xref: /titanic_50/usr/src/lib/libc/port/gen/insque.c (revision 7257d1b4d25bfac0c802847390e98a464fd787ac)
17c478bd9Sstevel@tonic-gate /*
27c478bd9Sstevel@tonic-gate  * CDDL HEADER START
37c478bd9Sstevel@tonic-gate  *
47c478bd9Sstevel@tonic-gate  * The contents of this file are subject to the terms of the
5*7257d1b4Sraf  * Common Development and Distribution License (the "License").
6*7257d1b4Sraf  * You may not use this file except in compliance with the License.
77c478bd9Sstevel@tonic-gate  *
87c478bd9Sstevel@tonic-gate  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
97c478bd9Sstevel@tonic-gate  * or http://www.opensolaris.org/os/licensing.
107c478bd9Sstevel@tonic-gate  * See the License for the specific language governing permissions
117c478bd9Sstevel@tonic-gate  * and limitations under the License.
127c478bd9Sstevel@tonic-gate  *
137c478bd9Sstevel@tonic-gate  * When distributing Covered Code, include this CDDL HEADER in each
147c478bd9Sstevel@tonic-gate  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
157c478bd9Sstevel@tonic-gate  * If applicable, add the following below this CDDL HEADER, with the
167c478bd9Sstevel@tonic-gate  * fields enclosed by brackets "[]" replaced with your own identifying
177c478bd9Sstevel@tonic-gate  * information: Portions Copyright [yyyy] [name of copyright owner]
187c478bd9Sstevel@tonic-gate  *
197c478bd9Sstevel@tonic-gate  * CDDL HEADER END
207c478bd9Sstevel@tonic-gate  */
21*7257d1b4Sraf 
227c478bd9Sstevel@tonic-gate /*
23*7257d1b4Sraf  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
247c478bd9Sstevel@tonic-gate  * Use is subject to license terms.
257c478bd9Sstevel@tonic-gate  */
267c478bd9Sstevel@tonic-gate 
277c478bd9Sstevel@tonic-gate /*	Copyright (c) 1988 AT&T	*/
287c478bd9Sstevel@tonic-gate /*	  All Rights Reserved  	*/
297c478bd9Sstevel@tonic-gate 
30*7257d1b4Sraf #pragma ident	"%Z%%M%	%I%	%E% SMI"
317c478bd9Sstevel@tonic-gate 
327c478bd9Sstevel@tonic-gate /*
337c478bd9Sstevel@tonic-gate  * insque() and remque() insert or remove an element from a queue.
347c478bd9Sstevel@tonic-gate  * The queue is built from a doubly linked list whose elements are
357c478bd9Sstevel@tonic-gate  * defined by a structure where the first member of the structure
367c478bd9Sstevel@tonic-gate  * points to the next element in the queue and the second member
377c478bd9Sstevel@tonic-gate  * of the structure points to the previous element in the queue.
387c478bd9Sstevel@tonic-gate  */
397c478bd9Sstevel@tonic-gate 
40*7257d1b4Sraf #pragma weak _insque = insque
41*7257d1b4Sraf #pragma weak _remque = remque
427c478bd9Sstevel@tonic-gate 
43*7257d1b4Sraf #include "lint.h"
447c478bd9Sstevel@tonic-gate #include <sys/types.h>
457c478bd9Sstevel@tonic-gate #include <stdlib.h>
467c478bd9Sstevel@tonic-gate #include <search.h>
477c478bd9Sstevel@tonic-gate 
487c478bd9Sstevel@tonic-gate void
insque(void * elem,void * pred)497c478bd9Sstevel@tonic-gate insque(void *elem, void *pred)
507c478bd9Sstevel@tonic-gate {
517c478bd9Sstevel@tonic-gate 	if (pred == NULL) {    /* This is the first element being inserted. */
527c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_forw = NULL;
537c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_back = NULL;
547c478bd9Sstevel@tonic-gate 	} else if (((struct qelem *)pred)->q_forw == NULL) {
557c478bd9Sstevel@tonic-gate 					/* The element is inserted at */
567c478bd9Sstevel@tonic-gate 					/* the end of the queue. */
577c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_forw = NULL;
587c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_back = pred;
597c478bd9Sstevel@tonic-gate 		((struct qelem *)pred)->q_forw = elem;
607c478bd9Sstevel@tonic-gate 	} else {		/* The element is inserted in the middle of */
617c478bd9Sstevel@tonic-gate 				/* the queue. */
627c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_forw = ((struct qelem *)pred)->q_forw;
637c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_back = pred;
647c478bd9Sstevel@tonic-gate 		((struct qelem *)pred)->q_forw->q_back = elem;
657c478bd9Sstevel@tonic-gate 		((struct qelem *)pred)->q_forw = elem;
667c478bd9Sstevel@tonic-gate 	}
677c478bd9Sstevel@tonic-gate }
687c478bd9Sstevel@tonic-gate 
697c478bd9Sstevel@tonic-gate void
remque(void * elem)707c478bd9Sstevel@tonic-gate remque(void *elem)
717c478bd9Sstevel@tonic-gate {
727c478bd9Sstevel@tonic-gate 	if (((struct qelem *)elem)->q_back == NULL) {
737c478bd9Sstevel@tonic-gate 					/* The first element is removed. */
747c478bd9Sstevel@tonic-gate 		if (((struct qelem *)elem)->q_forw == NULL)
757c478bd9Sstevel@tonic-gate 					/* The only element is removed. */
767c478bd9Sstevel@tonic-gate 			return;
777c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_forw->q_back = NULL;
787c478bd9Sstevel@tonic-gate 	} else if (((struct qelem *)elem)->q_forw == NULL) {
797c478bd9Sstevel@tonic-gate 					/* The last element is removed */
807c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_back->q_forw = NULL;
817c478bd9Sstevel@tonic-gate 	} else {	/* The middle element is removed. */
827c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_back->q_forw =
837c478bd9Sstevel@tonic-gate 		    ((struct qelem *)elem)->q_forw;
847c478bd9Sstevel@tonic-gate 		((struct qelem *)elem)->q_forw->q_back =
857c478bd9Sstevel@tonic-gate 		    ((struct qelem *)elem)->q_back;
867c478bd9Sstevel@tonic-gate 	}
877c478bd9Sstevel@tonic-gate }
88