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, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright (c) 1994, by Sun Microsytems, Inc. 24 */ 25 26 #pragma ident "%Z%%M% %I% %E% SMI" 27 28 /* 29 * Includes 30 */ 31 32 #include "queue.h" 33 #include "new.h" 34 35 36 /* 37 * queue_init() - initializes a queue_node to be unlinked. 38 */ 39 40 void queue_init(queue_node_t * q)41 queue_init(queue_node_t * q) 42 { 43 q->next_p = q->prev_p = q; 44 45 } /* end queue_init */ 46 47 48 /* 49 * queue_prepend() - prepends a queue_node to another in a list 50 */ 51 52 queue_node_t * queue_prepend(queue_node_t * h,queue_node_t * q)53 queue_prepend(queue_node_t * h, queue_node_t * q) 54 { 55 if (!h) 56 return ((q) ? q : NULL); 57 58 if (q) { 59 queue_node_t *qtail_p = q->prev_p; 60 queue_node_t *hnode_p = h->next_p; 61 62 hnode_p->prev_p = qtail_p; 63 h->next_p = q; 64 65 q->prev_p = h; 66 qtail_p->next_p = hnode_p; 67 } 68 return (h); 69 70 } /* end queue_prepend */ 71 72 73 /* 74 * queue_append() - appends a queue_node to another in a list 75 */ 76 77 queue_node_t * queue_append(queue_node_t * h,queue_node_t * q)78 queue_append(queue_node_t * h, queue_node_t * q) 79 { 80 if (!h) 81 return ((q) ? q : NULL); 82 83 if (q) { 84 queue_node_t *htail_p = h->prev_p; 85 queue_node_t *qtail_p = q->prev_p; 86 87 h->prev_p = qtail_p; 88 htail_p->next_p = q; 89 90 q->prev_p = htail_p; 91 qtail_p->next_p = h; 92 } 93 return (h); 94 95 } /* end queue_append */ 96 97 98 /* 99 * queue_remove() - removes a node from a list, returns a pointer to the next 100 * node in the list. 101 */ 102 103 queue_node_t * queue_remove(queue_node_t * q)104 queue_remove(queue_node_t * q) 105 { 106 queue_node_t *n; 107 108 n = q->next_p; 109 110 if (queue_isempty(q)) 111 return (NULL); 112 113 q->next_p->prev_p = q->prev_p; 114 q->prev_p->next_p = q->next_p; 115 116 q->next_p = q->prev_p = q; 117 118 return (n); 119 120 } /* end queue_remove */ 121 122 123 /* 124 * queue_isempty() 125 */ 126 127 boolean_t queue_isempty(queue_node_t * q)128 queue_isempty(queue_node_t * q) 129 { 130 return ((q->next_p == q)); 131 132 } /* queue_isempty */ 133 134 135 /* 136 * queue_next() - returns the next element in a queue, or NULL if the 137 * supplied previous item was the last. 138 */ 139 140 queue_node_t * queue_next(queue_node_t * h,queue_node_t * q)141 queue_next(queue_node_t * h, queue_node_t * q) 142 { 143 if (!h) 144 return (NULL); 145 146 if (!q) 147 return (h); 148 149 if (q->next_p == h) 150 return (NULL); 151 152 return (q->next_p); 153 154 } /* end queue_next */ 155