contrib/openbsm/compat/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  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  30  *
  31  * Derived from FreeBSD src/sys/sys/queue.h:1.63.
  32  */
  33
  34 #ifndef _COMPAT_QUEUE_H_
  35 #define _COMPAT_QUEUE_H_
  36
  37 #include <sys/cdefs.h>
  38
  39 /*
  40  * This file defines four types of data structures: singly-linked lists,
  41  * singly-linked tail queues, lists and tail queues.
  42  *
  43  * A singly-linked list is headed by a single forward pointer. The elements
  44  * are singly linked for minimum space and pointer manipulation overhead at
  45  * the expense of O(n) removal for arbitrary elements. New elements can be
  46  * added to the list after an existing element or at the head of the list.
  47  * Elements being removed from the head of the list should use the explicit
  48  * macro for this purpose for optimum efficiency. A singly-linked list may
  49  * only be traversed in the forward direction.  Singly-linked lists are ideal
  50  * for applications with large datasets and few or no removals or for
  51  * implementing a LIFO queue.
  52  *
  53  * A singly-linked tail queue is headed by a pair of pointers, one to the
  54  * head of the list and the other to the tail of the list. The elements are
  55  * singly linked for minimum space and pointer manipulation overhead at the
  56  * expense of O(n) removal for arbitrary elements. New elements can be added
  57  * to the list after an existing element, at the head of the list, or at the
  58  * end of the list. Elements being removed from the head of the tail queue
  59  * should use the explicit macro for this purpose for optimum efficiency.
  60  * A singly-linked tail queue may only be traversed in the forward direction.
  61  * Singly-linked tail queues are ideal for applications with large datasets
  62  * and few or no removals or for implementing a FIFO queue.
  63  *
  64  * A list is headed by a single forward pointer (or an array of forward
  65  * pointers for a hash table header). The elements are doubly linked
  66  * so that an arbitrary element can be removed without a need to
  67  * traverse the list. New elements can be added to the list before
  68  * or after an existing element or at the head of the list. A list
  69  * may only be traversed in the forward direction.
  70  *
  71  * A tail queue is headed by a pair of pointers, one to the head of the
  72  * list and the other to the tail of the list. The elements are doubly
  73  * linked 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 or
  75  * after an existing element, at the head of the list, or at the end of
  76  * the list. A tail queue may be traversed in either direction.
  77  *
  78  * For details on the use of these macros, see the queue(3) manual page.
  79  *
  80  *
  81  *                              SLIST   LIST    STAILQ  TAILQ
  82  * _HEAD                        +       +       +       +
  83  * _HEAD_INITIALIZER            +       +       +       +
  84  * _ENTRY                       +       +       +       +
  85  * _INIT                        +       +       +       +
  86  * _EMPTY                       +       +       +       +
  87  * _FIRST                       +       +       +       +
  88  * _NEXT                        +       +       +       +
  89  * _PREV                        -       -       -       +
  90  * _LAST                        -       -       +       +
  91  * _FOREACH                     +       +       +       +
  92  * _FOREACH_SAFE                +       +       +       +
  93  * _FOREACH_REVERSE             -       -       -       +
  94  * _FOREACH_REVERSE_SAFE        -       -       -       +
  95  * _INSERT_HEAD                 +       +       +       +
  96  * _INSERT_BEFORE               -       +       -       +
  97  * _INSERT_AFTER                +       +       +       +
  98  * _INSERT_TAIL                 -       -       +       +
  99  * _CONCAT                      -       -       +       +
 100  * _REMOVE_HEAD                 +       -       +       -
 101  * _REMOVE                      +       +       +       +
 102  *
 103  */
 104 #ifdef QUEUE_MACRO_DEBUG
 105 /* Store the last 2 places the queue element or head was altered */
 106 struct qm_trace {
 107         char * lastfile;
 108         int lastline;
 109         char * prevfile;
 110         int prevline;
 111 };
 112
 113 #define TRACEBUF        struct qm_trace trace;
 114 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 115
 116 #define QMD_TRACE_HEAD(head) do {                                       \
 117         (head)->trace.prevline = (head)->trace.lastline;                \
 118         (head)->trace.prevfile = (head)->trace.lastfile;                \
 119         (head)->trace.lastline = __LINE__;                              \
 120         (head)->trace.lastfile = __FILE__;                              \
 121 } while (0)
 122
 123 #define QMD_TRACE_ELEM(elem) do {                                       \
 124         (elem)->trace.prevline = (elem)->trace.lastline;                \
 125         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 126         (elem)->trace.lastline = __LINE__;                              \
 127         (elem)->trace.lastfile = __FILE__;                              \
 128 } while (0)
 129
 130 #else
 131 #define QMD_TRACE_ELEM(elem)
 132 #define QMD_TRACE_HEAD(head)
 133 #define TRACEBUF
 134 #define TRASHIT(x)
 135 #endif  /* QUEUE_MACRO_DEBUG */
 136
 137 /*
 138  * Singly-linked List declarations.
 139  */
 140 #define SLIST_HEAD(name, type)                                          \
 141 struct name {                                                           \
 142         struct type *slh_first; /* first element */                     \
 143 }
 144
 145 #define SLIST_HEAD_INITIALIZER(head)                                    \
 146         { NULL }
 147
 148 #define SLIST_ENTRY(type)                                               \
 149 struct {                                                                \
 150         struct type *sle_next;  /* next element */                      \
 151 }
 152
 153 /*
 154  * Singly-linked List functions.
 155  */
 156 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 157
 158 #define SLIST_FIRST(head)       ((head)->slh_first)
 159
 160 #define SLIST_FOREACH(var, head, field)                                 \
 161         for ((var) = SLIST_FIRST((head));                               \
 162             (var);                                                      \
 163             (var) = SLIST_NEXT((var), field))
 164
 165 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 166         for ((var) = SLIST_FIRST((head));                               \
 167             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 168             (var) = (tvar))
 169
 170 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 171         for ((varp) = &SLIST_FIRST((head));                             \
 172             ((var) = *(varp)) != NULL;                                  \
 173             (varp) = &SLIST_NEXT((var), field))
 174
 175 #define SLIST_INIT(head) do {                                           \
 176         SLIST_FIRST((head)) = NULL;                                     \
 177 } while (0)
 178
 179 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 180         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 181         SLIST_NEXT((slistelm), field) = (elm);                          \
 182 } while (0)
 183
 184 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 185         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 186         SLIST_FIRST((head)) = (elm);                                    \
 187 } while (0)
 188
 189 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 190
 191 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 192         if (SLIST_FIRST((head)) == (elm)) {                             \
 193                 SLIST_REMOVE_HEAD((head), field);                       \
 194         }                                                               \
 195         else {                                                          \
 196                 struct type *curelm = SLIST_FIRST((head));              \
 197                 while (SLIST_NEXT(curelm, field) != (elm))              \
 198                         curelm = SLIST_NEXT(curelm, field);             \
 199                 SLIST_NEXT(curelm, field) =                             \
 200                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
 201         }                                                               \
 202         TRASHIT((elm)->field.sle_next);                                 \
 203 } while (0)
 204
 205 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 206         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 207 } while (0)
 208
 209 /*
 210  * Singly-linked Tail queue declarations.
 211  */
 212 #define STAILQ_HEAD(name, type)                                         \
 213 struct name {                                                           \
 214         struct type *stqh_first;/* first element */                     \
 215         struct type **stqh_last;/* addr of last next element */         \
 216 }
 217
 218 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 219         { NULL, &(head).stqh_first }
 220
 221 #define STAILQ_ENTRY(type)                                              \
 222 struct {                                                                \
 223         struct type *stqe_next; /* next element */                      \
 224 }
 225
 226 /*
 227  * Singly-linked Tail queue functions.
 228  */
 229 #define STAILQ_CONCAT(head1, head2) do {                                \
 230         if (!STAILQ_EMPTY((head2))) {                                   \
 231                 *(head1)->stqh_last = (head2)->stqh_first;              \
 232                 (head1)->stqh_last = (head2)->stqh_last;                \
 233                 STAILQ_INIT((head2));                                   \
 234         }                                                               \
 235 } while (0)
 236
 237 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 238
 239 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 240
 241 #define STAILQ_FOREACH(var, head, field)                                \
 242         for((var) = STAILQ_FIRST((head));                               \
 243            (var);                                                       \
 244            (var) = STAILQ_NEXT((var), field))
 245
 246
 247 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 248         for ((var) = STAILQ_FIRST((head));                              \
 249             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 250             (var) = (tvar))
 251
 252 #define STAILQ_INIT(head) do {                                          \
 253         STAILQ_FIRST((head)) = NULL;                                    \
 254         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 255 } while (0)
 256
 257 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 258         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 259                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 260         STAILQ_NEXT((tqelm), field) = (elm);                            \
 261 } while (0)
 262
 263 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 264         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 265                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 266         STAILQ_FIRST((head)) = (elm);                                   \
 267 } while (0)
 268
 269 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 270         STAILQ_NEXT((elm), field) = NULL;                               \
 271         *(head)->stqh_last = (elm);                                     \
 272         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 273 } while (0)
 274
 275 #define STAILQ_LAST(head, type, field)                                  \
 276         (STAILQ_EMPTY((head)) ?                                         \
 277                 NULL :                                                  \
 278                 ((struct type *)                                        \
 279                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 280
 281 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 282
 283 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 284         if (STAILQ_FIRST((head)) == (elm)) {                            \
 285                 STAILQ_REMOVE_HEAD((head), field);                      \
 286         }                                                               \
 287         else {                                                          \
 288                 struct type *curelm = STAILQ_FIRST((head));             \
 289                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 290                         curelm = STAILQ_NEXT(curelm, field);            \
 291                 if ((STAILQ_NEXT(curelm, field) =                       \
 292                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
 293                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
 294         }                                                               \
 295         TRASHIT((elm)->field.stqe_next);                                \
 296 } while (0)
 297
 298 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 299         if ((STAILQ_FIRST((head)) =                                     \
 300              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 301                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 302 } while (0)
 303
 304 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 305         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
 306                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 307 } while (0)
 308
 309 /*
 310  * List declarations.
 311  */
 312 #define LIST_HEAD(name, type)                                           \
 313 struct name {                                                           \
 314         struct type *lh_first;  /* first element */                     \
 315 }
 316
 317 #define LIST_HEAD_INITIALIZER(head)                                     \
 318         { NULL }
 319
 320 #define LIST_ENTRY(type)                                                \
 321 struct {                                                                \
 322         struct type *le_next;   /* next element */                      \
 323         struct type **le_prev;  /* address of previous next element */  \
 324 }
 325
 326 /*
 327  * List functions.
 328  */
 329
 330 #if (defined(_KERNEL) && defined(INVARIANTS)) || defined(QUEUE_MACRO_DEBUG)
 331 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 332         if (LIST_FIRST((head)) != NULL &&                               \
 333             LIST_FIRST((head))->field.le_prev !=                        \
 334              &LIST_FIRST((head)))                                       \
 335                 panic("Bad list head %p first->prev != head", (head));  \
 336 } while (0)
 337
 338 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 339         if (LIST_NEXT((elm), field) != NULL &&                          \
 340             LIST_NEXT((elm), field)->field.le_prev !=                   \
 341              &((elm)->field.le_next))                                   \
 342                 panic("Bad link elm %p next->prev != elm", (elm));      \
 343 } while (0)
 344
 345 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 346         if (*(elm)->field.le_prev != (elm))                             \
 347                 panic("Bad link elm %p prev->next != elm", (elm));      \
 348 } while (0)
 349 #else
 350 #define QMD_LIST_CHECK_HEAD(head, field)
 351 #define QMD_LIST_CHECK_NEXT(elm, field)
 352 #define QMD_LIST_CHECK_PREV(elm, field)
 353 #endif /* (_KERNEL && INVARIANTS) || QUEUE_MACRO_DEBUG */
 354
 355 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 356
 357 #define LIST_FIRST(head)        ((head)->lh_first)
 358
 359 #define LIST_FOREACH(var, head, field)                                  \
 360         for ((var) = LIST_FIRST((head));                                \
 361             (var);                                                      \
 362             (var) = LIST_NEXT((var), field))
 363
 364 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 365         for ((var) = LIST_FIRST((head));                                \
 366             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 367             (var) = (tvar))
 368
 369 #define LIST_INIT(head) do {                                            \
 370         LIST_FIRST((head)) = NULL;                                      \
 371 } while (0)
 372
 373 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 374         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 375         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 376                 LIST_NEXT((listelm), field)->field.le_prev =            \
 377                     &LIST_NEXT((elm), field);                           \
 378         LIST_NEXT((listelm), field) = (elm);                            \
 379         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 380 } while (0)
 381
 382 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 383         QMD_LIST_CHECK_PREV(listelm, field);                            \
 384         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 385         LIST_NEXT((elm), field) = (listelm);                            \
 386         *(listelm)->field.le_prev = (elm);                              \
 387         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 388 } while (0)
 389
 390 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 391         QMD_LIST_CHECK_HEAD((head), field);                             \
 392         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 393                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 394         LIST_FIRST((head)) = (elm);                                     \
 395         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 396 } while (0)
 397
 398 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 399
 400 #define LIST_REMOVE(elm, field) do {                                    \
 401         QMD_LIST_CHECK_NEXT(elm, field);                                \
 402         QMD_LIST_CHECK_PREV(elm, field);                                \
 403         if (LIST_NEXT((elm), field) != NULL)                            \
 404                 LIST_NEXT((elm), field)->field.le_prev =                \
 405                     (elm)->field.le_prev;                               \
 406         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 407         TRASHIT((elm)->field.le_next);                                  \
 408         TRASHIT((elm)->field.le_prev);                                  \
 409 } while (0)
 410
 411 /*
 412  * Tail queue declarations.
 413  */
 414 #define TAILQ_HEAD(name, type)                                          \
 415 struct name {                                                           \
 416         struct type *tqh_first; /* first element */                     \
 417         struct type **tqh_last; /* addr of last next element */         \
 418         TRACEBUF                                                        \
 419 }
 420
 421 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 422         { NULL, &(head).tqh_first }
 423
 424 #define TAILQ_ENTRY(type)                                               \
 425 struct {                                                                \
 426         struct type *tqe_next;  /* next element */                      \
 427         struct type **tqe_prev; /* address of previous next element */  \
 428         TRACEBUF                                                        \
 429 }
 430
 431 /*
 432  * Tail queue functions.
 433  */
 434 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 435         if (!TAILQ_EMPTY(head2)) {                                      \
 436                 *(head1)->tqh_last = (head2)->tqh_first;                \
 437                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 438                 (head1)->tqh_last = (head2)->tqh_last;                  \
 439                 TAILQ_INIT((head2));                                    \
 440                 QMD_TRACE_HEAD(head1);                                  \
 441                 QMD_TRACE_HEAD(head2);                                  \
 442         }                                                               \
 443 } while (0)
 444
 445 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 446
 447 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 448
 449 #define TAILQ_FOREACH(var, head, field)                                 \
 450         for ((var) = TAILQ_FIRST((head));                               \
 451             (var);                                                      \
 452             (var) = TAILQ_NEXT((var), field))
 453
 454 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 455         for ((var) = TAILQ_FIRST((head));                               \
 456             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 457             (var) = (tvar))
 458
 459 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 460         for ((var) = TAILQ_LAST((head), headname);                      \
 461             (var);                                                      \
 462             (var) = TAILQ_PREV((var), headname, field))
 463
 464 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 465         for ((var) = TAILQ_LAST((head), headname);                      \
 466             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 467             (var) = (tvar))
 468
 469 #define TAILQ_INIT(head) do {                                           \
 470         TAILQ_FIRST((head)) = NULL;                                     \
 471         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 472         QMD_TRACE_HEAD(head);                                           \
 473 } while (0)
 474
 475 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 476         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 477                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 478                     &TAILQ_NEXT((elm), field);                          \
 479         else {                                                          \
 480                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 481                 QMD_TRACE_HEAD(head);                                   \
 482         }                                                               \
 483         TAILQ_NEXT((listelm), field) = (elm);                           \
 484         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 485         QMD_TRACE_ELEM(&(elm)->field);                                  \
 486         QMD_TRACE_ELEM(&listelm->field);                                \
 487 } while (0)
 488
 489 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 490         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 491         TAILQ_NEXT((elm), field) = (listelm);                           \
 492         *(listelm)->field.tqe_prev = (elm);                             \
 493         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 494         QMD_TRACE_ELEM(&(elm)->field);                                  \
 495         QMD_TRACE_ELEM(&listelm->field);                                \
 496 } while (0)
 497
 498 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 499         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 500                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 501                     &TAILQ_NEXT((elm), field);                          \
 502         else                                                            \
 503                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 504         TAILQ_FIRST((head)) = (elm);                                    \
 505         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 506         QMD_TRACE_HEAD(head);                                           \
 507         QMD_TRACE_ELEM(&(elm)->field);                                  \
 508 } while (0)
 509
 510 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 511         TAILQ_NEXT((elm), field) = NULL;                                \
 512         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 513         *(head)->tqh_last = (elm);                                      \
 514         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 515         QMD_TRACE_HEAD(head);                                           \
 516         QMD_TRACE_ELEM(&(elm)->field);                                  \
 517 } while (0)
 518
 519 #define TAILQ_LAST(head, headname)                                      \
 520         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 521
 522 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 523
 524 #define TAILQ_PREV(elm, headname, field)                                \
 525         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 526
 527 #define TAILQ_REMOVE(head, elm, field) do {                             \
 528         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 529                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 530                     (elm)->field.tqe_prev;                              \
 531         else {                                                          \
 532                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 533                 QMD_TRACE_HEAD(head);                                   \
 534         }                                                               \
 535         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 536         TRASHIT((elm)->field.tqe_next);                                 \
 537         TRASHIT((elm)->field.tqe_prev);                                 \
 538         QMD_TRACE_ELEM(&(elm)->field);                                  \
 539 } while (0)
 540
 541 #endif /* !_COMPAT_QUEUE_H_ */