1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
|
#
# Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
# 2011, 2012, 2013, 2014, 2015 Python Software Foundation; All Rights Reserved
#
# PSF license: https://docs.python.org/2/license.html
#
# PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
# --------------------------------------------
#
# 1. This LICENSE AGREEMENT is between the Python Software Foundation
# ("PSF"), and the Individual or Organization ("Licensee") accessing and
# otherwise using this software ("Python") in source or binary form and
# its associated documentation.
#
# 2. Subject to the terms and conditions of this License Agreement, PSF hereby
# grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce,
# analyze, test, perform and/or display publicly, prepare derivative works,
# distribute, and otherwise use Python alone or in any derivative version,
# provided, however, that PSF's License Agreement and PSF's notice of copyright,
# i.e., "Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
# 2011, 2012, 2013, 2014, 2015 Python Software Foundation; All Rights Reserved"
# are retained in Python alone or in any derivative version prepared by Licensee.
#
# 3. In the event Licensee prepares a derivative work that is based on
# or incorporates Python or any part thereof, and wants to make
# the derivative work available to others as provided herein, then
# Licensee hereby agrees to include in any such work a brief summary of
# the changes made to Python.
#
# 4. PSF is making Python available to Licensee on an "AS IS"
# basis. PSF MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
# IMPLIED. BY WAY OF EXAMPLE, BUT NOT LIMITATION, PSF MAKES NO AND
# DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS
# FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF PYTHON WILL NOT
# INFRINGE ANY THIRD PARTY RIGHTS.
#
# 5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON
# FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS
# A RESULT OF MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON,
# OR ANY DERIVATIVE THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
#
# 6. This License Agreement will automatically terminate upon a material
# breach of its terms and conditions.
#
# 7. Nothing in this License Agreement shall be deemed to create any
# relationship of agency, partnership, or joint venture between PSF and
# Licensee. This License Agreement does not grant permission to use PSF
# trademarks or trade name in a trademark sense to endorse or promote
# products or services of Licensee, or any third party.
#
# 8. By copying, installing or otherwise using Python, Licensee
# agrees to be bound by the terms and conditions of this License
# Agreement.
#
#
# The contents of this module are derived the base64 module of python 2.7, with
# the value of _b32tab modified to use the Base 32 Encoding with Extended Hex
# Alphabet, as specified in RFC 4648. Also, bytes literals are prefixed with
# 'b'.
from __future__ import unicode_literals
import struct
_b32tab = { 0: b'0', 1: b'1', 2: b'2', 3: b'3', 4: b'4', 5: b'5', 6: b'6', 7: b'7', 8: b'8', 9: b'9',
10: b'A', 11: b'B', 12: b'C', 13: b'D', 14: b'E', 15: b'F', 16: b'G', 17: b'H', 18: b'I', 19: b'J',
20: b'K', 21: b'L', 22: b'M', 23: b'N', 24: b'O', 25: b'P', 26: b'Q', 27: b'R', 28: b'S', 29: b'T',
30: b'U', 31: b'V' }
EMPTYSTRING = b''
b32alphabet = set(_b32tab.values())
def b32encode(s):
"""Encode a string using Base32.
s is the string to encode. The encoded string is returned.
"""
parts = []
quanta, leftover = divmod(len(s), 5)
# Pad the last quantum with zero bits if necessary
if leftover:
s += (b'\0' * (5 - leftover))
quanta += 1
for i in range(quanta):
# c1 and c2 are 16 bits wide, c3 is 8 bits wide. The intent of this
# code is to process the 40 bits in units of 5 bits. So we take the 1
# leftover bit of c1 and tack it onto c2. Then we take the 2 leftover
# bits of c2 and tack them onto c3. The shifts and masks are intended
# to give us values of exactly 5 bits in width.
c1, c2, c3 = struct.unpack(b'!HHB', s[i*5:(i+1)*5])
c2 += (c1 & 1) << 16 # 17 bits wide
c3 += (c2 & 3) << 8 # 10 bits wide
parts.extend([_b32tab[c1 >> 11], # bits 1 - 5
_b32tab[(c1 >> 6) & 0x1f], # bits 6 - 10
_b32tab[(c1 >> 1) & 0x1f], # bits 11 - 15
_b32tab[c2 >> 12], # bits 16 - 20 (1 - 5)
_b32tab[(c2 >> 7) & 0x1f], # bits 21 - 25 (6 - 10)
_b32tab[(c2 >> 2) & 0x1f], # bits 26 - 30 (11 - 15)
_b32tab[c3 >> 5], # bits 31 - 35 (1 - 5)
_b32tab[c3 & 0x1f], # bits 36 - 40 (1 - 5)
])
encoded = EMPTYSTRING.join(parts)
# Adjust for any leftover partial quanta
if leftover == 1:
return encoded[:-6] + b'======'
elif leftover == 2:
return encoded[:-4] + b'===='
elif leftover == 3:
return encoded[:-3] + b'==='
elif leftover == 4:
return encoded[:-1] + b'='
return encoded
|
