148 lines
5.3 KiB
Python
148 lines
5.3 KiB
Python
######################## BEGIN LICENSE BLOCK ########################
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# The Original Code is Mozilla Universal charset detector code.
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#
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# The Initial Developer of the Original Code is
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# Netscape Communications Corporation.
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# Portions created by the Initial Developer are Copyright (C) 2001
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# the Initial Developer. All Rights Reserved.
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#
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# Contributor(s):
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# Mark Pilgrim - port to Python
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# Shy Shalom - original C code
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
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# 02110-1301 USA
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######################### END LICENSE BLOCK #########################
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import logging
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import re
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from typing import Optional, Union
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from .enums import LanguageFilter, ProbingState
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INTERNATIONAL_WORDS_PATTERN = re.compile(
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b"[a-zA-Z]*[\x80-\xFF]+[a-zA-Z]*[^a-zA-Z\x80-\xFF]?"
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)
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class CharSetProber:
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SHORTCUT_THRESHOLD = 0.95
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def __init__(self, lang_filter: LanguageFilter = LanguageFilter.NONE) -> None:
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self._state = ProbingState.DETECTING
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self.active = True
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self.lang_filter = lang_filter
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self.logger = logging.getLogger(__name__)
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def reset(self) -> None:
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self._state = ProbingState.DETECTING
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@property
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def charset_name(self) -> Optional[str]:
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return None
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@property
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def language(self) -> Optional[str]:
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raise NotImplementedError
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def feed(self, byte_str: Union[bytes, bytearray]) -> ProbingState:
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raise NotImplementedError
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@property
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def state(self) -> ProbingState:
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return self._state
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def get_confidence(self) -> float:
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return 0.0
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@staticmethod
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def filter_high_byte_only(buf: Union[bytes, bytearray]) -> bytes:
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buf = re.sub(b"([\x00-\x7F])+", b" ", buf)
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return buf
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@staticmethod
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def filter_international_words(buf: Union[bytes, bytearray]) -> bytearray:
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"""
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We define three types of bytes:
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alphabet: english alphabets [a-zA-Z]
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international: international characters [\x80-\xFF]
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marker: everything else [^a-zA-Z\x80-\xFF]
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The input buffer can be thought to contain a series of words delimited
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by markers. This function works to filter all words that contain at
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least one international character. All contiguous sequences of markers
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are replaced by a single space ascii character.
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This filter applies to all scripts which do not use English characters.
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"""
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filtered = bytearray()
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# This regex expression filters out only words that have at-least one
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# international character. The word may include one marker character at
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# the end.
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words = INTERNATIONAL_WORDS_PATTERN.findall(buf)
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for word in words:
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filtered.extend(word[:-1])
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# If the last character in the word is a marker, replace it with a
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# space as markers shouldn't affect our analysis (they are used
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# similarly across all languages and may thus have similar
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# frequencies).
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last_char = word[-1:]
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if not last_char.isalpha() and last_char < b"\x80":
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last_char = b" "
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filtered.extend(last_char)
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return filtered
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@staticmethod
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def remove_xml_tags(buf: Union[bytes, bytearray]) -> bytes:
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"""
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Returns a copy of ``buf`` that retains only the sequences of English
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alphabet and high byte characters that are not between <> characters.
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This filter can be applied to all scripts which contain both English
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characters and extended ASCII characters, but is currently only used by
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``Latin1Prober``.
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"""
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filtered = bytearray()
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in_tag = False
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prev = 0
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buf = memoryview(buf).cast("c")
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for curr, buf_char in enumerate(buf):
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# Check if we're coming out of or entering an XML tag
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# https://github.com/python/typeshed/issues/8182
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if buf_char == b">": # type: ignore[comparison-overlap]
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prev = curr + 1
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in_tag = False
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# https://github.com/python/typeshed/issues/8182
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elif buf_char == b"<": # type: ignore[comparison-overlap]
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if curr > prev and not in_tag:
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# Keep everything after last non-extended-ASCII,
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# non-alphabetic character
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filtered.extend(buf[prev:curr])
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# Output a space to delimit stretch we kept
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filtered.extend(b" ")
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in_tag = True
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# If we're not in a tag...
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if not in_tag:
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# Keep everything after last non-extended-ASCII, non-alphabetic
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# character
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filtered.extend(buf[prev:])
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return filtered
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