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 */
26 #ifndef _LIST_H_
27 #define _LIST_H_
29 /**
30 * @file Classic doubly-link circular list implementation.
31 * For real usage examples of the linked list, see the file test/list.c
32 *
33 * Example:
34 * We need to keep a list of struct foo in the parent struct bar, i.e. what
35 * we want is something like this.
36 *
37 * struct bar {
38 * ...
39 * struct foo *list_of_foos; -----> struct foo {}, struct foo {}, struct foo{}
40 * ...
41 * }
42 *
43 * We need one list head in bar and a list element in all list_of_foos (both are of
44 * data type 'struct list').
45 *
46 * struct bar {
47 * ...
48 * struct list list_of_foos;
49 * ...
50 * }
51 *
52 * struct foo {
53 * ...
54 * struct list entry;
55 * ...
56 * }
57 *
58 * Now we initialize the list head:
59 *
60 * struct bar bar;
61 * ...
62 * list_init(&bar.list_of_foos);
63 *
64 * Then we create the first element and add it to this list:
65 *
66 * struct foo *foo = malloc(...);
67 * ....
68 * list_add(&foo->entry, &bar.list_of_foos);
69 *
70 * Repeat the above for each element you want to add to the list. Deleting
71 * works with the element itself.
72 * list_del(&foo->entry);
73 * free(foo);
74 *
75 * Note: calling list_del(&bar.list_of_foos) will set bar.list_of_foos to an empty
76 * list again.
77 *
78 * Looping through the list requires a 'struct foo' as iterator and the
79 * name of the field the subnodes use.
80 *
81 * struct foo *iterator;
82 * list_for_each_entry(iterator, &bar.list_of_foos, entry) {
83 * if (iterator->something == ...)
84 * ...
85 * }
86 *
87 * Note: You must not call list_del() on the iterator if you continue the
88 * loop. You need to run the safe for-each loop instead:
89 *
90 * struct foo *iterator, *next;
91 * list_for_each_entry_safe(iterator, next, &bar.list_of_foos, entry) {
92 * if (...)
93 * list_del(&iterator->entry);
94 * }
95 *
96 */
98 /**
99 * The linkage struct for list nodes. This struct must be part of your
100 * to-be-linked struct. struct list is required for both the head of the
101 * list and for each list node.
102 *
103 * Position and name of the struct list field is irrelevant.
104 * There are no requirements that elements of a list are of the same type.
105 * There are no requirements for a list head, any struct list can be a list
106 * head.
107 */
108 struct list {
109 struct list *next, *prev;
110 };
112 /**
113 * Initialize the list as an empty list.
114 *
115 * Example:
116 * list_init(&bar->list_of_foos);
117 *
118 * @param The list to initialized.
119 */
120 static void
121 list_init(struct list *list)
122 {
123 list->next = list->prev = list;
124 }
126 static inline void
127 __list_add(struct list *entry,
128 struct list *prev,
129 struct list *next)
130 {
131 next->prev = entry;
132 entry->next = next;
133 entry->prev = prev;
134 prev->next = entry;
135 }
137 /**
138 * Insert a new element after the given list head. The new element does not
139 * need to be initialised as empty list.
140 * The list changes from:
141 * head → some element → ...
142 * to
143 * head → new element → older element → ...
144 *
145 * Example:
146 * struct foo *newfoo = malloc(...);
147 * list_add(&newfoo->entry, &bar->list_of_foos);
148 *
149 * @param entry The new element to prepend to the list.
150 * @param head The existing list.
151 */
152 static inline void
153 list_add(struct list *entry, struct list *head)
154 {
155 __list_add(entry, head, head->next);
156 }
158 /**
159 * Append a new element to the end of the list given with this list head.
160 *
161 * The list changes from:
162 * head → some element → ... → lastelement
163 * to
164 * head → some element → ... → lastelement → new element
165 *
166 * Example:
167 * struct foo *newfoo = malloc(...);
168 * list_append(&newfoo->entry, &bar->list_of_foos);
169 *
170 * @param entry The new element to prepend to the list.
171 * @param head The existing list.
172 */
173 static inline void
174 list_append(struct list *entry, struct list *head)
175 {
176 __list_add(entry, head->prev, head);
177 }
180 static inline void
181 __list_del(struct list *prev, struct list *next)
182 {
183 next->prev = prev;
184 prev->next = next;
185 }
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 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 * list_del(&foo->entry);
198 *
199 * @param entry The element to remove.
200 */
201 static inline void
202 list_del(struct list *entry)
203 {
204 __list_del(entry->prev, entry->next);
205 list_init(entry);
206 }
208 /**
209 * Check if the list is empty.
210 *
211 * Example:
212 * 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 bool
217 list_is_empty(struct list *head)
218 {
219 return head->next == head;
220 }
222 /**
223 * Returns a pointer to the container of this list element.
224 *
225 * Example:
226 * struct foo* f;
227 * f = container_of(&foo->entry, struct foo, entry);
228 * assert(f == foo);
229 *
230 * @param ptr Pointer to the struct list.
231 * @param type Data type of the list element.
232 * @param member Member name of the struct list field in the list element.
233 * @return A pointer to the data struct containing the list head.
234 */
235 #ifndef container_of
236 #define container_of(ptr, type, member) \
237 (type *)((char *)(ptr) - (char *) &((type *)0)->member)
238 #endif
240 /**
241 * Alias of container_of
242 */
243 #define list_entry(ptr, type, member) \
244 container_of(ptr, type, member)
246 /**
247 * Retrieve the first list entry for the given list pointer.
248 *
249 * Example:
250 * struct foo *first;
251 * first = 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 list field in the list element.
256 * @return A pointer to the first list element.
257 */
258 #define list_first_entry(ptr, type, member) \
259 list_entry((ptr)->next, type, member)
261 /**
262 * Retrieve the last list entry for the given listpointer.
263 *
264 * Example:
265 * struct foo *first;
266 * first = 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 list field in the list element.
271 * @return A pointer to the last list element.
272 */
273 #define list_last_entry(ptr, type, member) \
274 list_entry((ptr)->prev, type, member)
276 #define __container_of(ptr, sample, member) \
277 (void *)((char *)(ptr) \
278 - ((char *)&(sample)->member - (char *)(sample)))
279 /**
280 * Loop through the list given by head and set pos to struct in the list.
281 *
282 * Example:
283 * struct foo *iterator;
284 * list_for_each_entry(iterator, &bar->list_of_foos, entry) {
285 * [modify iterator]
286 * }
287 *
288 * This macro is not safe for node deletion. Use list_for_each_entry_safe
289 * instead.
290 *
291 * @param pos Iterator variable of the type of the list elements.
292 * @param head List head
293 * @param member Member name of the struct list in the list elements.
294 *
295 */
296 #define list_for_each_entry(pos, head, member) \
297 for (pos = __container_of((head)->next, pos, member); \
298 &pos->member != (head); \
299 pos = __container_of(pos->member.next, pos, member))
301 /**
302 * Loop through the list, keeping a backup pointer to the element. This
303 * macro allows for the deletion of a list element while looping through the
304 * list.
305 *
306 * See list_for_each_entry for more details.
307 */
308 #define list_for_each_entry_safe(pos, tmp, head, member) \
309 for (pos = __container_of((head)->next, pos, member), \
310 tmp = __container_of(pos->member.next, pos, member); \
311 &pos->member != (head); \
312 pos = tmp, tmp = __container_of(pos->member.next, tmp, member))
314 #endif