base58.py

if str != bytes:
    # Python 3.x
    def ord(c):
        return c
    def chr(n):
        return bytes( (n,) )

__b58chars = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
__b58base = len(__b58chars)
b58chars = __b58chars

def encode(v):
    """ encode v, which is a string of bytes, to base58.
    """
    long_value = 0
    for (i, c) in enumerate(v[::-1]):
        if isinstance(c, str):
            c = ord(c)
        long_value += (256**i) * c

    result = ''
    while long_value >= __b58base:
        div, mod = divmod(long_value, __b58base)
        result = __b58chars[mod] + result
        long_value = div
    result = __b58chars[long_value] + result

    # Bitcoin does a little leading-zero-compression:
    # leading 0-bytes in the input become leading-1s
    nPad = 0
    for c in v:
        if c == 0:
            nPad += 1
        else:
            break

    return (__b58chars[0]*nPad) + result

def decode(v, length = None):
    """ decode v into a string of len bytes
    """
    long_value = 0
    for i, c in enumerate(v[::-1]):
        pos = __b58chars.find(c)
        assert pos != -1
        long_value += pos * (__b58base**i)

    result = bytes()
    while long_value >= 256:
        div, mod = divmod(long_value, 256)
        result = chr(mod) + result
        long_value = div
    result = chr(long_value) + result

    nPad = 0
    for c in v:
        if c == __b58chars[0]:
            nPad += 1
            continue
        break

    result = bytes(nPad) + result
    if length is not None and len(result) != length:
        return None

    return result