1
2 // attack.cpp
3
4 // includes
5
6 #include "board.h"
7 #include "colour.h"
8 #include "move.h"
9 #include "attack.h"
10 #include "piece.h"
11 #include "util.h"
12
13 // macros
14
15 #define DELTA_INC(delta) (DeltaInc[128+(delta)])
16 #define DELTA_MASK(delta) (DeltaMask[128+(delta)])
17
18 // "constants"
19
20 const sint8 KnightInc[8+1] = {
21 -33, -31, -18, -14, +14, +18, +31, +33, 0
22 };
23
24 const sint8 BishopInc[4+1] = {
25 -17, -15, +15, +17, 0
26 };
27
28 const sint8 RookInc[4+1] = {
29 -16, -1, +1, +16, 0
30 };
31
32 const sint8 QueenInc[8+1] = {
33 -17, -16, -15, -1, +1, +15, +16, +17, 0
34 };
35
36 const sint8 KingInc[8+1] = {
37 -17, -16, -15, -1, +1, +15, +16, +17, 0
38 };
39
40 // variables
41
42 static sint8 DeltaInc[256];
43 static uint8 DeltaMask[256];
44
45 // prototypes
46
47 // static bool delta_is_ok (int delta);
48 // static bool inc_is_ok (int inc);
49
50 // functions
51
52 // attack_init()
53
attack_init()54 void attack_init() {
55
56 int delta;
57 int dir, inc, dist;
58
59 for (delta = -128; delta < +128; delta++) {
60 DeltaInc[128+delta] = IncNone;
61 DeltaMask[128+delta] = 0;
62 }
63
64 DeltaMask[128-17] |= BlackPawnFlag;
65 DeltaMask[128-15] |= BlackPawnFlag;
66
67 DeltaMask[128+15] |= WhitePawnFlag;
68 DeltaMask[128+17] |= WhitePawnFlag;
69
70 for (dir = 0; dir < 8; dir++) {
71 delta = KnightInc[dir];
72 ASSERT(delta_is_ok(delta));
73 DeltaMask[128+delta] |= KnightFlag;
74 }
75
76 for (dir = 0; dir < 4; dir++) {
77 inc = BishopInc[dir];
78 ASSERT(inc!=IncNone);
79 for (dist = 1; dist < 8; dist++) {
80 delta = inc*dist;
81 ASSERT(delta_is_ok(delta));
82 ASSERT(DeltaInc[128+delta]==IncNone);
83 DeltaInc[128+delta] = inc;
84 DeltaMask[128+delta] |= BishopFlag;
85 }
86 }
87
88 for (dir = 0; dir < 4; dir++) {
89 inc = RookInc[dir];
90 ASSERT(inc!=IncNone);
91 for (dist = 1; dist < 8; dist++) {
92 delta = inc*dist;
93 ASSERT(delta_is_ok(delta));
94 ASSERT(DeltaInc[128+delta]==IncNone);
95 DeltaInc[128+delta] = inc;
96 DeltaMask[128+delta] |= RookFlag;
97 }
98 }
99
100 for (dir = 0; dir < 8; dir++) {
101 delta = KingInc[dir];
102 ASSERT(delta_is_ok(delta));
103 DeltaMask[128+delta] |= KingFlag;
104 }
105 }
106
107 // delta_is_ok()
108
109 // static bool delta_is_ok(int delta) {
110 //
111 // if (delta < -119 || delta > +119) return false;
112 //
113 // return true;
114 // }
115
116 // inc_is_ok()
117
118 // static bool inc_is_ok(int inc) {
119 //
120 // int dir;
121 //
122 // for (dir = 0; dir < 8; dir++) {
123 // if (KingInc[dir] == inc) return true;
124 // }
125 //
126 // return false;
127 // }
128
129 // is_in_check()
130
is_in_check(const board_t * board,int colour)131 bool is_in_check(const board_t * board, int colour) {
132
133 ASSERT(board_is_ok(board));
134 ASSERT(colour_is_ok(colour));
135
136 return is_attacked(board,king_pos(board,colour),colour_opp(colour));
137 }
138
139 // is_attacked()
140
is_attacked(const board_t * board,int to,int colour)141 bool is_attacked(const board_t * board, int to, int colour) {
142
143 const uint8 * ptr;
144 int from, piece;
145
146 ASSERT(board_is_ok(board));
147 ASSERT(square_is_ok(to));
148 ASSERT(colour_is_ok(colour));
149
150 for (ptr = board->list[colour]; (from=*ptr) != SquareNone; ptr++) {
151
152 piece = board->square[from];
153 ASSERT(colour_equal(piece,colour));
154
155 if (piece_attack(board,piece,from,to)) return true;
156 }
157
158 return false;
159 }
160
161 // piece_attack()
162
piece_attack(const board_t * board,int piece,int from,int to)163 bool piece_attack(const board_t * board, int piece, int from, int to) {
164
165 int delta;
166 int inc, sq;
167
168 ASSERT(board_is_ok(board));
169 ASSERT(piece_is_ok(piece));
170 ASSERT(square_is_ok(from));
171 ASSERT(square_is_ok(to));
172
173 delta = to - from;
174 ASSERT(delta_is_ok(delta));
175
176 if ((piece & DELTA_MASK(delta)) == 0) return false; // no pseudo-attack
177
178 if (!piece_is_slider(piece)) return true;
179
180 inc = DELTA_INC(delta);
181 ASSERT(inc_is_ok(inc));
182
183 for (sq = from+inc; sq != to; sq += inc) {
184 ASSERT(square_is_ok(sq));
185 if (board->square[sq] != Empty) return false; // blocker
186 }
187
188 return true;
189 }
190
191 // is_pinned()
192
is_pinned(const board_t * board,int from,int to,int colour)193 bool is_pinned(const board_t * board, int from, int to, int colour) {
194
195 int king;
196 int inc;
197 int sq, piece;
198
199 ASSERT(board!=NULL);
200 ASSERT(square_is_ok(from));
201 ASSERT(square_is_ok(to));
202 ASSERT(colour_is_ok(colour));
203
204 king = king_pos(board,colour);
205
206 inc = DELTA_INC(king-from);
207 if (inc == IncNone) return false; // not a line
208
209 sq = from;
210 do sq += inc; while (board->square[sq] == Empty);
211
212 if (sq != king) return false; // blocker
213
214 sq = from;
215 do sq -= inc; while ((piece=board->square[sq]) == Empty);
216
217 return square_is_ok(sq)
218 && (piece & DELTA_MASK(king-sq)) != 0
219 && piece_colour(piece) == colour_opp(colour)
220 && DELTA_INC(king-to) != inc;
221 }
222
223 // end of attack.cpp
224
225