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      1 /*
      2  *  Copyright (c) 1993 John Brezak
      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. The name of the author may be used to endorse or promote products
     14  *     derived from this software without specific prior written permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
     17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     18  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     19  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
     20  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     21  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     22  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
     24  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
     25  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 #if defined(LIBC_SCCS) && !defined(lint)
     31 __RCSID("$NetBSD: insque.c,v 1.3 2012/06/25 22:32:45 abs Exp $");
     32 #endif /* LIBC_SCCS and not lint */
     33 
     34 #include <assert.h>
     35 #include <search.h>
     36 
     37 struct qelem {
     38         struct qelem *q_forw;
     39         struct qelem *q_back;
     40 };
     41 
     42 void
     43 insque(void *entry, void *pred)
     44 {
     45 	struct qelem *e = (struct qelem *) entry;
     46 	struct qelem *p = (struct qelem *) pred;
     47 
     48 	_DIAGASSERT(e != 0);
     49 
     50 	e->q_back = p;
     51 	if (p) {
     52 		e->q_forw = p->q_forw;
     53 		if (p->q_forw)
     54 			p->q_forw->q_back = e;
     55 		p->q_forw = e;
     56 	} else
     57 		e->q_forw = 0;
     58 }
     59