1 /*
2 * Copyright © 2010 Intel Corporation
3 * Copyright © 2010 Francisco Jerez <currojerez@riseup.net>
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice (including the next
13 * paragraph) shall be included in all copies or substantial portions of the
14 * Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
22 * IN THE SOFTWARE.
23 *
24 */
25
26 #ifndef _GLVND_LIST_H_
27 #define _GLVND_LIST_H_
28
29 #include <stddef.h> /* offsetof() */
30
31 /**
32 * @file Classic doubly-link circular list implementation.
33 * For real usage examples of the linked list, see the file test/list.c
34 *
35 * Example:
36 * We need to keep a list of struct foo in the parent struct bar, i.e. what
37 * we want is something like this.
38 *
39 * struct bar {
40 * ...
41 * struct foo *list_of_foos; -----> struct foo {}, struct foo {}, struct foo{}
42 * ...
43 * }
44 *
45 * We need one list head in bar and a list element in all list_of_foos (both are of
46 * data type 'struct glvnd_list').
47 *
48 * struct bar {
49 * ...
50 * struct glvnd_list list_of_foos;
51 * ...
52 * }
53 *
54 * struct foo {
55 * ...
56 * struct glvnd_list entry;
57 * ...
58 * }
59 *
60 * Now we initialize the list head:
61 *
62 * struct bar bar;
63 * ...
64 * glvnd_list_init(&bar.list_of_foos);
65 *
66 * Then we create the first element and add it to this list:
67 *
68 * struct foo *foo = malloc(...);
69 * ....
70 * glvnd_list_add(&foo->entry, &bar.list_of_foos);
71 *
72 * Repeat the above for each element you want to add to the list. Deleting
73 * works with the element itself.
74 * glvnd_list_del(&foo->entry);
75 * free(foo);
76 *
77 * Note: calling glvnd_list_del(&bar.list_of_foos) will set bar.list_of_foos to an empty
78 * list again.
79 *
80 * Looping through the list requires a 'struct foo' as iterator and the
81 * name of the field the subnodes use.
82 *
83 * struct foo *iterator;
84 * glvnd_list_for_each_entry(iterator, &bar.list_of_foos, entry) {
85 * if (iterator->something == ...)
86 * ...
87 * }
88 *
89 * Note: You must not call glvnd_list_del() on the iterator if you continue the
90 * loop. You need to run the safe for-each loop instead:
91 *
92 * struct foo *iterator, *next;
93 * glvnd_list_for_each_entry_safe(iterator, next, &bar.list_of_foos, entry) {
94 * if (...)
95 * glvnd_list_del(&iterator->entry);
96 * }
97 *
98 */
99
100 /**
101 * The linkage struct for list nodes. This struct must be part of your
102 * to-be-linked struct. struct glvnd_list is required for both the head of the
103 * list and for each list node.
104 *
105 * Position and name of the struct glvnd_list field is irrelevant.
106 * There are no requirements that elements of a list are of the same type.
107 * There are no requirements for a list head, any struct glvnd_list can be a list
108 * head.
109 */
110 struct glvnd_list {
111 struct glvnd_list *next, *prev;
112 };
113
114 /**
115 * Initialize the list as an empty list.
116 *
117 * Example:
118 * glvnd_list_init(&bar->list_of_foos);
119 *
120 * @param The list to initialized.
121 */
122 static inline void
glvnd_list_init(struct glvnd_list * list)123 glvnd_list_init(struct glvnd_list *list)
124 {
125 list->next = list->prev = list;
126 }
127
128 static inline void
__glvnd_list_add(struct glvnd_list * entry,struct glvnd_list * prev,struct glvnd_list * next)129 __glvnd_list_add(struct glvnd_list *entry,
130 struct glvnd_list *prev, struct glvnd_list *next)
131 {
132 next->prev = entry;
133 entry->next = next;
134 entry->prev = prev;
135 prev->next = entry;
136 }
137
138 /**
139 * Insert a new element after the given list head. The new element does not
140 * need to be initialised as empty list.
141 * The list changes from:
142 * head → some element → ...
143 * to
144 * head → new element → older element → ...
145 *
146 * Example:
147 * struct foo *newfoo = malloc(...);
148 * glvnd_list_add(&newfoo->entry, &bar->list_of_foos);
149 *
150 * @param entry The new element to prepend to the list.
151 * @param head The existing list.
152 */
153 static inline void
glvnd_list_add(struct glvnd_list * entry,struct glvnd_list * head)154 glvnd_list_add(struct glvnd_list *entry, struct glvnd_list *head)
155 {
156 __glvnd_list_add(entry, head, head->next);
157 }
158
159 /**
160 * Append a new element to the end of the list given with this list head.
161 *
162 * The list changes from:
163 * head → some element → ... → lastelement
164 * to
165 * head → some element → ... → lastelement → new element
166 *
167 * Example:
168 * struct foo *newfoo = malloc(...);
169 * glvnd_list_append(&newfoo->entry, &bar->list_of_foos);
170 *
171 * @param entry The new element to prepend to the list.
172 * @param head The existing list.
173 */
174 static inline void
glvnd_list_append(struct glvnd_list * entry,struct glvnd_list * head)175 glvnd_list_append(struct glvnd_list *entry, struct glvnd_list *head)
176 {
177 __glvnd_list_add(entry, head->prev, head);
178 }
179
180 static inline void
__glvnd_list_del(struct glvnd_list * prev,struct glvnd_list * next)181 __glvnd_list_del(struct glvnd_list *prev, struct glvnd_list *next)
182 {
183 next->prev = prev;
184 prev->next = next;
185 }
186
187 /**
188 * Remove the element from the list it is in. Using this function will reset
189 * the pointers to/from this element so it is removed from the list. It does
190 * NOT free the element itself or manipulate it otherwise.
191 *
192 * Using glvnd_list_del on a pure list head (like in the example at the top of
193 * this file) will NOT remove the first element from
194 * the list but rather reset the list as empty list.
195 *
196 * Example:
197 * glvnd_list_del(&foo->entry);
198 *
199 * @param entry The element to remove.
200 */
201 static inline void
glvnd_list_del(struct glvnd_list * entry)202 glvnd_list_del(struct glvnd_list *entry)
203 {
204 __glvnd_list_del(entry->prev, entry->next);
205 glvnd_list_init(entry);
206 }
207
208 /**
209 * Check if the list is empty.
210 *
211 * Example:
212 * glvnd_list_is_empty(&bar->list_of_foos);
213 *
214 * @return True if the list contains one or more elements or False otherwise.
215 */
216 static inline int
glvnd_list_is_empty(struct glvnd_list * head)217 glvnd_list_is_empty(struct glvnd_list *head)
218 {
219 return head->next == head;
220 }
221
222 /**
223 * Returns a pointer to the container of this list element.
224 *
225 * Example:
226 * struct foo* f;
227 * f = glvnd_container_of(&foo->entry, struct foo, entry);
228 * assert(f == foo);
229 *
230 * @param ptr Pointer to the struct glvnd_list.
231 * @param type Data type of the list element.
232 * @param member Member name of the struct glvnd_list field in the list element.
233 * @return A pointer to the data struct containing the list head.
234 */
235 #ifndef glvnd_container_of
236 #define glvnd_container_of(ptr, type, member) \
237 (type *)((char *)(ptr) - offsetof(type, member))
238 #endif
239
240 /**
241 * Alias of glvnd_container_of
242 */
243 #define glvnd_list_entry(ptr, type, member) \
244 glvnd_container_of(ptr, type, member)
245
246 /**
247 * Retrieve the first list entry for the given list pointer.
248 *
249 * Example:
250 * struct foo *first;
251 * first = glvnd_list_first_entry(&bar->list_of_foos, struct foo, list_of_foos);
252 *
253 * @param ptr The list head
254 * @param type Data type of the list element to retrieve
255 * @param member Member name of the struct glvnd_list field in the list element.
256 * @return A pointer to the first list element.
257 */
258 #define glvnd_list_first_entry(ptr, type, member) \
259 glvnd_list_entry((ptr)->next, type, member)
260
261 /**
262 * Retrieve the last list entry for the given listpointer.
263 *
264 * Example:
265 * struct foo *first;
266 * first = glvnd_list_last_entry(&bar->list_of_foos, struct foo, list_of_foos);
267 *
268 * @param ptr The list head
269 * @param type Data type of the list element to retrieve
270 * @param member Member name of the struct glvnd_list field in the list element.
271 * @return A pointer to the last list element.
272 */
273 #define glvnd_list_last_entry(ptr, type, member) \
274 glvnd_list_entry((ptr)->prev, type, member)
275
276 #ifdef HAVE_TYPEOF
277 #define __glvnd_container_of(ptr, sample, member) \
278 glvnd_container_of(ptr, typeof(*sample), member)
279 #else
280 /* This implementation of __glvnd_container_of has undefined behavior according
281 * to the C standard, but it works in many cases. If your compiler doesn't
282 * support typeof() and fails with this implementation, please try a newer
283 * compiler.
284 */
285 #define __glvnd_container_of(ptr, sample, member) \
286 (void *)((char *)(ptr) \
287 - ((char *)&(sample)->member - (char *)(sample)))
288 #endif
289
290 /**
291 * Loop through the list given by head and set pos to struct in the list.
292 *
293 * Example:
294 * struct foo *iterator;
295 * glvnd_list_for_each_entry(iterator, &bar->list_of_foos, entry) {
296 * [modify iterator]
297 * }
298 *
299 * This macro is not safe for node deletion. Use glvnd_list_for_each_entry_safe
300 * instead.
301 *
302 * @param pos Iterator variable of the type of the list elements.
303 * @param head List head
304 * @param member Member name of the struct glvnd_list in the list elements.
305 *
306 */
307 #define glvnd_list_for_each_entry(pos, head, member) \
308 for (pos = __glvnd_container_of((head)->next, pos, member); \
309 &pos->member != (head); \
310 pos = __glvnd_container_of(pos->member.next, pos, member))
311
312 /**
313 * Loop through the list, keeping a backup pointer to the element. This
314 * macro allows for the deletion of a list element while looping through the
315 * list.
316 *
317 * See glvnd_list_for_each_entry for more details.
318 */
319 #define glvnd_list_for_each_entry_safe(pos, tmp, head, member) \
320 for (pos = __glvnd_container_of((head)->next, pos, member), \
321 tmp = __glvnd_container_of(pos->member.next, pos, member); \
322 &pos->member != (head); \
323 pos = tmp, tmp = __glvnd_container_of(pos->member.next, tmp, member))
324
325 /* NULL-Terminated List Interface
326 *
327 * The interface below does _not_ use the struct glvnd_list as described above.
328 * It is mainly for legacy structures that cannot easily be switched to
329 * struct glvnd_list.
330 *
331 * This interface is for structs like
332 * struct foo {
333 * [...]
334 * struct foo *next;
335 * [...]
336 * };
337 *
338 * The position and field name of "next" are arbitrary.
339 */
340
341 /**
342 * Init the element as null-terminated list.
343 *
344 * Example:
345 * struct foo *list = malloc();
346 * glvnd_nt_list_init(list, next);
347 *
348 * @param list The list element that will be the start of the list
349 * @param member Member name of the field pointing to next struct
350 */
351 #define glvnd_nt_list_init(_list, _member) \
352 (_list)->_member = NULL
353
354 /**
355 * Returns the next element in the list or NULL on termination.
356 *
357 * Example:
358 * struct foo *element = list;
359 * while ((element = glvnd_nt_list_next(element, next)) { }
360 *
361 * This macro is not safe for node deletion. Use glvnd_nt_list_for_each_entry_safe
362 * instead.
363 *
364 * @param list The list or current element.
365 * @param member Member name of the field pointing to next struct.
366 */
367 #define glvnd_nt_list_next(_list, _member) \
368 (_list)->_member
369
370 /**
371 * Iterate through each element in the list.
372 *
373 * Example:
374 * struct foo *iterator;
375 * glvnd_nt_list_for_each_entry(iterator, list, next) {
376 * [modify iterator]
377 * }
378 *
379 * @param entry Assigned to the current list element
380 * @param list The list to iterate through.
381 * @param member Member name of the field pointing to next struct.
382 */
383 #define glvnd_nt_list_for_each_entry(_entry, _list, _member) \
384 for (_entry = _list; _entry; _entry = (_entry)->_member)
385
386 /**
387 * Iterate through each element in the list, keeping a backup pointer to the
388 * element. This macro allows for the deletion of a list element while
389 * looping through the list.
390 *
391 * See glvnd_nt_list_for_each_entry for more details.
392 *
393 * @param entry Assigned to the current list element
394 * @param tmp The pointer to the next element
395 * @param list The list to iterate through.
396 * @param member Member name of the field pointing to next struct.
397 */
398 #define glvnd_nt_list_for_each_entry_safe(_entry, _tmp, _list, _member) \
399 for (_entry = _list, _tmp = (_entry) ? (_entry)->_member : NULL;\
400 _entry; \
401 _entry = _tmp, _tmp = (_tmp) ? (_tmp)->_member: NULL)
402
403 /**
404 * Append the element to the end of the list. This macro may be used to
405 * merge two lists.
406 *
407 * Example:
408 * struct foo *elem = malloc(...);
409 * glvnd_nt_list_init(elem, next)
410 * glvnd_nt_list_append(elem, list, struct foo, next);
411 *
412 * Resulting list order:
413 * list_item_0 -> list_item_1 -> ... -> elem_item_0 -> elem_item_1 ...
414 *
415 * @param entry An entry (or list) to append to the list
416 * @param list The list to append to. This list must be a valid list, not
417 * NULL.
418 * @param type The list type
419 * @param member Member name of the field pointing to next struct
420 */
421 #define glvnd_nt_list_append(_entry, _list, _type, _member) \
422 do { \
423 _type *__iterator = _list; \
424 while (__iterator->_member) { __iterator = __iterator->_member;}\
425 __iterator->_member = _entry; \
426 } while (0)
427
428 /**
429 * Insert the element at the next position in the list. This macro may be
430 * used to insert a list into a list.
431 *
432 * struct foo *elem = malloc(...);
433 * glvnd_nt_list_init(elem, next)
434 * glvnd_nt_list_insert(elem, list, struct foo, next);
435 *
436 * Resulting list order:
437 * list_item_0 -> elem_item_0 -> elem_item_1 ... -> list_item_1 -> ...
438 *
439 * @param entry An entry (or list) to append to the list
440 * @param list The list to insert to. This list must be a valid list, not
441 * NULL.
442 * @param type The list type
443 * @param member Member name of the field pointing to next struct
444 */
445 #define glvnd_nt_list_insert(_entry, _list, _type, _member) \
446 do { \
447 glvnd_nt_list_append((_list)->_member, _entry, _type, _member); \
448 (_list)->_member = _entry; \
449 } while (0)
450
451 /**
452 * Delete the entry from the list by iterating through the list and
453 * removing any reference from the list to the entry.
454 *
455 * Example:
456 * struct foo *elem = <assign to right element>
457 * glvnd_nt_list_del(elem, list, struct foo, next);
458 *
459 * @param entry The entry to delete from the list. entry is always
460 * re-initialized as a null-terminated list.
461 * @param list The list containing the entry, set to the new list without
462 * the removed entry.
463 * @param type The list type
464 * @param member Member name of the field pointing to the next entry
465 */
466 #define glvnd_nt_list_del(_entry, _list, _type, _member) \
467 do { \
468 _type *__e = _entry; \
469 if (__e == NULL || _list == NULL) break; \
470 if ((_list) == __e) { \
471 _list = __e->_member; \
472 } else { \
473 _type *__prev = _list; \
474 while (__prev->_member && __prev->_member != __e) \
475 __prev = glvnd_nt_list_next(__prev, _member); \
476 if (__prev->_member) \
477 __prev->_member = __e->_member; \
478 } \
479 glvnd_nt_list_init(__e, _member); \
480 } while(0)
481
482 #endif
483