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282 lines
12 KiB
Python
282 lines
12 KiB
Python
# Character encoding routines
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# Copyright 2010-2020 Kurt McKee <contactme@kurtmckee.org>
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# Copyright 2002-2008 Mark Pilgrim
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# All rights reserved.
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#
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# This file is a part of feedparser.
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#
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# Redistribution and use in source and binary forms, with or without modification,
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# are permitted provided that the following conditions are met:
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#
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# * Redistributions of source code must retain the above copyright notice,
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# this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS'
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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import cgi
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import codecs
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import re
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try:
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try:
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import cchardet as chardet
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except ImportError:
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import chardet
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except ImportError:
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chardet = None
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lazy_chardet_encoding = None
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else:
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def lazy_chardet_encoding(data):
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return chardet.detect(data)['encoding'] or ''
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from .exceptions import (
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CharacterEncodingOverride,
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CharacterEncodingUnknown,
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NonXMLContentType,
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)
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# Each marker represents some of the characters of the opening XML
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# processing instruction ('<?xm') in the specified encoding.
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EBCDIC_MARKER = b'\x4C\x6F\xA7\x94'
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UTF16BE_MARKER = b'\x00\x3C\x00\x3F'
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UTF16LE_MARKER = b'\x3C\x00\x3F\x00'
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UTF32BE_MARKER = b'\x00\x00\x00\x3C'
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UTF32LE_MARKER = b'\x3C\x00\x00\x00'
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ZERO_BYTES = '\x00\x00'
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# Match the opening XML declaration.
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# Example: <?xml version="1.0" encoding="utf-8"?>
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RE_XML_DECLARATION = re.compile(r'^<\?xml[^>]*?>')
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# Capture the value of the XML processing instruction's encoding attribute.
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# Example: <?xml version="1.0" encoding="utf-8"?>
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RE_XML_PI_ENCODING = re.compile(br'^<\?.*encoding=[\'"](.*?)[\'"].*\?>')
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def convert_to_utf8(http_headers, data, result):
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"""Detect and convert the character encoding to UTF-8.
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http_headers is a dictionary
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data is a raw string (not Unicode)"""
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# This is so much trickier than it sounds, it's not even funny.
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# According to RFC 3023 ('XML Media Types'), if the HTTP Content-Type
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# is application/xml, application/*+xml,
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# application/xml-external-parsed-entity, or application/xml-dtd,
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# the encoding given in the charset parameter of the HTTP Content-Type
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# takes precedence over the encoding given in the XML prefix within the
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# document, and defaults to 'utf-8' if neither are specified. But, if
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# the HTTP Content-Type is text/xml, text/*+xml, or
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# text/xml-external-parsed-entity, the encoding given in the XML prefix
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# within the document is ALWAYS IGNORED and only the encoding given in
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# the charset parameter of the HTTP Content-Type header should be
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# respected, and it defaults to 'us-ascii' if not specified.
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# Furthermore, discussion on the atom-syntax mailing list with the
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# author of RFC 3023 leads me to the conclusion that any document
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# served with a Content-Type of text/* and no charset parameter
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# must be treated as us-ascii. (We now do this.) And also that it
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# must always be flagged as non-well-formed. (We now do this too.)
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# If Content-Type is unspecified (input was local file or non-HTTP source)
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# or unrecognized (server just got it totally wrong), then go by the
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# encoding given in the XML prefix of the document and default to
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# 'iso-8859-1' as per the HTTP specification (RFC 2616).
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# Then, assuming we didn't find a character encoding in the HTTP headers
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# (and the HTTP Content-type allowed us to look in the body), we need
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# to sniff the first few bytes of the XML data and try to determine
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# whether the encoding is ASCII-compatible. Section F of the XML
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# specification shows the way here:
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# http://www.w3.org/TR/REC-xml/#sec-guessing-no-ext-info
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# If the sniffed encoding is not ASCII-compatible, we need to make it
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# ASCII compatible so that we can sniff further into the XML declaration
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# to find the encoding attribute, which will tell us the true encoding.
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# Of course, none of this guarantees that we will be able to parse the
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# feed in the declared character encoding (assuming it was declared
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# correctly, which many are not). iconv_codec can help a lot;
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# you should definitely install it if you can.
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# http://cjkpython.i18n.org/
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bom_encoding = ''
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xml_encoding = ''
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# Look at the first few bytes of the document to guess what
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# its encoding may be. We only need to decode enough of the
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# document that we can use an ASCII-compatible regular
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# expression to search for an XML encoding declaration.
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# The heuristic follows the XML specification, section F:
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# http://www.w3.org/TR/REC-xml/#sec-guessing-no-ext-info
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# Check for BOMs first.
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if data[:4] == codecs.BOM_UTF32_BE:
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bom_encoding = 'utf-32be'
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data = data[4:]
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elif data[:4] == codecs.BOM_UTF32_LE:
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bom_encoding = 'utf-32le'
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data = data[4:]
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elif data[:2] == codecs.BOM_UTF16_BE and data[2:4] != ZERO_BYTES:
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bom_encoding = 'utf-16be'
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data = data[2:]
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elif data[:2] == codecs.BOM_UTF16_LE and data[2:4] != ZERO_BYTES:
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bom_encoding = 'utf-16le'
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data = data[2:]
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elif data[:3] == codecs.BOM_UTF8:
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bom_encoding = 'utf-8'
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data = data[3:]
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# Check for the characters '<?xm' in several encodings.
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elif data[:4] == EBCDIC_MARKER:
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bom_encoding = 'cp037'
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elif data[:4] == UTF16BE_MARKER:
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bom_encoding = 'utf-16be'
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elif data[:4] == UTF16LE_MARKER:
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bom_encoding = 'utf-16le'
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elif data[:4] == UTF32BE_MARKER:
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bom_encoding = 'utf-32be'
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elif data[:4] == UTF32LE_MARKER:
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bom_encoding = 'utf-32le'
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tempdata = data
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try:
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if bom_encoding:
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tempdata = data.decode(bom_encoding).encode('utf-8')
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except (UnicodeDecodeError, LookupError):
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# feedparser recognizes UTF-32 encodings that aren't
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# available in Python 2.4 and 2.5, so it's possible to
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# encounter a LookupError during decoding.
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xml_encoding_match = None
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else:
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xml_encoding_match = RE_XML_PI_ENCODING.match(tempdata)
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if xml_encoding_match:
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xml_encoding = xml_encoding_match.groups()[0].decode('utf-8').lower()
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# Normalize the xml_encoding if necessary.
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if bom_encoding and (xml_encoding in (
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'u16', 'utf-16', 'utf16', 'utf_16',
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'u32', 'utf-32', 'utf32', 'utf_32',
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'iso-10646-ucs-2', 'iso-10646-ucs-4',
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'csucs4', 'csunicode', 'ucs-2', 'ucs-4'
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)):
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xml_encoding = bom_encoding
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# Find the HTTP Content-Type and, hopefully, a character
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# encoding provided by the server. The Content-Type is used
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# to choose the "correct" encoding among the BOM encoding,
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# XML declaration encoding, and HTTP encoding, following the
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# heuristic defined in RFC 3023.
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http_content_type = http_headers.get('content-type') or ''
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http_content_type, params = cgi.parse_header(http_content_type)
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http_encoding = params.get('charset', '').replace("'", "")
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if isinstance(http_encoding, bytes):
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http_encoding = http_encoding.decode('utf-8', 'ignore')
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acceptable_content_type = 0
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application_content_types = ('application/xml', 'application/xml-dtd',
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'application/xml-external-parsed-entity')
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text_content_types = ('text/xml', 'text/xml-external-parsed-entity')
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if (
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http_content_type in application_content_types
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or (
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http_content_type.startswith('application/')
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and http_content_type.endswith('+xml')
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)
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):
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acceptable_content_type = 1
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rfc3023_encoding = http_encoding or xml_encoding or 'utf-8'
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elif (
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http_content_type in text_content_types
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or (
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http_content_type.startswith('text/')
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and http_content_type.endswith('+xml')
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)
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):
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acceptable_content_type = 1
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rfc3023_encoding = http_encoding or 'us-ascii'
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elif http_content_type.startswith('text/'):
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rfc3023_encoding = http_encoding or 'us-ascii'
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elif http_headers and 'content-type' not in http_headers:
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rfc3023_encoding = xml_encoding or 'iso-8859-1'
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else:
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rfc3023_encoding = xml_encoding or 'utf-8'
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# gb18030 is a superset of gb2312, so always replace gb2312
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# with gb18030 for greater compatibility.
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if rfc3023_encoding.lower() == 'gb2312':
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rfc3023_encoding = 'gb18030'
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if xml_encoding.lower() == 'gb2312':
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xml_encoding = 'gb18030'
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# there are four encodings to keep track of:
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# - http_encoding is the encoding declared in the Content-Type HTTP header
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# - xml_encoding is the encoding declared in the <?xml declaration
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# - bom_encoding is the encoding sniffed from the first 4 bytes of the XML data
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# - rfc3023_encoding is the actual encoding, as per RFC 3023 and a variety of other conflicting specifications
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error = None
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if http_headers and (not acceptable_content_type):
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if 'content-type' in http_headers:
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msg = '%s is not an XML media type' % http_headers['content-type']
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else:
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msg = 'no Content-type specified'
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error = NonXMLContentType(msg)
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# determine character encoding
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known_encoding = 0
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tried_encodings = []
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# try: HTTP encoding, declared XML encoding, encoding sniffed from BOM
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for proposed_encoding in (rfc3023_encoding, xml_encoding, bom_encoding,
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lazy_chardet_encoding, 'utf-8', 'windows-1252', 'iso-8859-2'):
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if callable(proposed_encoding):
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proposed_encoding = proposed_encoding(data)
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if not proposed_encoding:
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continue
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if proposed_encoding in tried_encodings:
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continue
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tried_encodings.append(proposed_encoding)
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try:
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data = data.decode(proposed_encoding)
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except (UnicodeDecodeError, LookupError):
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pass
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else:
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known_encoding = 1
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# Update the encoding in the opening XML processing instruction.
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new_declaration = '''<?xml version='1.0' encoding='utf-8'?>'''
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if RE_XML_DECLARATION.search(data):
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data = RE_XML_DECLARATION.sub(new_declaration, data)
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else:
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data = new_declaration + '\n' + data
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data = data.encode('utf-8')
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break
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# if still no luck, give up
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if not known_encoding:
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error = CharacterEncodingUnknown(
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'document encoding unknown, I tried ' +
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'%s, %s, utf-8, windows-1252, and iso-8859-2 but nothing worked' %
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(rfc3023_encoding, xml_encoding))
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rfc3023_encoding = ''
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elif proposed_encoding != rfc3023_encoding:
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error = CharacterEncodingOverride(
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'document declared as %s, but parsed as %s' %
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(rfc3023_encoding, proposed_encoding))
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rfc3023_encoding = proposed_encoding
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result['encoding'] = rfc3023_encoding
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if error:
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result['bozo'] = True
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result['bozo_exception'] = error
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return data
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