base64_test_implementation.py

# Copyright MFDGaming 2021

base64_table = r"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

def b64encode(value: bytes) -> str:
    result = ""
    padding = 0
    for i in range(2):
        if len(value) * 8 % 6 != 0:
            padding += 1
            value += b"\x00"
        else:
            break
    for i in range(0, len(value), 3):
        prt24 = value[i] << 16 | value[i + 1] << 8 | value[i + 2]
        for ii in range(0, 4 - (padding if i == len(value) - padding - 2 else 0)):
            index = (prt24 >> (18 - (6 * ii))) & 63
            result += base64_table[index]
    return result + "=" * padding

def b64decode(value: str) -> bytes:
    result = b""
    tb = []
    padding = 0
    for entry in value:
        if entry == "=":
            padding += 1
        else:
            tb.append(base64_table.index(entry))
    for i in range(0, 3):
        if len(tb) % 4:
            tb.append(0)
        else:
            break
    for i in range(0, len(tb), 4):
        prt24 = (((tb[i] << 6) | tb[i + 1]) << 12) | ((tb[i + 2] << 6) | tb[i + 3])
        result += bytes([(prt24 >> 16) & 0xff])
        result += bytes([(prt24 >> 8) & 0xff])
        result += bytes([prt24 & 0xff])
    return result[:-padding]

print(b64encode(b"Hello world"))

print(b64decode("CgAACQQAZW5jaAoBAAAAAgIAaWQAAAIDAGx2bAEAAAA="))

print(b64decode(b64encode(b"Hello world")))