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allow.c revision 1.9 
      1 /*	$NetBSD: allow.c,v 1.9 2024/08/22 20:46:40 rillig Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1980, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. Neither the name of the University nor the names of its contributors
     16  *    may be used to endorse or promote products derived from this software
     17  *    without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     29  * SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #ifndef lint
     34 #if 0
     35 static char sccsid[] = "@(#)allow.c	8.1 (Berkeley) 5/31/93";
     36 #else
     37 __RCSID("$NetBSD: allow.c,v 1.9 2024/08/22 20:46:40 rillig Exp $");
     38 #endif
     39 #endif /* not lint */
     40 
     41 #include "back.h"
     42 
     43 int
     44 movallow(struct move *mm)
     45 {
     46 	int     i, m, iold;
     47 
     48 	if (mm->d0)
     49 		mswap(mm);
     50 	m = (mm->D0 == mm->D1 ? 4 : 2);
     51 	for (i = 0; i < 4; i++)
     52 		mm->p[i] = bar;
     53 	i = iold = 0;
     54 	while (i < m) {
     55 		if (*offptr == 15)
     56 			break;
     57 		mm->h[i] = 0;
     58 		if (board[bar]) {
     59 			if (i == 1 || m == 4)
     60 				mm->g[i] = bar + cturn * mm->D1;
     61 			else
     62 				mm->g[i] = bar + cturn * mm->D0;
     63 			if (makmove(mm, i) != 0) {
     64 				if (mm->d0 || m == 4)
     65 					break;
     66 				mswap(mm);
     67 				movback(mm, i);
     68 				if (i > iold)
     69 					iold = i;
     70 				for (i = 0; i < 4; i++)
     71 					mm->p[i] = bar;
     72 				i = 0;
     73 			} else
     74 				i++;
     75 			continue;
     76 		}
     77 		if ((mm->p[i] += cturn) == home) {
     78 			if (i > iold)
     79 				iold = i;
     80 			if (m == 2 && i) {
     81 				movback(mm, i);
     82 				mm->p[i--] = bar;
     83 				if (mm->p[i] != bar)
     84 					continue;
     85 				else
     86 					break;
     87 			}
     88 			if (mm->d0 || m == 4)
     89 				break;
     90 			mswap(mm);
     91 			movback(mm, i);
     92 			for (i = 0; i < 4; i++)
     93 				mm->p[i] = bar;
     94 			i = 0;
     95 			continue;
     96 		}
     97 		if (i == 1 || m == 4)
     98 			mm->g[i] = mm->p[i] + cturn * mm->D1;
     99 		else
    100 			mm->g[i] = mm->p[i] + cturn * mm->D0;
    101 		if (mm->g[i] * cturn > home) {
    102 			if (*offptr >= 0)
    103 				mm->g[i] = home;
    104 			else
    105 				continue;
    106 		}
    107 		if (board[mm->p[i]] * cturn > 0 && makmove(mm, i) == 0)
    108 			i++;
    109 	}
    110 	movback(mm, i);
    111 	return (iold > i ? iold : i);
    112 }
    113