/*
 *  Empire - A multi-player, client/server Internet based war game.
 *  Copyright (C) 1986-2020, Dave Pare, Jeff Bailey, Thomas Ruschak,
 *                Ken Stevens, Steve McClure, Markus Armbruster
 *
 *  Empire 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 *  ---
 *
 *  See files README, COPYING and CREDITS in the root of the source
 *  tree for related information and legal notices.  It is expected
 *  that future projects/authors will amend these files as needed.
 *
 *  ---
 *
 *  queue.c: Various queue routines (for lists)
 *
 *  Known contributors to this file:
 *     Markus Armbruster, 2014
 */

#include <config.h>

#include <stddef.h>
#include "queue.h"

void
emp_insque(struct emp_qelem *elem, struct emp_qelem *queue)
{
    struct emp_qelem *next;

    next = queue->q_forw;
    queue->q_forw = elem;
    elem->q_forw = next;
    elem->q_back = queue;
    next->q_back = elem;
}

void
emp_remque(struct emp_qelem *elem)
{
    if (!elem)
	return;
    if (elem->q_forw)
	elem->q_forw->q_back = elem->q_back;
    if (elem->q_back)
	elem->q_back->q_forw = elem->q_forw;
}

int
emp_quelen(struct emp_qelem *queue)
{
    struct emp_qelem *qp;
    int len;

    for (qp = queue->q_forw, len = 0; qp != queue; qp = qp->q_forw, len++)
	;
    return len;
}

struct emp_qelem *
emp_searchque(struct emp_qelem *queue, void *key,
	      int (*test)(struct emp_qelem *, void *))
{
    struct emp_qelem *qp;

    for (qp = queue->q_forw; qp != queue; qp = qp->q_forw) {
	if (test(qp, key))
	    return qp;
    }
    return NULL;
}

void
emp_initque(struct emp_qelem *elem)
{
    elem->q_forw = elem;
    elem->q_back = elem;
}