1 /* Licensed under BSD-MIT - see LICENSE file for details */
2 #ifndef CCAN_LIST_H
3 #define CCAN_LIST_H
4 #include <stdbool.h>
5 #include <assert.h>
6 #include <ccan/container_of/container_of.h>
7 #include <ccan/check_type/check_type.h>
8
9 /**
10 * struct list_node - an entry in a doubly-linked list
11 * @next: next entry (self if empty)
12 * @prev: previous entry (self if empty)
13 *
14 * This is used as an entry in a linked list.
15 * Example:
16 * struct child {
17 * const char *name;
18 * // Linked list of all us children.
19 * struct list_node list;
20 * };
21 */
22 struct list_node
23 {
24 struct list_node *next, *prev;
25 };
26
27 /**
28 * struct list_head - the head of a doubly-linked list
29 * @h: the list_head (containing next and prev pointers)
30 *
31 * This is used as the head of a linked list.
32 * Example:
33 * struct parent {
34 * const char *name;
35 * struct list_head children;
36 * unsigned int num_children;
37 * };
38 */
39 struct list_head
40 {
41 struct list_node n;
42 };
43
44 /**
45 * list_check - check head of a list for consistency
46 * @h: the list_head
47 * @abortstr: the location to print on aborting, or NULL.
48 *
49 * Because list_nodes have redundant information, consistency checking between
50 * the back and forward links can be done. This is useful as a debugging check.
51 * If @abortstr is non-NULL, that will be printed in a diagnostic if the list
52 * is inconsistent, and the function will abort.
53 *
54 * Returns the list head if the list is consistent, NULL if not (it
55 * can never return NULL if @abortstr is set).
56 *
57 * See also: list_check_node()
58 *
59 * Example:
60 * static void dump_parent(struct parent *p)
61 * {
62 * struct child *c;
63 *
64 * printf("%s (%u children):\n", p->name, p->num_children);
65 * list_check(&p->children, "bad child list");
66 * list_for_each(&p->children, c, list)
67 * printf(" -> %s\n", c->name);
68 * }
69 */
70 struct list_head *list_check(const struct list_head *h, const char *abortstr);
71
72 /**
73 * list_check_node - check node of a list for consistency
74 * @n: the list_node
75 * @abortstr: the location to print on aborting, or NULL.
76 *
77 * Check consistency of the list node is in (it must be in one).
78 *
79 * See also: list_check()
80 *
81 * Example:
82 * static void dump_child(const struct child *c)
83 * {
84 * list_check_node(&c->list, "bad child list");
85 * printf("%s\n", c->name);
86 * }
87 */
88 struct list_node *list_check_node(const struct list_node *n,
89 const char *abortstr);
90
91 #ifdef CCAN_LIST_DEBUG
92 #define list_debug(h) list_check((h), __func__)
93 #define list_debug_node(n) list_check_node((n), __func__)
94 #else
95 #define list_debug(h) (h)
96 #define list_debug_node(n) (n)
97 #endif
98
99 /**
100 * LIST_HEAD_INIT - initializer for an empty list_head
101 * @name: the name of the list.
102 *
103 * Explicit initializer for an empty list.
104 *
105 * See also:
106 * LIST_HEAD, list_head_init()
107 *
108 * Example:
109 * static struct list_head my_list = LIST_HEAD_INIT(my_list);
110 */
111 #define LIST_HEAD_INIT(name) { { &name.n, &name.n } }
112
113 /**
114 * LIST_HEAD - define and initialize an empty list_head
115 * @name: the name of the list.
116 *
117 * The LIST_HEAD macro defines a list_head and initializes it to an empty
118 * list. It can be prepended by "static" to define a static list_head.
119 *
120 * See also:
121 * LIST_HEAD_INIT, list_head_init()
122 *
123 * Example:
124 * static LIST_HEAD(my_global_list);
125 */
126 #define LIST_HEAD(name) \
127 struct list_head name = LIST_HEAD_INIT(name)
128
129 /**
130 * list_head_init - initialize a list_head
131 * @h: the list_head to set to the empty list
132 *
133 * Example:
134 * ...
135 * struct parent *parent = malloc(sizeof(*parent));
136 *
137 * list_head_init(&parent->children);
138 * parent->num_children = 0;
139 */
list_head_init(struct list_head * h)140 static inline void list_head_init(struct list_head *h)
141 {
142 h->n.next = h->n.prev = &h->n;
143 }
144
145 /**
146 * list_add - add an entry at the start of a linked list.
147 * @h: the list_head to add the node to
148 * @n: the list_node to add to the list.
149 *
150 * The list_node does not need to be initialized; it will be overwritten.
151 * Example:
152 * struct child *child = malloc(sizeof(*child));
153 *
154 * child->name = "marvin";
155 * list_add(&parent->children, &child->list);
156 * parent->num_children++;
157 */
list_add(struct list_head * h,struct list_node * n)158 static inline void list_add(struct list_head *h, struct list_node *n)
159 {
160 n->next = h->n.next;
161 n->prev = &h->n;
162 h->n.next->prev = n;
163 h->n.next = n;
164 (void)list_debug(h);
165 }
166
167 /**
168 * list_add_before - add an entry before another entry.
169 * @h: the list_head to add the node to (we use it for debug purposes, can be NULL)
170 * @n: the list_node to add to the list.
171 * @p: the list_node of the other entry
172 *
173 * The list_node does not need to be initialized; it will be overwritten.
174 */
list_add_before(struct list_head * h,struct list_node * n,struct list_node * p)175 static inline void list_add_before(struct list_head *h, struct list_node *n,
176 struct list_node *p)
177 {
178 n->next = p;
179 n->prev = p->prev;
180 p->prev = n;
181 n->prev->next = n;
182 if (h)
183 (void)list_debug(h);
184 }
185
186 /**
187 * list_add_tail - add an entry at the end of a linked list.
188 * @h: the list_head to add the node to
189 * @n: the list_node to add to the list.
190 *
191 * The list_node does not need to be initialized; it will be overwritten.
192 * Example:
193 * list_add_tail(&parent->children, &child->list);
194 * parent->num_children++;
195 */
list_add_tail(struct list_head * h,struct list_node * n)196 static inline void list_add_tail(struct list_head *h, struct list_node *n)
197 {
198 n->next = &h->n;
199 n->prev = h->n.prev;
200 h->n.prev->next = n;
201 h->n.prev = n;
202 (void)list_debug(h);
203 }
204
205 /**
206 * list_empty - is a list empty?
207 * @h: the list_head
208 *
209 * If the list is empty, returns true.
210 *
211 * Example:
212 * assert(list_empty(&parent->children) == (parent->num_children == 0));
213 */
list_empty(const struct list_head * h)214 static inline bool list_empty(const struct list_head *h)
215 {
216 (void)list_debug(h);
217 return h->n.next == &h->n;
218 }
219
220 /**
221 * list_empty_nocheck - is a list empty?
222 * @h: the list_head
223 *
224 * If the list is empty, returns true. This doesn't perform any
225 * debug check for list consistency, so it can be called without
226 * locks, racing with the list being modified. This is ok for
227 * checks where an incorrect result is not an issue (optimized
228 * bail out path for example).
229 */
list_empty_nocheck(const struct list_head * h)230 static inline bool list_empty_nocheck(const struct list_head *h)
231 {
232 return h->n.next == &h->n;
233 }
234
235 /**
236 * list_del - delete an entry from an (unknown) linked list.
237 * @n: the list_node to delete from the list.
238 *
239 * Note that this leaves @n in an undefined state; it can be added to
240 * another list, but not deleted again.
241 *
242 * See also:
243 * list_del_from()
244 *
245 * Example:
246 * list_del(&child->list);
247 * parent->num_children--;
248 */
list_del(struct list_node * n)249 static inline void list_del(struct list_node *n)
250 {
251 (void)list_debug_node(n);
252 n->next->prev = n->prev;
253 n->prev->next = n->next;
254 #ifdef CCAN_LIST_DEBUG
255 /* Catch use-after-del. */
256 n->next = n->prev = NULL;
257 #endif
258 }
259
260 /**
261 * list_del_from - delete an entry from a known linked list.
262 * @h: the list_head the node is in.
263 * @n: the list_node to delete from the list.
264 *
265 * This explicitly indicates which list a node is expected to be in,
266 * which is better documentation and can catch more bugs.
267 *
268 * See also: list_del()
269 *
270 * Example:
271 * list_del_from(&parent->children, &child->list);
272 * parent->num_children--;
273 */
list_del_from(struct list_head * h,struct list_node * n)274 static inline void list_del_from(struct list_head *h, struct list_node *n)
275 {
276 #ifdef CCAN_LIST_DEBUG
277 {
278 /* Thorough check: make sure it was in list! */
279 struct list_node *i;
280 for (i = h->n.next; i != n; i = i->next)
281 assert(i != &h->n);
282 }
283 #endif /* CCAN_LIST_DEBUG */
284
285 /* Quick test that catches a surprising number of bugs. */
286 assert(!list_empty(h));
287 list_del(n);
288 }
289
290 /**
291 * list_entry - convert a list_node back into the structure containing it.
292 * @n: the list_node
293 * @type: the type of the entry
294 * @member: the list_node member of the type
295 *
296 * Example:
297 * // First list entry is children.next; convert back to child.
298 * child = list_entry(parent->children.n.next, struct child, list);
299 *
300 * See Also:
301 * list_top(), list_for_each()
302 */
303 #define list_entry(n, type, member) container_of(n, type, member)
304
305 /**
306 * list_top - get the first entry in a list
307 * @h: the list_head
308 * @type: the type of the entry
309 * @member: the list_node member of the type
310 *
311 * If the list is empty, returns NULL.
312 *
313 * Example:
314 * struct child *first;
315 * first = list_top(&parent->children, struct child, list);
316 * if (!first)
317 * printf("Empty list!\n");
318 */
319 #define list_top(h, type, member) \
320 ((type *)list_top_((h), list_off_(type, member)))
321
list_top_(const struct list_head * h,size_t off)322 static inline const void *list_top_(const struct list_head *h, size_t off)
323 {
324 if (list_empty(h))
325 return NULL;
326 return (const char *)h->n.next - off;
327 }
328
329 /**
330 * list_pop - get the first entry in a list and dequeue it
331 * @h: the list_head
332 * @type: the type of the entry
333 * @member: the list_node member of the type
334 */
335 #define list_pop(h, type, member) \
336 ((type *)list_pop_((h), list_off_(type, member)))
list_pop_(struct list_head * h,size_t off)337 static inline const void *list_pop_(struct list_head *h, size_t off)
338 {
339 struct list_node *n;
340
341 if (list_empty(h))
342 return NULL;
343 n = h->n.next;
344 list_del(n);
345 return (const char *)n - off;
346 }
347
348 /**
349 * list_tail - get the last entry in a list
350 * @h: the list_head
351 * @type: the type of the entry
352 * @member: the list_node member of the type
353 *
354 * If the list is empty, returns NULL.
355 *
356 * Example:
357 * struct child *last;
358 * last = list_tail(&parent->children, struct child, list);
359 * if (!last)
360 * printf("Empty list!\n");
361 */
362 #define list_tail(h, type, member) \
363 ((type *)list_tail_((h), list_off_(type, member)))
364
list_tail_(const struct list_head * h,size_t off)365 static inline const void *list_tail_(const struct list_head *h, size_t off)
366 {
367 if (list_empty(h))
368 return NULL;
369 return (const char *)h->n.prev - off;
370 }
371
372 /**
373 * list_for_each - iterate through a list.
374 * @h: the list_head (warning: evaluated multiple times!)
375 * @i: the structure containing the list_node
376 * @member: the list_node member of the structure
377 *
378 * This is a convenient wrapper to iterate @i over the entire list. It's
379 * a for loop, so you can break and continue as normal.
380 *
381 * Example:
382 * list_for_each(&parent->children, child, list)
383 * printf("Name: %s\n", child->name);
384 */
385 #define list_for_each(h, i, member) \
386 list_for_each_off(h, i, list_off_var_(i, member))
387
388 /**
389 * list_for_each_rev - iterate through a list backwards.
390 * @h: the list_head
391 * @i: the structure containing the list_node
392 * @member: the list_node member of the structure
393 *
394 * This is a convenient wrapper to iterate @i over the entire list. It's
395 * a for loop, so you can break and continue as normal.
396 *
397 * Example:
398 * list_for_each_rev(&parent->children, child, list)
399 * printf("Name: %s\n", child->name);
400 */
401 #define list_for_each_rev(h, i, member) \
402 for (i = container_of_var(list_debug(h)->n.prev, i, member); \
403 &i->member != &(h)->n; \
404 i = container_of_var(i->member.prev, i, member))
405
406 /**
407 * list_for_each_safe - iterate through a list, maybe during deletion
408 * @h: the list_head
409 * @i: the structure containing the list_node
410 * @nxt: the structure containing the list_node
411 * @member: the list_node member of the structure
412 *
413 * This is a convenient wrapper to iterate @i over the entire list. It's
414 * a for loop, so you can break and continue as normal. The extra variable
415 * @nxt is used to hold the next element, so you can delete @i from the list.
416 *
417 * Example:
418 * struct child *next;
419 * list_for_each_safe(&parent->children, child, next, list) {
420 * list_del(&child->list);
421 * parent->num_children--;
422 * }
423 */
424 #define list_for_each_safe(h, i, nxt, member) \
425 list_for_each_safe_off(h, i, nxt, list_off_var_(i, member))
426
427 /**
428 * list_for_each_off - iterate through a list of memory regions.
429 * @h: the list_head
430 * @i: the pointer to a memory region which contains list node data.
431 * @off: offset(relative to @i) at which list node data resides.
432 *
433 * This is a low-level wrapper to iterate @i over the entire list, used to
434 * implement all oher, more high-level, for-each constructs. It's a for loop,
435 * so you can break and continue as normal.
436 *
437 * WARNING! Being the low-level macro that it is, this wrapper doesn't know
438 * nor care about the type of @i. The only assumtion made is that @i points
439 * to a chunk of memory that at some @offset, relative to @i, contains a
440 * properly filled `struct node_list' which in turn contains pointers to
441 * memory chunks and it's turtles all the way down. With all that in mind
442 * remember that given the wrong pointer/offset couple this macro will
443 * happily churn all you memory until SEGFAULT stops it, in other words
444 * caveat emptor.
445 *
446 * It is worth mentioning that one of legitimate use-cases for that wrapper
447 * is operation on opaque types with known offset for `struct list_node'
448 * member(preferably 0), because it allows you not to disclose the type of
449 * @i.
450 *
451 * Example:
452 * list_for_each_off(&parent->children, child,
453 * offsetof(struct child, list))
454 * printf("Name: %s\n", child->name);
455 */
456 #define list_for_each_off(h, i, off) \
457 for (i = list_node_to_off_(list_debug(h)->n.next, (off)); \
458 list_node_from_off_((void *)i, (off)) != &(h)->n; \
459 i = list_node_to_off_(list_node_from_off_((void *)i, (off))->next, \
460 (off)))
461
462 /**
463 * list_for_each_safe_off - iterate through a list of memory regions, maybe
464 * during deletion
465 * @h: the list_head
466 * @i: the pointer to a memory region which contains list node data.
467 * @nxt: the structure containing the list_node
468 * @off: offset(relative to @i) at which list node data resides.
469 *
470 * For details see `list_for_each_off' and `list_for_each_safe'
471 * descriptions.
472 *
473 * Example:
474 * list_for_each_safe_off(&parent->children, child,
475 * next, offsetof(struct child, list))
476 * printf("Name: %s\n", child->name);
477 */
478 #define list_for_each_safe_off(h, i, nxt, off) \
479 for (i = list_node_to_off_(list_debug(h)->n.next, (off)), \
480 nxt = list_node_to_off_(list_node_from_off_(i, (off))->next, \
481 (off)); \
482 list_node_from_off_(i, (off)) != &(h)->n; \
483 i = nxt, \
484 nxt = list_node_to_off_(list_node_from_off_(i, (off))->next, \
485 (off)))
486
487
488 /* Other -off variants. */
489 #define list_entry_off(n, type, off) \
490 ((type *)list_node_from_off_((n), (off)))
491
492 #define list_head_off(h, type, off) \
493 ((type *)list_head_off((h), (off)))
494
495 #define list_tail_off(h, type, off) \
496 ((type *)list_tail_((h), (off)))
497
498 #define list_add_off(h, n, off) \
499 list_add((h), list_node_from_off_((n), (off)))
500
501 #define list_del_off(n, off) \
502 list_del(list_node_from_off_((n), (off)))
503
504 #define list_del_from_off(h, n, off) \
505 list_del_from(h, list_node_from_off_((n), (off)))
506
507 /* Offset helper functions so we only single-evaluate. */
list_node_to_off_(struct list_node * node,size_t off)508 static inline void *list_node_to_off_(struct list_node *node, size_t off)
509 {
510 return (void *)((char *)node - off);
511 }
list_node_from_off_(void * ptr,size_t off)512 static inline struct list_node *list_node_from_off_(void *ptr, size_t off)
513 {
514 return (struct list_node *)((char *)ptr + off);
515 }
516
517 /* Get the offset of the member, but make sure it's a list_node. */
518 #define list_off_(type, member) \
519 (container_off(type, member) + \
520 check_type(((type *)0)->member, struct list_node))
521
522 #define list_off_var_(var, member) \
523 (container_off_var(var, member) + \
524 check_type(var->member, struct list_node))
525
526 #endif /* CCAN_LIST_H */
527