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