Python/ciphers/base64_cipher.py

def encodeBase64(text):
    base64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

    r = ""  # the result
    c = 3 - len(text) % 3  # the length of padding
    p = "=" * c  # the padding
    s = text + "\0" * c  # the text to encode

    i = 0
    while i < len(s):
        if i > 0 and ((i / 3 * 4) % 76) == 0:
            r = r + "\r\n"

        n = (ord(s[i]) << 16) + (ord(s[i + 1]) << 8) + ord(s[i + 2])

        n1 = (n >> 18) & 63
        n2 = (n >> 12) & 63
        n3 = (n >> 6) & 63
        n4 = n & 63

        r += base64chars[n1] + base64chars[n2] + base64chars[n3] + base64chars[n4]
        i += 3

    return r[0 : len(r) - len(p)] + p


def decodeBase64(text):
    base64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    s = ""

    for i in text:
        if i in base64chars:
            s += i
            c = ""
        else:
            if i == "=":
                c += "="

    p = ""
    if c == "=":
        p = "A"
    else:
        if c == "==":
            p = "AA"

    r = ""
    s = s + p

    i = 0
    while i < len(s):
        n = (
            (base64chars.index(s[i]) << 18)
            + (base64chars.index(s[i + 1]) << 12)
            + (base64chars.index(s[i + 2]) << 6)
            + base64chars.index(s[i + 3])
        )

        r += chr((n >> 16) & 255) + chr((n >> 8) & 255) + chr(n & 255)

        i += 4

    return r[0 : len(r) - len(p)]


def main():
    print(encodeBase64("WELCOME to base64 encoding"))
    print(decodeBase64(encodeBase64("WELCOME to base64 encoding")))


if __name__ == "__main__":
    main()