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   1 /*!\file sys/queue.h
   2  *
   3  */
   4
   5 /*
   6  * Copyright (c) 1991, 1993
   7  *      The Regents of the University of California.  All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. All advertising materials mentioning features or use of this software
  18  *    must display the following acknowledgement:
  19  *      This product includes software developed by the University of
  20  *      California, Berkeley and its contributors.
  21  * 4. Neither the name of the University nor the names of its contributors
  22  *    may be used to endorse or promote products derived from this software
  23  *    without specific prior written permission.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35  * SUCH DAMAGE.
  36  *
  37  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  38  */
  39
  40 #ifndef __SYS_QUEUE_H
  41 #define __SYS_QUEUE_H
  42
  43 /*
  44  * This file defines three types of data structures: lists, tail queues,
  45  * and circular queues.
  46  *
  47  * A list is headed by a single forward pointer (or an array of forward
  48  * pointers for a hash table header). The elements are doubly linked
  49  * so that an arbitrary element can be removed without a need to
  50  * traverse the list. New elements can be added to the list before
  51  * or after an existing element or at the head of the list. A list
  52  * may only be traversed in the forward direction.
  53  *
  54  * A tail queue is headed by a pair of pointers, one to the head of the
  55  * list and the other to the tail of the list. The elements are doubly
  56  * linked so that an arbitrary element can be removed without a need to
  57  * traverse the list. New elements can be added to the list before or
  58  * after an existing element, at the head of the list, or at the end of
  59  * the list. A tail queue may only be traversed in the forward direction.
  60  *
  61  * A circle queue is headed by a pair of pointers, one to the head of the
  62  * list and the other to the tail of the list. The elements are doubly
  63  * linked so that an arbitrary element can be removed without a need to
  64  * traverse the list. New elements can be added to the list before or after
  65  * an existing element, at the head of the list, or at the end of the list.
  66  * A circle queue may be traversed in either direction, but has a more
  67  * complex end of list detection.
  68  *
  69  * For details on the use of these macros, see the queue(3) manual page.
  70  */
  71
  72 /*
  73  * List definitions.
  74  */
  75 #define LIST_HEAD(name, type)                                           \
  76 struct name {                                                           \
  77         struct type *lh_first;  /* first element */                     \
  78 }
  79
  80 #define LIST_ENTRY(type)                                                \
  81 struct {                                                                \
  82         struct type *le_next;   /* next element */                      \
  83         struct type **le_prev;  /* address of previous next element */  \
  84 }
  85
  86 /*
  87  * List functions.
  88  */
  89 #define LIST_INIT(head) {                                               \
  90         (head)->lh_first = NULL;                                        \
  91 }
  92
  93 #define LIST_INSERT_AFTER(listelm, elm, field) {                        \
  94         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
  95                 (listelm)->field.le_next->field.le_prev =               \
  96                     &(elm)->field.le_next;                              \
  97         (listelm)->field.le_next = (elm);                               \
  98         (elm)->field.le_prev = &(listelm)->field.le_next;               \
  99 }
 100
 101 #define LIST_INSERT_BEFORE(listelm, elm, field) {                       \
 102         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 103         (elm)->field.le_next = (listelm);                               \
 104         *(listelm)->field.le_prev = (elm);                              \
 105         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 106 }
 107
 108 #define LIST_INSERT_HEAD(head, elm, field) {                            \
 109         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 110                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 111         (head)->lh_first = (elm);                                       \
 112         (elm)->field.le_prev = &(head)->lh_first;                       \
 113 }
 114
 115 #define LIST_REMOVE(elm, field) {                                       \
 116         if ((elm)->field.le_next != NULL)                               \
 117                 (elm)->field.le_next->field.le_prev =                   \
 118                     (elm)->field.le_prev;                               \
 119         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 120 }
 121
 122 /*
 123  * Tail queue definitions.
 124  */
 125 #define TAILQ_HEAD(name, type)                                          \
 126 struct name {                                                           \
 127         struct type *tqh_first; /* first element */                     \
 128         struct type **tqh_last; /* addr of last next element */         \
 129 }
 130
 131 #define TAILQ_ENTRY(type)                                               \
 132 struct {                                                                \
 133         struct type *tqe_next;  /* next element */                      \
 134         struct type **tqe_prev; /* address of previous next element */  \
 135 }
 136
 137 /*
 138  * Tail queue functions.
 139  */
 140 #define TAILQ_INIT(head) {                                              \
 141         (head)->tqh_first = NULL;                                       \
 142         (head)->tqh_last = &(head)->tqh_first;                          \
 143 }
 144
 145 #define TAILQ_INSERT_HEAD(head, elm, field) {                           \
 146         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 147                 (head)->tqh_first->field.tqe_prev =                     \
 148                     &(elm)->field.tqe_next;                             \
 149         else                                                            \
 150                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 151         (head)->tqh_first = (elm);                                      \
 152         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 153 }
 154
 155 #define TAILQ_INSERT_TAIL(head, elm, field) {                           \
 156         (elm)->field.tqe_next = NULL;                                   \
 157         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 158         *(head)->tqh_last = (elm);                                      \
 159         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 160 }
 161
 162 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) {                 \
 163         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 164                 (elm)->field.tqe_next->field.tqe_prev =                 \
 165                     &(elm)->field.tqe_next;                             \
 166         else                                                            \
 167                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 168         (listelm)->field.tqe_next = (elm);                              \
 169         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 170 }
 171
 172 #define TAILQ_INSERT_BEFORE(listelm, elm, field) {                      \
 173         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 174         (elm)->field.tqe_next = (listelm);                              \
 175         *(listelm)->field.tqe_prev = (elm);                             \
 176         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 177 }
 178
 179 #define TAILQ_REMOVE(head, elm, field) {                                \
 180         if (((elm)->field.tqe_next) != NULL)                            \
 181                 (elm)->field.tqe_next->field.tqe_prev =                 \
 182                     (elm)->field.tqe_prev;                              \
 183         else                                                            \
 184                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 185         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 186 }
 187
 188 /*
 189  * Circular queue definitions.
 190  */
 191 #define CIRCLEQ_HEAD(name, type)                                        \
 192 struct name {                                                           \
 193         struct type *cqh_first;         /* first element */             \
 194         struct type *cqh_last;          /* last element */              \
 195 }
 196
 197 #define CIRCLEQ_ENTRY(type)                                             \
 198 struct {                                                                \
 199         struct type *cqe_next;          /* next element */              \
 200         struct type *cqe_prev;          /* previous element */          \
 201 }
 202
 203 /*
 204  * Circular queue functions.
 205  */
 206 #define CIRCLEQ_INIT(head) {                                            \
 207         (head)->cqh_first = (void *)(head);                             \
 208         (head)->cqh_last = (void *)(head);                              \
 209 }
 210
 211 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) {               \
 212         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 213         (elm)->field.cqe_prev = (listelm);                              \
 214         if ((listelm)->field.cqe_next == (void *)(head))                \
 215                 (head)->cqh_last = (elm);                               \
 216         else                                                            \
 217                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 218         (listelm)->field.cqe_next = (elm);                              \
 219 }
 220
 221 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) {              \
 222         (elm)->field.cqe_next = (listelm);                              \
 223         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 224         if ((listelm)->field.cqe_prev == (void *)(head))                \
 225                 (head)->cqh_first = (elm);                              \
 226         else                                                            \
 227                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 228         (listelm)->field.cqe_prev = (elm);                              \
 229 }
 230
 231 #define CIRCLEQ_INSERT_HEAD(head, elm, field) {                         \
 232         (elm)->field.cqe_next = (head)->cqh_first;                      \
 233         (elm)->field.cqe_prev = (void *)(head);                         \
 234         if ((head)->cqh_last == (void *)(head))                         \
 235                 (head)->cqh_last = (elm);                               \
 236         else                                                            \
 237                 (head)->cqh_first->field.cqe_prev = (elm);              \
 238         (head)->cqh_first = (elm);                                      \
 239 }
 240
 241 #define CIRCLEQ_INSERT_TAIL(head, elm, field) {                         \
 242         (elm)->field.cqe_next = (void *)(head);                         \
 243         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 244         if ((head)->cqh_first == (void *)(head))                        \
 245                 (head)->cqh_first = (elm);                              \
 246         else                                                            \
 247                 (head)->cqh_last->field.cqe_next = (elm);               \
 248         (head)->cqh_last = (elm);                                       \
 249 }
 250
 251 #define CIRCLEQ_REMOVE(head, elm, field) {                              \
 252         if ((elm)->field.cqe_next == (void *)(head))                    \
 253                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 254         else                                                            \
 255                 (elm)->field.cqe_next->field.cqe_prev =                 \
 256                     (elm)->field.cqe_prev;                              \
 257         if ((elm)->field.cqe_prev == (void *)(head))                    \
 258                 (head)->cqh_first = (elm)->field.cqe_next;              \
 259         else                                                            \
 260                 (elm)->field.cqe_prev->field.cqe_next =                 \
 261                     (elm)->field.cqe_next;                              \
 262 }
 263 #endif