backgammon/common_source/allow.c

   1 /*
   2  * Copyright (c) 1980 Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #ifndef lint
  35 /*static char sccsid[] = "from: @(#)allow.c     5.4 (Berkeley) 6/1/90";*/
  36 static char rcsid[] = "$Id: allow.c,v 1.2 1993/08/01 18:56:46 mycroft Exp $";
  37 #endif /* not lint */
  38
  39 #include "back.h"
  40
  41 movallow ()  {
  42
  43         register int    i, m, iold;
  44         int             r;
  45
  46         if (d0)
  47                 swap;
  48         m = (D0 == D1? 4: 2);
  49         for (i = 0; i < 4; i++)
  50                 p[i] = bar;
  51         i = iold = 0;
  52         while (i < m)  {
  53                 if (*offptr == 15)
  54                         break;
  55                 h[i] = 0;
  56                 if (board[bar])  {
  57                         if (i == 1 || m == 4)
  58                                 g[i] = bar+cturn*D1;
  59                         else
  60                                 g[i] = bar+cturn*D0;
  61                         if (r = makmove(i))  {
  62                                 if (d0 || m == 4)
  63                                         break;
  64                                 swap;
  65                                 movback (i);
  66                                 if (i > iold)
  67                                         iold = i;
  68                                 for (i = 0; i < 4; i++)
  69                                         p[i] = bar;
  70                                 i = 0;
  71                         } else
  72                                 i++;
  73                         continue;
  74                 }
  75                 if ((p[i] += cturn) == home)  {
  76                         if (i > iold)
  77                                 iold = i;
  78                         if (m == 2 && i)  {
  79                                 movback(i);
  80                                 p[i--] = bar;
  81                                 if (p[i] != bar)
  82                                         continue;
  83                                 else
  84                                         break;
  85                         }
  86                         if (d0 || m == 4)
  87                                 break;
  88                         swap;
  89                         movback (i);
  90                         for (i = 0; i < 4; i++)
  91                                 p[i] = bar;
  92                         i = 0;
  93                         continue;
  94                 }
  95                 if (i == 1 || m == 4)
  96                         g[i] = p[i]+cturn*D1;
  97                 else
  98                         g[i] = p[i]+cturn*D0;
  99                 if (g[i]*cturn > home)  {
 100                         if (*offptr >= 0)
 101                                 g[i] = home;
 102                         else
 103                                 continue;
 104                 }
 105                 if (board[p[i]]*cturn > 0 && (r = makmove(i)) == 0)
 106                         i++;
 107         }
 108         movback (i);
 109         return (iold > i? iold: i);
 110 }