Flutter ffi with stockfish chess engine

[Muhammad Aliah]

Hi.

I'm working on chess app using flutter.

I have already added  Stockfish source code c++ to my flutter project,

but the problem is it's not clear to me how to open stream in flutter to deal with stockfish uci.

I'll appreciate any help .

Thank you in advance.

[Daco Harkes]

Hi Muhammad,

Nice to meet you.

Can you be more specific?

What data are you trying to get from where to where?

Do you have a code sample or API?

Kind regards,

 •  Daco Harkes
 •  Software Engineer
 •  dacoh...@google.com 

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[Muhammad Aliah]

I use c++ sample code,

 I need to get data from this code,

void UCI::command(const string& cmd) {
  istringstream is(cmd);

  string token;
  is >> skipws >> token;

  if (token == "quit" || token == "stop" || token == "ponderhit")
  {
      // The GUI sends 'ponderhit' to tell us to ponder on the same move the
      // opponent has played. In case Signals.stopOnPonderhit is set we are
      // waiting for 'ponderhit' to stop the search (for instance because we
      // already ran out of time), otherwise we should continue searching but
      // switch from pondering to normal search.
      if (token != "ponderhit" || Search::Signals.stopOnPonderhit)
      {
          Search::Signals.stop = true;
          Threads.main()->notify_one(); // Could be sleeping
      }
      else
          Search::Limits.ponder = false;
  }
  else if (token == "perft" || token == "divide")
  {
      int depth;
      stringstream ss;

      is >> depth;
      ss << Options["Hash"]    << " "
         << Options["Threads"] << " " << depth << " current " << token;

      benchmark(currentPos, ss);
  }
  else if (token == "key")
      sync_cout << hex << uppercase << setfill('0')
                << "position key: "   << setw(16) << currentPos.key()
                << "\nmaterial key: " << setw(16) << currentPos.material_key()
                << "\npawn key:     " << setw(16) << currentPos.pawn_key()
                << dec << nouppercase << setfill(' ') << sync_endl;

  else if (token == "uci")
      sync_cout << "id name " << engine_info(true)
                << "\n"       << Options
                << "\nuciok"  << sync_endl;

  else if (token == "eval")
  {
      Search::RootColor = currentPos.side_to_move(); // Ensure it is set
      sync_cout << Eval::trace(currentPos) << sync_endl;
  }
  else if (token == "ucinewgame") TT.clear();
  else if (token == "go")         go(currentPos, is);
  else if (token == "position")   position(currentPos, is);
  else if (token == "setoption")  setoption(is);
  else if (token == "flip")       currentPos.flip();
  else if (token == "bench")      benchmark(currentPos, is);
  else if (token == "d")          sync_cout << currentPos.pretty() << sync_endl;
  else if (token == "isready")    sync_cout << "readyok" << sync_endl;
  else
      sync_cout << "Unknown command: " << cmd << sync_endl;
}

[Daco Harkes]

Hey Muhammad,

C++ strings do not have a predictable memory layout, so we only support plain C char*. That means you'll have to write a small wrapper function with char* as argument type.

How to link the native C/C++ code into your Flutter app you can read here. (Did you manage to invoke a simple hello_world() in C from Dart through the FFI? That way you know that your application setup is working, before looking at connecting to stockfish.)

Kind regards,

 •  Daco Harkes
 •  Software Engineer
 •  dacoh...@google.com 

To view this discussion on the web visit https://groups.google.com/d/msgid/dart-ffi/1fcf723d-0ce6-485d-8e81-b4ce5ef36bc4n%40googlegroups.com.