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#include "../search.h"
#include <assert.h>
#include <inttypes.h>
bitboard_t get_white_pawn_forwardmoves(moves_t* moves, position_t position) {
bitboard_t enemy_bitboard = blacks(position);
bitboard_t friendly_pieces =
position.bitboards[WHITE_KING] |
position.bitboards[WHITE_QUEEN] |
position.bitboards[WHITE_ROOK] |
position.bitboards[WHITE_BISHOP] |
position.bitboards[WHITE_KNIGHT] |
position.bitboards[WHITE_PAWN];
bitboard_t friendly_pawns = position.bitboards[WHITE_PAWN];
bitboard_t y = friendly_pieces | enemy_bitboard;
bitboard_t x = ~((friendly_pawns << 8) & y) & (friendly_pawns << 8);
bitboard_t first_move_x = x & BITMASK_RANK_3;
first_move_x |= (first_move_x << 8) & (~y);
x |= first_move_x;
return x;
}
bitboard_t get_black_pawn_forwardmoves(moves_t* moves, position_t position) {
bitboard_t enemy_bitboard = whites(position);
bitboard_t friendly_pieces =
position.bitboards[BLACK_KING] |
position.bitboards[BLACK_QUEEN] |
position.bitboards[BLACK_ROOK] |
position.bitboards[BLACK_BISHOP] |
position.bitboards[BLACK_KNIGHT] |
position.bitboards[BLACK_PAWN];
bitboard_t friendly_pawns = position.bitboards[BLACK_PAWN];
bitboard_t y = friendly_pieces | enemy_bitboard;
bitboard_t x = ~((friendly_pawns >> 8) & y) & (friendly_pawns >> 8);
bitboard_t first_move_x = x & BITMASK_RANK_6;
first_move_x |= (first_move_x >> 8) & (~y);
x |= first_move_x;
return x;
}
void get_pawn_moves(moves_t* moves, position_t position) {
assert_valid_position(position);
bitboard_t forward_moves;
bitboard_t friendly_pawns;
bitboard_t enemy_bitboard;
if (position.turn == WHITE_TURN) {
forward_moves = get_white_pawn_forwardmoves(moves, position);
friendly_pawns = position.bitboards[WHITE_PAWN];
enemy_bitboard = blacks(position);
} else {
forward_moves = get_black_pawn_forwardmoves(moves, position);
friendly_pawns = position.bitboards[BLACK_PAWN];
enemy_bitboard = whites(position);
}
bitboard_t file_masks[8] = {
BITMASK_FILE_A,
BITMASK_FILE_B,
BITMASK_FILE_C,
BITMASK_FILE_D,
BITMASK_FILE_E,
BITMASK_FILE_F,
BITMASK_FILE_G,
BITMASK_FILE_H,
};
for (int i = 0; i < 8; i++) {
bitboard_t item = file_masks[i] & forward_moves;
bitboard_t pawns = file_masks[i] & friendly_pawns;
int from = __builtin_ctzll(pawns);
pawns &= (pawns - 1);
int next_from = __builtin_ctzll(pawns);
if (pawns == 0) next_from = 64; // to work around UB
while (item) {
int to = __builtin_ctzll(item);
if (to > next_from) {
from = next_from;
pawns &= (pawns - 1);
next_from = __builtin_ctzll(pawns);
if (pawns == 0) next_from = 64;
}
item &= (item - 1);
add_move(moves, from, to);
}
}
if (position.passantable_column != 0) {
bitboard_t PASSANT_RANK;
int rank_shift;
int from_shift;
if (position.turn == WHITE_TURN) {
PASSANT_RANK = BITMASK_RANK_5;
rank_shift = 40;
from_shift = -9;
} else {
PASSANT_RANK = BITMASK_RANK_4;
from_shift = 7;
rank_shift = 16;
}
int left = 0, right = 0;
if (position.passantable_column > 1) left = position.passantable_column - 1;
if (position.passantable_column < 8) right = position.passantable_column + 1;
if (left != 0) {
bitboard_t MASK = file_masks[left - 1] & friendly_pawns & PASSANT_RANK;
if (MASK != 0) {
add_move(
moves,
left + rank_shift + from_shift,
position.passantable_column + rank_shift - 1
);
}
}
if (right != 0) {
bitboard_t MASK = file_masks[right - 1] & friendly_pawns & PASSANT_RANK;
if (MASK != 0) {
add_move(
moves,
right + rank_shift + from_shift,
position.passantable_column + rank_shift - 1
);
}
}
}
bitboard_t ATTACK_MASK;
int shift;
if (position.turn == WHITE_TURN) {
shift = 0;
} else {
shift = -16;
}
for (int i = 0; i < 8; i++) {
if (i == 0) ATTACK_MASK = 512;
else if (i == 7) ATTACK_MASK = 128;
else {
ATTACK_MASK = 640;
}
bitboard_t pawns = file_masks[i] & friendly_pawns;
while (pawns) {
int from = __builtin_ctzll(pawns);
pawns &= pawns - 1;
bitboard_t MASK;
if (from + shift > 0) {
MASK = ATTACK_MASK << (from + shift);
} else {
MASK = ATTACK_MASK >> -(from + shift);
}
MASK &= enemy_bitboard;
while (MASK) {
int to = __builtin_ctzll(MASK);
MASK &= MASK - 1;
add_move(moves, from, to);
}
}
}
}
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