1 /* Licensed under BSD-MIT - see LICENSE file for details */
6 #include <ccan/container_of/container_of.h>
7 #include <ccan/check_type/check_type.h>
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)
14 * This is used as an entry in a linked list.
18 * // Linked list of all us children.
19 * struct list_node list;
24 struct list_node *next, *prev;
28 * struct list_head - the head of a doubly-linked list
29 * @h: the list_head (containing next and prev pointers)
31 * This is used as the head of a linked list.
35 * struct list_head children;
36 * unsigned int num_children;
45 * list_check - check head of a list for consistency
47 * @abortstr: the location to print on aborting, or NULL.
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.
54 * Returns the list head if the list is consistent, NULL if not (it
55 * can never return NULL if @abortstr is set).
57 * See also: list_check_node()
60 * static void dump_parent(struct parent *p)
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);
70 struct list_head *list_check(const struct list_head *h, const char *abortstr);
73 * list_check_node - check node of a list for consistency
75 * @abortstr: the location to print on aborting, or NULL.
77 * Check consistency of the list node is in (it must be in one).
79 * See also: list_check()
82 * static void dump_child(const struct child *c)
84 * list_check_node(&c->list, "bad child list");
85 * printf("%s\n", c->name);
88 struct list_node *list_check_node(const struct list_node *n,
89 const char *abortstr);
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__)
95 #define list_debug(h) (h)
96 #define list_debug_node(n) (n)
100 * LIST_HEAD_INIT - initializer for an empty list_head
101 * @name: the name of the list.
103 * Explicit initializer for an empty list.
106 * LIST_HEAD, list_head_init()
109 * static struct list_head my_list = LIST_HEAD_INIT(my_list);
111 #define LIST_HEAD_INIT(name) { { &name.n, &name.n } }
114 * LIST_HEAD - define and initialize an empty list_head
115 * @name: the name of the list.
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.
121 * LIST_HEAD_INIT, list_head_init()
124 * static LIST_HEAD(my_global_list);
126 #define LIST_HEAD(name) \
127 struct list_head name = LIST_HEAD_INIT(name)
130 * list_head_init - initialize a list_head
131 * @h: the list_head to set to the empty list
135 * struct parent *parent = malloc(sizeof(*parent));
137 * list_head_init(&parent->children);
138 * parent->num_children = 0;
140 static inline void list_head_init(struct list_head *h)
142 h->n.next = h->n.prev = &h->n;
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.
150 * The list_node does not need to be initialized; it will be overwritten.
152 * struct child *child = malloc(sizeof(*child));
154 * child->name = "marvin";
155 * list_add(&parent->children, &child->list);
156 * parent->num_children++;
158 static inline void list_add(struct list_head *h, struct list_node *n)
168 * list_add_tail - add an entry at the end of a linked list.
169 * @h: the list_head to add the node to
170 * @n: the list_node to add to the list.
172 * The list_node does not need to be initialized; it will be overwritten.
174 * list_add_tail(&parent->children, &child->list);
175 * parent->num_children++;
177 static inline void list_add_tail(struct list_head *h, struct list_node *n)
187 * list_empty - is a list empty?
190 * If the list is empty, returns true.
193 * assert(list_empty(&parent->children) == (parent->num_children == 0));
195 static inline bool list_empty(const struct list_head *h)
198 return h->n.next == &h->n;
202 * list_del - delete an entry from an (unknown) linked list.
203 * @n: the list_node to delete from the list.
205 * Note that this leaves @n in an undefined state; it can be added to
206 * another list, but not deleted again.
212 * list_del(&child->list);
213 * parent->num_children--;
215 static inline void list_del(struct list_node *n)
217 (void)list_debug_node(n);
218 n->next->prev = n->prev;
219 n->prev->next = n->next;
220 #ifdef CCAN_LIST_DEBUG
221 /* Catch use-after-del. */
222 n->next = n->prev = NULL;
227 * list_del_from - delete an entry from a known linked list.
228 * @h: the list_head the node is in.
229 * @n: the list_node to delete from the list.
231 * This explicitly indicates which list a node is expected to be in,
232 * which is better documentation and can catch more bugs.
234 * See also: list_del()
237 * list_del_from(&parent->children, &child->list);
238 * parent->num_children--;
240 static inline void list_del_from(struct list_head *h, struct list_node *n)
242 #ifdef CCAN_LIST_DEBUG
244 /* Thorough check: make sure it was in list! */
246 for (i = h->n.next; i != n; i = i->next)
249 #endif /* CCAN_LIST_DEBUG */
251 /* Quick test that catches a surprising number of bugs. */
252 assert(!list_empty(h));
257 * list_entry - convert a list_node back into the structure containing it.
259 * @type: the type of the entry
260 * @member: the list_node member of the type
263 * // First list entry is children.next; convert back to child.
264 * child = list_entry(parent->children.n.next, struct child, list);
267 * list_top(), list_for_each()
269 #define list_entry(n, type, member) container_of(n, type, member)
272 * list_top - get the first entry in a list
274 * @type: the type of the entry
275 * @member: the list_node member of the type
277 * If the list is empty, returns NULL.
280 * struct child *first;
281 * first = list_top(&parent->children, struct child, list);
283 * printf("Empty list!\n");
285 #define list_top(h, type, member) \
286 ((type *)list_top_((h), list_off_(type, member)))
288 static inline const void *list_top_(const struct list_head *h, size_t off)
292 return (const char *)h->n.next - off;
296 * list_tail - get the last entry in a list
298 * @type: the type of the entry
299 * @member: the list_node member of the type
301 * If the list is empty, returns NULL.
304 * struct child *last;
305 * last = list_tail(&parent->children, struct child, list);
307 * printf("Empty list!\n");
309 #define list_tail(h, type, member) \
310 ((type *)list_tail_((h), list_off_(type, member)))
312 static inline const void *list_tail_(const struct list_head *h, size_t off)
316 return (const char *)h->n.prev - off;
320 * list_for_each - iterate through a list.
321 * @h: the list_head (warning: evaluated multiple times!)
322 * @i: the structure containing the list_node
323 * @member: the list_node member of the structure
325 * This is a convenient wrapper to iterate @i over the entire list. It's
326 * a for loop, so you can break and continue as normal.
329 * list_for_each(&parent->children, child, list)
330 * printf("Name: %s\n", child->name);
332 #define list_for_each(h, i, member) \
333 list_for_each_off(h, i, list_off_var_(i, member))
336 * list_for_each_rev - iterate through a list backwards.
338 * @i: the structure containing the list_node
339 * @member: the list_node member of the structure
341 * This is a convenient wrapper to iterate @i over the entire list. It's
342 * a for loop, so you can break and continue as normal.
345 * list_for_each_rev(&parent->children, child, list)
346 * printf("Name: %s\n", child->name);
348 #define list_for_each_rev(h, i, member) \
349 for (i = container_of_var(list_debug(h)->n.prev, i, member); \
350 &i->member != &(h)->n; \
351 i = container_of_var(i->member.prev, i, member))
354 * list_for_each_safe - iterate through a list, maybe during deletion
356 * @i: the structure containing the list_node
357 * @nxt: the structure containing the list_node
358 * @member: the list_node member of the structure
360 * This is a convenient wrapper to iterate @i over the entire list. It's
361 * a for loop, so you can break and continue as normal. The extra variable
362 * @nxt is used to hold the next element, so you can delete @i from the list.
365 * struct child *next;
366 * list_for_each_safe(&parent->children, child, next, list) {
367 * list_del(&child->list);
368 * parent->num_children--;
371 #define list_for_each_safe(h, i, nxt, member) \
372 list_for_each_safe_off(h, i, nxt, list_off_var_(i, member))
375 * list_for_each_off - iterate through a list of memory regions.
377 * @i: the pointer to a memory region wich contains list node data.
378 * @off: offset(relative to @i) at which list node data resides.
380 * This is a low-level wrapper to iterate @i over the entire list, used to
381 * implement all oher, more high-level, for-each constructs. It's a for loop,
382 * so you can break and continue as normal.
384 * WARNING! Being the low-level macro that it is, this wrapper doesn't know
385 * nor care about the type of @i. The only assumtion made is that @i points
386 * to a chunk of memory that at some @offset, relative to @i, contains a
387 * properly filled `struct node_list' which in turn contains pointers to
388 * memory chunks and it's turtles all the way down. Whith all that in mind
389 * remember that given the wrong pointer/offset couple this macro will
390 * happilly churn all you memory untill SEGFAULT stops it, in other words
393 * It is worth mentioning that one of legitimate use-cases for that wrapper
394 * is operation on opaque types with known offset for `struct list_node'
395 * member(preferably 0), because it allows you not to disclose the type of
399 * list_for_each_off(&parent->children, child,
400 * offsetof(struct child, list))
401 * printf("Name: %s\n", child->name);
403 #define list_for_each_off(h, i, off) \
404 for (i = list_node_to_off_(list_debug(h)->n.next, (off)); \
405 list_node_from_off_((void *)i, (off)) != &(h)->n; \
406 i = list_node_to_off_(list_node_from_off_((void *)i, (off))->next, \
410 * list_for_each_safe_off - iterate through a list of memory regions, maybe
413 * @i: the pointer to a memory region wich contains list node data.
414 * @nxt: the structure containing the list_node
415 * @off: offset(relative to @i) at which list node data resides.
417 * For details see `list_for_each_off' and `list_for_each_safe'
421 * list_for_each_safe_off(&parent->children, child,
422 * next, offsetof(struct child, list))
423 * printf("Name: %s\n", child->name);
425 #define list_for_each_safe_off(h, i, nxt, off) \
426 for (i = list_node_to_off_(list_debug(h)->n.next, (off)), \
427 nxt = list_node_to_off_(list_node_from_off_(i, (off))->next, \
429 list_node_from_off_(i, (off)) != &(h)->n; \
431 nxt = list_node_to_off_(list_node_from_off_(i, (off))->next, \
435 /* Other -off variants. */
436 #define list_entry_off(n, type, off) \
437 ((type *)list_node_from_off_((n), (off)))
439 #define list_head_off(h, type, off) \
440 ((type *)list_head_off((h), (off)))
442 #define list_tail_off(h, type, off) \
443 ((type *)list_tail_((h), (off)))
445 #define list_add_off(h, n, off) \
446 list_add((h), list_node_from_off_((n), (off)))
448 #define list_del_off(n, off) \
449 list_del(list_node_from_off_((n), (off)))
451 #define list_del_from_off(h, n, off) \
452 list_del_from(h, list_node_from_off_((n), (off)))
454 /* Offset helper functions so we only single-evaluate. */
455 static inline void *list_node_to_off_(struct list_node *node, size_t off)
457 return (void *)((char *)node - off);
459 static inline struct list_node *list_node_from_off_(void *ptr, size_t off)
461 return (struct list_node *)((char *)ptr + off);
464 /* Get the offset of the member, but make sure it's a list_node. */
465 #define list_off_(type, member) \
466 (container_off(type, member) + \
467 check_type(((type *)0)->member, struct list_node))
469 #define list_off_var_(var, member) \
470 (container_off_var(var, member) + \
471 check_type(var->member, struct list_node))
473 #endif /* CCAN_LIST_H */