding`` is the :class:`webencodings.Encoding` object
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that was used.
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If ``rules`` contains an ``@import`` rule, this is
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the `environment encoding`_ for the imported stylesheet.
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.. _environment encoding:
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https://www.w3.org/TR/css-syntax/#environment-encoding
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.. code-block:: python
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response = urlopen('http://example.net/foo.css')
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rules, encoding = parse_stylesheet_bytes(
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css_bytes=response.read(),
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# Python 3.x
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protocol_encoding=response.info().get_content_type().get_param('charset'),
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# Python 2.x
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protocol_encoding=response.info().gettype().getparam('charset'),
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)
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for rule in rules:
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...
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"""
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css_unicode, encoding = decode_stylesheet_bytes(
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css_bytes, protocol_encoding, environment_encoding)
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stylesheet = parse_stylesheet(css_unicode, skip_comments, skip_whitespace)
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return stylesheet, encoding
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