include/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: src/sys/sys/queue.h,v 1.48 2002/04/17 14:00:37 tmm Exp $
  35  */
  36
  37 #ifndef _SYS_QUEUE_H_
  38 #define _SYS_QUEUE_H_
  39
  40 //#include <machine/ansi.h>     /* for __offsetof */
  41 #include <stddef.h>     /* for __offsetof */
  42
  43
  44
  45
  46 /*
  47  * This file defines four types of data structures: singly-linked lists,
  48  * singly-linked tail queues, lists and tail queues.
  49  *
  50  * A singly-linked list is headed by a single forward pointer. The elements
  51  * are singly linked for minimum space and pointer manipulation overhead at
  52  * the expense of O(n) removal for arbitrary elements. New elements can be
  53  * added to the list after an existing element or at the head of the list.
  54  * Elements being removed from the head of the list should use the explicit
  55  * macro for this purpose for optimum efficiency. A singly-linked list may
  56  * only be traversed in the forward direction.  Singly-linked lists are ideal
  57  * for applications with large datasets and few or no removals or for
  58  * implementing a LIFO queue.
  59  *
  60  * A singly-linked tail queue is headed by a pair of pointers, one to the
  61  * head of the list and the other to the tail of the list. The elements are
  62  * singly linked for minimum space and pointer manipulation overhead at the
  63  * expense of O(n) removal for arbitrary elements. New elements can be added
  64  * to the list after an existing element, at the head of the list, or at the
  65  * end of the list. Elements being removed from the head of the tail queue
  66  * should use the explicit macro for this purpose for optimum efficiency.
  67  * A singly-linked tail queue may only be traversed in the forward direction.
  68  * Singly-linked tail queues are ideal for applications with large datasets
  69  * and few or no removals or for implementing a FIFO queue.
  70  *
  71  * A list is headed by a single forward pointer (or an array of forward
  72  * pointers for a hash table header). The elements are doubly linked
  73  * so that an arbitrary element can be removed without a need to
  74  * traverse the list. New elements can be added to the list before
  75  * or after an existing element or at the head of the list. A list
  76  * may only be traversed in the forward direction.
  77  *
  78  * A tail queue is headed by a pair of pointers, one to the head of the
  79  * list and the other to the tail of the list. The elements are doubly
  80  * linked so that an arbitrary element can be removed without a need to
  81  * traverse the list. New elements can be added to the list before or
  82  * after an existing element, at the head of the list, or at the end of
  83  * the list. A tail queue may be traversed in either direction.
  84  *
  85  * For details on the use of these macros, see the queue(3) manual page.
  86  *
  87  *
  88  *                      SLIST   LIST    STAILQ  TAILQ
  89  * _HEAD                +       +       +       +
  90  * _HEAD_INITIALIZER    +       +       +       +
  91  * _ENTRY               +       +       +       +
  92  * _INIT                +       +       +       +
  93  * _EMPTY               +       +       +       +
  94  * _FIRST               +       +       +       +
  95  * _NEXT                +       +       +       +
  96  * _PREV                -       -       -       +
  97  * _LAST                -       -       +       +
  98  * _FOREACH             +       +       +       +
  99  * _FOREACH_REVERSE     -       -       -       +
 100  * _INSERT_HEAD         +       +       +       +
 101  * _INSERT_BEFORE       -       +       -       +
 102  * _INSERT_AFTER        +       +       +       +
 103  * _INSERT_TAIL         -       -       +       +
 104  * _CONCAT              -       -       +       +
 105  * _REMOVE_HEAD         +       -       +       -
 106  * _REMOVE              +       +       +       +
 107  *
 108  */
 109
 110 /*
 111  * Singly-linked List declarations.
 112  */
 113 #define SLIST_HEAD(name, type)                                          \
 114 struct name {                                                           \
 115         struct type *slh_first; /* first element */                     \
 116 }
 117
 118 #define SLIST_HEAD_INITIALIZER(head)                                    \
 119         { NULL }
 120
 121 #define SLIST_ENTRY(type)                                               \
 122 struct {                                                                \
 123         struct type *sle_next;  /* next element */                      \
 124 }
 125
 126 /*
 127  * Singly-linked List functions.
 128  */
 129 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 130
 131 #define SLIST_FIRST(head)       ((head)->slh_first)
 132
 133 #define SLIST_FOREACH(var, head, field)                                 \
 134         for ((var) = SLIST_FIRST((head));                               \
 135             (var);                                                      \
 136             (var) = SLIST_NEXT((var), field))
 137
 138 #define SLIST_INIT(head) do {                                           \
 139         SLIST_FIRST((head)) = NULL;                                     \
 140 } while (0)
 141
 142 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 143         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 144         SLIST_NEXT((slistelm), field) = (elm);                          \
 145 } while (0)
 146
 147 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 148         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 149         SLIST_FIRST((head)) = (elm);                                    \
 150 } while (0)
 151
 152 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 153
 154 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 155         if (SLIST_FIRST((head)) == (elm)) {                             \
 156                 SLIST_REMOVE_HEAD((head), field);                       \
 157         }                                                               \
 158         else {                                                          \
 159                 struct type *curelm = SLIST_FIRST((head));              \
 160                 while (SLIST_NEXT(curelm, field) != (elm))              \
 161                         curelm = SLIST_NEXT(curelm, field);             \
 162                 SLIST_NEXT(curelm, field) =                             \
 163                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
 164         }                                                               \
 165 } while (0)
 166
 167 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 168         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 169 } while (0)
 170
 171 /*
 172  * Singly-linked Tail queue declarations.
 173  */
 174 #define STAILQ_HEAD(name, type)                                         \
 175 struct name {                                                           \
 176         struct type *stqh_first;/* first element */                     \
 177         struct type **stqh_last;/* addr of last next element */         \
 178 }
 179
 180 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 181         { NULL, &(head).stqh_first }
 182
 183 #define STAILQ_ENTRY(type)                                              \
 184 struct {                                                                \
 185         struct type *stqe_next; /* next element */                      \
 186 }
 187
 188 /*
 189  * Singly-linked Tail queue functions.
 190  */
 191 #define STAILQ_CONCAT(head1, head2) do {                                \
 192         if (!STAILQ_EMPTY((head2))) {                                   \
 193                 *(head1)->stqh_last = (head2)->stqh_first;              \
 194                 (head1)->stqh_last = (head2)->stqh_last;                \
 195                 STAILQ_INIT((head2));                                   \
 196         }                                                               \
 197 } while (0)
 198
 199 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 200
 201 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 202
 203 #define STAILQ_FOREACH(var, head, field)                                \
 204         for((var) = STAILQ_FIRST((head));                               \
 205            (var);                                                       \
 206            (var) = STAILQ_NEXT((var), field))
 207
 208 #define STAILQ_INIT(head) do {                                          \
 209         STAILQ_FIRST((head)) = NULL;                                    \
 210         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 211 } while (0)
 212
 213 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 214         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 215                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 216         STAILQ_NEXT((tqelm), field) = (elm);                            \
 217 } while (0)
 218
 219 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 220         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 221                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 222         STAILQ_FIRST((head)) = (elm);                                   \
 223 } while (0)
 224
 225 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 226         STAILQ_NEXT((elm), field) = NULL;                               \
 227         *(head)->stqh_last = (elm);                                     \
 228         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 229 } while (0)
 230
 231 #define STAILQ_LAST(head, type, field)                                  \
 232         (STAILQ_EMPTY((head)) ?                                         \
 233                 NULL :                                                  \
 234                 ((struct type *)                                        \
 235                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 236
 237 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 238
 239 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 240         if (STAILQ_FIRST((head)) == (elm)) {                            \
 241                 STAILQ_REMOVE_HEAD((head), field);                      \
 242         }                                                               \
 243         else {                                                          \
 244                 struct type *curelm = STAILQ_FIRST((head));             \
 245                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 246                         curelm = STAILQ_NEXT(curelm, field);            \
 247                 if ((STAILQ_NEXT(curelm, field) =                       \
 248                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
 249                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
 250         }                                                               \
 251 } while (0)
 252
 253 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 254         if ((STAILQ_FIRST((head)) =                                     \
 255              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 256                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 257 } while (0)
 258
 259 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 260         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
 261                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 262 } while (0)
 263
 264 /*
 265  * List declarations.
 266  */
 267 #define LIST_HEAD(name, type)                                           \
 268 struct name {                                                           \
 269         struct type *lh_first;  /* first element */                     \
 270 }
 271
 272 #define LIST_HEAD_INITIALIZER(head)                                     \
 273         { NULL }
 274
 275 #define LIST_ENTRY(type)                                                \
 276 struct {                                                                \
 277         struct type *le_next;   /* next element */                      \
 278         struct type **le_prev;  /* address of previous next element */  \
 279 }
 280
 281 /*
 282  * List functions.
 283  */
 284
 285 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 286
 287 #define LIST_FIRST(head)        ((head)->lh_first)
 288
 289 #define LIST_FOREACH(var, head, field)                                  \
 290         for ((var) = LIST_FIRST((head));                                \
 291             (var);                                                      \
 292             (var) = LIST_NEXT((var), field))
 293
 294 #define LIST_INIT(head) do {                                            \
 295         LIST_FIRST((head)) = NULL;                                      \
 296 } while (0)
 297
 298 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 299         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 300                 LIST_NEXT((listelm), field)->field.le_prev =            \
 301                     &LIST_NEXT((elm), field);                           \
 302         LIST_NEXT((listelm), field) = (elm);                            \
 303         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 304 } while (0)
 305
 306 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 307         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 308         LIST_NEXT((elm), field) = (listelm);                            \
 309         *(listelm)->field.le_prev = (elm);                              \
 310         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 311 } while (0)
 312
 313 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 314         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 315                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 316         LIST_FIRST((head)) = (elm);                                     \
 317         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 318 } while (0)
 319
 320 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 321
 322 #define LIST_REMOVE(elm, field) do {                                    \
 323         if (LIST_NEXT((elm), field) != NULL)                            \
 324                 LIST_NEXT((elm), field)->field.le_prev =                \
 325                     (elm)->field.le_prev;                               \
 326         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 327 } while (0)
 328
 329 /*
 330  * Tail queue declarations.
 331  */
 332 #define TAILQ_HEAD(name, type)                                          \
 333 struct name {                                                           \
 334         struct type *tqh_first; /* first element */                     \
 335         struct type **tqh_last; /* addr of last next element */         \
 336 }
 337
 338 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 339         { NULL, &(head).tqh_first }
 340
 341 #define TAILQ_ENTRY(type)                                               \
 342 struct {                                                                \
 343         struct type *tqe_next;  /* next element */                      \
 344         struct type **tqe_prev; /* address of previous next element */  \
 345 }
 346
 347 /*
 348  * Tail queue functions.
 349  */
 350 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 351         if (!TAILQ_EMPTY(head2)) {                                      \
 352                 *(head1)->tqh_last = (head2)->tqh_first;                \
 353                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 354                 (head1)->tqh_last = (head2)->tqh_last;                  \
 355                 TAILQ_INIT((head2));                                    \
 356         }                                                               \
 357 } while (0)
 358
 359 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 360
 361 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 362
 363 #define TAILQ_FOREACH(var, head, field)                                 \
 364         for ((var) = TAILQ_FIRST((head));                               \
 365             (var);                                                      \
 366             (var) = TAILQ_NEXT((var), field))
 367
 368 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 369         for ((var) = TAILQ_LAST((head), headname);                      \
 370             (var);                                                      \
 371             (var) = TAILQ_PREV((var), headname, field))
 372
 373 #define TAILQ_INIT(head) do {                                           \
 374         TAILQ_FIRST((head)) = NULL;                                     \
 375         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 376 } while (0)
 377
 378 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 379         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 380                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 381                     &TAILQ_NEXT((elm), field);                          \
 382         else                                                            \
 383                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 384         TAILQ_NEXT((listelm), field) = (elm);                           \
 385         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 386 } while (0)
 387
 388 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 389         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 390         TAILQ_NEXT((elm), field) = (listelm);                           \
 391         *(listelm)->field.tqe_prev = (elm);                             \
 392         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 393 } while (0)
 394
 395 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 396         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 397                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 398                     &TAILQ_NEXT((elm), field);                          \
 399         else                                                            \
 400                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 401         TAILQ_FIRST((head)) = (elm);                                    \
 402         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 403 } while (0)
 404
 405 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 406         TAILQ_NEXT((elm), field) = NULL;                                \
 407         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 408         *(head)->tqh_last = (elm);                                      \
 409         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 410 } while (0)
 411
 412 #define TAILQ_LAST(head, headname)                                      \
 413         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 414
 415 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 416
 417 #define TAILQ_PREV(elm, headname, field)                                \
 418         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 419
 420 #define TAILQ_REMOVE(head, elm, field) do {                             \
 421         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 422                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 423                     (elm)->field.tqe_prev;                              \
 424         else                                                            \
 425                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 426         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 427 } while (0)
 428
 429
 430 #ifdef _KERNEL
 431
 432 /*
 433  * XXX insque() and remque() are an old way of handling certain queues.
 434  * They bogusly assumes that all queue heads look alike.
 435  */
 436
 437 struct quehead {
 438         struct quehead *qh_link;
 439         struct quehead *qh_rlink;
 440 };
 441
 442 #ifdef  __GNUC__
 443
 444 static __inline void
 445 insque(void *a, void *b)
 446 {
 447         struct quehead *element = (struct quehead *)a,
 448                  *head = (struct quehead *)b;
 449
 450         element->qh_link = head->qh_link;
 451         element->qh_rlink = head;
 452         head->qh_link = element;
 453         element->qh_link->qh_rlink = element;
 454 }
 455
 456 static __inline void
 457 remque(void *a)
 458 {
 459         struct quehead *element = (struct quehead *)a;
 460
 461         element->qh_link->qh_rlink = element->qh_rlink;
 462         element->qh_rlink->qh_link = element->qh_link;
 463         element->qh_rlink = 0;
 464 }
 465
 466 #else /* !__GNUC__ */
 467
 468 void    insque(void *a, void *b);
 469 void    remque(void *a);
 470
 471 #endif /* __GNUC__ */
 472
 473 #endif /* _KERNEL */
 474
 475 #endif /* !_SYS_QUEUE_H_ */