engine/src/bitboard.c

@@ -76,6 +76,53 @@ static int pop_lsb_index(uint64_t *bb) {
     return idx;
 }
 
+static inline uint64_t ray_attacks(int start_square, int delta_file, int delta_rank, uint64_t occupied)
+{
+    uint64_t attacks = 0;
+
+    int start_file = start_square % 8;
+    int start_rank = start_square / 8;
+
+    int next_file = start_file + delta_file;
+    int next_rank = start_rank + delta_rank;
+
+    while (next_file >= 0 && next_file < 8 && next_rank >= 0 && next_rank < 8) {
+        int next_square = next_rank * 8 + next_file;
+        uint64_t next_bit = 1ULL << next_square;
+
+        // can attack this square
+        attacks |= next_bit;
+
+        // blocker: include it, then stop
+        if (occupied & next_bit)
+            break;
+
+        next_file += delta_file;
+        next_rank += delta_rank;
+    }
+
+    return attacks;
+}
+
+static inline uint64_t rook_attacks(int square, uint64_t occupied) {
+    return  ray_attacks(square, +1,  0, occupied)   // east
+          | ray_attacks(square, -1,  0, occupied)   // west
+          | ray_attacks(square,  0, +1, occupied)   // north
+          | ray_attacks(square,  0, -1, occupied);  // south
+}
+
+static inline uint64_t bishop_attacks(int square, uint64_t occupied) {
+    return  ray_attacks(square, +1, +1, occupied)   // NE
+          | ray_attacks(square, -1, +1, occupied)   // NW
+          | ray_attacks(square, +1, -1, occupied)   // SE
+          | ray_attacks(square, -1, -1, occupied);  // SW
+}
+
+static inline uint64_t queen_attacks(int square, uint64_t occupied) {
+    // Simply combine both types of attacks
+    return rook_attacks(square, occupied) | bishop_attacks(square, occupied);
+}
+
 void print_board(const struct Board *b) {
     static const char PIECE_CH[12] = {
         'P','N','B','R','Q','K',