xref: /openbmc/qemu/include/qemu/queue.h (revision 92d09502)
1 /*      $NetBSD: queue.h,v 1.52 2009/04/20 09:56:08 mschuett Exp $ */
2 
3 /*
4  * QEMU version: Copy from netbsd, removed debug code, removed some of
5  * the implementations.  Left in singly-linked lists, lists, simple
6  * queues, and tail queues.
7  */
8 
9 /*
10  * Copyright (c) 1991, 1993
11  *      The Regents of the University of California.  All rights reserved.
12  *
13  * Redistribution and use in source and binary forms, with or without
14  * modification, are permitted provided that the following conditions
15  * are met:
16  * 1. Redistributions of source code must retain the above copyright
17  *    notice, this list of conditions and the following disclaimer.
18  * 2. Redistributions in binary form must reproduce the above copyright
19  *    notice, this list of conditions and the following disclaimer in the
20  *    documentation and/or other materials provided with the distribution.
21  * 3. Neither the name of the University nor the names of its contributors
22  *    may be used to endorse or promote products derived from this software
23  *    without specific prior written permission.
24  *
25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35  * SUCH DAMAGE.
36  *
37  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
38  */
39 
40 #ifndef QEMU_SYS_QUEUE_H
41 #define QEMU_SYS_QUEUE_H
42 
43 /*
44  * This file defines four types of data structures: singly-linked lists,
45  * lists, simple queues, and tail queues.
46  *
47  * A singly-linked list is headed by a single forward pointer. The
48  * elements are singly linked for minimum space and pointer manipulation
49  * overhead at the expense of O(n) removal for arbitrary elements. New
50  * elements can be added to the list after an existing element or at the
51  * head of the list.  Elements being removed from the head of the list
52  * should use the explicit macro for this purpose for optimum
53  * efficiency. A singly-linked list may only be traversed in the forward
54  * direction.  Singly-linked lists are ideal for applications with large
55  * datasets and few or no removals or for implementing a LIFO queue.
56  *
57  * A list is headed by a single forward pointer (or an array of forward
58  * pointers for a hash table header). The elements are doubly linked
59  * so that an arbitrary element can be removed without a need to
60  * traverse the list. New elements can be added to the list before
61  * or after an existing element or at the head of the list. A list
62  * may only be traversed in the forward direction.
63  *
64  * A simple queue is headed by a pair of pointers, one the head of the
65  * list and the other to the tail of the list. The elements are singly
66  * linked to save space, so elements can only be removed from the
67  * head of the list. New elements can be added to the list after
68  * an existing element, at the head of the list, or at the end of the
69  * list. A simple queue 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 /*
82  * List definitions.
83  */
84 #define QLIST_HEAD(name, type)                                          \
85 struct name {                                                           \
86         struct type *lh_first;  /* first element */                     \
87 }
88 
89 #define QLIST_HEAD_INITIALIZER(head)                                    \
90         { NULL }
91 
92 #define QLIST_ENTRY(type)                                               \
93 struct {                                                                \
94         struct type *le_next;   /* next element */                      \
95         struct type **le_prev;  /* address of previous next element */  \
96 }
97 
98 /*
99  * List functions.
100  */
101 #define QLIST_INIT(head) do {                                           \
102         (head)->lh_first = NULL;                                        \
103 } while (/*CONSTCOND*/0)
104 
105 #define QLIST_SWAP(dstlist, srclist, field) do {                        \
106         void *tmplist;                                                  \
107         tmplist = (srclist)->lh_first;                                  \
108         (srclist)->lh_first = (dstlist)->lh_first;                      \
109         if ((srclist)->lh_first != NULL) {                              \
110             (srclist)->lh_first->field.le_prev = &(srclist)->lh_first;  \
111         }                                                               \
112         (dstlist)->lh_first = tmplist;                                  \
113         if ((dstlist)->lh_first != NULL) {                              \
114             (dstlist)->lh_first->field.le_prev = &(dstlist)->lh_first;  \
115         }                                                               \
116 } while (/*CONSTCOND*/0)
117 
118 #define QLIST_INSERT_AFTER(listelm, elm, field) do {                    \
119         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
120                 (listelm)->field.le_next->field.le_prev =               \
121                     &(elm)->field.le_next;                              \
122         (listelm)->field.le_next = (elm);                               \
123         (elm)->field.le_prev = &(listelm)->field.le_next;               \
124 } while (/*CONSTCOND*/0)
125 
126 #define QLIST_INSERT_BEFORE(listelm, elm, field) do {                   \
127         (elm)->field.le_prev = (listelm)->field.le_prev;                \
128         (elm)->field.le_next = (listelm);                               \
129         *(listelm)->field.le_prev = (elm);                              \
130         (listelm)->field.le_prev = &(elm)->field.le_next;               \
131 } while (/*CONSTCOND*/0)
132 
133 #define QLIST_INSERT_HEAD(head, elm, field) do {                        \
134         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
135                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
136         (head)->lh_first = (elm);                                       \
137         (elm)->field.le_prev = &(head)->lh_first;                       \
138 } while (/*CONSTCOND*/0)
139 
140 #define QLIST_REMOVE(elm, field) do {                                   \
141         if ((elm)->field.le_next != NULL)                               \
142                 (elm)->field.le_next->field.le_prev =                   \
143                     (elm)->field.le_prev;                               \
144         *(elm)->field.le_prev = (elm)->field.le_next;                   \
145         (elm)->field.le_next = NULL;                                    \
146         (elm)->field.le_prev = NULL;                                    \
147 } while (/*CONSTCOND*/0)
148 
149 /*
150  * Like QLIST_REMOVE() but safe to call when elm is not in a list
151  */
152 #define QLIST_SAFE_REMOVE(elm, field) do {                              \
153         if ((elm)->field.le_prev != NULL) {                             \
154                 if ((elm)->field.le_next != NULL)                       \
155                         (elm)->field.le_next->field.le_prev =           \
156                             (elm)->field.le_prev;                       \
157                 *(elm)->field.le_prev = (elm)->field.le_next;           \
158                 (elm)->field.le_next = NULL;                            \
159                 (elm)->field.le_prev = NULL;                            \
160         }                                                               \
161 } while (/*CONSTCOND*/0)
162 
163 /* Is elm in a list? */
164 #define QLIST_IS_INSERTED(elm, field) ((elm)->field.le_prev != NULL)
165 
166 #define QLIST_FOREACH(var, head, field)                                 \
167         for ((var) = ((head)->lh_first);                                \
168                 (var);                                                  \
169                 (var) = ((var)->field.le_next))
170 
171 #define QLIST_FOREACH_SAFE(var, head, field, next_var)                  \
172         for ((var) = ((head)->lh_first);                                \
173                 (var) && ((next_var) = ((var)->field.le_next), 1);      \
174                 (var) = (next_var))
175 
176 /*
177  * List access methods.
178  */
179 #define QLIST_EMPTY(head)                ((head)->lh_first == NULL)
180 #define QLIST_FIRST(head)                ((head)->lh_first)
181 #define QLIST_NEXT(elm, field)           ((elm)->field.le_next)
182 
183 
184 /*
185  * Singly-linked List definitions.
186  */
187 #define QSLIST_HEAD(name, type)                                          \
188 struct name {                                                           \
189         struct type *slh_first; /* first element */                     \
190 }
191 
192 #define QSLIST_HEAD_INITIALIZER(head)                                    \
193         { NULL }
194 
195 #define QSLIST_ENTRY(type)                                               \
196 struct {                                                                \
197         struct type *sle_next;  /* next element */                      \
198 }
199 
200 /*
201  * Singly-linked List functions.
202  */
203 #define QSLIST_INIT(head) do {                                           \
204         (head)->slh_first = NULL;                                       \
205 } while (/*CONSTCOND*/0)
206 
207 #define QSLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
208         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
209         (slistelm)->field.sle_next = (elm);                             \
210 } while (/*CONSTCOND*/0)
211 
212 #define QSLIST_INSERT_HEAD(head, elm, field) do {                        \
213         (elm)->field.sle_next = (head)->slh_first;                       \
214         (head)->slh_first = (elm);                                       \
215 } while (/*CONSTCOND*/0)
216 
217 #define QSLIST_INSERT_HEAD_ATOMIC(head, elm, field) do {                     \
218         typeof(elm) save_sle_next;                                           \
219         do {                                                                 \
220             save_sle_next = (elm)->field.sle_next = (head)->slh_first;       \
221         } while (qatomic_cmpxchg(&(head)->slh_first, save_sle_next, (elm)) !=\
222                  save_sle_next);                                             \
223 } while (/*CONSTCOND*/0)
224 
225 #define QSLIST_MOVE_ATOMIC(dest, src) do {                               \
226         (dest)->slh_first = qatomic_xchg(&(src)->slh_first, NULL);       \
227 } while (/*CONSTCOND*/0)
228 
229 #define QSLIST_REMOVE_HEAD(head, field) do {                             \
230         typeof((head)->slh_first) elm = (head)->slh_first;               \
231         (head)->slh_first = elm->field.sle_next;                         \
232         elm->field.sle_next = NULL;                                      \
233 } while (/*CONSTCOND*/0)
234 
235 #define QSLIST_REMOVE_AFTER(slistelm, field) do {                       \
236         typeof(slistelm) next = (slistelm)->field.sle_next;             \
237         (slistelm)->field.sle_next = next->field.sle_next;              \
238         next->field.sle_next = NULL;                                    \
239 } while (/*CONSTCOND*/0)
240 
241 #define QSLIST_REMOVE(head, elm, type, field) do {                      \
242     if ((head)->slh_first == (elm)) {                                   \
243         QSLIST_REMOVE_HEAD((head), field);                              \
244     } else {                                                            \
245         struct type *curelm = (head)->slh_first;                        \
246         while (curelm->field.sle_next != (elm))                         \
247             curelm = curelm->field.sle_next;                            \
248         curelm->field.sle_next = curelm->field.sle_next->field.sle_next; \
249         (elm)->field.sle_next = NULL;                                   \
250     }                                                                   \
251 } while (/*CONSTCOND*/0)
252 
253 #define QSLIST_FOREACH(var, head, field)                                 \
254         for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)
255 
256 #define QSLIST_FOREACH_SAFE(var, head, field, tvar)                      \
257         for ((var) = QSLIST_FIRST((head));                               \
258             (var) && ((tvar) = QSLIST_NEXT((var), field), 1);            \
259             (var) = (tvar))
260 
261 /*
262  * Singly-linked List access methods.
263  */
264 #define QSLIST_EMPTY(head)       ((head)->slh_first == NULL)
265 #define QSLIST_FIRST(head)       ((head)->slh_first)
266 #define QSLIST_NEXT(elm, field)  ((elm)->field.sle_next)
267 
268 
269 /*
270  * Simple queue definitions.
271  */
272 #define QSIMPLEQ_HEAD(name, type)                                       \
273 struct name {                                                           \
274     struct type *sqh_first;    /* first element */                      \
275     struct type **sqh_last;    /* addr of last next element */          \
276 }
277 
278 #define QSIMPLEQ_HEAD_INITIALIZER(head)                                 \
279     { NULL, &(head).sqh_first }
280 
281 #define QSIMPLEQ_ENTRY(type)                                            \
282 struct {                                                                \
283     struct type *sqe_next;    /* next element */                        \
284 }
285 
286 /*
287  * Simple queue functions.
288  */
289 #define QSIMPLEQ_INIT(head) do {                                        \
290     (head)->sqh_first = NULL;                                           \
291     (head)->sqh_last = &(head)->sqh_first;                              \
292 } while (/*CONSTCOND*/0)
293 
294 #define QSIMPLEQ_INSERT_HEAD(head, elm, field) do {                     \
295     if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)            \
296         (head)->sqh_last = &(elm)->field.sqe_next;                      \
297     (head)->sqh_first = (elm);                                          \
298 } while (/*CONSTCOND*/0)
299 
300 #define QSIMPLEQ_INSERT_TAIL(head, elm, field) do {                     \
301     (elm)->field.sqe_next = NULL;                                       \
302     *(head)->sqh_last = (elm);                                          \
303     (head)->sqh_last = &(elm)->field.sqe_next;                          \
304 } while (/*CONSTCOND*/0)
305 
306 #define QSIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {           \
307     if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)    \
308         (head)->sqh_last = &(elm)->field.sqe_next;                      \
309     (listelm)->field.sqe_next = (elm);                                  \
310 } while (/*CONSTCOND*/0)
311 
312 #define QSIMPLEQ_REMOVE_HEAD(head, field) do {                          \
313     typeof((head)->sqh_first) elm = (head)->sqh_first;                  \
314     if (((head)->sqh_first = elm->field.sqe_next) == NULL)              \
315         (head)->sqh_last = &(head)->sqh_first;                          \
316     elm->field.sqe_next = NULL;                                         \
317 } while (/*CONSTCOND*/0)
318 
319 #define QSIMPLEQ_SPLIT_AFTER(head, elm, field, removed) do {            \
320     QSIMPLEQ_INIT(removed);                                             \
321     if (((removed)->sqh_first = (head)->sqh_first) != NULL) {           \
322         if (((head)->sqh_first = (elm)->field.sqe_next) == NULL) {      \
323             (head)->sqh_last = &(head)->sqh_first;                      \
324         }                                                               \
325         (removed)->sqh_last = &(elm)->field.sqe_next;                   \
326         (elm)->field.sqe_next = NULL;                                   \
327     }                                                                   \
328 } while (/*CONSTCOND*/0)
329 
330 #define QSIMPLEQ_REMOVE(head, elm, type, field) do {                    \
331     if ((head)->sqh_first == (elm)) {                                   \
332         QSIMPLEQ_REMOVE_HEAD((head), field);                            \
333     } else {                                                            \
334         struct type *curelm = (head)->sqh_first;                        \
335         while (curelm->field.sqe_next != (elm))                         \
336             curelm = curelm->field.sqe_next;                            \
337         if ((curelm->field.sqe_next =                                   \
338             curelm->field.sqe_next->field.sqe_next) == NULL)            \
339                 (head)->sqh_last = &(curelm)->field.sqe_next;           \
340         (elm)->field.sqe_next = NULL;                                   \
341     }                                                                   \
342 } while (/*CONSTCOND*/0)
343 
344 #define QSIMPLEQ_FOREACH(var, head, field)                              \
345     for ((var) = ((head)->sqh_first);                                   \
346         (var);                                                          \
347         (var) = ((var)->field.sqe_next))
348 
349 #define QSIMPLEQ_FOREACH_SAFE(var, head, field, next)                   \
350     for ((var) = ((head)->sqh_first);                                   \
351         (var) && ((next = ((var)->field.sqe_next)), 1);                 \
352         (var) = (next))
353 
354 #define QSIMPLEQ_CONCAT(head1, head2) do {                              \
355     if (!QSIMPLEQ_EMPTY((head2))) {                                     \
356         *(head1)->sqh_last = (head2)->sqh_first;                        \
357         (head1)->sqh_last = (head2)->sqh_last;                          \
358         QSIMPLEQ_INIT((head2));                                         \
359     }                                                                   \
360 } while (/*CONSTCOND*/0)
361 
362 #define QSIMPLEQ_PREPEND(head1, head2) do {                             \
363     if (!QSIMPLEQ_EMPTY((head2))) {                                     \
364         *(head2)->sqh_last = (head1)->sqh_first;                        \
365         (head1)->sqh_first = (head2)->sqh_first;                          \
366         QSIMPLEQ_INIT((head2));                                         \
367     }                                                                   \
368 } while (/*CONSTCOND*/0)
369 
370 #define QSIMPLEQ_LAST(head, type, field)                                \
371     (QSIMPLEQ_EMPTY((head)) ?                                           \
372         NULL :                                                          \
373             ((struct type *)(void *)                                    \
374         ((char *)((head)->sqh_last) - offsetof(struct type, field))))
375 
376 /*
377  * Simple queue access methods.
378  */
379 #define QSIMPLEQ_EMPTY_ATOMIC(head) \
380     (qatomic_read(&((head)->sqh_first)) == NULL)
381 #define QSIMPLEQ_EMPTY(head)        ((head)->sqh_first == NULL)
382 #define QSIMPLEQ_FIRST(head)        ((head)->sqh_first)
383 #define QSIMPLEQ_NEXT(elm, field)   ((elm)->field.sqe_next)
384 
385 typedef struct QTailQLink {
386     void *tql_next;
387     struct QTailQLink *tql_prev;
388 } QTailQLink;
389 
390 /*
391  * Tail queue definitions.  The union acts as a poor man template, as if
392  * it were QTailQLink<type>.
393  */
394 #define QTAILQ_HEAD(name, type)                                         \
395 union name {                                                            \
396         struct type *tqh_first;       /* first element */               \
397         QTailQLink tqh_circ;          /* link for circular backwards list */ \
398 }
399 
400 #define QTAILQ_HEAD_INITIALIZER(head)                                   \
401         { .tqh_circ = { NULL, &(head).tqh_circ } }
402 
403 #define QTAILQ_ENTRY(type)                                              \
404 union {                                                                 \
405         struct type *tqe_next;        /* next element */                \
406         QTailQLink tqe_circ;          /* link for circular backwards list */ \
407 }
408 
409 /*
410  * Tail queue functions.
411  */
412 #define QTAILQ_INIT(head) do {                                          \
413         (head)->tqh_first = NULL;                                       \
414         (head)->tqh_circ.tql_prev = &(head)->tqh_circ;                  \
415 } while (/*CONSTCOND*/0)
416 
417 #define QTAILQ_INSERT_HEAD(head, elm, field) do {                       \
418         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
419             (head)->tqh_first->field.tqe_circ.tql_prev =                \
420                 &(elm)->field.tqe_circ;                                 \
421         else                                                            \
422             (head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ;         \
423         (head)->tqh_first = (elm);                                      \
424         (elm)->field.tqe_circ.tql_prev = &(head)->tqh_circ;             \
425 } while (/*CONSTCOND*/0)
426 
427 #define QTAILQ_INSERT_TAIL(head, elm, field) do {                       \
428         (elm)->field.tqe_next = NULL;                                   \
429         (elm)->field.tqe_circ.tql_prev = (head)->tqh_circ.tql_prev;     \
430         (head)->tqh_circ.tql_prev->tql_next = (elm);                    \
431         (head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ;             \
432 } while (/*CONSTCOND*/0)
433 
434 #define QTAILQ_INSERT_AFTER(head, listelm, elm, field) do {             \
435         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
436             (elm)->field.tqe_next->field.tqe_circ.tql_prev =            \
437                 &(elm)->field.tqe_circ;                                 \
438         else                                                            \
439             (head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ;         \
440         (listelm)->field.tqe_next = (elm);                              \
441         (elm)->field.tqe_circ.tql_prev = &(listelm)->field.tqe_circ;    \
442 } while (/*CONSTCOND*/0)
443 
444 #define QTAILQ_INSERT_BEFORE(listelm, elm, field) do {                       \
445         (elm)->field.tqe_circ.tql_prev = (listelm)->field.tqe_circ.tql_prev; \
446         (elm)->field.tqe_next = (listelm);                                   \
447         (listelm)->field.tqe_circ.tql_prev->tql_next = (elm);                \
448         (listelm)->field.tqe_circ.tql_prev = &(elm)->field.tqe_circ;         \
449 } while (/*CONSTCOND*/0)
450 
451 #define QTAILQ_REMOVE(head, elm, field) do {                            \
452         if (((elm)->field.tqe_next) != NULL)                            \
453             (elm)->field.tqe_next->field.tqe_circ.tql_prev =            \
454                 (elm)->field.tqe_circ.tql_prev;                         \
455         else                                                            \
456             (head)->tqh_circ.tql_prev = (elm)->field.tqe_circ.tql_prev; \
457         (elm)->field.tqe_circ.tql_prev->tql_next = (elm)->field.tqe_next; \
458         (elm)->field.tqe_circ.tql_prev = NULL;                          \
459         (elm)->field.tqe_circ.tql_next = NULL;                          \
460         (elm)->field.tqe_next = NULL;                                   \
461 } while (/*CONSTCOND*/0)
462 
463 /* remove @left, @right and all elements in between from @head */
464 #define QTAILQ_REMOVE_SEVERAL(head, left, right, field) do {            \
465         if (((right)->field.tqe_next) != NULL)                          \
466             (right)->field.tqe_next->field.tqe_circ.tql_prev =          \
467                 (left)->field.tqe_circ.tql_prev;                        \
468         else                                                            \
469             (head)->tqh_circ.tql_prev = (left)->field.tqe_circ.tql_prev; \
470         (left)->field.tqe_circ.tql_prev->tql_next = (right)->field.tqe_next; \
471     } while (/*CONSTCOND*/0)
472 
473 #define QTAILQ_FOREACH(var, head, field)                                \
474         for ((var) = ((head)->tqh_first);                               \
475                 (var);                                                  \
476                 (var) = ((var)->field.tqe_next))
477 
478 #define QTAILQ_FOREACH_SAFE(var, head, field, next_var)                 \
479         for ((var) = ((head)->tqh_first);                               \
480                 (var) && ((next_var) = ((var)->field.tqe_next), 1);     \
481                 (var) = (next_var))
482 
483 #define QTAILQ_FOREACH_REVERSE(var, head, field)                        \
484         for ((var) = QTAILQ_LAST(head);                                 \
485                 (var);                                                  \
486                 (var) = QTAILQ_PREV(var, field))
487 
488 #define QTAILQ_FOREACH_REVERSE_SAFE(var, head, field, prev_var)         \
489         for ((var) = QTAILQ_LAST(head);                                 \
490              (var) && ((prev_var) = QTAILQ_PREV(var, field), 1);        \
491              (var) = (prev_var))
492 
493 /*
494  * Tail queue access methods.
495  */
496 #define QTAILQ_EMPTY(head)               ((head)->tqh_first == NULL)
497 #define QTAILQ_FIRST(head)               ((head)->tqh_first)
498 #define QTAILQ_NEXT(elm, field)          ((elm)->field.tqe_next)
499 #define QTAILQ_IN_USE(elm, field)        ((elm)->field.tqe_circ.tql_prev != NULL)
500 
501 #define QTAILQ_LINK_PREV(link)                                          \
502         ((link).tql_prev->tql_prev->tql_next)
503 #define QTAILQ_LAST(head)                                               \
504         ((typeof((head)->tqh_first)) QTAILQ_LINK_PREV((head)->tqh_circ))
505 #define QTAILQ_PREV(elm, field)                                         \
506         ((typeof((elm)->field.tqe_next)) QTAILQ_LINK_PREV((elm)->field.tqe_circ))
507 
508 #define field_at_offset(base, offset, type)                                    \
509         ((type *) (((char *) (base)) + (offset)))
510 
511 /*
512  * Raw access of elements of a tail queue head.  Offsets are all zero
513  * because it's a union.
514  */
515 #define QTAILQ_RAW_FIRST(head)                                                 \
516         field_at_offset(head, 0, void *)
517 #define QTAILQ_RAW_TQH_CIRC(head)                                              \
518         field_at_offset(head, 0, QTailQLink)
519 
520 /*
521  * Raw access of elements of a tail entry
522  */
523 #define QTAILQ_RAW_NEXT(elm, entry)                                            \
524         field_at_offset(elm, entry, void *)
525 #define QTAILQ_RAW_TQE_CIRC(elm, entry)                                        \
526         field_at_offset(elm, entry, QTailQLink)
527 /*
528  * Tail queue traversal using pointer arithmetic.
529  */
530 #define QTAILQ_RAW_FOREACH(elm, head, entry)                                   \
531         for ((elm) = *QTAILQ_RAW_FIRST(head);                                  \
532              (elm);                                                            \
533              (elm) = *QTAILQ_RAW_NEXT(elm, entry))
534 /*
535  * Tail queue insertion using pointer arithmetic.
536  */
537 #define QTAILQ_RAW_INSERT_TAIL(head, elm, entry) do {                           \
538         *QTAILQ_RAW_NEXT(elm, entry) = NULL;                                    \
539         QTAILQ_RAW_TQE_CIRC(elm, entry)->tql_prev = QTAILQ_RAW_TQH_CIRC(head)->tql_prev; \
540         QTAILQ_RAW_TQH_CIRC(head)->tql_prev->tql_next = (elm);                  \
541         QTAILQ_RAW_TQH_CIRC(head)->tql_prev = QTAILQ_RAW_TQE_CIRC(elm, entry);  \
542 } while (/*CONSTCOND*/0)
543 
544 #define QLIST_RAW_FIRST(head)                                                  \
545         field_at_offset(head, 0, void *)
546 
547 #define QLIST_RAW_NEXT(elm, entry)                                             \
548         field_at_offset(elm, entry, void *)
549 
550 #define QLIST_RAW_PREVIOUS(elm, entry)                                         \
551         field_at_offset(elm, entry + sizeof(void *), void *)
552 
553 #define QLIST_RAW_FOREACH(elm, head, entry)                                    \
554         for ((elm) = *QLIST_RAW_FIRST(head);                                   \
555              (elm);                                                            \
556              (elm) = *QLIST_RAW_NEXT(elm, entry))
557 
558 #define QLIST_RAW_INSERT_AFTER(head, prev, elem, entry) do {                   \
559         *QLIST_RAW_NEXT(prev, entry) = elem;                                   \
560         *QLIST_RAW_PREVIOUS(elem, entry) = QLIST_RAW_NEXT(prev, entry);        \
561         *QLIST_RAW_NEXT(elem, entry) = NULL;                                   \
562 } while (0)
563 
564 #define QLIST_RAW_INSERT_HEAD(head, elm, entry) do {                           \
565         void *first = *QLIST_RAW_FIRST(head);                                  \
566         *QLIST_RAW_FIRST(head) = elm;                                          \
567         *QLIST_RAW_PREVIOUS(elm, entry) = QLIST_RAW_FIRST(head);               \
568         if (first) {                                                           \
569             *QLIST_RAW_NEXT(elm, entry) = first;                               \
570             *QLIST_RAW_PREVIOUS(first, entry) = QLIST_RAW_NEXT(elm, entry);    \
571         } else {                                                               \
572             *QLIST_RAW_NEXT(elm, entry) = NULL;                                \
573         }                                                                      \
574 } while (0)
575 
576 #endif /* QEMU_SYS_QUEUE_H */
577