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# Base91 encode/decode for Python 2 and Python 3
#
# Copyright (c) 2012 Adrien Beraud
# Copyright (c) 2015 Guillaume Jacquenot
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
# * Neither the name of Adrien Beraud, Wisdom Vibes Pte. Ltd., nor the names
# of its contributors may be used to endorse or promote products derived
# from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
import struct
base91_alphabet = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '!', '#', '$',
'%', '&', '(', ')', '*', '+', ',', '.', '/', ':', ';', '<', '=',
'>', '?', '@', '[', ']', '^', '_', '`', '{', '|', '}', '~', '"']
decode_table = dict((v, k) for k, v in enumerate(base91_alphabet))
def decode(encoded_str):
''' Decode Base91 string to a bytearray '''
v = -1
b = 0
n = 0
out = bytearray()
for strletter in encoded_str:
if not strletter in decode_table:
continue
c = decode_table[strletter]
if (v < 0):
v = c
else:
v += c * 91
b |= v << n
n += 13 if (v & 8191) > 88 else 14
while True:
out += struct.pack('B', b & 255)
b >>= 8
n -= 8
if not n > 7:
break
v = -1
if v + 1:
out += struct.pack('B', (b | v << n) & 255)
return out
def encode(bindata):
''' Encode a bytearray to a Base91 string '''
b = 0
n = 0
out = ''
for count in range(len(bindata)):
byte = bindata[count:count + 1]
b |= struct.unpack('B', byte)[0] << n
n += 8
if n > 13:
v = b & 8191
if v > 88:
b >>= 13
n -= 13
else:
v = b & 16383
b >>= 14
n -= 14
out += base91_alphabet[v % 91] + base91_alphabet[v // 91]
if n:
out += base91_alphabet[b % 91]
if n > 7 or b > 90:
out += base91_alphabet[b // 91]
return out
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