docs: private static int tryHexToInt(byte b)
      {
          if (b >= '0' && b <= '9')
              return b - '0';
          if (b >= 'A' && b <= 'F')
              return b - 'A' + 10;
          if (b >= 'a' && b <= 'f')
              return b - 'a' + 10;
          return -1;
      }