282 lines
8.0 KiB
C
282 lines
8.0 KiB
C
/* fen.c - fen notation.
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*
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* Copyright (C) 2021-2024 Bruno Raoult ("br")
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* Licensed under the GNU General Public License v3.0 or later.
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* Some rights reserved. See COPYING.
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*
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* You should have received a copy of the GNU General Public License along with this
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* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
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*
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* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdbool.h>
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#include <string.h>
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#include <ctype.h>
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#include <debug.h>
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#include <bug.h>
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#include "chessdefs.h"
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#include "position.h"
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#include "fen.h"
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#include "piece.h"
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#include "util.h"
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/* FEN description:
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* 1 : pieces on board (no space allowed):
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* - rank 8 first, '/' between ranks
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* - piece is usual piece notation(PNBRQK), black lowercase.
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* - empty: number of consecutive empty squares (digit)
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* 2 : next move (w or b)
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* 3 : Castling capabilities: "-" if none, KQ/kq if white/black can castle
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* on K or Q side
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* 4 : en-passant: "-" if none. If pawn just moved 2 squares, indicate target
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* en-passant square (e.g. for e2-e4 this field is e3)
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* 5 : half moves since last capture or pawn advance (for 50 moves rule)
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* 6 : full moves, starts at 1, increments after black move
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*
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* Examples:
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*
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* starting position:
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* rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
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* after 1.e4 e6 2.e5 d5
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* rnbqkbnr/ppp2ppp/4p3/3pP3/8/8/PPPP1PPP/RNBQKBNR w KQkq d6 0 3
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* 3.Nc3 Nc6 4.Rb1 Rb8 5.Nf3 h5 6.Be2
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* 1rbqkbnr/ppp2pp1/2n1p3/3pP2p/8/2N2N2/PPPPBPPP/1RBQK2R b Kk - 1 6
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* 6...Be7
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* 1rbqk1nr/ppp1bpp1/2n1p3/3pP2p/8/2N2N2/PPPPBPPP/1RBQK2R w Kk - 2 7
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* 7.Nxd5 h4 8.g4
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* 1rbqk1nr/ppp1bpp1/2n1p3/3NP3/6Pp/5N2/PPPPBP1P/1RBQK2R b Kk g3 0 8
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*/
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/* chess startup position FEN */
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const char *startfen="rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
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/* next must follow 'piece_type' enum values (pawn is 1, king is 6) */
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static const char *pieces_str = " PNBRQK";
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/* And this one must follow 'castle' enum order (also same as usual FEN) */
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static const char *castle_str = "KQkq";
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#define SKIP_BLANK(p) for(;isspace(*(p)); (p)++)
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/**
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* startpos - create a game start position
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* @pos: a position pointer or NULL
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*
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* See @fen2pos function.
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*
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* @return: the pos position.
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*/
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position *startpos(position *pos)
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{
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return fen2pos(pos, startfen);
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}
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/**
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* fen2pos - make a position from a fen string
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* @pos: a position pointer or NULL
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* @fen: a valid fen string
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*
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* If @pos is NULL, a position will be allocated with malloc(1),
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* that should be freed by caller.
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*
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* @return: the pos position, or NULL if error.
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*/
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position *fen2pos(position *pos, const char *fen)
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{
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const char *cur = fen;
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char *p;
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short rank, file, color, tmp;
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int consumed, err_line = 0, err_pos, err_char;
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position tmppos;
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pos_clear(&tmppos);
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/* 1) get piece placement information
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*/
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for (rank = 7, file = 0; *cur && !isspace(*cur); ++cur) {
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if (*cur == '/') { /* next rank */
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rank--;
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file = 0;
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continue;
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}
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if (isdigit(*cur)) { /* empty square(s) */
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file += *cur - '0';
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continue;
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}
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color = isupper(*cur)? WHITE: BLACK;
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if ((p = strchr(pieces_str, toupper(*cur)))) { /* valid piece letter */
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# ifdef DEBUG_FEN
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log_i(5, "f=%d r=%d *p=%c piece=%c color=%d ppos=%ld\n",
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file, rank, *cur, *p, color, p - pieces_str);
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# endif
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pos_set_sq(&tmppos, p - pieces_str, color, file, rank);
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file++;
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} else { /* error */
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err_line = __LINE__, err_char = *cur, err_pos = cur - fen;
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goto end;
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}
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}
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SKIP_BLANK(cur);
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/* 2) next turn color
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*/
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tmppos.turn = *cur++ == 'w' ? WHITE : BLACK;
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SKIP_BLANK(cur);
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/* 3) castle rights
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*/
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if (*cur == '-') {
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cur++;
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} else {
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for (; *cur && !isspace(*cur); ++cur) {
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if ((p = strchr(castle_str, *cur))) { /* valid castle letter */
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tmppos.castle |= 1 << (p - castle_str);
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} else {
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err_line = __LINE__, err_char = *cur, err_pos = cur - fen;
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goto end;
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}
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}
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}
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SKIP_BLANK(cur);
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/* 4) en passant
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*/
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tmppos.en_passant = 0;
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if (*cur == '-') {
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cur++;
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} else {
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tmppos.en_passant = BB(C2FILE(*cur), C2RANK(*(cur+1)));
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cur += 2;
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}
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SKIP_BLANK(cur);
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/* 5) half moves since last capture or pawn move (50 moves rule)
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*/
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sscanf(cur, "%hd%n", &tmppos.clock_50, &consumed);
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cur += consumed;
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SKIP_BLANK(cur);
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/* 6) current full move number, starting with 1
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*/
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printf ("remain=[%s]\n", cur);
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sscanf(cur, "%hd", &tmp);
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printf ("tmp=[%d]\n", tmp);
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if (tmp <= 0) /* fix faulty numbers*/
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tmp = 1;
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printf ("tmp2=[%d]\n", tmp);
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tmp = 2 * (tmp - 1) + (tmppos.turn == BLACK); /* plies, +1 if black turn */
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printf ("tmp3=[%d]\n", tmp);
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tmppos.plycount = tmp;
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# ifdef DEBUG_FEN
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for (rank = 7; rank >= 0; --rank) {
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for (file = 0; file < 8; ++file) {
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log(5, "%02x ", tmppos.board[BB(file, rank)]);
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}
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log(5, "\n");
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}
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log(5, "turn=%d 50_rule=%d curply=%d\n",
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tmppos.turn, tmppos.clock_50, tmppos.plycount);
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# endif
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end:
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if (warn(err_line, "FEN error line %d: pos=%d char=%#x(%c)\n",
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err_line, err_pos, err_char, err_char)) {
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return NULL;
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}
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if (!pos)
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pos = pos_new();
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else
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pos_clear(pos);
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*pos = tmppos;
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return pos;
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}
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/**
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* pos2fen - make a FEN string from a position.
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* @pos: a position pointer
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* @fen: destination FEN char*, or NULL
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*
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* If @fen is NULL, a 100 bytes memory will be allocated with malloc(1),
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* that should be freed by caller.
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*
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* Note: If @fen is given, no check is done on its length, but to
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* be on secure side, it should be at least 90 bytes. See:
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* https://chess.stackexchange.com/questions/30004/longest-possible-fen
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* For convenience, use FENSTRLEN.
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*
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* @return: the pos position, or NULL if error.
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*/
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char *pos2fen(const position *pos, char *fen)
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{
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int cur = 0;
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if (!fen)
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fen = safe_malloc(92);
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/* 1) position
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*/
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for (int rank = RANK_8; rank >= RANK_1; --rank) {
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printf("r=%d 1=%d\n", rank, RANK_1);
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for (int file = FILE_A; file <= FILE_H;) {
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printf(" f=%d H=%d\n", file, FILE_H);
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square sq = BB(file, rank);
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printf(" sq=%d\n", sq);
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piece piece = PIECE(pos->board[sq]);
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color color = COLOR(pos->board[sq]);
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if (pos->board[sq] == EMPTY) {
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int len = 0;
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for (; file <= FILE_H && pos->board[BB(file,rank)] == EMPTY; file++)
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len++;
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fen[cur++] = '0' + len;
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} else {
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char c = pieces_str[piece];
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fen[cur++] = color == WHITE? c: tolower(c);
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file++;
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}
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fen[cur]=0; puts(fen);
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}
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fen[cur++] = rank == RANK_1? ' ': '/';
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}
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/* 2) next turn color
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*/
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fen[cur++] = pos->turn == WHITE? 'w': 'b';
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fen[cur++] = ' ';
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/* 3) castle rights
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*/
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if (pos->castle == 0) {
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fen[cur++] = '-';
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} else {
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//static char *
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for (int i = 0; i < 4; ++i)
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if (pos->castle & mask(i))
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fen[cur++] = castle_str[i];
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}
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fen[cur++] = ' ';
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/* 4) en passant
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*/
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if (!pos->en_passant) {
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fen[cur++] = '-';
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} else {
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fen[cur++] = FILE2C(BBfile(pos->en_passant));
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fen[cur++] = RANK2C(BBrank(pos->en_passant));
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}
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fen[cur++] = ' ';
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/* 5) moves since last capture or pawn move (50 moves rule)
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* 6) current full move number, starting with 1
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*/
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sprintf(fen+cur, "%d %d", pos->clock_50,
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1 + (pos->plycount - (pos->turn == BLACK)) / 2);
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return fen;
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}
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