octet += digit;
    }
    if (octet > 255) {
      throw new NumberFormatException();
    }
    return (byte) octet;
  }

  /** Returns a -1 if unable to parse */
  private static int tryParseDecimal(String string, int start, int end) {
    int decimal = 0;
    int max = Integer.MAX_VALUE / 10; // for int overflow detection
    for (int i = start; i < end; i++) {
      if (decimal > max) {
        return -1;