dbm/include/queue.h

   1 /*
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. ***REMOVED*** - see
  14  *    ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change
  15  * 4. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  *      @(#)queue.h     8.3 (Berkeley) 12/13/93
  32  */
  33
  34 #ifndef _QUEUE_H_
  35 #define _QUEUE_H_
  36
  37 /*
  38  * This file defines three types of data structures: lists, tail queues,
  39  * and circular queues.
  40  *
  41  * A list is headed by a single forward pointer (or an array of forward
  42  * pointers for a hash table header). The elements are doubly linked
  43  * so that an arbitrary element can be removed without a need to
  44  * traverse the list. New elements can be added to the list after
  45  * an existing element or at the head of the list. A list may only be
  46  * traversed in the forward direction.
  47  *
  48  * A tail queue is headed by a pair of pointers, one to the head of the
  49  * list and the other to the tail of the list. The elements are doubly
  50  * linked so that an arbitrary element can be removed without a need to
  51  * traverse the list. New elements can be added to the list after
  52  * an existing element, at the head of the list, or at the end of the
  53  * list. A tail queue may only be traversed in the forward direction.
  54  *
  55  * A circle queue is headed by a pair of pointers, one to the head of the
  56  * list and the other to the tail of the list. The elements are doubly
  57  * linked so that an arbitrary element can be removed without a need to
  58  * traverse the list. New elements can be added to the list before or after
  59  * an existing element, at the head of the list, or at the end of the list.
  60  * A circle queue may be traversed in either direction, but has a more
  61  * complex end of list detection.
  62  *
  63  * For details on the use of these macros, see the queue(3) manual page.
  64  */
  65
  66 /*
  67  * List definitions.
  68  */
  69 #define LIST_HEAD(name, type)                                           \
  70 struct name {                                                           \
  71         struct type *lh_first;  /* first element */                     \
  72 }
  73
  74 #define LIST_ENTRY(type)                                                \
  75 struct {                                                                \
  76         struct type *le_next;   /* next element */                      \
  77         struct type **le_prev;  /* address of previous next element */  \
  78 }
  79
  80 /*
  81  * List functions.
  82  */
  83 #define LIST_INIT(head) {                                               \
  84         (head)->lh_first = NULL;                                        \
  85 }
  86
  87 #define LIST_INSERT_AFTER(listelm, elm, field) {                        \
  88         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
  89                 (listelm)->field.le_next->field.le_prev =               \
  90                     &(elm)->field.le_next;                              \
  91         (listelm)->field.le_next = (elm);                               \
  92         (elm)->field.le_prev = &(listelm)->field.le_next;               \
  93 }
  94
  95 #define LIST_INSERT_HEAD(head, elm, field) {                            \
  96         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
  97                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
  98         (head)->lh_first = (elm);                                       \
  99         (elm)->field.le_prev = &(head)->lh_first;                       \
 100 }
 101
 102 #define LIST_REMOVE(elm, field) {                                       \
 103         if ((elm)->field.le_next != NULL)                               \
 104                 (elm)->field.le_next->field.le_prev =                   \
 105                     (elm)->field.le_prev;                               \
 106         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 107 }
 108
 109 /*
 110  * Tail queue definitions.
 111  */
 112 #define TAILQ_HEAD(name, type)                                          \
 113 struct name {                                                           \
 114         struct type *tqh_first; /* first element */                     \
 115         struct type **tqh_last; /* addr of last next element */         \
 116 }
 117
 118 #define TAILQ_ENTRY(type)                                               \
 119 struct {                                                                \
 120         struct type *tqe_next;  /* next element */                      \
 121         struct type **tqe_prev; /* address of previous next element */  \
 122 }
 123
 124 /*
 125  * Tail queue functions.
 126  */
 127 #define TAILQ_INIT(head) {                                              \
 128         (head)->tqh_first = NULL;                                       \
 129         (head)->tqh_last = &(head)->tqh_first;                          \
 130 }
 131
 132 #define TAILQ_INSERT_HEAD(head, elm, field) {                           \
 133         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 134                 (elm)->field.tqe_next->field.tqe_prev =                 \
 135                     &(elm)->field.tqe_next;                             \
 136         else                                                            \
 137                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 138         (head)->tqh_first = (elm);                                      \
 139         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 140 }
 141
 142 #define TAILQ_INSERT_TAIL(head, elm, field) {                           \
 143         (elm)->field.tqe_next = NULL;                                   \
 144         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 145         *(head)->tqh_last = (elm);                                      \
 146         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 147 }
 148
 149 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) {                 \
 150         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 151                 (elm)->field.tqe_next->field.tqe_prev =                 \
 152                     &(elm)->field.tqe_next;                             \
 153         else                                                            \
 154                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 155         (listelm)->field.tqe_next = (elm);                              \
 156         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 157 }
 158
 159 #define TAILQ_REMOVE(head, elm, field) {                                \
 160         if (((elm)->field.tqe_next) != NULL)                            \
 161                 (elm)->field.tqe_next->field.tqe_prev =                 \
 162                     (elm)->field.tqe_prev;                              \
 163         else                                                            \
 164                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 165         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 166 }
 167
 168 /*
 169  * Circular queue definitions.
 170  */
 171 #define CIRCLEQ_HEAD(name, type)                                        \
 172 struct name {                                                           \
 173         struct type *cqh_first;         /* first element */             \
 174         struct type *cqh_last;          /* last element */              \
 175 }
 176
 177 #define CIRCLEQ_ENTRY(type)                                             \
 178 struct {                                                                \
 179         struct type *cqe_next;          /* next element */              \
 180         struct type *cqe_prev;          /* previous element */          \
 181 }
 182
 183 /*
 184  * Circular queue functions.
 185  */
 186 #define CIRCLEQ_INIT(head) {                                            \
 187         (head)->cqh_first = (void *)(head);                             \
 188         (head)->cqh_last = (void *)(head);                              \
 189 }
 190
 191 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) {               \
 192         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 193         (elm)->field.cqe_prev = (listelm);                              \
 194         if ((listelm)->field.cqe_next == (void *)(head))                \
 195                 (head)->cqh_last = (elm);                               \
 196         else                                                            \
 197                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 198         (listelm)->field.cqe_next = (elm);                              \
 199 }
 200
 201 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) {              \
 202         (elm)->field.cqe_next = (listelm);                              \
 203         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 204         if ((listelm)->field.cqe_prev == (void *)(head))                \
 205                 (head)->cqh_first = (elm);                              \
 206         else                                                            \
 207                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 208         (listelm)->field.cqe_prev = (elm);                              \
 209 }
 210
 211 #define CIRCLEQ_INSERT_HEAD(head, elm, field) {                         \
 212         (elm)->field.cqe_next = (head)->cqh_first;                      \
 213         (elm)->field.cqe_prev = (void *)(head);                         \
 214         if ((head)->cqh_last == (void *)(head))                         \
 215                 (head)->cqh_last = (elm);                               \
 216         else                                                            \
 217                 (head)->cqh_first->field.cqe_prev = (elm);              \
 218         (head)->cqh_first = (elm);                                      \
 219 }
 220
 221 #define CIRCLEQ_INSERT_TAIL(head, elm, field) {                         \
 222         (elm)->field.cqe_next = (void *)(head);                         \
 223         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 224         if ((head)->cqh_first == (void *)(head))                        \
 225                 (head)->cqh_first = (elm);                              \
 226         else                                                            \
 227                 (head)->cqh_last->field.cqe_next = (elm);               \
 228         (head)->cqh_last = (elm);                                       \
 229 }
 230
 231 #define CIRCLEQ_REMOVE(head, elm, field) {                              \
 232         if ((elm)->field.cqe_next == (void *)(head))                    \
 233                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 234         else                                                            \
 235                 (elm)->field.cqe_next->field.cqe_prev =                 \
 236                     (elm)->field.cqe_prev;                              \
 237         if ((elm)->field.cqe_prev == (void *)(head))                    \
 238                 (head)->cqh_first = (elm)->field.cqe_next;              \
 239         else                                                            \
 240                 (elm)->field.cqe_prev->field.cqe_next =                 \
 241                     (elm)->field.cqe_next;                              \
 242 }
 243 #endif  /* !_QUEUE_H_ */