bool posCanMakeMove(const Pos *pos, Move move) {
// Sanity checks and special case.
assert(moveIsValid(move) || move==MoveNone);
if (move==MoveNone)
return true;
// Use local variables to simulate having made the move.
Colour stm=moveGetColour(move);
assert(stm==posGetSTM(pos));
Colour xstm=colourSwap(stm);
BB occ=posGetBBAll(pos);
BB opp=posGetBBColour(pos, xstm);
Sq fromSq=moveGetFromSq(move);
Sq toSq=moveGetToSq(move);
BB fromBB=bbSq(fromSq);
BB toBB=bbSq(toSq);
Sq kingSq=posGetKingSq(pos, stm);
if (fromSq==kingSq)
kingSq=toSq; // King move.
occ&=~fromBB; // Move piece.
occ|=toBB;
opp&=~toBB; // Potentially capture opp piece (so it cannot attack us later).
if (moveGetToPieceType(move)==PieceTypePawn && sqFile(fromSq)!=sqFile(toSq) && posGetPieceOnSq(pos, toSq)==PieceNone) {
// En-passent capture.
assert(pos->data->epSq==toSq);
occ^=bbSq(toSq^8);
opp^=bbSq(toSq^8);
}
// Make a list of squares we need to ensure are unattacked.
BB checkSquares=bbSq(kingSq);
if (moveIsCastling(move))
checkSquares|=fromBB|bbSq((toSq+fromSq)/2);
// Test for attacks to any of checkSquares.
// Pawns are done setwise.
BB oppPawns=(posGetBBPiece(pos, pieceMake(PieceTypePawn, xstm)) & opp);
if (bbForwardOne(bbWingify(oppPawns), xstm) & checkSquares)
return false;
// Pieces are checked for each square in checkSquares (which usually only has a single bit set anyway).
while(checkSquares) {
Sq sq=bbScanReset(&checkSquares);
// Knights.
if (attacksKnight(sq) & opp & posGetBBPiece(pos, pieceMake(PieceTypeKnight, xstm)))
return false;
// Bishops and diagonal queen moves.
if (attacksBishop(sq, occ) & opp &
(posGetBBPiece(pos, pieceMake(PieceTypeBishopL, xstm)) |
posGetBBPiece(pos, pieceMake(PieceTypeBishopD, xstm)) |
posGetBBPiece(pos, pieceMake(PieceTypeQueen, xstm))))
return false;
// Rooks and orthogonal queen moves.
if (attacksRook(sq, occ) & opp &
(posGetBBPiece(pos, pieceMake(PieceTypeRook, xstm)) |
posGetBBPiece(pos, pieceMake(PieceTypeQueen, xstm))))
return false;
// King.
if (attacksKing(sq) & opp & posGetBBPiece(pos, pieceMake(PieceTypeKing, xstm)))
return false;
}
return true;
}
bool moveIsDP(Move move) {
assert(moveIsValid(move));
int toRank=sqRank(moveGetToSqRaw(move));
int fromRank=sqRank(moveGetFromSq(move));
return (moveGetToPieceType(move)==PieceTypePawn && abs(toRank-fromRank)==2);
}
