sys/sys/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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  34  * $FreeBSD$
  35  */
  36
  37 #ifndef _SYS_QUEUE_H_
  38 #define _SYS_QUEUE_H_
  39
  40 #include <machine/ansi.h>       /* for __offsetof */
  41
  42 /*
  43  * This file defines five types of data structures: singly-linked lists,
  44  * singly-linked tail queues, lists, tail queues, and circular queues.
  45  *
  46  * A singly-linked list is headed by a single forward pointer. The elements
  47  * are singly linked for minimum space and pointer manipulation overhead at
  48  * the expense of O(n) removal for arbitrary elements. New elements can be
  49  * added to the list after an existing element or at the head of the list.
  50  * Elements being removed from the head of the list should use the explicit
  51  * macro for this purpose for optimum efficiency. A singly-linked list may
  52  * only be traversed in the forward direction.  Singly-linked lists are ideal
  53  * for applications with large datasets and few or no removals or for
  54  * implementing a LIFO queue.
  55  *
  56  * A singly-linked tail queue is headed by a pair of pointers, one to the
  57  * head of the list and the other to the tail of the list. The elements are
  58  * singly linked for minimum space and pointer manipulation overhead at the
  59  * expense of O(n) removal for arbitrary elements. New elements can be added
  60  * to the list after an existing element, at the head of the list, or at the
  61  * end of the list. Elements being removed from the head of the tail queue
  62  * should use the explicit macro for this purpose for optimum efficiency.
  63  * A singly-linked tail queue may only be traversed in the forward direction.
  64  * Singly-linked tail queues are ideal for applications with large datasets
  65  * and few or no removals or for implementing a FIFO queue.
  66  *
  67  * A list is headed by a single forward pointer (or an array of forward
  68  * pointers for a hash table header). The elements are doubly linked
  69  * so that an arbitrary element can be removed without a need to
  70  * traverse the list. New elements can be added to the list before
  71  * or after an existing element or at the head of the list. A list
  72  * may only be traversed in the forward direction.
  73  *
  74  * A tail queue is headed by a pair of pointers, one to the head of the
  75  * list and the other to the tail of the list. The elements are doubly
  76  * linked so that an arbitrary element can be removed without a need to
  77  * traverse the list. New elements can be added to the list before or
  78  * after an existing element, at the head of the list, or at the end of
  79  * the list. A tail queue may be traversed in either direction.
  80  *
  81  * For details on the use of these macros, see the queue(3) manual page.
  82  *
  83  *
  84  *                      SLIST   LIST    STAILQ  TAILQ
  85  * _HEAD                +       +       +       +
  86  * _HEAD_INITIALIZER    +       +       +       +
  87  * _ENTRY               +       +       +       +
  88  * _INIT                +       +       +       +
  89  * _EMPTY               +       +       +       +
  90  * _FIRST               +       +       +       +
  91  * _NEXT                +       +       +       +
  92  * _PREV                -       -       -       +
  93  * _LAST                -       -       +       +
  94  * _FOREACH             +       +       +       +
  95  * _FOREACH_REVERSE     -       -       -       +
  96  * _INSERT_HEAD         +       +       +       +
  97  * _INSERT_BEFORE       -       +       -       +
  98  * _INSERT_AFTER        +       +       +       +
  99  * _INSERT_TAIL         -       -       +       +
 100  * _REMOVE_HEAD         +       -       +       -
 101  * _REMOVE              +       +       +       +
 102  *
 103  */
 104
 105 /*
 106  * Singly-linked List declarations.
 107  */
 108 #define SLIST_HEAD(name, type)                                          \
 109 struct name {                                                           \
 110         struct type *slh_first; /* first element */                     \
 111 }
 112
 113 #define SLIST_HEAD_INITIALIZER(head)                                    \
 114         { NULL }
 115
 116 #define SLIST_ENTRY(type)                                               \
 117 struct {                                                                \
 118         struct type *sle_next;  /* next element */                      \
 119 }
 120
 121 /*
 122  * Singly-linked List functions.
 123  */
 124 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 125
 126 #define SLIST_FIRST(head)       ((head)->slh_first)
 127
 128 #define SLIST_FOREACH(var, head, field)                                 \
 129         for ((var) = SLIST_FIRST((head));                               \
 130             (var);                                                      \
 131             (var) = SLIST_NEXT((var), field))
 132
 133 #define SLIST_INIT(head) do {                                           \
 134         SLIST_FIRST((head)) = NULL;                                     \
 135 } while (0)
 136
 137 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 138         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 139         SLIST_NEXT((slistelm), field) = (elm);                          \
 140 } while (0)
 141
 142 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 143         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 144         SLIST_FIRST((head)) = (elm);                                    \
 145 } while (0)
 146
 147 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 148
 149 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 150         if (SLIST_FIRST((head)) == (elm)) {                             \
 151                 SLIST_REMOVE_HEAD((head), field);                       \
 152         }                                                               \
 153         else {                                                          \
 154                 struct type *curelm = SLIST_FIRST((head));              \
 155                 while (SLIST_NEXT(curelm, field) != (elm))              \
 156                         curelm = SLIST_NEXT(curelm, field);             \
 157                 SLIST_NEXT(curelm, field) =                             \
 158                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
 159         }                                                               \
 160 } while (0)
 161
 162 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 163         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 164 } while (0)
 165
 166 /*
 167  * Singly-linked Tail queue declarations.
 168  */
 169 #define STAILQ_HEAD(name, type)                                         \
 170 struct name {                                                           \
 171         struct type *stqh_first;/* first element */                     \
 172         struct type **stqh_last;/* addr of last next element */         \
 173 }
 174
 175 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 176         { NULL, &(head).stqh_first }
 177
 178 #define STAILQ_ENTRY(type)                                              \
 179 struct {                                                                \
 180         struct type *stqe_next; /* next element */                      \
 181 }
 182
 183 /*
 184  * Singly-linked Tail queue functions.
 185  */
 186 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 187
 188 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 189
 190 #define STAILQ_FOREACH(var, head, field)                                \
 191         for((var) = STAILQ_FIRST((head));                               \
 192            (var);                                                       \
 193            (var) = STAILQ_NEXT((var), field))
 194
 195 #define STAILQ_INIT(head) do {                                          \
 196         STAILQ_FIRST((head)) = NULL;                                    \
 197         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 198 } while (0)
 199
 200 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 201         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 202                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 203         STAILQ_NEXT((tqelm), field) = (elm);                            \
 204 } while (0)
 205
 206 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 207         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 208                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 209         STAILQ_FIRST((head)) = (elm);                                   \
 210 } while (0)
 211
 212 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 213         STAILQ_NEXT((elm), field) = NULL;                               \
 214         *(head)->stqh_last = (elm);                                     \
 215         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 216 } while (0)
 217
 218 #define STAILQ_LAST(head, type, field)                                  \
 219         (STAILQ_EMPTY(head) ?                                           \
 220                 NULL :                                                  \
 221                 ((struct type *)                                        \
 222                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 223
 224 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 225
 226 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 227         if (STAILQ_FIRST((head)) == (elm)) {                            \
 228                 STAILQ_REMOVE_HEAD(head, field);                        \
 229         }                                                               \
 230         else {                                                          \
 231                 struct type *curelm = STAILQ_FIRST((head));             \
 232                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 233                         curelm = STAILQ_NEXT(curelm, field);            \
 234                 if ((STAILQ_NEXT(curelm, field) =                       \
 235                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
 236                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
 237         }                                                               \
 238 } while (0)
 239
 240 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 241         if ((STAILQ_FIRST((head)) =                                     \
 242              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 243                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 244 } while (0)
 245
 246 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 247         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
 248                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 249 } while (0)
 250
 251 /*
 252  * List declarations.
 253  */
 254 #define LIST_HEAD(name, type)                                           \
 255 struct name {                                                           \
 256         struct type *lh_first;  /* first element */                     \
 257 }
 258
 259 #define LIST_HEAD_INITIALIZER(head)                                     \
 260         { NULL }
 261
 262 #define LIST_ENTRY(type)                                                \
 263 struct {                                                                \
 264         struct type *le_next;   /* next element */                      \
 265         struct type **le_prev;  /* address of previous next element */  \
 266 }
 267
 268 /*
 269  * List functions.
 270  */
 271
 272 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 273
 274 #define LIST_FIRST(head)        ((head)->lh_first)
 275
 276 #define LIST_FOREACH(var, head, field)                                  \
 277         for ((var) = LIST_FIRST((head));                                \
 278             (var);                                                      \
 279             (var) = LIST_NEXT((var), field))
 280
 281 #define LIST_INIT(head) do {                                            \
 282         LIST_FIRST((head)) = NULL;                                      \
 283 } while (0)
 284
 285 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 286         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 287                 LIST_NEXT((listelm), field)->field.le_prev =            \
 288                     &LIST_NEXT((elm), field);                           \
 289         LIST_NEXT((listelm), field) = (elm);                            \
 290         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 291 } while (0)
 292
 293 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 294         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 295         LIST_NEXT((elm), field) = (listelm);                            \
 296         *(listelm)->field.le_prev = (elm);                              \
 297         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 298 } while (0)
 299
 300 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 301         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 302                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 303         LIST_FIRST((head)) = (elm);                                     \
 304         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 305 } while (0)
 306
 307 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 308
 309 #define LIST_REMOVE(elm, field) do {                                    \
 310         if (LIST_NEXT((elm), field) != NULL)                            \
 311                 LIST_NEXT((elm), field)->field.le_prev =                \
 312                     (elm)->field.le_prev;                               \
 313         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 314 } while (0)
 315
 316 /*
 317  * Tail queue declarations.
 318  */
 319 #define TAILQ_HEAD(name, type)                                          \
 320 struct name {                                                           \
 321         struct type *tqh_first; /* first element */                     \
 322         struct type **tqh_last; /* addr of last next element */         \
 323 }
 324
 325 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 326         { NULL, &(head).tqh_first }
 327
 328 #define TAILQ_ENTRY(type)                                               \
 329 struct {                                                                \
 330         struct type *tqe_next;  /* next element */                      \
 331         struct type **tqe_prev; /* address of previous next element */  \
 332 }
 333
 334 /*
 335  * Tail queue functions.
 336  */
 337 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 338
 339 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 340
 341 #define TAILQ_FOREACH(var, head, field)                                 \
 342         for ((var) = TAILQ_FIRST((head));                               \
 343             (var);                                                      \
 344             (var) = TAILQ_NEXT((var), field))
 345
 346 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 347         for ((var) = TAILQ_LAST((head), headname);                      \
 348             (var);                                                      \
 349             (var) = TAILQ_PREV((var), headname, field))
 350
 351 #define TAILQ_INIT(head) do {                                           \
 352         TAILQ_FIRST((head)) = NULL;                                     \
 353         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 354 } while (0)
 355
 356 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 357         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 358                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 359                     &TAILQ_NEXT((elm), field);                          \
 360         else                                                            \
 361                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 362         TAILQ_NEXT((listelm), field) = (elm);                           \
 363         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 364 } while (0)
 365
 366 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 367         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 368         TAILQ_NEXT((elm), field) = (listelm);                           \
 369         *(listelm)->field.tqe_prev = (elm);                             \
 370         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 371 } while (0)
 372
 373 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 374         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 375                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 376                     &TAILQ_NEXT((elm), field);                          \
 377         else                                                            \
 378                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 379         TAILQ_FIRST((head)) = (elm);                                    \
 380         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 381 } while (0)
 382
 383 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 384         TAILQ_NEXT((elm), field) = NULL;                                \
 385         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 386         *(head)->tqh_last = (elm);                                      \
 387         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 388 } while (0)
 389
 390 #define TAILQ_LAST(head, headname)                                      \
 391         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 392
 393 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 394
 395 #define TAILQ_PREV(elm, headname, field)                                \
 396         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 397
 398 #define TAILQ_REMOVE(head, elm, field) do {                             \
 399         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 400                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 401                     (elm)->field.tqe_prev;                              \
 402         else                                                            \
 403                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 404         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 405 } while (0)
 406
 407
 408 #ifdef _KERNEL
 409
 410 /*
 411  * XXX insque() and remque() are an old way of handling certain queues.
 412  * They bogusly assumes that all queue heads look alike.
 413  */
 414
 415 struct quehead {
 416         struct quehead *qh_link;
 417         struct quehead *qh_rlink;
 418 };
 419
 420 #ifdef  __GNUC__
 421
 422 static __inline void
 423 insque(void *a, void *b)
 424 {
 425         struct quehead *element = a, *head = b;
 426
 427         element->qh_link = head->qh_link;
 428         element->qh_rlink = head;
 429         head->qh_link = element;
 430         element->qh_link->qh_rlink = element;
 431 }
 432
 433 static __inline void
 434 remque(void *a)
 435 {
 436         struct quehead *element = a;
 437
 438         element->qh_link->qh_rlink = element->qh_rlink;
 439         element->qh_rlink->qh_link = element->qh_link;
 440         element->qh_rlink = 0;
 441 }
 442
 443 #else /* !__GNUC__ */
 444
 445 void    insque __P((void *a, void *b));
 446 void    remque __P((void *a));
 447
 448 #endif /* __GNUC__ */
 449
 450 #endif /* _KERNEL */
 451
 452 #endif /* !_SYS_QUEUE_H_ */