1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 22 /* 23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 /* Copyright (c) 1988 AT&T */ 28 /* All Rights Reserved */ 29 30 /* 31 * insque() and remque() insert or remove an element from a queue. 32 * The queue is built from a doubly linked list whose elements are 33 * defined by a structure where the first member of the structure 34 * points to the next element in the queue and the second member 35 * of the structure points to the previous element in the queue. 36 */ 37 38 #pragma weak _insque = insque 39 #pragma weak _remque = remque 40 41 #include "lint.h" 42 #include <sys/types.h> 43 #include <stdlib.h> 44 #include <search.h> 45 46 void insque(void * elem,void * pred)47insque(void *elem, void *pred) 48 { 49 if (pred == NULL) { /* This is the first element being inserted. */ 50 ((struct qelem *)elem)->q_forw = NULL; 51 ((struct qelem *)elem)->q_back = NULL; 52 } else if (((struct qelem *)pred)->q_forw == NULL) { 53 /* The element is inserted at */ 54 /* the end of the queue. */ 55 ((struct qelem *)elem)->q_forw = NULL; 56 ((struct qelem *)elem)->q_back = pred; 57 ((struct qelem *)pred)->q_forw = elem; 58 } else { /* The element is inserted in the middle of */ 59 /* the queue. */ 60 ((struct qelem *)elem)->q_forw = ((struct qelem *)pred)->q_forw; 61 ((struct qelem *)elem)->q_back = pred; 62 ((struct qelem *)pred)->q_forw->q_back = elem; 63 ((struct qelem *)pred)->q_forw = elem; 64 } 65 } 66 67 void remque(void * elem)68remque(void *elem) 69 { 70 if (((struct qelem *)elem)->q_back == NULL) { 71 /* The first element is removed. */ 72 if (((struct qelem *)elem)->q_forw == NULL) 73 /* The only element is removed. */ 74 return; 75 ((struct qelem *)elem)->q_forw->q_back = NULL; 76 } else if (((struct qelem *)elem)->q_forw == NULL) { 77 /* The last element is removed */ 78 ((struct qelem *)elem)->q_back->q_forw = NULL; 79 } else { /* The middle element is removed. */ 80 ((struct qelem *)elem)->q_back->q_forw = 81 ((struct qelem *)elem)->q_forw; 82 ((struct qelem *)elem)->q_forw->q_back = 83 ((struct qelem *)elem)->q_back; 84 } 85 } 86