- checkersCnt++;
- checksq = pop_1st_bit(&b);
-
- assert(color_of(pos.piece_on(checksq)) == flip(us));
-
- switch (type_of(pos.piece_on(checksq)))
- {
- case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
- case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
- case QUEEN:
- // If queen and king are far we can safely remove all the squares attacked
- // in the other direction becuase are not reachable by the king anyway.
- if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
- sliderAttacks |= QueenPseudoAttacks[checksq];
-
- // Otherwise, if king and queen are adjacent and on a diagonal line, we need to
- // use real rook attacks to check if king is safe to move in the other direction.
- // For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
- else
- sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
-
- default:
- break;
- }
+ ++checkersCnt;
+ checksq = pop_lsb(&b);
+
+ assert(color_of(pos.piece_on(checksq)) == ~us);
+
+ if (type_of(pos.piece_on(checksq)) > KNIGHT) // A slider
+ sliderAttacks |= LineBB[checksq][ksq] ^ checksq;
+