blob: 1bb1784edf9c8235db2949d016e7d08ecdb5d577 (
plain)
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
|
"""Python implementation of Z85 85-bit encoding
Z85 encoding is a plaintext encoding for a bytestring interpreted as 32bit integers.
Since the chunks are 32bit, a bytestring must be a multiple of 4 bytes.
See ZMQ RFC 32 for details.
"""
# Copyright (C) PyZMQ Developers
# Distributed under the terms of the Modified BSD License.
import sys
import struct
PY3 = sys.version_info[0] >= 3
# Z85CHARS is the base 85 symbol table
Z85CHARS = b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#"
# Z85MAP maps integers in [0,84] to the appropriate character in Z85CHARS
Z85MAP = dict([(c, idx) for idx, c in enumerate(Z85CHARS)])
_85s = [ 85**i for i in range(5) ][::-1]
def encode(rawbytes):
"""encode raw bytes into Z85"""
# Accepts only byte arrays bounded to 4 bytes
if len(rawbytes) % 4:
raise ValueError("length must be multiple of 4, not %i" % len(rawbytes))
nvalues = len(rawbytes) / 4
values = struct.unpack('>%dI' % nvalues, rawbytes)
encoded = []
for v in values:
for offset in _85s:
encoded.append(Z85CHARS[(v // offset) % 85])
# In Python 3, encoded is a list of integers (obviously?!)
if PY3:
return bytes(encoded)
else:
return b''.join(encoded)
def decode(z85bytes):
"""decode Z85 bytes to raw bytes"""
if len(z85bytes) % 5:
raise ValueError("Z85 length must be multiple of 5, not %i" % len(z85bytes))
nvalues = len(z85bytes) / 5
values = []
for i in range(0, len(z85bytes), 5):
value = 0
for j, offset in enumerate(_85s):
value += Z85MAP[z85bytes[i+j]] * offset
values.append(value)
return struct.pack('>%dI' % nvalues, *values)
|
