base58 decoder.py

from typing import Mapping, Union

# 58 character alphabet used
BITCOIN_ALPHABET = \
    b'123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
RIPPLE_ALPHABET = b'rpshnaf39wBUDNEGHJKLM4PQRST7VWXYZ2bcdeCg65jkm8oFqi1tuvAxyz'
XRP_ALPHABET = RIPPLE_ALPHABET

def scrub_input(v: Union[str, bytes]) -> bytes:
    if isinstance(v, str):
        v = v.encode('ascii')

    return v

def _get_base58_decode_map(alphabet: bytes,
                           autofix: bool) -> Mapping[int, int]:
    invmap = {char: index for index, char in enumerate(alphabet)}

    if autofix:
        groups = [b'0Oo', b'Il1']
        for group in groups:
            pivots = [c for c in group if c in invmap]
            if len(pivots) == 1:
                for alternative in group:
                    invmap[alternative] = invmap[pivots[0]]

    return invmap

def b58decode_int(
    v: Union[str, bytes], alphabet: bytes = BITCOIN_ALPHABET, *,
    autofix: bool = False
) -> int:
    """
    Decode a Base58 encoded string as an integer
    """
    if b' ' not in alphabet:
        v = v.rstrip()
    v = scrub_input(v)

    map = _get_base58_decode_map(alphabet, autofix=autofix)

    decimal = 0
    base = len(alphabet)
    try:
        for char in v:
            decimal = decimal * base + map[char]
    except KeyError as e:
        raise ValueError(
            "Invalid character {!r}".format(chr(e.args[0]))
        ) from None
    return decimal

def b58decode(
    v: Union[str, bytes], alphabet: bytes = BITCOIN_ALPHABET, *,
    autofix: bool = False
) -> bytes:
    """
    Decode a Base58 encoded string
    """
    v = v.rstrip()
    v = scrub_input(v)

    origlen = len(v)
    v = v.lstrip(alphabet[0:1])
    newlen = len(v)

    acc = b58decode_int(v, alphabet=alphabet, autofix=autofix)

    return acc.to_bytes(origlen - newlen + (acc.bit_length() + 7) // 8, 'big')

#hello
print(b58decode("Cn8eVZg"))