backgammon/common_source/allow.c

   1 /*      $NetBSD: allow.c,v 1.4 1997/10/10 08:59:41 lukem 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. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by the University of
  18  *      California, Berkeley and its contributors.
  19  * 4. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 #include <sys/cdefs.h>
  37 #ifndef lint
  38 #if 0
  39 static char sccsid[] = "@(#)allow.c     8.1 (Berkeley) 5/31/93";
  40 #else
  41 __RCSID("$NetBSD: allow.c,v 1.4 1997/10/10 08:59:41 lukem Exp $");
  42 #endif
  43 #endif /* not lint */
  44
  45 #include "back.h"
  46
  47 int
  48 movallow()
  49 {
  50         int     i, m, iold;
  51         int     r;
  52
  53         if (d0)
  54                 swap;
  55         m = (D0 == D1 ? 4 : 2);
  56         for (i = 0; i < 4; i++)
  57                 p[i] = bar;
  58         i = iold = 0;
  59         while (i < m) {
  60                 if (*offptr == 15)
  61                         break;
  62                 h[i] = 0;
  63                 if (board[bar]) {
  64                         if (i == 1 || m == 4)
  65                                 g[i] = bar + cturn * D1;
  66                         else
  67                                 g[i] = bar + cturn * D0;
  68                         if ((r = makmove(i)) != 0) {
  69                                 if (d0 || m == 4)
  70                                         break;
  71                                 swap;
  72                                 movback(i);
  73                                 if (i > iold)
  74                                         iold = i;
  75                                 for (i = 0; i < 4; i++)
  76                                         p[i] = bar;
  77                                 i = 0;
  78                         } else
  79                                 i++;
  80                         continue;
  81                 }
  82                 if ((p[i] += cturn) == home) {
  83                         if (i > iold)
  84                                 iold = i;
  85                         if (m == 2 && i) {
  86                                 movback(i);
  87                                 p[i--] = bar;
  88                                 if (p[i] != bar)
  89                                         continue;
  90                                 else
  91                                         break;
  92                         }
  93                         if (d0 || m == 4)
  94                                 break;
  95                         swap;
  96                         movback(i);
  97                         for (i = 0; i < 4; i++)
  98                                 p[i] = bar;
  99                         i = 0;
 100                         continue;
 101                 }
 102                 if (i == 1 || m == 4)
 103                         g[i] = p[i] + cturn * D1;
 104                 else
 105                         g[i] = p[i] + cturn * D0;
 106                 if (g[i] * cturn > home) {
 107                         if (*offptr >= 0)
 108                                 g[i] = home;
 109                         else
 110                                 continue;
 111                 }
 112                 if (board[p[i]] * cturn > 0 && (r = makmove(i)) == 0)
 113                         i++;
 114         }
 115         movback(i);
 116         return (iold > i ? iold : i);
 117 }