135 lines
4.3 KiB
C++
135 lines
4.3 KiB
C++
#include "movegen.h"
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namespace chess {
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namespace {
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void add_promotions(MoveList& list, Square from, Square to) {
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list.add(Move::make(from, to, PROMOTION, QUEEN));
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list.add(Move::make(from, to, PROMOTION, ROOK));
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list.add(Move::make(from, to, PROMOTION, BISHOP));
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list.add(Move::make(from, to, PROMOTION, KNIGHT));
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}
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void generate_castling(const Position& pos, MoveList& list) {
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if (pos.in_check()) return;
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Color us = pos.side_to_move(), them = ~us;
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Bitboard occ = pos.pieces();
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auto attacked = [&](Square sq) { return (pos.attackers_to(sq) & pos.pieces(them)) != 0; };
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if (us == WHITE) {
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if (pos.can_castle(WHITE, KINGSIDE) &&
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!(occ & (square_bb(F1) | square_bb(G1))) && !attacked(F1) && !attacked(G1))
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list.add(Move::make(E1, G1, CASTLING));
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if (pos.can_castle(WHITE, QUEENSIDE) &&
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!(occ & (square_bb(B1) | square_bb(C1) | square_bb(D1))) && !attacked(D1) && !attacked(C1))
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list.add(Move::make(E1, C1, CASTLING));
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} else {
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if (pos.can_castle(BLACK, KINGSIDE) &&
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!(occ & (square_bb(F8) | square_bb(G8))) && !attacked(F8) && !attacked(G8))
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list.add(Move::make(E8, G8, CASTLING));
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if (pos.can_castle(BLACK, QUEENSIDE) &&
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!(occ & (square_bb(B8) | square_bb(C8) | square_bb(D8))) && !attacked(D8) && !attacked(C8))
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list.add(Move::make(E8, C8, CASTLING));
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}
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}
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} // namespace
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void generate_pseudo(const Position& pos, MoveList& list) {
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Color us = pos.side_to_move(), them = ~us;
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Bitboard occ = pos.pieces();
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Bitboard targets = ~pos.pieces(us); // empty squares or enemy pieces
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Bitboard theirs = pos.pieces(them);
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// Pawns
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int push = (us == WHITE) ? 8 : -8;
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Rank promoRank = (us == WHITE) ? RANK_8 : RANK_1;
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Rank startRank = (us == WHITE) ? RANK_2 : RANK_7;
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Bitboard b = pos.pieces(us, PAWN);
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while (b) {
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Square s = pop_lsb(b);
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Square t = Square(int(s) + push);
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if (!(occ & square_bb(t))) {
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if (rank_of(t) == promoRank) {
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add_promotions(list, s, t);
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} else {
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list.add(Move::make(s, t));
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if (rank_of(s) == startRank) {
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Square t2 = Square(int(t) + push);
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if (!(occ & square_bb(t2))) list.add(Move::make(s, t2));
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}
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}
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}
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Bitboard caps = PawnAttacks[us][s] & theirs;
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while (caps) {
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Square c = pop_lsb(caps);
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if (rank_of(c) == promoRank) add_promotions(list, s, c);
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else list.add(Move::make(s, c));
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}
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if (pos.ep_square() != SQ_NONE && (PawnAttacks[us][s] & square_bb(pos.ep_square())))
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list.add(Move::make(s, pos.ep_square(), EN_PASSANT));
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}
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// Knights
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b = pos.pieces(us, KNIGHT);
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while (b) {
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Square s = pop_lsb(b);
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Bitboard a = KnightAttacks[s] & targets;
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while (a) list.add(Move::make(s, pop_lsb(a)));
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}
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// Bishops
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b = pos.pieces(us, BISHOP);
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while (b) {
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Square s = pop_lsb(b);
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Bitboard a = bishop_attacks(s, occ) & targets;
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while (a) list.add(Move::make(s, pop_lsb(a)));
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}
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// Rooks
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b = pos.pieces(us, ROOK);
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while (b) {
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Square s = pop_lsb(b);
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Bitboard a = rook_attacks(s, occ) & targets;
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while (a) list.add(Move::make(s, pop_lsb(a)));
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}
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// Queens
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b = pos.pieces(us, QUEEN);
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while (b) {
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Square s = pop_lsb(b);
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Bitboard a = queen_attacks(s, occ) & targets;
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while (a) list.add(Move::make(s, pop_lsb(a)));
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}
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// King (non-castling)
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{
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Square s = pos.king_square(us);
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Bitboard a = KingAttacks[s] & targets;
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while (a) list.add(Move::make(s, pop_lsb(a)));
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}
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}
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void Position::generate_legal(MoveList& list) {
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list.count = 0;
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MoveList pseudo;
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generate_pseudo(*this, pseudo);
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Color us = sideToMove;
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for (Move m : pseudo) {
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do_move(m);
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// After do_move, sideToMove is the opponent; the move is legal iff the
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// side that just moved did not leave its own king attacked.
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bool legal = (attackers_to(king_square(us)) & pieces(sideToMove)) == 0;
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undo_move(m);
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if (legal) list.add(m);
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}
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generate_castling(*this, list); // already fully legal
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}
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} // namespace chess
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