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Import of Empire 4.2.12

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Markus Armbruster 2003-08-23 12:23:04 +00:00
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src/lib/as/as_extend.c Normal file
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/*
* A* Search - A search library used in Empire to determine paths between
* objects.
* Copyright (C) 1990-1998 Phil Lapsley
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <stdio.h>
#include <stdlib.h>
#include "as.h"
#if !defined(lint) && !defined(SABER)
static char sccsid[] = "@(#)as_extend.c 1.2 11/13/90";
#endif /* not lint */
/*
* Extend the queue by neighbors. This entails getting the
* coordinates of all the neighbors, figuring out their lower bound
* costs, throwing away ones that are more expensive than ones we
* already have, sorting, tand then merging into the queue.
*/
struct as_queue *
as_extend(struct as_data *adp)
{
struct as_queue *qp;
int i;
struct as_queue *head;
head = adp->head;
/* Find the neighboring coordinates. */
i = (*adp->neighbor)(head->np->c, adp->neighbor_coords, adp->userdata);
if (i == 0)
return (NULL);
/*
* Get rid of neighbors that are more costly than ones we already have,
* and sort the rest into an array of as_nodes.
*/
i = as_winnow(adp, adp->neighbor_coords, i);
if (i < 0)
return (NULL);
if (i > 1)
qsort(adp->neighbor_nodes, i,
sizeof (*adp->neighbor_nodes),
(qsort_func_t) as_costcomp);
/* remove old coord from head of queue and add to list of tried */
qp = head;
head = head->next;
if (head)
head->prev = NULL;
if (adp->tried) {
adp->tried->prev = qp;
qp->next = adp->tried;
adp->tried = qp;
} else
adp->tried = qp;
adp->tried->np->flags |= AS_TRIED;
head = as_merge(adp, head, adp->neighbor_nodes);
return (head);
}