contrib/testgen/base58.py

   1 '''
   2 Bitcoin base58 encoding and decoding.
   3
   4 Based on https://bitcointalk.org/index.php?topic=1026.0 (public domain)
   5 '''
   6 import hashlib
   7
   8 # for compatibility with following code...
   9 class SHA256:
  10     new = hashlib.sha256
  11
  12 if str != bytes:
  13     # Python 3.x
  14     def ord(c):
  15         return c
  16     def chr(n):
  17         return bytes( (n,) )
  18
  19 __b58chars = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
  20 __b58base = len(__b58chars)
  21 b58chars = __b58chars
  22
  23 def b58encode(v):
  24     """ encode v, which is a string of bytes, to base58.
  25     """
  26     long_value = 0
  27     for (i, c) in enumerate(v[::-1]):
  28         long_value += (256**i) * ord(c)
  29
  30     result = ''
  31     while long_value >= __b58base:
  32         div, mod = divmod(long_value, __b58base)
  33         result = __b58chars[mod] + result
  34         long_value = div
  35     result = __b58chars[long_value] + result
  36
  37     # Bitcoin does a little leading-zero-compression:
  38     # leading 0-bytes in the input become leading-1s
  39     nPad = 0
  40     for c in v:
  41         if c == '\0': nPad += 1
  42         else: break
  43
  44     return (__b58chars[0]*nPad) + result
  45
  46 def b58decode(v, length = None):
  47     """ decode v into a string of len bytes
  48     """
  49     long_value = 0
  50     for (i, c) in enumerate(v[::-1]):
  51         long_value += __b58chars.find(c) * (__b58base**i)
  52
  53     result = bytes()
  54     while long_value >= 256:
  55         div, mod = divmod(long_value, 256)
  56         result = chr(mod) + result
  57         long_value = div
  58     result = chr(long_value) + result
  59
  60     nPad = 0
  61     for c in v:
  62         if c == __b58chars[0]: nPad += 1
  63         else: break
  64
  65     result = chr(0)*nPad + result
  66     if length is not None and len(result) != length:
  67         return None
  68
  69     return result
  70
  71 def checksum(v):
  72     """Return 32-bit checksum based on SHA256"""
  73     return SHA256.new(SHA256.new(v).digest()).digest()[0:4]
  74
  75 def b58encode_chk(v):
  76     """b58encode a string, with 32-bit checksum"""
  77     return b58encode(v + checksum(v))
  78
  79 def b58decode_chk(v):
  80     """decode a base58 string, check and remove checksum"""
  81     result = b58decode(v)
  82     if result is None:
  83         return None
  84     h3 = checksum(result[:-4])
  85     if result[-4:] == checksum(result[:-4]):
  86         return result[:-4]
  87     else:
  88         return None
  89
  90 def get_bcaddress_version(strAddress):
  91     """ Returns None if strAddress is invalid.  Otherwise returns integer version of address. """
  92     addr = b58decode_chk(strAddress)
  93     if addr is None or len(addr)!=21: return None
  94     version = addr[0]
  95     return ord(version)
  96
  97 if __name__ == '__main__':
  98     # Test case (from http://gitorious.org/bitcoin/python-base58.git)
  99     assert get_bcaddress_version('15VjRaDX9zpbA8LVnbrCAFzrVzN7ixHNsC') is 0
 100     _ohai = 'o hai'.encode('ascii')
 101     _tmp = b58encode(_ohai)
 102     assert _tmp == 'DYB3oMS'
 103     assert b58decode(_tmp, 5) == _ohai
 104     print("Tests passed")