contrib/testgen/base58.py

   1 # Copyright (c) 2012-2017 The Bitcoin Core developers
   2 # Distributed under the MIT software license, see the accompanying
   3 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4 '''
   5 Bitcoin base58 encoding and decoding.
   6
   7 Based on https://bitcointalk.org/index.php?topic=1026.0 (public domain)
   8 '''
   9 import hashlib
  10
  11 # for compatibility with following code...
  12 class SHA256:
  13     new = hashlib.sha256
  14
  15 if str != bytes:
  16     # Python 3.x
  17     def ord(c):
  18         return c
  19     def chr(n):
  20         return bytes( (n,) )
  21
  22 __b58chars = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
  23 __b58base = len(__b58chars)
  24 b58chars = __b58chars
  25
  26 def b58encode(v):
  27     """ encode v, which is a string of bytes, to base58.
  28     """
  29     long_value = 0
  30     for (i, c) in enumerate(v[::-1]):
  31         long_value += (256**i) * ord(c)
  32
  33     result = ''
  34     while long_value >= __b58base:
  35         div, mod = divmod(long_value, __b58base)
  36         result = __b58chars[mod] + result
  37         long_value = div
  38     result = __b58chars[long_value] + result
  39
  40     # Bitcoin does a little leading-zero-compression:
  41     # leading 0-bytes in the input become leading-1s
  42     nPad = 0
  43     for c in v:
  44         if c == '\0': nPad += 1
  45         else: break
  46
  47     return (__b58chars[0]*nPad) + result
  48
  49 def b58decode(v, length = None):
  50     """ decode v into a string of len bytes
  51     """
  52     long_value = 0
  53     for (i, c) in enumerate(v[::-1]):
  54         long_value += __b58chars.find(c) * (__b58base**i)
  55
  56     result = bytes()
  57     while long_value >= 256:
  58         div, mod = divmod(long_value, 256)
  59         result = chr(mod) + result
  60         long_value = div
  61     result = chr(long_value) + result
  62
  63     nPad = 0
  64     for c in v:
  65         if c == __b58chars[0]: nPad += 1
  66         else: break
  67
  68     result = chr(0)*nPad + result
  69     if length is not None and len(result) != length:
  70         return None
  71
  72     return result
  73
  74 def checksum(v):
  75     """Return 32-bit checksum based on SHA256"""
  76     return SHA256.new(SHA256.new(v).digest()).digest()[0:4]
  77
  78 def b58encode_chk(v):
  79     """b58encode a string, with 32-bit checksum"""
  80     return b58encode(v + checksum(v))
  81
  82 def b58decode_chk(v):
  83     """decode a base58 string, check and remove checksum"""
  84     result = b58decode(v)
  85     if result is None:
  86         return None
  87     if result[-4:] == checksum(result[:-4]):
  88         return result[:-4]
  89     else:
  90         return None
  91
  92 def get_bcaddress_version(strAddress):
  93     """ Returns None if strAddress is invalid.  Otherwise returns integer version of address. """
  94     addr = b58decode_chk(strAddress)
  95     if addr is None or len(addr)!=21: return None
  96     version = addr[0]
  97     return ord(version)
  98
  99 if __name__ == '__main__':
 100     # Test case (from http://gitorious.org/bitcoin/python-base58.git)
 101     assert get_bcaddress_version('15VjRaDX9zpbA8LVnbrCAFzrVzN7ixHNsC') is 0
 102     _ohai = 'o hai'.encode('ascii')
 103     _tmp = b58encode(_ohai)
 104     assert _tmp == 'DYB3oMS'
 105     assert b58decode(_tmp, 5) == _ohai
 106     print("Tests passed")