docs: byte[] encodeLikeAnEngineer(final byte[] input) {
  
          if (input == null) {
              throw new NullPointerException("input");
          }
  
          final byte[] output = new byte[input.length << 1];
  
          int index = 0; // index in output
          for (int i = 0; i < input.length; i++) {
              output[index++] = (byte) encodeHalf((input[i] >> 4) & 0x0F);
              output[index++] = (byte) encodeHalf((input[i] & 0x0F));
          }
  
          return output;
      }