base64 encode

base64_encode.py

def base64_unit(input_bytes):
    base64_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    padding = {1: 2, 2: 1, 0: 0}[len(input_bytes) % 3]
    while len(input_bytes) < 3:
        input_bytes += b'\x00'

    num = int.from_bytes(input_bytes, byteorder='big')
    o = []
    count = 0
    for j in range(18, -1, -6):
        if count + padding >= 4:
            o.append("=")

            count += 1
            continue
        index = num >> j & 0x3F
        o.append(base64_chars[index])
        count += 1
    return "".join(o)
    
def base64_encode(input_bytes):
    o = []
    for i in range(0, len(input_bytes), 3):
        unit = input_bytes[i: i+3]
        o.append(base64_unit(unit))
    return "".join(o)