1 # Base91 encode/decode for Python 2 and Python 3
3 # Copyright (c) 2012 Adrien Beraud
4 # Copyright (c) 2015 Guillaume Jacquenot
7 # Redistribution and use in source and binary forms, with or without
8 # modification, are permitted provided that the following conditions are met:
10 # * Redistributions of source code must retain the above copyright notice,
11 # this list of conditions and the following disclaimer.
12 # * Redistributions in binary form must reproduce the above copyright notice,
13 # this list of conditions and the following disclaimer in the documentation
14 # and/or other materials provided with the distribution.
15 # * Neither the name of Adrien Beraud, Wisdom Vibes Pte. Ltd., nor the names
16 # of its contributors may be used to endorse or promote products derived
17 # from this software without specific prior written permission.
19 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
20 # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
22 # DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
23 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
25 # SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
26 # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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28 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 base91_alphabet = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
33 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
34 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
35 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
36 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '!', '#', '$',
37 '%', '&', '(', ')', '*', '+', ',', '.', '/', ':', ';', '<', '=',
38 '>', '?', '@', '[', ']', '^', '_', '`', '{', '|', '}', '~', '"']
40 decode_table = dict((v, k) for k, v in enumerate(base91_alphabet))
43 def decode(encoded_str):
44 ''' Decode Base91 string to a bytearray '''
49 for strletter in encoded_str:
50 if not strletter in decode_table:
52 c = decode_table[strletter]
58 n += 13 if (v & 8191) > 88 else 14
60 out += struct.pack('B', b & 255)
67 out += struct.pack('B', (b | v << n) & 255)
72 ''' Encode a bytearray to a Base91 string '''
76 for count in range(len(bindata)):
77 byte = bindata[count:count + 1]
78 b |= struct.unpack('B', byte)[0] << n
89 out += base91_alphabet[v % 91] + base91_alphabet[v // 91]
91 out += base91_alphabet[b % 91]
93 out += base91_alphabet[b // 91]