src/engine/moves/king.c


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#include "../moves.h"

void get_king_moves(moves_t* moves, position_t position) {
  assert_valid_position(position);

  bitboard_t friendly_king;
  int king_square;
  bitboard_t friendly_pieces;
  if (position.turn == WHITE_TURN) {
    friendly_pieces = whites(position);
    friendly_king = position.bitboards[WHITE_KING];
  } else {
    friendly_pieces = blacks(position);
    friendly_king = position.bitboards[BLACK_KING];
  }
  king_square = __builtin_ctzll(friendly_king);

  bitboard_t movement;
  if (king_square >= 10) {
    movement = 920078ULL << (king_square - 10);
  } else {
    movement = 920078ULL >> -(king_square - 10);
  }
  if (friendly_king & BITMASK_FILE_A) {
    movement &= BITMASK_FILE_A | BITMASK_FILE_B;
  } else if (friendly_king & BITMASK_FILE_H) {
    movement &= BITMASK_FILE_G | BITMASK_FILE_H;
  }

  movement &= ~friendly_pieces;
  while (movement) {
    int to = __builtin_ctzll(movement);
    movement &= movement - 1;
    add_move(moves, king_square, to);
  }
}