"""
z = []
for i in range(26):
    z = z + [chr(ord('A')+i)]
for i in range(26):
    z = z + [chr(ord('a')+i)]
for i in range(10):
    z = z + [chr(ord('0')+i)]
z = z + ['+','/']
"""

z = ('A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
     'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
     'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
     'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
     '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/')

def encode(a):
    assert type(a) == bytes
    r = len(a)%3
    if r == 1:
        a = a + bytes((0,0))
    elif r == 2:
        a = a + bytes((0,))
    n = len(a)//3
    b = ''
    for i in range(n):
        h1 = a[i*3]//4
        h2 = (a[i*3]-h1*4)*16 + a[i*3+1]//16
        h3 = (a[i*3+1]%16)*4 + a[i*3+2]//64
        h4 = a[i*3+2]%64
        b = b + z[h1]+z[h2]+z[h3]+z[h4]
    if r == 1:
        # return b # DEBUG
        return b[:-2]+'=='
    elif r == 2:
        # return b # DEBUG
        return b[:-1]+'='
    else:
        return b

def decode(b):
    assert type(b) == str
    if b[-1] == '=':
        b = b[:-1]+'A'
        if b[-2] == '=':
            anhang = 2
            b = b[:-2] + 'AA'
        else:
            anhang = 1
    else:
        anhang = 0
    n = len(b)//4
    a = bytes(0)
    for i in range(n):
        a = a + bytes((z.index(b[i*4])*4+z.index(b[i*4+1])//16,))
        a = a + bytes(((z.index(b[i*4+1])&15)*16+z.index(b[i*4+2])//4,))
        a = a + bytes(((z.index(b[i*4+2])&3)*64+z.index(b[i*4+3]),))
    if anhang == 1:
        return a[:-1]
    elif anhang == 2:
        return a[:-2]
    else:
        return a    

if __name__ == "__main__":
    import base64
    print(encode(bytes('Polyfon zwitschernd aßen Mäxchens Vögel Rüben, Joghurt und Quark','utf-8')))
    print(base64.b64encode(bytes('Polyfon zwitschernd aßen Mäxchens Vögel Rüben, Joghurt und Quark','utf-8')))
    print('UG9seWZvbiB6d2l0c2NoZXJuZCBhw59lbiBNw6R4Y2hlbnMgVsO2Z2VsIFLDvGJlbiwgSm9naHVydCB1bmQgUXVhcms=')
    print(str(decode('UG9seWZvbiB6d2l0c2NoZXJuZCBhw59lbiBNw6R4Y2hlbnMgVsO2Z2VsIFLDvGJlbiwgSm9naHVydCB1bmQgUXVhcms='),'utf-8'))
    print(encode(bytes('ABCDäöüß','utf-8')))
    print(base64.b64encode(bytes('ABCDäöüß','utf-8')))
    print(encode(bytes('abcäöüß','utf-8')))
    print(base64.b64encode(bytes('abcäöüß','utf-8')))
    h = encode(bytes('abäöüß','utf-8'))
    print(h)
    print(str(decode(h),'utf-8'))
    print(base64.b64encode(bytes('abäöüß','utf-8')))