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  * $P4: //depot/projects/trustedbsd/openbsm/compat/queue.h#3 $
  33  */
  34
  35 #ifndef _COMPAT_QUEUE_H_
  36 #define _COMPAT_QUEUE_H_
  37
  38 #include <sys/cdefs.h>
  39
  40 /*
  41  * This file defines four types of data structures: singly-linked lists,
  42  * singly-linked tail queues, lists and tail queues.
  43  *
  44  * A singly-linked list is headed by a single forward pointer. The elements
  45  * are singly linked for minimum space and pointer manipulation overhead at
  46  * the expense of O(n) removal for arbitrary elements. New elements can be
  47  * added to the list after an existing element or at the head of the list.
  48  * Elements being removed from the head of the list should use the explicit
  49  * macro for this purpose for optimum efficiency. A singly-linked list may
  50  * only be traversed in the forward direction.  Singly-linked lists are ideal
  51  * for applications with large datasets and few or no removals or for
  52  * implementing a LIFO queue.
  53  *
  54  * A singly-linked tail queue is headed by a pair of pointers, one to the
  55  * head of the list and the other to the tail of the list. The elements are
  56  * singly linked for minimum space and pointer manipulation overhead at the
  57  * expense of O(n) removal for arbitrary elements. New elements can be added
  58  * to the list after an existing element, at the head of the list, or at the
  59  * end of the list. Elements being removed from the head of the tail queue
  60  * should use the explicit macro for this purpose for optimum efficiency.
  61  * A singly-linked tail queue may only be traversed in the forward direction.
  62  * Singly-linked tail queues are ideal for applications with large datasets
  63  * and few or no removals or for implementing a FIFO queue.
  64  *
  65  * A list is headed by a single forward pointer (or an array of forward
  66  * pointers for a hash table header). The elements are doubly linked
  67  * so that an arbitrary element can be removed without a need to
  68  * traverse the list. New elements can be added to the list before
  69  * or after an existing element or at the head of the list. A list
  70  * may only be traversed in the forward direction.
  71  *
  72  * A tail queue is headed by a pair of pointers, one to the head of the
  73  * list and the other to the tail of the list. The elements are doubly
  74  * linked so that an arbitrary element can be removed without a need to
  75  * traverse the list. New elements can be added to the list before or
  76  * after an existing element, at the head of the list, or at the end of
  77  * the list. A tail queue may be traversed in either direction.
  78  *
  79  * For details on the use of these macros, see the queue(3) manual page.
  80  *
  81  *
  82  *                              SLIST   LIST    STAILQ  TAILQ
  83  * _HEAD                        +       +       +       +
  84  * _HEAD_INITIALIZER            +       +       +       +
  85  * _ENTRY                       +       +       +       +
  86  * _INIT                        +       +       +       +
  87  * _EMPTY                       +       +       +       +
  88  * _FIRST                       +       +       +       +
  89  * _NEXT                        +       +       +       +
  90  * _PREV                        -       -       -       +
  91  * _LAST                        -       -       +       +
  92  * _FOREACH                     +       +       +       +
  93  * _FOREACH_SAFE                +       +       +       +
  94  * _FOREACH_REVERSE             -       -       -       +
  95  * _FOREACH_REVERSE_SAFE        -       -       -       +
  96  * _INSERT_HEAD                 +       +       +       +
  97  * _INSERT_BEFORE               -       +       -       +
  98  * _INSERT_AFTER                +       +       +       +
  99  * _INSERT_TAIL                 -       -       +       +
 100  * _CONCAT                      -       -       +       +
 101  * _REMOVE_HEAD                 +       -       +       -
 102  * _REMOVE                      +       +       +       +
 103  *
 104  */
 105 #ifdef QUEUE_MACRO_DEBUG
 106 /* Store the last 2 places the queue element or head was altered */
 107 struct qm_trace {
 108         char * lastfile;
 109         int lastline;
 110         char * prevfile;
 111         int prevline;
 112 };
 113
 114 #define TRACEBUF        struct qm_trace trace;
 115 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 116
 117 #define QMD_TRACE_HEAD(head) do {                                       \
 118         (head)->trace.prevline = (head)->trace.lastline;                \
 119         (head)->trace.prevfile = (head)->trace.lastfile;                \
 120         (head)->trace.lastline = __LINE__;                              \
 121         (head)->trace.lastfile = __FILE__;                              \
 122 } while (0)
 123
 124 #define QMD_TRACE_ELEM(elem) do {                                       \
 125         (elem)->trace.prevline = (elem)->trace.lastline;                \
 126         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 127         (elem)->trace.lastline = __LINE__;                              \
 128         (elem)->trace.lastfile = __FILE__;                              \
 129 } while (0)
 130
 131 #else
 132 #define QMD_TRACE_ELEM(elem)
 133 #define QMD_TRACE_HEAD(head)
 134 #define TRACEBUF
 135 #define TRASHIT(x)
 136 #endif  /* QUEUE_MACRO_DEBUG */
 137
 138 /*
 139  * Singly-linked List declarations.
 140  */
 141 #define SLIST_HEAD(name, type)                                          \
 142 struct name {                                                           \
 143         struct type *slh_first; /* first element */                     \
 144 }
 145
 146 #define SLIST_HEAD_INITIALIZER(head)                                    \
 147         { NULL }
 148
 149 #define SLIST_ENTRY(type)                                               \
 150 struct {                                                                \
 151         struct type *sle_next;  /* next element */                      \
 152 }
 153
 154 /*
 155  * Singly-linked List functions.
 156  */
 157 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 158
 159 #define SLIST_FIRST(head)       ((head)->slh_first)
 160
 161 #define SLIST_FOREACH(var, head, field)                                 \
 162         for ((var) = SLIST_FIRST((head));                               \
 163             (var);                                                      \
 164             (var) = SLIST_NEXT((var), field))
 165
 166 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 167         for ((var) = SLIST_FIRST((head));                               \
 168             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 169             (var) = (tvar))
 170
 171 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 172         for ((varp) = &SLIST_FIRST((head));                             \
 173             ((var) = *(varp)) != NULL;                                  \
 174             (varp) = &SLIST_NEXT((var), field))
 175
 176 #define SLIST_INIT(head) do {                                           \
 177         SLIST_FIRST((head)) = NULL;                                     \
 178 } while (0)
 179
 180 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 181         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 182         SLIST_NEXT((slistelm), field) = (elm);                          \
 183 } while (0)
 184
 185 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 186         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 187         SLIST_FIRST((head)) = (elm);                                    \
 188 } while (0)
 189
 190 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 191
 192 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 193         if (SLIST_FIRST((head)) == (elm)) {                             \
 194                 SLIST_REMOVE_HEAD((head), field);                       \
 195         }                                                               \
 196         else {                                                          \
 197                 struct type *curelm = SLIST_FIRST((head));              \
 198                 while (SLIST_NEXT(curelm, field) != (elm))              \
 199                         curelm = SLIST_NEXT(curelm, field);             \
 200                 SLIST_NEXT(curelm, field) =                             \
 201                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
 202         }                                                               \
 203         TRASHIT((elm)->field.sle_next);                                 \
 204 } while (0)
 205
 206 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 207         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 208 } while (0)
 209
 210 /*
 211  * Singly-linked Tail queue declarations.
 212  */
 213 #define STAILQ_HEAD(name, type)                                         \
 214 struct name {                                                           \
 215         struct type *stqh_first;/* first element */                     \
 216         struct type **stqh_last;/* addr of last next element */         \
 217 }
 218
 219 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 220         { NULL, &(head).stqh_first }
 221
 222 #define STAILQ_ENTRY(type)                                              \
 223 struct {                                                                \
 224         struct type *stqe_next; /* next element */                      \
 225 }
 226
 227 /*
 228  * Singly-linked Tail queue functions.
 229  */
 230 #define STAILQ_CONCAT(head1, head2) do {                                \
 231         if (!STAILQ_EMPTY((head2))) {                                   \
 232                 *(head1)->stqh_last = (head2)->stqh_first;              \
 233                 (head1)->stqh_last = (head2)->stqh_last;                \
 234                 STAILQ_INIT((head2));                                   \
 235         }                                                               \
 236 } while (0)
 237
 238 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 239
 240 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 241
 242 #define STAILQ_FOREACH(var, head, field)                                \
 243         for((var) = STAILQ_FIRST((head));                               \
 244            (var);                                                       \
 245            (var) = STAILQ_NEXT((var), field))
 246
 247
 248 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 249         for ((var) = STAILQ_FIRST((head));                              \
 250             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 251             (var) = (tvar))
 252
 253 #define STAILQ_INIT(head) do {                                          \
 254         STAILQ_FIRST((head)) = NULL;                                    \
 255         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 256 } while (0)
 257
 258 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 259         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 260                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 261         STAILQ_NEXT((tqelm), field) = (elm);                            \
 262 } while (0)
 263
 264 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 265         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 266                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 267         STAILQ_FIRST((head)) = (elm);                                   \
 268 } while (0)
 269
 270 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 271         STAILQ_NEXT((elm), field) = NULL;                               \
 272         *(head)->stqh_last = (elm);                                     \
 273         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 274 } while (0)
 275
 276 #define STAILQ_LAST(head, type, field)                                  \
 277         (STAILQ_EMPTY((head)) ?                                         \
 278                 NULL :                                                  \
 279                 ((struct type *)                                        \
 280                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 281
 282 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 283
 284 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 285         if (STAILQ_FIRST((head)) == (elm)) {                            \
 286                 STAILQ_REMOVE_HEAD((head), field);                      \
 287         }                                                               \
 288         else {                                                          \
 289                 struct type *curelm = STAILQ_FIRST((head));             \
 290                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 291                         curelm = STAILQ_NEXT(curelm, field);            \
 292                 if ((STAILQ_NEXT(curelm, field) =                       \
 293                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
 294                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
 295         }                                                               \
 296         TRASHIT((elm)->field.stqe_next);                                \
 297 } while (0)
 298
 299 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 300         if ((STAILQ_FIRST((head)) =                                     \
 301              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 302                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 303 } while (0)
 304
 305 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 306         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
 307                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 308 } while (0)
 309
 310 /*
 311  * List declarations.
 312  */
 313 #define LIST_HEAD(name, type)                                           \
 314 struct name {                                                           \
 315         struct type *lh_first;  /* first element */                     \
 316 }
 317
 318 #define LIST_HEAD_INITIALIZER(head)                                     \
 319         { NULL }
 320
 321 #define LIST_ENTRY(type)                                                \
 322 struct {                                                                \
 323         struct type *le_next;   /* next element */                      \
 324         struct type **le_prev;  /* address of previous next element */  \
 325 }
 326
 327 /*
 328  * List functions.
 329  */
 330
 331 #if (defined(_KERNEL) && defined(INVARIANTS)) || defined(QUEUE_MACRO_DEBUG)
 332 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 333         if (LIST_FIRST((head)) != NULL &&                               \
 334             LIST_FIRST((head))->field.le_prev !=                        \
 335              &LIST_FIRST((head)))                                       \
 336                 panic("Bad list head %p first->prev != head", (head));  \
 337 } while (0)
 338
 339 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 340         if (LIST_NEXT((elm), field) != NULL &&                          \
 341             LIST_NEXT((elm), field)->field.le_prev !=                   \
 342              &((elm)->field.le_next))                                   \
 343                 panic("Bad link elm %p next->prev != elm", (elm));      \
 344 } while (0)
 345
 346 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 347         if (*(elm)->field.le_prev != (elm))                             \
 348                 panic("Bad link elm %p prev->next != elm", (elm));      \
 349 } while (0)
 350 #else
 351 #define QMD_LIST_CHECK_HEAD(head, field)
 352 #define QMD_LIST_CHECK_NEXT(elm, field)
 353 #define QMD_LIST_CHECK_PREV(elm, field)
 354 #endif /* (_KERNEL && INVARIANTS) || QUEUE_MACRO_DEBUG */
 355
 356 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 357
 358 #define LIST_FIRST(head)        ((head)->lh_first)
 359
 360 #define LIST_FOREACH(var, head, field)                                  \
 361         for ((var) = LIST_FIRST((head));                                \
 362             (var);                                                      \
 363             (var) = LIST_NEXT((var), field))
 364
 365 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 366         for ((var) = LIST_FIRST((head));                                \
 367             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 368             (var) = (tvar))
 369
 370 #define LIST_INIT(head) do {                                            \
 371         LIST_FIRST((head)) = NULL;                                      \
 372 } while (0)
 373
 374 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 375         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 376         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 377                 LIST_NEXT((listelm), field)->field.le_prev =            \
 378                     &LIST_NEXT((elm), field);                           \
 379         LIST_NEXT((listelm), field) = (elm);                            \
 380         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 381 } while (0)
 382
 383 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 384         QMD_LIST_CHECK_PREV(listelm, field);                            \
 385         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 386         LIST_NEXT((elm), field) = (listelm);                            \
 387         *(listelm)->field.le_prev = (elm);                              \
 388         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 389 } while (0)
 390
 391 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 392         QMD_LIST_CHECK_HEAD((head), field);                             \
 393         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 394                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 395         LIST_FIRST((head)) = (elm);                                     \
 396         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 397 } while (0)
 398
 399 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 400
 401 #define LIST_REMOVE(elm, field) do {                                    \
 402         QMD_LIST_CHECK_NEXT(elm, field);                                \
 403         QMD_LIST_CHECK_PREV(elm, field);                                \
 404         if (LIST_NEXT((elm), field) != NULL)                            \
 405                 LIST_NEXT((elm), field)->field.le_prev =                \
 406                     (elm)->field.le_prev;                               \
 407         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 408         TRASHIT((elm)->field.le_next);                                  \
 409         TRASHIT((elm)->field.le_prev);                                  \
 410 } while (0)
 411
 412 /*
 413  * Tail queue declarations.
 414  */
 415 #define TAILQ_HEAD(name, type)                                          \
 416 struct name {                                                           \
 417         struct type *tqh_first; /* first element */                     \
 418         struct type **tqh_last; /* addr of last next element */         \
 419         TRACEBUF                                                        \
 420 }
 421
 422 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 423         { NULL, &(head).tqh_first }
 424
 425 #define TAILQ_ENTRY(type)                                               \
 426 struct {                                                                \
 427         struct type *tqe_next;  /* next element */                      \
 428         struct type **tqe_prev; /* address of previous next element */  \
 429         TRACEBUF                                                        \
 430 }
 431
 432 /*
 433  * Tail queue functions.
 434  */
 435 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 436         if (!TAILQ_EMPTY(head2)) {                                      \
 437                 *(head1)->tqh_last = (head2)->tqh_first;                \
 438                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 439                 (head1)->tqh_last = (head2)->tqh_last;                  \
 440                 TAILQ_INIT((head2));                                    \
 441                 QMD_TRACE_HEAD(head1);                                  \
 442                 QMD_TRACE_HEAD(head2);                                  \
 443         }                                                               \
 444 } while (0)
 445
 446 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 447
 448 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 449
 450 #define TAILQ_FOREACH(var, head, field)                                 \
 451         for ((var) = TAILQ_FIRST((head));                               \
 452             (var);                                                      \
 453             (var) = TAILQ_NEXT((var), field))
 454
 455 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 456         for ((var) = TAILQ_FIRST((head));                               \
 457             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 458             (var) = (tvar))
 459
 460 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 461         for ((var) = TAILQ_LAST((head), headname);                      \
 462             (var);                                                      \
 463             (var) = TAILQ_PREV((var), headname, field))
 464
 465 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 466         for ((var) = TAILQ_LAST((head), headname);                      \
 467             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 468             (var) = (tvar))
 469
 470 #define TAILQ_INIT(head) do {                                           \
 471         TAILQ_FIRST((head)) = NULL;                                     \
 472         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 473         QMD_TRACE_HEAD(head);                                           \
 474 } while (0)
 475
 476 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 477         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 478                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 479                     &TAILQ_NEXT((elm), field);                          \
 480         else {                                                          \
 481                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 482                 QMD_TRACE_HEAD(head);                                   \
 483         }                                                               \
 484         TAILQ_NEXT((listelm), field) = (elm);                           \
 485         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 486         QMD_TRACE_ELEM(&(elm)->field);                                  \
 487         QMD_TRACE_ELEM(&listelm->field);                                \
 488 } while (0)
 489
 490 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 491         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 492         TAILQ_NEXT((elm), field) = (listelm);                           \
 493         *(listelm)->field.tqe_prev = (elm);                             \
 494         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 495         QMD_TRACE_ELEM(&(elm)->field);                                  \
 496         QMD_TRACE_ELEM(&listelm->field);                                \
 497 } while (0)
 498
 499 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 500         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 501                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 502                     &TAILQ_NEXT((elm), field);                          \
 503         else                                                            \
 504                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 505         TAILQ_FIRST((head)) = (elm);                                    \
 506         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 507         QMD_TRACE_HEAD(head);                                           \
 508         QMD_TRACE_ELEM(&(elm)->field);                                  \
 509 } while (0)
 510
 511 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 512         TAILQ_NEXT((elm), field) = NULL;                                \
 513         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 514         *(head)->tqh_last = (elm);                                      \
 515         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 516         QMD_TRACE_HEAD(head);                                           \
 517         QMD_TRACE_ELEM(&(elm)->field);                                  \
 518 } while (0)
 519
 520 #define TAILQ_LAST(head, headname)                                      \
 521         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 522
 523 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 524
 525 #define TAILQ_PREV(elm, headname, field)                                \
 526         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 527
 528 #define TAILQ_REMOVE(head, elm, field) do {                             \
 529         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 530                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 531                     (elm)->field.tqe_prev;                              \
 532         else {                                                          \
 533                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 534                 QMD_TRACE_HEAD(head);                                   \
 535         }                                                               \
 536         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 537         TRASHIT((elm)->field.tqe_next);                                 \
 538         TRASHIT((elm)->field.tqe_prev);                                 \
 539         QMD_TRACE_ELEM(&(elm)->field);                                  \
 540 } while (0)
 541
 542 #endif /* !_COMPAT_QUEUE_H_ */