static int digit(char c) {
      return (c < 128) ? asciiDigits[c] : -1;
    }
  }

  /**
   * Parses the specified string as a signed decimal long value. The ASCII character {@code '-'} (
   * <code>'&#92;u002D'</code>) is recognized as the minus sign.
   *
   * <p>Unlike {@link Long#parseLong(String)}, this method returns {@code null} instead of throwing