code: public static long parseLong(byte[] bytes, int from, int to) {
          long result = 0;
          for (int i = from; i < to && i < bytes.length; i++) {
              result *= 10;
              result += (bytes[i] - (byte) '0');
          }
          return result;
      }
docs: parses only positive numbers
  
  @param bytes   bytes of string value
  @param from    index to start from
  @param to      index to end at
  @return integer value