1 /*
2 * Copyright (c) 2013-2015 Wind River Systems, Inc.
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7 /**
8 * @file
9 * @brief Doubly-linked list implementation
10 *
11 * Doubly-linked list implementation using inline macros/functions.
12 * This API is not thread safe, and thus if a list is used across threads,
13 * calls to functions must be protected with synchronization primitives.
14 *
15 * The lists are expected to be initialized such that both the head and tail
16 * pointers point to the list itself. Initializing the lists in such a fashion
17 * simplifies the adding and removing of nodes to/from the list.
18 */
19
20 #ifndef ZEPHYR_INCLUDE_SYS_DLIST_H_
21 #define ZEPHYR_INCLUDE_SYS_DLIST_H_
22
23 #include <stddef.h>
24 #include <stdbool.h>
25 #include <zephyr/toolchain.h>
26
27 #ifdef __cplusplus
28 extern "C" {
29 #endif
30
31 /**
32 * @defgroup doubly-linked-list_apis Doubly-linked list
33 * @ingroup datastructure_apis
34 * @{
35 */
36
37 struct _dnode {
38 union {
39 struct _dnode *head; /* ptr to head of list (sys_dlist_t) */
40 struct _dnode *next; /* ptr to next node (sys_dnode_t) */
41 };
42 union {
43 struct _dnode *tail; /* ptr to tail of list (sys_dlist_t) */
44 struct _dnode *prev; /* ptr to previous node (sys_dnode_t) */
45 };
46 };
47
48 typedef struct _dnode sys_dlist_t;
49 typedef struct _dnode sys_dnode_t;
50
51
52 /**
53 * @brief Provide the primitive to iterate on a list
54 * Note: the loop is unsafe and thus __dn should not be removed
55 *
56 * User _MUST_ add the loop statement curly braces enclosing its own code:
57 *
58 * SYS_DLIST_FOR_EACH_NODE(l, n) {
59 * <user code>
60 * }
61 *
62 * This and other SYS_DLIST_*() macros are not thread safe.
63 *
64 * @param __dl A pointer on a sys_dlist_t to iterate on
65 * @param __dn A sys_dnode_t pointer to peek each node of the list
66 */
67 #define SYS_DLIST_FOR_EACH_NODE(__dl, __dn) \
68 for (__dn = sys_dlist_peek_head(__dl); __dn != NULL; \
69 __dn = sys_dlist_peek_next(__dl, __dn))
70
71 /**
72 * @brief Provide the primitive to iterate on a list, from a node in the list
73 * Note: the loop is unsafe and thus __dn should not be removed
74 *
75 * User _MUST_ add the loop statement curly braces enclosing its own code:
76 *
77 * SYS_DLIST_ITERATE_FROM_NODE(l, n) {
78 * <user code>
79 * }
80 *
81 * Like SYS_DLIST_FOR_EACH_NODE(), but __dn already contains a node in the list
82 * where to start searching for the next entry from. If NULL, it starts from
83 * the head.
84 *
85 * This and other SYS_DLIST_*() macros are not thread safe.
86 *
87 * @param __dl A pointer on a sys_dlist_t to iterate on
88 * @param __dn A sys_dnode_t pointer to peek each node of the list;
89 * it contains the starting node, or NULL to start from the head
90 */
91 #define SYS_DLIST_ITERATE_FROM_NODE(__dl, __dn) \
92 for (__dn = __dn ? sys_dlist_peek_next_no_check(__dl, __dn) \
93 : sys_dlist_peek_head(__dl); \
94 __dn != NULL; \
95 __dn = sys_dlist_peek_next(__dl, __dn))
96
97 /**
98 * @brief Provide the primitive to safely iterate on a list
99 * Note: __dn can be removed, it will not break the loop.
100 *
101 * User _MUST_ add the loop statement curly braces enclosing its own code:
102 *
103 * SYS_DLIST_FOR_EACH_NODE_SAFE(l, n, s) {
104 * <user code>
105 * }
106 *
107 * This and other SYS_DLIST_*() macros are not thread safe.
108 *
109 * @param __dl A pointer on a sys_dlist_t to iterate on
110 * @param __dn A sys_dnode_t pointer to peek each node of the list
111 * @param __dns A sys_dnode_t pointer for the loop to run safely
112 */
113 #define SYS_DLIST_FOR_EACH_NODE_SAFE(__dl, __dn, __dns) \
114 for (__dn = sys_dlist_peek_head(__dl), \
115 __dns = sys_dlist_peek_next(__dl, __dn); \
116 __dn != NULL; __dn = __dns, \
117 __dns = sys_dlist_peek_next(__dl, __dn))
118
119 /*
120 * @brief Provide the primitive to resolve the container of a list node
121 * Note: it is safe to use with NULL pointer nodes
122 *
123 * @param __dn A pointer on a sys_dnode_t to get its container
124 * @param __cn Container struct type pointer
125 * @param __n The field name of sys_dnode_t within the container struct
126 */
127 #define SYS_DLIST_CONTAINER(__dn, __cn, __n) \
128 ((__dn != NULL) ? CONTAINER_OF(__dn, __typeof__(*__cn), __n) : NULL)
129 /*
130 * @brief Provide the primitive to peek container of the list head
131 *
132 * @param __dl A pointer on a sys_dlist_t to peek
133 * @param __cn Container struct type pointer
134 * @param __n The field name of sys_dnode_t within the container struct
135 */
136 #define SYS_DLIST_PEEK_HEAD_CONTAINER(__dl, __cn, __n) \
137 SYS_DLIST_CONTAINER(sys_dlist_peek_head(__dl), __cn, __n)
138
139 /*
140 * @brief Provide the primitive to peek the next container
141 *
142 * @param __dl A pointer on a sys_dlist_t to peek
143 * @param __cn Container struct type pointer
144 * @param __n The field name of sys_dnode_t within the container struct
145 */
146 #define SYS_DLIST_PEEK_NEXT_CONTAINER(__dl, __cn, __n) \
147 ((__cn != NULL) ? \
148 SYS_DLIST_CONTAINER(sys_dlist_peek_next(__dl, &(__cn->__n)), \
149 __cn, __n) : NULL)
150
151 /**
152 * @brief Provide the primitive to iterate on a list under a container
153 * Note: the loop is unsafe and thus __cn should not be detached
154 *
155 * User _MUST_ add the loop statement curly braces enclosing its own code:
156 *
157 * SYS_DLIST_FOR_EACH_CONTAINER(l, c, n) {
158 * <user code>
159 * }
160 *
161 * @param __dl A pointer on a sys_dlist_t to iterate on
162 * @param __cn A pointer to peek each entry of the list
163 * @param __n The field name of sys_dnode_t within the container struct
164 */
165 #define SYS_DLIST_FOR_EACH_CONTAINER(__dl, __cn, __n) \
166 for (__cn = SYS_DLIST_PEEK_HEAD_CONTAINER(__dl, __cn, __n); \
167 __cn != NULL; \
168 __cn = SYS_DLIST_PEEK_NEXT_CONTAINER(__dl, __cn, __n))
169
170 /**
171 * @brief Provide the primitive to safely iterate on a list under a container
172 * Note: __cn can be detached, it will not break the loop.
173 *
174 * User _MUST_ add the loop statement curly braces enclosing its own code:
175 *
176 * SYS_DLIST_FOR_EACH_CONTAINER_SAFE(l, c, cn, n) {
177 * <user code>
178 * }
179 *
180 * @param __dl A pointer on a sys_dlist_t to iterate on
181 * @param __cn A pointer to peek each entry of the list
182 * @param __cns A pointer for the loop to run safely
183 * @param __n The field name of sys_dnode_t within the container struct
184 */
185 #define SYS_DLIST_FOR_EACH_CONTAINER_SAFE(__dl, __cn, __cns, __n) \
186 for (__cn = SYS_DLIST_PEEK_HEAD_CONTAINER(__dl, __cn, __n), \
187 __cns = SYS_DLIST_PEEK_NEXT_CONTAINER(__dl, __cn, __n); \
188 __cn != NULL; __cn = __cns, \
189 __cns = SYS_DLIST_PEEK_NEXT_CONTAINER(__dl, __cn, __n))
190
191 /**
192 * @brief initialize list to its empty state
193 *
194 * @param list the doubly-linked list
195 */
196
sys_dlist_init(sys_dlist_t * list)197 static inline void sys_dlist_init(sys_dlist_t *list)
198 {
199 list->head = (sys_dnode_t *)list;
200 list->tail = (sys_dnode_t *)list;
201 }
202
203 #define SYS_DLIST_STATIC_INIT(ptr_to_list) { {(ptr_to_list)}, {(ptr_to_list)} }
204
205 /**
206 * @brief initialize node to its state when not in a list
207 *
208 * @param node the node
209 */
210
sys_dnode_init(sys_dnode_t * node)211 static inline void sys_dnode_init(sys_dnode_t *node)
212 {
213 node->next = NULL;
214 node->prev = NULL;
215 }
216
217 /**
218 * @brief check if a node is a member of any list
219 *
220 * @param node the node
221 *
222 * @return true if node is linked into a list, false if it is not
223 */
224
sys_dnode_is_linked(const sys_dnode_t * node)225 static inline bool sys_dnode_is_linked(const sys_dnode_t *node)
226 {
227 return node->next != NULL;
228 }
229
230 /**
231 * @brief check if a node is the list's head
232 *
233 * @param list the doubly-linked list to operate on
234 * @param node the node to check
235 *
236 * @return true if node is the head, false otherwise
237 */
238
sys_dlist_is_head(sys_dlist_t * list,sys_dnode_t * node)239 static inline bool sys_dlist_is_head(sys_dlist_t *list, sys_dnode_t *node)
240 {
241 return list->head == node;
242 }
243
244 /**
245 * @brief check if a node is the list's tail
246 *
247 * @param list the doubly-linked list to operate on
248 * @param node the node to check
249 *
250 * @return true if node is the tail, false otherwise
251 */
252
sys_dlist_is_tail(sys_dlist_t * list,sys_dnode_t * node)253 static inline bool sys_dlist_is_tail(sys_dlist_t *list, sys_dnode_t *node)
254 {
255 return list->tail == node;
256 }
257
258 /**
259 * @brief check if the list is empty
260 *
261 * @param list the doubly-linked list to operate on
262 *
263 * @return true if empty, false otherwise
264 */
265
sys_dlist_is_empty(sys_dlist_t * list)266 static inline bool sys_dlist_is_empty(sys_dlist_t *list)
267 {
268 return list->head == list;
269 }
270
271 /**
272 * @brief check if more than one node present
273 *
274 * This and other sys_dlist_*() functions are not thread safe.
275 *
276 * @param list the doubly-linked list to operate on
277 *
278 * @return true if multiple nodes, false otherwise
279 */
280
sys_dlist_has_multiple_nodes(sys_dlist_t * list)281 static inline bool sys_dlist_has_multiple_nodes(sys_dlist_t *list)
282 {
283 return list->head != list->tail;
284 }
285
286 /**
287 * @brief get a reference to the head item in the list
288 *
289 * @param list the doubly-linked list to operate on
290 *
291 * @return a pointer to the head element, NULL if list is empty
292 */
293
sys_dlist_peek_head(sys_dlist_t * list)294 static inline sys_dnode_t *sys_dlist_peek_head(sys_dlist_t *list)
295 {
296 return sys_dlist_is_empty(list) ? NULL : list->head;
297 }
298
299 /**
300 * @brief get a reference to the head item in the list
301 *
302 * The list must be known to be non-empty.
303 *
304 * @param list the doubly-linked list to operate on
305 *
306 * @return a pointer to the head element
307 */
308
sys_dlist_peek_head_not_empty(sys_dlist_t * list)309 static inline sys_dnode_t *sys_dlist_peek_head_not_empty(sys_dlist_t *list)
310 {
311 return list->head;
312 }
313
314 /**
315 * @brief get a reference to the next item in the list, node is not NULL
316 *
317 * Faster than sys_dlist_peek_next() if node is known not to be NULL.
318 *
319 * @param list the doubly-linked list to operate on
320 * @param node the node from which to get the next element in the list
321 *
322 * @return a pointer to the next element from a node, NULL if node is the tail
323 */
324
sys_dlist_peek_next_no_check(sys_dlist_t * list,sys_dnode_t * node)325 static inline sys_dnode_t *sys_dlist_peek_next_no_check(sys_dlist_t *list,
326 sys_dnode_t *node)
327 {
328 return (node == list->tail) ? NULL : node->next;
329 }
330
331 /**
332 * @brief get a reference to the next item in the list
333 *
334 * @param list the doubly-linked list to operate on
335 * @param node the node from which to get the next element in the list
336 *
337 * @return a pointer to the next element from a node, NULL if node is the tail
338 * or NULL (when node comes from reading the head of an empty list).
339 */
340
sys_dlist_peek_next(sys_dlist_t * list,sys_dnode_t * node)341 static inline sys_dnode_t *sys_dlist_peek_next(sys_dlist_t *list,
342 sys_dnode_t *node)
343 {
344 return (node != NULL) ? sys_dlist_peek_next_no_check(list, node) : NULL;
345 }
346
347 /**
348 * @brief get a reference to the previous item in the list, node is not NULL
349 *
350 * Faster than sys_dlist_peek_prev() if node is known not to be NULL.
351 *
352 * @param list the doubly-linked list to operate on
353 * @param node the node from which to get the previous element in the list
354 *
355 * @return a pointer to the previous element from a node, NULL if node is the
356 * tail
357 */
358
sys_dlist_peek_prev_no_check(sys_dlist_t * list,sys_dnode_t * node)359 static inline sys_dnode_t *sys_dlist_peek_prev_no_check(sys_dlist_t *list,
360 sys_dnode_t *node)
361 {
362 return (node == list->head) ? NULL : node->prev;
363 }
364
365 /**
366 * @brief get a reference to the previous item in the list
367 *
368 * @param list the doubly-linked list to operate on
369 * @param node the node from which to get the previous element in the list
370 *
371 * @return a pointer to the previous element from a node, NULL if node is the
372 * tail or NULL (when node comes from reading the head of an empty
373 * list).
374 */
375
sys_dlist_peek_prev(sys_dlist_t * list,sys_dnode_t * node)376 static inline sys_dnode_t *sys_dlist_peek_prev(sys_dlist_t *list,
377 sys_dnode_t *node)
378 {
379 return (node != NULL) ? sys_dlist_peek_prev_no_check(list, node) : NULL;
380 }
381
382 /**
383 * @brief get a reference to the tail item in the list
384 *
385 * @param list the doubly-linked list to operate on
386 *
387 * @return a pointer to the tail element, NULL if list is empty
388 */
389
sys_dlist_peek_tail(sys_dlist_t * list)390 static inline sys_dnode_t *sys_dlist_peek_tail(sys_dlist_t *list)
391 {
392 return sys_dlist_is_empty(list) ? NULL : list->tail;
393 }
394
395 /**
396 * @brief add node to tail of list
397 *
398 * This and other sys_dlist_*() functions are not thread safe.
399 *
400 * @param list the doubly-linked list to operate on
401 * @param node the element to append
402 */
403
sys_dlist_append(sys_dlist_t * list,sys_dnode_t * node)404 static inline void sys_dlist_append(sys_dlist_t *list, sys_dnode_t *node)
405 {
406 sys_dnode_t *const tail = list->tail;
407
408 node->next = list;
409 node->prev = tail;
410
411 tail->next = node;
412 list->tail = node;
413 }
414
415 /**
416 * @brief add node to head of list
417 *
418 * This and other sys_dlist_*() functions are not thread safe.
419 *
420 * @param list the doubly-linked list to operate on
421 * @param node the element to append
422 */
423
sys_dlist_prepend(sys_dlist_t * list,sys_dnode_t * node)424 static inline void sys_dlist_prepend(sys_dlist_t *list, sys_dnode_t *node)
425 {
426 sys_dnode_t *const head = list->head;
427
428 node->next = head;
429 node->prev = list;
430
431 head->prev = node;
432 list->head = node;
433 }
434
435 /**
436 * @brief Insert a node into a list
437 *
438 * Insert a node before a specified node in a dlist.
439 *
440 * @param successor the position before which "node" will be inserted
441 * @param node the element to insert
442 */
sys_dlist_insert(sys_dnode_t * successor,sys_dnode_t * node)443 static inline void sys_dlist_insert(sys_dnode_t *successor, sys_dnode_t *node)
444 {
445 sys_dnode_t *const prev = successor->prev;
446
447 node->prev = prev;
448 node->next = successor;
449 prev->next = node;
450 successor->prev = node;
451 }
452
453 /**
454 * @brief insert node at position
455 *
456 * Insert a node in a location depending on a external condition. The cond()
457 * function checks if the node is to be inserted _before_ the current node
458 * against which it is checked.
459 * This and other sys_dlist_*() functions are not thread safe.
460 *
461 * @param list the doubly-linked list to operate on
462 * @param node the element to insert
463 * @param cond a function that determines if the current node is the correct
464 * insert point
465 * @param data parameter to cond()
466 */
467
sys_dlist_insert_at(sys_dlist_t * list,sys_dnode_t * node,int (* cond)(sys_dnode_t * node,void * data),void * data)468 static inline void sys_dlist_insert_at(sys_dlist_t *list, sys_dnode_t *node,
469 int (*cond)(sys_dnode_t *node, void *data), void *data)
470 {
471 if (sys_dlist_is_empty(list)) {
472 sys_dlist_append(list, node);
473 } else {
474 sys_dnode_t *pos = sys_dlist_peek_head(list);
475
476 while ((pos != NULL) && (cond(pos, data) == 0)) {
477 pos = sys_dlist_peek_next(list, pos);
478 }
479 if (pos != NULL) {
480 sys_dlist_insert(pos, node);
481 } else {
482 sys_dlist_append(list, node);
483 }
484 }
485 }
486
487 /**
488 * @brief remove a specific node from a list
489 *
490 * The list is implicit from the node. The node must be part of a list.
491 * This and other sys_dlist_*() functions are not thread safe.
492 *
493 * @param node the node to remove
494 */
495
sys_dlist_remove(sys_dnode_t * node)496 static inline void sys_dlist_remove(sys_dnode_t *node)
497 {
498 sys_dnode_t *const prev = node->prev;
499 sys_dnode_t *const next = node->next;
500
501 prev->next = next;
502 next->prev = prev;
503 sys_dnode_init(node);
504 }
505
506 /**
507 * @brief get the first node in a list
508 *
509 * This and other sys_dlist_*() functions are not thread safe.
510 *
511 * @param list the doubly-linked list to operate on
512 *
513 * @return the first node in the list, NULL if list is empty
514 */
515
sys_dlist_get(sys_dlist_t * list)516 static inline sys_dnode_t *sys_dlist_get(sys_dlist_t *list)
517 {
518 sys_dnode_t *node = NULL;
519
520 if (!sys_dlist_is_empty(list)) {
521 node = list->head;
522 sys_dlist_remove(node);
523 }
524
525 return node;
526 }
527
528 /** @} */
529
530 #ifdef __cplusplus
531 }
532 #endif
533
534 #endif /* ZEPHYR_INCLUDE_SYS_DLIST_H_ */
535
