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 #pragma ident "%Z%%M% %I% %E% SMI" 31 32 /* 33 * insque() and remque() insert or remove an element from a queue. 34 * The queue is built from a doubly linked list whose elements are 35 * defined by a structure where the first member of the structure 36 * points to the next element in the queue and the second member 37 * of the structure points to the previous element in the queue. 38 */ 39 40 #pragma weak _insque = insque 41 #pragma weak _remque = remque 42 43 #include "lint.h" 44 #include <sys/types.h> 45 #include <stdlib.h> 46 #include <search.h> 47 48 void 49 insque(void *elem, void *pred) 50 { 51 if (pred == NULL) { /* This is the first element being inserted. */ 52 ((struct qelem *)elem)->q_forw = NULL; 53 ((struct qelem *)elem)->q_back = NULL; 54 } else if (((struct qelem *)pred)->q_forw == NULL) { 55 /* The element is inserted at */ 56 /* the end of the queue. */ 57 ((struct qelem *)elem)->q_forw = NULL; 58 ((struct qelem *)elem)->q_back = pred; 59 ((struct qelem *)pred)->q_forw = elem; 60 } else { /* The element is inserted in the middle of */ 61 /* the queue. */ 62 ((struct qelem *)elem)->q_forw = ((struct qelem *)pred)->q_forw; 63 ((struct qelem *)elem)->q_back = pred; 64 ((struct qelem *)pred)->q_forw->q_back = elem; 65 ((struct qelem *)pred)->q_forw = elem; 66 } 67 } 68 69 void 70 remque(void *elem) 71 { 72 if (((struct qelem *)elem)->q_back == NULL) { 73 /* The first element is removed. */ 74 if (((struct qelem *)elem)->q_forw == NULL) 75 /* The only element is removed. */ 76 return; 77 ((struct qelem *)elem)->q_forw->q_back = NULL; 78 } else if (((struct qelem *)elem)->q_forw == NULL) { 79 /* The last element is removed */ 80 ((struct qelem *)elem)->q_back->q_forw = NULL; 81 } else { /* The middle element is removed. */ 82 ((struct qelem *)elem)->q_back->q_forw = 83 ((struct qelem *)elem)->q_forw; 84 ((struct qelem *)elem)->q_forw->q_back = 85 ((struct qelem *)elem)->q_back; 86 } 87 } 88