Fix race condition in holding command

Prevent race conditions in bughouse by updating the holdings
with the captured piece instead of completely overriding them,
given that the GUI provides this optional information.

Closes #73.

diff --git a/src/xboard.cpp b/src/xboard.cpp
index 69e7252..80bd7df 100644 (file)
--- a/src/xboard.cpp
+++ b/src/xboard.cpp
@@ -259,8 +259,19 @@ void StateMachine::process_command(Position& pos, std::string token, std::istrin
       if (   std::getline(is, token, '[') && std::getline(is, white_holdings, ']')
           && std::getline(is, token, '[') && std::getline(is, black_holdings, ']'))
       {
-          std::transform(black_holdings.begin(), black_holdings.end(), black_holdings.begin(), ::tolower);
-          std::string fen = pos.fen(false, false, white_holdings + black_holdings);
+          std::string fen;
+          char color, pieceType;
+          // Use the obtained holding if available to avoid race conditions
+          if (is >> color && is >> pieceType)
+          {
+              fen = pos.fen();
+              fen.insert(fen.find(']'), 1, toupper(color) == 'B' ? tolower(pieceType) : toupper(pieceType));
+          }
+          else
+          {
+              std::transform(black_holdings.begin(), black_holdings.end(), black_holdings.begin(), ::tolower);
+              fen = pos.fen(false, false, white_holdings + black_holdings);
+          }
           setboard(pos, states, fen);
       }
       // restart search