ChessBoolean chess_generate_is_square_attacked(const ChessPosition* position, ChessSquare sq, ChessColor color)
{
ChessSquare from;
ChessPiece piece;
int dirs, dir, d, dist;
/* Check for knight attacks */
dirs = jump_dirs[sq];
for (d = 0; d < 8; d++)
{
dir = dirs_array[d];
if ((dir & dirs) == 0)
continue;
from = sq + jumps_array[d];
piece = chess_position_piece(position, from);
if (chess_position_piece(position, from) == chess_piece_of_color(CHESS_PIECE_WHITE_KNIGHT, color))
return CHESS_TRUE;
}
for (d = 0; d < 8; d++)
{
dir = dirs_array[d];
from = sq;
dist = 1;
do
{
dirs = slide_dirs[from];
if ((dir & dirs) == 0)
break;
from += slides_array[d];
piece = chess_position_piece(position, from);
if (piece != CHESS_PIECE_NONE && chess_piece_color(piece) == color)
{
switch (piece)
{
case CHESS_PIECE_WHITE_QUEEN:
case CHESS_PIECE_BLACK_QUEEN:
return CHESS_TRUE;
case CHESS_PIECE_WHITE_BISHOP:
case CHESS_PIECE_BLACK_BISHOP:
if (dir & bishop_dirs)
return CHESS_TRUE;
break;
case CHESS_PIECE_WHITE_ROOK:
case CHESS_PIECE_BLACK_ROOK:
if (dir & rook_dirs)
return CHESS_TRUE;
break;
case CHESS_PIECE_WHITE_KING:
case CHESS_PIECE_BLACK_KING:
if (dist == 1)
return CHESS_TRUE;
break;
case CHESS_PIECE_WHITE_PAWN:
if (dist == 1 && dir & (DIR_SE | DIR_SW))
return CHESS_TRUE;
break;
case CHESS_PIECE_BLACK_PAWN:
if (dist == 1 && dir & (DIR_NE | DIR_NW))
return CHESS_TRUE;
break;
case CHESS_PIECE_WHITE_KNIGHT:
case CHESS_PIECE_BLACK_KNIGHT:
break;
default:
assert(CHESS_FALSE);
break;
}
}
dist++;
} while (piece == CHESS_PIECE_NONE);
}
return CHESS_FALSE;
}
void chess_position_undo_move(ChessPosition* position, ChessUnmove unmove)
{
ChessSquare from = chess_unmove_from(unmove);
ChessSquare to = chess_unmove_to(unmove);
ChessUnmoveCaptured captured = chess_unmove_captured(unmove);
ChessUnmoveEp ep = chess_unmove_ep(unmove);
ChessPiece piece;
ChessColor other = position->to_move;
ChessColor color = chess_color_other(other);
ChessFile file;
if (from == 0 && to == 0)
{
/* Null move */
piece = CHESS_PIECE_NONE;
}
else
{
if (chess_unmove_promotion(unmove))
piece = chess_piece_of_color(CHESS_PIECE_WHITE_PAWN, color);
else
piece = position->piece[to];
assert(color == chess_piece_color(piece));
/* Unmove the piece */
position->piece[from] = piece;
position->piece[to] = captured_piece(captured, other);
/* Handle castling */
if (piece == CHESS_PIECE_WHITE_KING && from == CHESS_SQUARE_E1)
{
if (to == CHESS_SQUARE_G1)
{
position->piece[CHESS_SQUARE_F1] = CHESS_PIECE_NONE;
position->piece[CHESS_SQUARE_H1] = CHESS_PIECE_WHITE_ROOK;
}
else if (to == CHESS_SQUARE_C1)
{
position->piece[CHESS_SQUARE_D1] = CHESS_PIECE_NONE;
position->piece[CHESS_SQUARE_A1] = CHESS_PIECE_WHITE_ROOK;
}
}
else if (piece == CHESS_PIECE_BLACK_KING && from == CHESS_SQUARE_E8)
{
if (to == CHESS_SQUARE_G8)
{
position->piece[CHESS_SQUARE_F8] = CHESS_PIECE_NONE;
position->piece[CHESS_SQUARE_H8] = CHESS_PIECE_BLACK_ROOK;
}
else if (to == CHESS_SQUARE_C8)
{
position->piece[CHESS_SQUARE_D8] = CHESS_PIECE_NONE;
position->piece[CHESS_SQUARE_A8] = CHESS_PIECE_BLACK_ROOK;
}
}
position->castle = chess_unmove_castle(unmove);
}
/* Handle ep */
if (ep == CHESS_UNMOVE_EP_NONE)
{
position->ep = CHESS_FILE_INVALID;
}
else if (ep == CHESS_UNMOVE_EP_CAPTURE)
{
assert(piece == CHESS_PIECE_WHITE_PAWN || piece == CHESS_PIECE_BLACK_PAWN);
/* Restore the captured pawn */
file = chess_square_file(to);
if (color == CHESS_COLOR_WHITE)
position->piece[chess_square_from_fr(file, CHESS_RANK_5)] = CHESS_PIECE_BLACK_PAWN;
else
position->piece[chess_square_from_fr(file, CHESS_RANK_4)] = CHESS_PIECE_WHITE_PAWN;
position->ep = file;
}
else
{
position->ep = ep - CHESS_UNMOVE_EP_AVAILABLE;
}
/* Update king positions */
if (piece == CHESS_PIECE_WHITE_KING)
position->wking = from;
else if (piece == CHESS_PIECE_BLACK_KING)
position->bking = from;
/* Update move counters */
position->fifty = chess_unmove_fifty(unmove);
position->to_move = color;
if (position->to_move == CHESS_COLOR_BLACK)
position->move_num--;
}
static ChessMove gen_next(ChessMoveGenerator* gen)
{
const ChessPosition* position = gen->position;
ChessPiece piece;
ChessColor color = chess_position_to_move(position);
ChessPiece target;
int dirs, dir;
int piece_dirs;
ChessRank start_rank, end_rank;
int slide;
int capture_dirs;
ChessFile ep_file;
ChessSquare ep;
ChessMove move;
if (gen->promote != CHESS_MOVE_PROMOTE_NONE)
{
gen_pawn_promotes:
if (++gen->promote <= CHESS_MOVE_PROMOTE_QUEEN)
return chess_move_make_promote(gen->sq, gen->to, gen->promote);
gen->promote = CHESS_MOVE_PROMOTE_NONE;
}
for (; gen->sq <= CHESS_SQUARE_H8; gen->sq++)
{
piece = chess_position_piece(position, gen->sq);
if (piece == CHESS_PIECE_NONE)
continue;
if (color != chess_piece_color(piece))
continue;
switch (piece)
{
case CHESS_PIECE_WHITE_PAWN:
case CHESS_PIECE_BLACK_PAWN:
start_rank = (color == CHESS_COLOR_WHITE) ? CHESS_RANK_2 : CHESS_RANK_7;
end_rank = (color == CHESS_COLOR_WHITE) ? CHESS_RANK_8 : CHESS_RANK_1;
slide = (color == CHESS_COLOR_WHITE) ? SLIDE_N : SLIDE_S;
capture_dirs = (color == CHESS_COLOR_WHITE) ? DIR_NE | DIR_NW : DIR_SE | DIR_SW;
dirs = capture_dirs & slide_dirs[gen->sq];
ep_file = chess_position_ep(position);
ep = (ep_file == CHESS_FILE_INVALID) ? CHESS_SQUARE_INVALID :
chess_square_from_fr(ep_file, (color == CHESS_COLOR_WHITE) ? CHESS_RANK_6 : CHESS_RANK_3);
if (gen->d == 0)
{
if (gen->to == CHESS_SQUARE_INVALID)
{
gen->to = gen->sq + slide;
if (chess_position_piece(position, gen->to) == CHESS_PIECE_NONE)
{
if (chess_square_rank(gen->to) == end_rank)
goto gen_pawn_promotes;
else
return chess_move_make(gen->sq, gen->to);
}
}
else if (chess_square_rank(gen->sq) == start_rank && gen->to == gen->sq + slide)
{
gen->to += slide;
if (chess_position_piece(position, gen->to) == CHESS_PIECE_NONE)
return chess_move_make(gen->sq, gen->to);
}
gen->to = CHESS_SQUARE_INVALID;
gen->d = 1;
}
while (gen->d < 8)
{
if (dirs_array[gen->d] & dirs)
{
gen->to = gen->sq + slides_array[gen->d];
piece = chess_position_piece(position, gen->to);
gen->d += 2;
if (piece != CHESS_PIECE_NONE && chess_piece_color(piece) != color)
{
if (chess_square_rank(gen->to) == end_rank)
goto gen_pawn_promotes;
else
return chess_move_make(gen->sq, gen->to);
}
else if (gen->to == ep)
{
return chess_move_make(gen->sq, gen->to);
}
}
else
{
gen->d += 2;
}
}
gen->to = CHESS_SQUARE_INVALID;
gen->d = 0;
break;
case CHESS_PIECE_WHITE_KNIGHT:
case CHESS_PIECE_BLACK_KNIGHT:
dirs = jump_dirs[gen->sq];
for (; gen->d < 8; gen->d++)
{
dir = dirs_array[gen->d];
if ((dir & dirs) == 0)
continue;
gen->to = gen->sq + jumps_array[gen->d];
target = chess_position_piece(position, gen->to);
if (target == CHESS_PIECE_NONE || chess_piece_color(target) != color)
{
gen->d++;
return chess_move_make(gen->sq, gen->to);
}
}
gen->to = CHESS_SQUARE_INVALID;
gen->d = 0;
break;
case CHESS_PIECE_WHITE_BISHOP:
case CHESS_PIECE_BLACK_BISHOP:
piece_dirs = bishop_dirs;
goto gen_slide_moves;
case CHESS_PIECE_WHITE_ROOK:
case CHESS_PIECE_BLACK_ROOK:
piece_dirs = rook_dirs;
goto gen_slide_moves;
case CHESS_PIECE_WHITE_QUEEN:
case CHESS_PIECE_BLACK_QUEEN:
piece_dirs = queen_dirs;
gen_slide_moves:
while (gen->d < 8)
{
dir = dirs_array[gen->d] & piece_dirs;
if (gen->to == CHESS_SQUARE_INVALID)
gen->to = gen->sq;
do
{
dirs = slide_dirs[gen->to];
if ((dir & dirs) == 0)
break;
gen->to += slides_array[gen->d];
target = chess_position_piece(position, gen->to);
if (target == CHESS_PIECE_NONE)
return chess_move_make(gen->sq, gen->to);
else if (chess_piece_color(target) != color)
{
move = chess_move_make(gen->sq, gen->to);
gen->d++;
gen->to = CHESS_SQUARE_INVALID;
return move;
}
} while (target == CHESS_PIECE_NONE);
gen->to = CHESS_SQUARE_INVALID;
gen->d++;
}
gen->to = CHESS_SQUARE_INVALID;
gen->d = 0;
break;
case CHESS_PIECE_WHITE_KING:
case CHESS_PIECE_BLACK_KING:
dirs = slide_dirs[gen->sq];
for (; gen->d < 8; gen->d++)
{
dir = dirs_array[gen->d];
if ((dir & dirs) == 0)
continue;
gen->to = gen->sq + slides_array[gen->d];
target = chess_position_piece(position, gen->to);
if (target == CHESS_PIECE_NONE || chess_piece_color(target) != color)
{
gen->d++;
return chess_move_make(gen->sq, gen->to);
}
}
gen->to = CHESS_SQUARE_INVALID;
gen->d = 0;
break;
default:
assert(0);
break;
}
}
if (gen->castle == -1)
{
if (!chess_position_is_check(position))
gen->castle = chess_position_castle(position);
else {
gen->castle = CHESS_CASTLE_STATE_NONE;
}
}
if (color == CHESS_COLOR_WHITE)
{
if ((gen->castle & CHESS_CASTLE_STATE_WK)
&& chess_position_piece(position, CHESS_SQUARE_F1) == CHESS_PIECE_NONE
&& chess_position_piece(position, CHESS_SQUARE_G1) == CHESS_PIECE_NONE
&& !chess_generate_is_square_attacked(position, CHESS_SQUARE_F1, CHESS_COLOR_BLACK)
&& !chess_generate_is_square_attacked(position, CHESS_SQUARE_G1, CHESS_COLOR_BLACK))
{
gen->castle &= ~CHESS_CASTLE_STATE_WK;
return chess_move_make(CHESS_SQUARE_E1, CHESS_SQUARE_G1);
}
if ((gen->castle & CHESS_CASTLE_STATE_WQ)
&& chess_position_piece(position, CHESS_SQUARE_B1) == CHESS_PIECE_NONE
&& chess_position_piece(position, CHESS_SQUARE_C1) == CHESS_PIECE_NONE
&& chess_position_piece(position, CHESS_SQUARE_D1) == CHESS_PIECE_NONE
&& !chess_generate_is_square_attacked(position, CHESS_SQUARE_D1, CHESS_COLOR_BLACK)
&& !chess_generate_is_square_attacked(position, CHESS_SQUARE_C1, CHESS_COLOR_BLACK))
{
gen->castle &= ~CHESS_CASTLE_STATE_WQ;
return chess_move_make(CHESS_SQUARE_E1, CHESS_SQUARE_C1);
}
}
else
{
if ((gen->castle & CHESS_CASTLE_STATE_BK)
&& chess_position_piece(position, CHESS_SQUARE_F8) == CHESS_PIECE_NONE
&& chess_position_piece(position, CHESS_SQUARE_G8) == CHESS_PIECE_NONE
&& !chess_generate_is_square_attacked(position, CHESS_SQUARE_F8, CHESS_COLOR_WHITE)
&& !chess_generate_is_square_attacked(position, CHESS_SQUARE_G8, CHESS_COLOR_WHITE))
{
gen->castle &= ~CHESS_CASTLE_STATE_BK;
return chess_move_make(CHESS_SQUARE_E8, CHESS_SQUARE_G8);
}
if ((gen->castle & CHESS_CASTLE_STATE_BQ)
&& chess_position_piece(position, CHESS_SQUARE_B8) == CHESS_PIECE_NONE
&& chess_position_piece(position, CHESS_SQUARE_C8) == CHESS_PIECE_NONE
&& chess_position_piece(position, CHESS_SQUARE_D8) == CHESS_PIECE_NONE
&& !chess_generate_is_square_attacked(position, CHESS_SQUARE_D8, CHESS_COLOR_WHITE)
&& !chess_generate_is_square_attacked(position, CHESS_SQUARE_C8, CHESS_COLOR_WHITE))
{
gen->castle &= ~CHESS_CASTLE_STATE_BQ;
return chess_move_make(CHESS_SQUARE_E8, CHESS_SQUARE_C8);
}
}
return 0;
}
