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authorxiubuzhe <xiubuzhe@sina.com>2023-10-08 20:59:00 +0800
committerxiubuzhe <xiubuzhe@sina.com>2023-10-08 20:59:00 +0800
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+######################## 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 .enums import 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=None):
+ self._state = None
+ self.lang_filter = lang_filter
+ self.logger = logging.getLogger(__name__)
+
+ def reset(self):
+ self._state = ProbingState.DETECTING
+
+ @property
+ def charset_name(self):
+ return None
+
+ def feed(self, byte_str):
+ raise NotImplementedError
+
+ @property
+ def state(self):
+ return self._state
+
+ def get_confidence(self):
+ return 0.0
+
+ @staticmethod
+ def filter_high_byte_only(buf):
+ buf = re.sub(b"([\x00-\x7F])+", b" ", buf)
+ return buf
+
+ @staticmethod
+ def filter_international_words(buf):
+ """
+ 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):
+ """
+ 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
+ if buf_char == b">":
+ prev = curr + 1
+ in_tag = False
+ elif buf_char == b"<":
+ 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