public void FindPinnedPieces()
{
var ownKingSquare = Bitwise.FirstSetSquare(GetKing(ColorToMove));
var ownPieces = ColorOccupancy[(int)ColorToMove];
var enemyRankFileAttackers = GetRooks(ColorLastMoved) | GetQueens(ColorLastMoved);
var enemyDiagonalAttackers = GetBishops(ColorLastMoved) | GetQueens(ColorLastMoved);
var enemyPieces = ColorOccupancy[(int)ColorLastMoved];
// Find pieces pinned to own king by enemy rank / file attackers.
PinnedPieces = 0;
Square attackerSquare;
while ((attackerSquare = Bitwise.PopFirstSetSquare(ref enemyRankFileAttackers)) != Square.Illegal)
{
var betweenSquares = Board.RankFileBetweenSquares[(int)attackerSquare][(int)ownKingSquare];
if (betweenSquares == 0)
{
continue;
}
if ((betweenSquares & enemyPieces) == 0)
{
// No enemy pieces between enemy attacker and own king.
var pinnedPieces = betweenSquares & ownPieces;
if (Bitwise.CountSetBits(pinnedPieces) == 1)
{
// Exactly one own piece between enemy attacker and own king.
// Piece is pinned to own king.
PinnedPieces |= pinnedPieces;
}
}
}
// Find pieces pinned to own king by enemy diagonal attackers.
while ((attackerSquare = Bitwise.PopFirstSetSquare(ref enemyDiagonalAttackers)) != Square.Illegal)
{
var betweenSquares = Board.DiagonalBetweenSquares[(int)attackerSquare][(int)ownKingSquare];
if (betweenSquares == 0)
{
continue;
}
if ((betweenSquares & enemyPieces) == 0)
{
// No enemy pieces between enemy attacker and own king.
var pinnedPieces = betweenSquares & ownPieces;
if (Bitwise.CountSetBits(pinnedPieces) == 1)
{
// Exactly one own piece between enemy attacker and own king.
// Piece is pinned to own king.
PinnedPieces |= pinnedPieces;
}
}
}
}
private void GenerateKingMoves(MoveGeneration moveGeneration, ulong fromSquareMask, ulong toSquareMask)
{
var king = GetKing(ColorToMove) & fromSquareMask;
if (king == 0)
{
return;
}
var unOrEnemyOccupiedSquares = ~ColorOccupancy[(int)ColorToMove];
var enemyOccupiedSquares = ColorOccupancy[(int)ColorLastMoved];
var attacker = PieceHelper.GetPieceOfColor(ColorlessPiece.King, ColorToMove);
ulong move;
var fromSquare = Bitwise.FirstSetSquare(king);
if (fromSquare == Square.Illegal)
{
return;
}
var kingDestinations = moveGeneration switch
{
MoveGeneration.AllMoves => Board.KingMoveMasks[(int)fromSquare] & unOrEnemyOccupiedSquares & toSquareMask,
MoveGeneration.OnlyCaptures => Board.KingMoveMasks[(int)fromSquare] & enemyOccupiedSquares & toSquareMask,
MoveGeneration.OnlyNonCaptures => Board.KingMoveMasks[(int)fromSquare] & ~Occupancy & toSquareMask,
_ => throw new Exception($"{moveGeneration} move generation not supported.")
};
Square toSquare;
while ((toSquare = Bitwise.PopFirstSetSquare(ref kingDestinations)) != Square.Illegal)
{
var victim = GetPiece(toSquare);
move = Move.Null;
Move.SetPiece(ref move, attacker);
Move.SetFrom(ref move, fromSquare);
Move.SetTo(ref move, toSquare);
if (victim != Piece.None)
{
Move.SetCaptureAttacker(ref move, attacker);
}
Move.SetCaptureVictim(ref move, victim);
Move.SetIsKingMove(ref move, true);
Moves[MoveIndex] = move;
MoveIndex++;
}
if (moveGeneration != MoveGeneration.OnlyCaptures)
{
for (var boardSide = BoardSide.Queen; boardSide <= BoardSide.King; boardSide++)
{
var castleEmptySquaresMask = Board.CastleEmptySquaresMask[(int)ColorToMove][(int)boardSide];
if (!KingInCheck && Game.Castling.Permitted(Castling, ColorToMove, boardSide) && ((Occupancy & castleEmptySquaresMask) == 0))
{
// Castle
toSquare = Board.CastleToSquares[(int)ColorToMove][(int)boardSide];
if ((Board.SquareMasks[(int)toSquare] & toSquareMask) > 0)
{
move = Move.Null;
Move.SetPiece(ref move, attacker);
Move.SetFrom(ref move, fromSquare);
Move.SetTo(ref move, toSquare);
Move.SetIsCastling(ref move, true);
Move.SetIsKingMove(ref move, true);
Moves[MoveIndex] = move;
MoveIndex++;
}
}
}
}
}
