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