# Matasano Crypto Challenge - Set 1 Challenge 1


def numericCh(ch):
    '''
    returns the numeric ascii representation of a given character
    Assumes that all characteres are lower case
    '''
    if ch.isalpha():
        return ord(ch) - ord('a') + 10
    else:
        return ord(ch) - ord('0') 
        
def encodeHexStrToRawBytes(hexString):
    '''
    Converts HexString to hexadecimal raw bytes, saves on a list and returns it
    Assumes that the len of hexString is a multiple of 2
    '''
    return [numericCh(hexString[i]) << 4 | numericCh(hexString[i+1]) for i in range(0, len(hexString), 2)]
        
hexString = '49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d'
rawBytes = encodeHexStrToRawBytes(hexString)


def decodeRawBytesToBase64(rawBytes):
    '''
    Decode a sequence of hexadecimal raw bytes to the base 64
    '''
    b64Map = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
    encodedString = []    
    pad = len(rawBytes) % 3
    
    if pad == 1:
        rawBytes.append(0)
        rawBytes.append(0)
    elif pad == 2:
        rawBytes.append(0)
    for i in range(0, len(rawBytes), 3):    
        encodedString.append(b64Map[rawBytes[i] >> 0b10])   
        encodedString.append(b64Map[((rawBytes[i] & 0b11) << 0b100) | (rawBytes[i+1] >> 0b100)])
        encodedString.append(b64Map[((rawBytes[i+1] & 0b1111) << 0b10) | (rawBytes[i+2] >> 0b110)])
        encodedString.append(b64Map[rawBytes[i+2] & 0b111111])
    if pad > 0:
        while pad != 0:
            encodedString.append(b64Map[-1])
            pad -= 1
    return encodedString
                

hexString = '49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d'
rawBytes = encodeHexStrToRawBytes(hexString)     
encodedString = decodeRawBytesToBase64(rawBytes)