code: private static int base64toInt(char c, byte[] alphaToInt) {
          int result = alphaToInt[c];
          if (result < 0) {
              throw new IllegalArgumentException("Illegal character " + c);
          }
          return result;
      }
docs: Translates the specified character, which is assumed to be in the "Base 64 Alphabet" into its equivalent 6-bit
  positive integer.
  
  @throw IllegalArgumentException or ArrayOutOfBoundsException if c is not in the Base64 Alphabet.
  @param c [ellipsis]
  @param alphaToInt [ellipsis]
  @return [ellipsis]