backgammon/common_source/allow.c

   1 /*      $NetBSD: allow.c,v 1.8 2012/10/13 19:19:38 dholland 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 1.8 2012/10/13 19:19:38 dholland 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         int     r;
  48
  49         if (mm->d0)
  50                 mswap(mm);
  51         m = (mm->D0 == mm->D1 ? 4 : 2);
  52         for (i = 0; i < 4; i++)
  53                 mm->p[i] = bar;
  54         i = iold = 0;
  55         while (i < m) {
  56                 if (*offptr == 15)
  57                         break;
  58                 mm->h[i] = 0;
  59                 if (board[bar]) {
  60                         if (i == 1 || m == 4)
  61                                 mm->g[i] = bar + cturn * mm->D1;
  62                         else
  63                                 mm->g[i] = bar + cturn * mm->D0;
  64                         if ((r = makmove(mm, i)) != 0) {
  65                                 if (mm->d0 || m == 4)
  66                                         break;
  67                                 mswap(mm);
  68                                 movback(mm, i);
  69                                 if (i > iold)
  70                                         iold = i;
  71                                 for (i = 0; i < 4; i++)
  72                                         mm->p[i] = bar;
  73                                 i = 0;
  74                         } else
  75                                 i++;
  76                         continue;
  77                 }
  78                 if ((mm->p[i] += cturn) == home) {
  79                         if (i > iold)
  80                                 iold = i;
  81                         if (m == 2 && i) {
  82                                 movback(mm, i);
  83                                 mm->p[i--] = bar;
  84                                 if (mm->p[i] != bar)
  85                                         continue;
  86                                 else
  87                                         break;
  88                         }
  89                         if (mm->d0 || m == 4)
  90                                 break;
  91                         mswap(mm);
  92                         movback(mm, i);
  93                         for (i = 0; i < 4; i++)
  94                                 mm->p[i] = bar;
  95                         i = 0;
  96                         continue;
  97                 }
  98                 if (i == 1 || m == 4)
  99                         mm->g[i] = mm->p[i] + cturn * mm->D1;
 100                 else
 101                         mm->g[i] = mm->p[i] + cturn * mm->D0;
 102                 if (mm->g[i] * cturn > home) {
 103                         if (*offptr >= 0)
 104                                 mm->g[i] = home;
 105                         else
 106                                 continue;
 107                 }
 108                 if (board[mm->p[i]] * cturn > 0 && (r = makmove(mm, i)) == 0)
 109                         i++;
 110         }
 111         movback(mm, i);
 112         return (iold > i ? iold : i);
 113 }