Split off fog area bitboard creation and use it as additional fen() a…

…rgument

src/position.cpp

@@ -681,7 +681,7 @@ Position& Position::set(const string& code, Color c, StateInfo* si) {
 /// Position::fen() returns a FEN representation of the position. In case of
 /// Chess960 the Shredder-FEN notation is used. This is mainly a debugging function.
 
-string Position::fen(bool sfen, bool showPromoted, int countStarted, std::string holdings) const {
+string Position::fen(bool sfen, bool showPromoted, int countStarted, std::string holdings, Bitboard fogArea) const {
 
   int emptyCnt;
   std::ostringstream ss;
@@ -690,15 +690,15 @@ string Position::fen(bool sfen, bool showPromoted, int countStarted, std::string
   {
       for (File f = FILE_A; f <= max_file(); ++f)
       {
-          for (emptyCnt = 0; f <= max_file() && !(pieces() & make_square(f, r)); ++f)
+          for (emptyCnt = 0; f <= max_file() && !(pieces() & make_square(f, r)) && !(fogArea & make_square(f, r)); ++f)
               ++emptyCnt;
 
           if (emptyCnt)
               ss << emptyCnt;
 
           if (f <= max_file())
           {
-              if (empty(make_square(f, r)))
+              if (empty(make_square(f, r)) || fogArea & make_square(f, r))
                   // Wall square
                   ss << "*";
               else if (unpromoted_piece_on(make_square(f, r)))
@@ -825,41 +825,6 @@ string Position::fen(bool sfen, bool showPromoted, int countStarted, std::string
 }
 
 
-/// Position::fog_fen() returns a Fog of War (dark chess) FEN representation
-/// of the position. Squares where current player can't move to are filled with
-/// NO_PIECE (wall squares)
-
-string Position::fog_fen(bool sfen, bool showPromoted, int countStarted, std::string holdings) {
-  Color us = sideToMove;
-  Bitboard fog;
-
-  // Our own pieces are visible
-  Bitboard visible = pieces(us);
-
-  // Squares where we can move to are visible as well
-  for (const auto& m : MoveList<LEGAL>(*this))
-  {
-    Square to = to_sq(m);
-    visible |= to;
-  }
-
-  // Everything else is invisible
-  fog = ~visible & board_bb();
-
-  // Fill in invisible squares with walls
-  while (fog)
-  {
-    Square sq = pop_lsb(fog);
-    if (piece_on(sq)) remove_piece(sq);
-
-    st->wallSquares |= sq;
-    byTypeBB[ALL_PIECES] |= sq;
-  }
-
-  return fen(sfen, showPromoted, countStarted, holdings);
-}
-
-
 /// Position::slider_blockers() returns a bitboard of all the pieces (both colors)
 /// that are blocking attacks on the square 's' from 'sliders'. A piece blocks a
 /// slider if removing that piece from the board would result in a position where

src/position.h

@@ -114,8 +114,7 @@ class Position {
   // FEN string input/output
   Position& set(const Variant* v, const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th, bool sfen = false);
   Position& set(const std::string& code, Color c, StateInfo* si);
-  std::string fen(bool sfen = false, bool showPromoted = false, int countStarted = 0, std::string holdings = "-") const;
-  std::string fog_fen(bool sfen = false, bool showPromoted = false, int countStarted = 0, std::string holdings = "-");
+  std::string fen(bool sfen = false, bool showPromoted = false, int countStarted = 0, std::string holdings = "-", Bitboard fogArea = 0) const;
 
   // Variant rule properties
   const Variant* variant() const;
@@ -329,6 +328,7 @@ class Position {
   Score psq_score() const;
   Value non_pawn_material(Color c) const;
   Value non_pawn_material() const;
+  Bitboard fog_area() const;
 
   // Position consistency check, for debugging
   bool pos_is_ok() const;
@@ -1408,6 +1408,20 @@ inline Piece Position::captured_piece() const {
   return st->capturedPiece;
 }
 
+inline Bitboard Position::fog_area() const {
+  Bitboard b = board_bb();
+  // Our own pieces are visible
+  Bitboard visible = pieces(sideToMove);
+  // Squares where we can move to are visible as well
+  for (const auto& m : MoveList<LEGAL>(*this))
+  {
+    Square to = to_sq(m);
+    visible |= to;
+  }
+  // Everything else is invisible
+  return ~visible & b;
+}
+
 inline const std::string Position::piece_to_partner() const {
   if (!st->capturedPiece) return std::string();
   Color color = color_of(st->capturedPiece);

src/pyffish.cpp

@@ -389,15 +389,15 @@ extern "C" PyObject* pyffish_getFogFEN(PyObject* self, PyObject *args) {
     Position pos;
     const char *fen, *variant;
 
-    int chess960 = false;
+    int chess960 = false, sfen = false, showPromoted = false, countStarted = 0;
     if (!PyArg_ParseTuple(args, "ss|p", &fen, &variant, &chess960)) {
         return NULL;
     }
     StateListPtr states(new std::deque<StateInfo>(1));
     buildPosition(pos, states, variant, fen, moveList, chess960);
 
     Py_XDECREF(moveList);
-    return Py_BuildValue("s", pos.fog_fen().c_str());
+    return Py_BuildValue("s", pos.fen(sfen, showPromoted, countStarted, "-", pos.fog_area()).c_str());
 }
 
 static PyMethodDef PyFFishMethods[] = {