mirror of
https://github.com/gryf/ebook-converter.git
synced 2026-02-13 04:15:52 +01:00
45 lines
1.2 KiB
Python
45 lines
1.2 KiB
Python
import io
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from ebook_converter import polyglot
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def base64_decode(raw):
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# First try the python implementation as it is faster
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try:
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return polyglot.from_base64_bytes(raw)
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except Exception:
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pass
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# Try a more robust version (adapted from FBReader sources)
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A, Z, a, z, zero, nine, plus, slash, equal = bytearray(b'AZaz09+/=')
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raw = bytearray(raw)
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out = io.BytesIO()
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pos = 0
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while pos < len(raw):
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tot = 0
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i = 0
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while i < 4 and pos < len(raw):
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byt = raw[pos]
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pos += 1
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num = 0
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if A <= byt <= Z:
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num = byt - A
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elif a <= byt <= z:
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num = byt - a + 26
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elif zero <= byt <= nine:
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num = byt - zero + 52
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else:
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num = {plus: 62, slash: 63, equal: 64}.get(byt, None)
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if num is None:
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# Ignore this byte
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continue
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tot += num << (6 * (3 - i))
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i += 1
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triple = bytearray(3)
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for j in (2, 1, 0):
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triple[j] = tot & 0xff
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tot >>= 8
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out.write(bytes(triple))
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return out.getvalue()
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