/*
** movefromto.c  Copyright 1991 Kent Paul Dolan,
**               Mountain View, CA, USA 94039-0755
**
** Written to satisfy an inquiry on USENet's rec.games.programmer newsgroup.
** May be freely used or modified in any non-commercial work.  Copyrighted
** only to prevent patenting by someone else.
*/

#include <stdio.h>
#include "townmaze.h"
#include "townproto.h"

#ifdef __STDC__
void movefromto(int *fromlist,int *fromcount,int *tolist,int *tocount,
                int newstat,int cellnum)
#else
int movefromto(fromlist,fromcount,tolist,tocount,newstat,cellnum)
  int *fromlist;
  int *fromcount;
  int *tolist;
  int *tocount;
  int newstat;
  int cellnum;
#endif
{

  int oldnext;
  int oldprev;

/*
** Save vital existing links.
*/

  oldnext = statlist[cellnum].next;
  oldprev = statlist[cellnum].prev;

/*
** Unlink cell from old position somewhere in fromlist.
*/

  if (statlist[cellnum].next != NOPOINTER)
    statlist[oldnext].prev = statlist[cellnum].prev;

  if (statlist[cellnum].prev != NOPOINTER)
    statlist[oldprev].next = statlist[cellnum].next;
  else *fromlist = statlist[cellnum].next;

/*
** Link cell into new position at head of tolist.
*/

  statlist[cellnum].next = *tolist;

  statlist[cellnum].prev = NOPOINTER;

  if (*tolist != NOPOINTER)
    statlist[*tolist].prev = cellnum;

  *tolist = cellnum;

/*
** Update list length counts.
*/

  (*fromcount)--;
  (*tocount)++;

/*
** update cell status
*/

	  statlist[cellnum].status = newstat;

  return;
}