mirror of https://github.com/morpheus65535/bazarr
316 lines
12 KiB
Python
316 lines
12 KiB
Python
"""
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This gives other modules access to the gritty details about characters and the
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encodings that use them.
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"""
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from __future__ import annotations
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import html
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import itertools
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import re
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import unicodedata
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# These are the encodings we will try to fix in ftfy, in the
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# order that they should be tried.
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CHARMAP_ENCODINGS = [
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"latin-1",
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"sloppy-windows-1252",
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"sloppy-windows-1251",
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"sloppy-windows-1250",
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"sloppy-windows-1253",
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"sloppy-windows-1254",
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"iso-8859-2",
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"macroman",
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"cp437",
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]
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SINGLE_QUOTE_RE = re.compile("[\u02bc\u2018-\u201b]")
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DOUBLE_QUOTE_RE = re.compile("[\u201c-\u201f]")
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def _build_regexes():
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"""
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ENCODING_REGEXES contain reasonably fast ways to detect if we
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could represent a given string in a given encoding. The simplest one is
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the 'ascii' detector, which of course just determines if all characters
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are between U+0000 and U+007F.
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"""
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# Define a regex that matches ASCII text.
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encoding_regexes = {"ascii": re.compile("^[\x00-\x7f]*$")}
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for encoding in CHARMAP_ENCODINGS:
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# Make a sequence of characters that bytes \x80 to \xFF decode to
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# in each encoding, as well as byte \x1A, which is used to represent
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# the replacement character <20> in the sloppy-* encodings.
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byte_range = bytes(list(range(0x80, 0x100)) + [0x1A])
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charlist = byte_range.decode(encoding)
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# The rest of the ASCII bytes -- bytes \x00 to \x19 and \x1B
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# to \x7F -- will decode as those ASCII characters in any encoding we
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# support, so we can just include them as ranges. This also lets us
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# not worry about escaping regex special characters, because all of
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# them are in the \x1B to \x7F range.
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regex = "^[\x00-\x19\x1b-\x7f{0}]*$".format(charlist)
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encoding_regexes[encoding] = re.compile(regex)
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return encoding_regexes
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ENCODING_REGEXES = _build_regexes()
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def _build_html_entities():
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entities = {}
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# Create a dictionary based on the built-in HTML5 entity dictionary.
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# Add a limited set of HTML entities that we'll also decode if they've
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# been case-folded to uppercase, such as decoding &NTILDE; as "Ñ".
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for name, char in html.entities.html5.items(): # type: ignore
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if name.endswith(";"):
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entities["&" + name] = char
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# Restrict the set of characters we can attempt to decode if their
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# name has been uppercased. If we tried to handle all entity names,
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# the results would be ambiguous.
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if name == name.lower():
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name_upper = name.upper()
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entity_upper = "&" + name_upper
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if html.unescape(entity_upper) == entity_upper:
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entities[entity_upper] = char.upper()
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return entities
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HTML_ENTITY_RE = re.compile(r"&#?[0-9A-Za-z]{1,24};")
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HTML_ENTITIES = _build_html_entities()
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def possible_encoding(text, encoding):
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"""
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Given text and a single-byte encoding, check whether that text could have
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been decoded from that single-byte encoding.
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In other words, check whether it can be encoded in that encoding, possibly
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sloppily.
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"""
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return bool(ENCODING_REGEXES[encoding].match(text))
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def _build_control_char_mapping():
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"""
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Build a translate mapping that strips likely-unintended control characters.
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See :func:`ftfy.fixes.remove_control_chars` for a description of these
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codepoint ranges and why they should be removed.
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"""
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control_chars: dict[int, None] = {}
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for i in itertools.chain(
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range(0x00, 0x09),
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[0x0B],
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range(0x0E, 0x20),
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[0x7F],
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range(0x206A, 0x2070),
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[0xFEFF],
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range(0xFFF9, 0xFFFD),
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):
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control_chars[i] = None
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return control_chars
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CONTROL_CHARS = _build_control_char_mapping()
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# Recognize UTF-8 sequences that would be valid if it weren't for a b'\xa0'
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# that some Windows-1252 program converted to a plain space.
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#
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# The smaller values are included on a case-by-case basis, because we don't want
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# to decode likely input sequences to unlikely characters. These are the ones
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# that *do* form likely characters before 0xa0:
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#
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# 0xc2 -> U+A0 NO-BREAK SPACE
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# 0xc3 -> U+E0 LATIN SMALL LETTER A WITH GRAVE
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# 0xc5 -> U+160 LATIN CAPITAL LETTER S WITH CARON
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# 0xce -> U+3A0 GREEK CAPITAL LETTER PI
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# 0xd0 -> U+420 CYRILLIC CAPITAL LETTER ER
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# 0xd9 -> U+660 ARABIC-INDIC DIGIT ZERO
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#
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# In three-character sequences, we exclude some lead bytes in some cases.
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#
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# When the lead byte is immediately followed by 0xA0, we shouldn't accept
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# a space there, because it leads to some less-likely character ranges:
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#
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# 0xe0 -> Samaritan script
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# 0xe1 -> Mongolian script (corresponds to Latin-1 'á' which is too common)
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#
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# We accept 0xe2 and 0xe3, which cover many scripts. Bytes 0xe4 and
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# higher point mostly to CJK characters, which we generally don't want to
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# decode near Latin lowercase letters.
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#
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# In four-character sequences, the lead byte must be F0, because that accounts
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# for almost all of the usage of high-numbered codepoints (tag characters whose
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# UTF-8 starts with the byte F3 are only used in some rare new emoji sequences).
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#
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# This is meant to be applied to encodings of text that tests true for `is_bad`.
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# Any of these could represent characters that legitimately appear surrounded by
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# spaces, particularly U+C5 (Å), which is a word in multiple languages!
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#
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# We should consider checking for b'\x85' being converted to ... in the future.
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# I've seen it once, but the text still wasn't recoverable.
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ALTERED_UTF8_RE = re.compile(
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b"[\xc2\xc3\xc5\xce\xd0\xd9][ ]"
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b"|[\xe2\xe3][ ][\x80-\x84\x86-\x9f\xa1-\xbf]"
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b"|[\xe0-\xe3][\x80-\x84\x86-\x9f\xa1-\xbf][ ]"
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b"|[\xf0][ ][\x80-\xbf][\x80-\xbf]"
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b"|[\xf0][\x80-\xbf][ ][\x80-\xbf]"
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b"|[\xf0][\x80-\xbf][\x80-\xbf][ ]"
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)
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# This expression matches UTF-8 and CESU-8 sequences where some of the
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# continuation bytes have been lost. The byte 0x1a (sometimes written as ^Z) is
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# used within ftfy to represent a byte that produced the replacement character
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# \ufffd. We don't know which byte it was, but we can at least decode the UTF-8
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# sequence as \ufffd instead of failing to re-decode it at all.
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#
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# In some cases, we allow the ASCII '?' in place of \ufffd, but at most once per
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# sequence.
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LOSSY_UTF8_RE = re.compile(
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b"[\xc2-\xdf][\x1a]"
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b"|[\xc2-\xc3][?]"
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b"|\xed[\xa0-\xaf][\x1a?]\xed[\xb0-\xbf][\x1a?\x80-\xbf]"
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b"|\xed[\xa0-\xaf][\x1a?\x80-\xbf]\xed[\xb0-\xbf][\x1a?]"
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b"|[\xe0-\xef][\x1a?][\x1a\x80-\xbf]"
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b"|[\xe0-\xef][\x1a\x80-\xbf][\x1a?]"
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b"|[\xf0-\xf4][\x1a?][\x1a\x80-\xbf][\x1a\x80-\xbf]"
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b"|[\xf0-\xf4][\x1a\x80-\xbf][\x1a?][\x1a\x80-\xbf]"
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b"|[\xf0-\xf4][\x1a\x80-\xbf][\x1a\x80-\xbf][\x1a?]"
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b"|\x1a"
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)
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# This regex matches C1 control characters, which occupy some of the positions
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# in the Latin-1 character map that Windows assigns to other characters instead.
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C1_CONTROL_RE = re.compile(r"[\x80-\x9f]")
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# A translate mapping that breaks ligatures made of Latin letters. While
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# ligatures may be important to the representation of other languages, in Latin
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# letters they tend to represent a copy/paste error. It omits ligatures such
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# as æ that are frequently used intentionally.
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#
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# This list additionally includes some Latin digraphs that represent two
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# characters for legacy encoding reasons, not for typographical reasons.
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#
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# Ligatures and digraphs may also be separated by NFKC normalization, but that
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# is sometimes more normalization than you want.
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LIGATURES = {
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ord("IJ"): "IJ", # Dutch ligatures
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ord("ij"): "ij",
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ord("ʼn"): "ʼn", # Afrikaans digraph meant to avoid auto-curled quote
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ord("DZ"): "DZ", # Serbian/Croatian digraphs for Cyrillic conversion
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ord("Dz"): "Dz",
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ord("dz"): "dz",
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ord("DŽ"): "DŽ",
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ord("Dž"): "Dž",
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ord("dž"): "dž",
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ord("LJ"): "LJ",
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ord("Lj"): "Lj",
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ord("lj"): "lj",
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ord("NJ"): "NJ",
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ord("Nj"): "Nj",
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ord("nj"): "nj",
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ord("ff"): "ff", # Latin typographical ligatures
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ord("fi"): "fi",
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ord("fl"): "fl",
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ord("ffi"): "ffi",
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ord("ffl"): "ffl",
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ord("ſt"): "ſt",
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ord("st"): "st",
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}
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def _build_width_map():
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"""
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Build a translate mapping that replaces halfwidth and fullwidth forms
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with their standard-width forms.
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"""
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# Though it's not listed as a fullwidth character, we'll want to convert
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# U+3000 IDEOGRAPHIC SPACE to U+20 SPACE on the same principle, so start
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# with that in the dictionary.
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width_map = {0x3000: " "}
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for i in range(0xFF01, 0xFFF0):
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char = chr(i)
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alternate = unicodedata.normalize("NFKC", char)
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if alternate != char:
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width_map[i] = alternate
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return width_map
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WIDTH_MAP = _build_width_map()
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# Character classes that help us pinpoint embedded mojibake. These can
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# include common characters, because we'll also check them for 'badness'.
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UTF8_CLUES = {
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# Letters that decode to 0xC2 - 0xDF in a Latin-1-like encoding
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"utf8_first_of_2": (
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"ÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßĂĆČĎĐĘĚĞİĹŃŇŐŘŞŢŮŰ"
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"ΒΓΔΕΖΗΘΙΚΛΜΝΞΟΠΡΣΤΥΦΧΨΩΪΫάέήίВГДЕЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЫЬЭЮЯ"
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),
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# Letters that decode to 0xE0 - 0xEF in a Latin-1-like encoding
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"utf8_first_of_3": ("àáâãäåæçèéêëìíîïăćčďęěĺŕΰαβγδεζηθικλμνξοабвгдежзийклмноп"),
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# Letters that decode to 0xF0 or 0xF3 in a Latin-1-like encoding.
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# (Other leading bytes correspond only to unassigned codepoints)
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"utf8_first_of_4": ("ðóđğπσру"),
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# Letters that decode to 0x80 - 0xBF in a Latin-1-like encoding,
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# including a space standing in for 0xA0
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"utf8_continuation": (
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"\x80-\xbf"
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"ĄąĽľŁłŒœŚśŞşŠšŤťŸŹźŻżŽžƒˆˇ˘˛˜˝΄΅"
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"ΆΈΉΊΌΎΏЁЂЃЄЅІЇЈЉЊЋЌЎЏёђѓєѕіїјљњћќўџҐґ"
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"–—―‘’‚“”„†‡•…‰‹›€№™"
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" "
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),
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# Letters that decode to 0x80 - 0xBF in a Latin-1-like encoding,
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# and don't usually stand for themselves when adjacent to mojibake.
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# This excludes spaces, dashes, quotation marks, and ellipses.
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"utf8_continuation_strict": (
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"\x80-\xbf"
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"ĄąĽľŁłŒœŚśŞşŠšŤťŸŹźŻżŽžƒˆˇ˘˛˜˝΄΅"
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"ΆΈΉΊΌΎΏЁЂЃЄЅІЇЈЉЊЋЌЎЏёђѓєѕіїјљњћќўџҐґ"
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"†‡•‰‹›€№™"
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),
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}
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# This regex uses UTF8_CLUES to find sequences of likely mojibake.
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# It matches them with + so that several adjacent UTF-8-looking sequences
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# get coalesced into one, allowing them to be fixed more efficiently
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# and not requiring every individual subsequence to be detected as 'badness'.
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#
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# We accept spaces in place of "utf8_continuation", because spaces might have
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# been intended to be U+A0 NO-BREAK SPACE.
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#
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# We do a lookbehind to make sure the previous character isn't a
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# "utf8_continuation_strict" character, so that we don't fix just a few
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# characters in a huge garble and make the situation worse.
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#
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# Unfortunately, the matches to this regular expression won't show their
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# surrounding context, and including context would make the expression much
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# less efficient. The 'badness' rules that require context, such as a preceding
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# lowercase letter, will prevent some cases of inconsistent UTF-8 from being
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# fixed when they don't see it.
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UTF8_DETECTOR_RE = re.compile(
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"""
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(?<! [{utf8_continuation_strict}])
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(
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[{utf8_first_of_2}] [{utf8_continuation}]
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[{utf8_first_of_3}] [{utf8_continuation}]{{2}}
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[{utf8_first_of_4}] [{utf8_continuation}]{{3}}
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)+
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""".format(
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**UTF8_CLUES
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),
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re.VERBOSE,
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)
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