BOOL _PositionStruct::LegalMove(int mv) const {
int sqSrc, sqDst, sqPin;
int pcSelfSide, pcSrc, pcDst, nDelta;
sqSrc = SRC(mv);
pcSrc = ucpcSquares[sqSrc];
pcSelfSide = SIDE_TAG(sdPlayer);
if ((pcSrc & pcSelfSide) == 0) {
return FALSE;
}
sqDst = DST(mv);
pcDst = ucpcSquares[sqDst];
if ((pcDst & pcSelfSide) != 0) {
return FALSE;
}
switch (pcSrc - pcSelfSide) {
case PIECE_KING:
return IN_FORT(sqDst) && KING_SPAN(sqSrc, sqDst);
case PIECE_ADVISOR:
return IN_FORT(sqDst) && ADVISOR_SPAN(sqSrc, sqDst);
case PIECE_BISHOP:
return SAME_HALF(sqSrc, sqDst) && BISHOP_SPAN(sqSrc, sqDst) &&
ucpcSquares[BISHOP_PIN(sqSrc, sqDst)] == 0;
case PIECE_KNIGHT:
sqPin = KNIGHT_PIN(sqSrc, sqDst);
return sqPin != sqSrc && ucpcSquares[sqPin] == 0;
case PIECE_ROOK:
case PIECE_CANNON:
if (SAME_RANK(sqSrc, sqDst)) {
nDelta = (sqDst < sqSrc ? -1 : 1);
} else if (SAME_FILE(sqSrc, sqDst)) {
nDelta = (sqDst < sqSrc ? -16 : 16);
} else {
return FALSE;
}
sqPin = sqSrc + nDelta;
while (sqPin != sqDst && ucpcSquares[sqPin] == 0) {
sqPin += nDelta;
}
if (sqPin == sqDst) {
return pcDst == 0 || pcSrc - pcSelfSide == PIECE_ROOK;
} else if (pcDst != 0 && pcSrc - pcSelfSide == PIECE_CANNON) {
sqPin += nDelta;
while (sqPin != sqDst && ucpcSquares[sqPin] == 0) {
sqPin += nDelta;
}
return sqPin == sqDst;
} else {
return FALSE;
}
case PIECE_PAWN:
if (AWAY_HALF(sqDst, sdPlayer) && (sqDst == sqSrc - 1 || sqDst == sqSrc + 1)) {
return TRUE;
}
return sqDst == SQUARE_FORWARD(sqSrc, sdPlayer);
default:
return FALSE;
}
}
// 棋子保护判断
bool PositionStruct::Protected(int sd, int sqSrc, int sqExcept) const {
// 参数"sqExcept"表示排除保护的棋子(指格子编号)，考虑被牵制子的保护时，需要排除牵制目标子的保护
int i, sqDst, sqPin, pc, x, y, nSideTag;
SlideMaskStruct *lpsmsRank, *lpsmsFile;
// 棋子保护判断包括以下几个步骤：
__ASSERT_SQUARE(sqSrc);
nSideTag = SIDE_TAG(sd);
if (HOME_HALF(sqSrc, sd)) {
if (IN_FORT(sqSrc)) {
// 1. 判断受到帅(将)的保护
sqDst = ucsqPieces[nSideTag + KING_FROM];
if (sqDst != 0 && sqDst != sqExcept) {
__ASSERT_SQUARE(sqDst);
if (KING_SPAN(sqSrc, sqDst)) {
return true;
}
}
// 2. 判断受到仕(士)的保护
for (i = ADVISOR_FROM; i <= ADVISOR_TO; i ++) {
sqDst = ucsqPieces[nSideTag + i];
if (sqDst != 0 && sqDst != sqExcept) {
__ASSERT_SQUARE(sqDst);
if (ADVISOR_SPAN(sqSrc, sqDst)) {
return true;
}
}
}
}
// 3. 判断受到相(象)的保护
for (i = BISHOP_FROM; i <= BISHOP_TO; i ++) {
sqDst = ucsqPieces[nSideTag + i];
if (sqDst != 0 && sqDst != sqExcept) {
__ASSERT_SQUARE(sqDst);
if (BISHOP_SPAN(sqSrc, sqDst) && ucpcSquares[BISHOP_PIN(sqSrc, sqDst)] == 0) {
return true;
}
}
}
} else {
// 4. 判断受到过河兵(卒)横向的保护
for (sqDst = sqSrc - 1; sqDst <= sqSrc + 1; sqDst += 2) {
// 如果棋子在边线，那么断言不成立
// __ASSERT_SQUARE(sqDst);
if (sqDst != sqExcept) {
pc = ucpcSquares[sqDst];
if ((pc & nSideTag) != 0 && PIECE_INDEX(pc) >= PAWN_FROM) {
return true;
}
}
}
}
// 5. 判断受到兵(卒)纵向的保护
sqDst = SQUARE_BACKWARD(sqSrc, sd);
// 如果棋子在底线，那么断言不成立
// __ASSERT_SQUARE(sqDst);
if (sqDst != sqExcept) {
pc = ucpcSquares[sqDst];
if ((pc & nSideTag) != 0 && PIECE_INDEX(pc) >= PAWN_FROM) {
return true;
}
}
// 6. 判断受到马的保护
for (i = KNIGHT_FROM; i <= KNIGHT_TO; i ++) {
sqDst = ucsqPieces[nSideTag + i];
if (sqDst != 0 && sqDst != sqExcept) {
__ASSERT_SQUARE(sqDst);
sqPin = KNIGHT_PIN(sqDst, sqSrc); // 注意，sqSrc和sqDst是反的！
if (sqPin != sqDst && ucpcSquares[sqPin] == 0) {
return true;
}
}
}
x = FILE_X(sqSrc);
y = RANK_Y(sqSrc);
lpsmsRank = RankMaskPtr(x, y);
lpsmsFile = FileMaskPtr(x, y);
// 7. 判断受到车的保护，参阅"position.cpp"里的"CheckedBy()"函数
for (i = ROOK_FROM; i <= ROOK_TO; i ++) {
sqDst = ucsqPieces[nSideTag + i];
if (sqDst != 0 && sqDst != sqSrc && sqDst != sqExcept) {
if (x == FILE_X(sqDst)) {
if ((lpsmsFile->wRookCap & PreGen.wBitFileMask[sqDst]) != 0) {
return true;
}
} else if (y == RANK_Y(sqDst)) {
if ((lpsmsRank->wRookCap & PreGen.wBitRankMask[sqDst]) != 0) {
return true;
}
}
}
}
// 8. 判断受到炮的保护，参阅"position.cpp"里的"CheckedBy()"函数
for (i = CANNON_FROM; i <= CANNON_TO; i ++) {
sqDst = ucsqPieces[nSideTag + i];
if (sqDst && sqDst != sqSrc && sqDst != sqExcept) {
if (x == FILE_X(sqDst)) {
if ((lpsmsFile->wCannonCap & PreGen.wBitFileMask[sqDst]) != 0) {
return true;
}
} else if (y == RANK_Y(sqDst)) {
if ((lpsmsRank->wCannonCap & PreGen.wBitRankMask[sqDst]) != 0) {
return true;
}
}
}
}
return false;
}