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// attack.c
// includes
#include "board.h"
#include "colour.h"
#include "move.h"
#include "attack.h"
#include "piece.h"
#include "util.h"
// macros
#define DELTA_INC(delta) (DeltaInc[128+(delta)])
#define DELTA_MASK(delta) (DeltaMask[128+(delta)])
// "constants"
const sint8 KnightInc[8+1] = {
-33, -31, -18, -14, +14, +18, +31, +33, 0
};
const sint8 BishopInc[4+1] = {
-17, -15, +15, +17, 0
};
const sint8 RookInc[4+1] = {
-16, -1, +1, +16, 0
};
const sint8 QueenInc[8+1] = {
-17, -16, -15, -1, +1, +15, +16, +17, 0
};
const sint8 KingInc[8+1] = {
-17, -16, -15, -1, +1, +15, +16, +17, 0
};
// variables
static sint8 DeltaInc[256];
static uint8 DeltaMask[256];
// prototypes
static bool delta_is_ok (int delta);
static bool inc_is_ok (int inc);
// functions
// attack_init()
void attack_init() {
int delta;
int dir, inc, dist;
for (delta = -128; delta < +128; delta++) {
DeltaInc[128+delta] = IncNone;
DeltaMask[128+delta] = 0;
}
DeltaMask[128-17] |= BlackPawnFlag;
DeltaMask[128-15] |= BlackPawnFlag;
DeltaMask[128+15] |= WhitePawnFlag;
DeltaMask[128+17] |= WhitePawnFlag;
for (dir = 0; dir < 8; dir++) {
delta = KnightInc[dir];
ASSERT(delta_is_ok(delta));
DeltaMask[128+delta] |= KnightFlag;
}
for (dir = 0; dir < 4; dir++) {
inc = BishopInc[dir];
ASSERT(inc!=IncNone);
for (dist = 1; dist < 8; dist++) {
delta = inc*dist;
ASSERT(delta_is_ok(delta));
ASSERT(DeltaInc[128+delta]==IncNone);
DeltaInc[128+delta] = inc;
DeltaMask[128+delta] |= BishopFlag;
}
}
for (dir = 0; dir < 4; dir++) {
inc = RookInc[dir];
ASSERT(inc!=IncNone);
for (dist = 1; dist < 8; dist++) {
delta = inc*dist;
ASSERT(delta_is_ok(delta));
ASSERT(DeltaInc[128+delta]==IncNone);
DeltaInc[128+delta] = inc;
DeltaMask[128+delta] |= RookFlag;
}
}
for (dir = 0; dir < 8; dir++) {
delta = KingInc[dir];
ASSERT(delta_is_ok(delta));
DeltaMask[128+delta] |= KingFlag;
}
}
// delta_is_ok()
static bool delta_is_ok(int delta) {
if (delta < -119 || delta > +119) return FALSE;
return TRUE;
}
// inc_is_ok()
static bool inc_is_ok(int inc) {
int dir;
for (dir = 0; dir < 8; dir++) {
if (KingInc[dir] == inc) return TRUE;
}
return FALSE;
}
// is_in_check()
bool is_in_check(const board_t * board, int colour) {
ASSERT(board_is_ok(board));
ASSERT(colour_is_ok(colour));
return is_attacked(board,king_pos(board,colour),colour_opp(colour));
}
// is_attacked()
bool is_attacked(const board_t * board, int to, int colour) {
const uint8 * ptr;
int from, piece;
ASSERT(board_is_ok(board));
ASSERT(square_is_ok(to));
ASSERT(colour_is_ok(colour));
for (ptr = board->list[colour]; (from=*ptr) != SquareNone; ptr++) {
piece = board->square[from];
ASSERT(colour_equal(piece,colour));
if (piece_attack(board,piece,from,to)) return TRUE;
}
return FALSE;
}
// piece_attack()
bool piece_attack(const board_t * board, int piece, int from, int to) {
int delta;
int inc, sq;
ASSERT(board_is_ok(board));
ASSERT(piece_is_ok(piece));
ASSERT(square_is_ok(from));
ASSERT(square_is_ok(to));
delta = to - from;
ASSERT(delta_is_ok(delta));
if ((piece & DELTA_MASK(delta)) == 0) return FALSE; // no pseudo-attack
if (!piece_is_slider(piece)) return TRUE;
inc = DELTA_INC(delta);
ASSERT(inc_is_ok(inc));
for (sq = from+inc; sq != to; sq += inc) {
ASSERT(square_is_ok(sq));
if (board->square[sq] != Empty) return FALSE; // blocker
}
return TRUE;
}
// is_pinned()
bool is_pinned(const board_t * board, int from, int to, int colour) {
int king;
int inc;
int sq, piece;
ASSERT(board!=NULL);
ASSERT(square_is_ok(from));
ASSERT(square_is_ok(to));
ASSERT(colour_is_ok(colour));
king = king_pos(board,colour);
inc = DELTA_INC(king-from);
if (inc == IncNone) return FALSE; // not a line
sq = from;
do sq += inc; while (board->square[sq] == Empty);
if (sq != king) return FALSE; // blocker
sq = from;
do sq -= inc; while ((piece=board->square[sq]) == Empty);
return square_is_ok(sq)
&& (piece & DELTA_MASK(king-sq)) != 0
&& piece_colour(piece) == colour_opp(colour)
&& DELTA_INC(king-to) != inc;
}
// end of attack.cpp
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