Current File : //usr/lib/calibre/calibre/ebooks/fb2/__init__.py
#!/usr/bin/env python3
__license__ = 'GPL v3'
__copyright__ = '2012, Kovid Goyal <kovid@kovidgoyal.net>'
__docformat__ = 'restructuredtext en'
def base64_decode(raw):
from io import BytesIO
from polyglot.binary import from_base64_bytes
# First try the python implementation as it is faster
try:
return from_base64_bytes(raw)
except Exception:
pass
# Try a more robust version (adapted from FBReader sources)
A, Z, a, z, zero, nine, plus, slash, equal = bytearray(b'AZaz09+/=')
raw = bytearray(raw)
out = BytesIO()
pos = 0
while pos < len(raw):
tot = 0
i = 0
while i < 4 and pos < len(raw):
byt = raw[pos]
pos += 1
num = 0
if A <= byt <= Z:
num = byt - A
elif a <= byt <= z:
num = byt - a + 26
elif zero <= byt <= nine:
num = byt - zero + 52
else:
num = {plus:62, slash:63, equal:64}.get(byt, None)
if num is None:
# Ignore this byte
continue
tot += num << (6 * (3 - i))
i += 1
triple = bytearray(3)
for j in (2, 1, 0):
triple[j] = tot & 0xff
tot >>= 8
out.write(bytes(triple))
return out.getvalue()
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