forked from varia/varia.website
105 lines
2.9 KiB
Python
105 lines
2.9 KiB
Python
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from __future__ import annotations
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from collections.abc import Sequence
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import functools
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import re
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DECODE_DEFAULT_CHARS = ";/?:@&=+$,#"
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DECODE_COMPONENT_CHARS = ""
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decode_cache: dict[str, list[str]] = {}
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def get_decode_cache(exclude: str) -> Sequence[str]:
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if exclude in decode_cache:
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return decode_cache[exclude]
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cache: list[str] = []
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decode_cache[exclude] = cache
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for i in range(128):
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ch = chr(i)
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cache.append(ch)
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for i in range(len(exclude)):
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ch_code = ord(exclude[i])
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cache[ch_code] = "%" + ("0" + hex(ch_code)[2:].upper())[-2:]
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return cache
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# Decode percent-encoded string.
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#
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def decode(string: str, exclude: str = DECODE_DEFAULT_CHARS) -> str:
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cache = get_decode_cache(exclude)
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repl_func = functools.partial(repl_func_with_cache, cache=cache)
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return re.sub(r"(%[a-f0-9]{2})+", repl_func, string, flags=re.IGNORECASE)
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def repl_func_with_cache(match: re.Match, cache: Sequence[str]) -> str:
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seq = match.group()
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result = ""
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i = 0
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l = len(seq) # noqa: E741
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while i < l:
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b1 = int(seq[i + 1 : i + 3], 16)
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if b1 < 0x80:
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result += cache[b1]
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i += 3 # emulate JS for loop statement3
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continue
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if (b1 & 0xE0) == 0xC0 and (i + 3 < l):
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# 110xxxxx 10xxxxxx
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b2 = int(seq[i + 4 : i + 6], 16)
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if (b2 & 0xC0) == 0x80:
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all_bytes = bytes((b1, b2))
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try:
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result += all_bytes.decode()
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except UnicodeDecodeError:
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result += "\ufffd" * 2
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i += 3
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i += 3 # emulate JS for loop statement3
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continue
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if (b1 & 0xF0) == 0xE0 and (i + 6 < l):
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# 1110xxxx 10xxxxxx 10xxxxxx
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b2 = int(seq[i + 4 : i + 6], 16)
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b3 = int(seq[i + 7 : i + 9], 16)
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if (b2 & 0xC0) == 0x80 and (b3 & 0xC0) == 0x80:
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all_bytes = bytes((b1, b2, b3))
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try:
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result += all_bytes.decode()
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except UnicodeDecodeError:
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result += "\ufffd" * 3
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i += 6
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i += 3 # emulate JS for loop statement3
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continue
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if (b1 & 0xF8) == 0xF0 and (i + 9 < l):
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# 111110xx 10xxxxxx 10xxxxxx 10xxxxxx
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b2 = int(seq[i + 4 : i + 6], 16)
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b3 = int(seq[i + 7 : i + 9], 16)
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b4 = int(seq[i + 10 : i + 12], 16)
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if (b2 & 0xC0) == 0x80 and (b3 & 0xC0) == 0x80 and (b4 & 0xC0) == 0x80:
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all_bytes = bytes((b1, b2, b3, b4))
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try:
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result += all_bytes.decode()
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except UnicodeDecodeError:
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result += "\ufffd" * 4
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i += 9
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i += 3 # emulate JS for loop statement3
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continue
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result += "\ufffd"
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i += 3 # emulate JS for loop statement3
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return result
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