1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef LIST_H
3 #define LIST_H
4
5 #include <stddef.h>
6
7 #include "list_types.h"
8
9 /* Are two types/vars the same type (ignoring qualifiers)? */
10 #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
11
12 /**
13 * container_of - cast a member of a structure out to the containing structure
14 * @ptr: the pointer to the member.
15 * @type: the type of the container struct this is embedded in.
16 * @member: the name of the member within the struct.
17 *
18 */
19 #define container_of(ptr, type, member) ({ \
20 void *__mptr = (void *)(ptr); \
21 _Static_assert(__same_type(*(ptr), ((type *)0)->member) || \
22 __same_type(*(ptr), void), \
23 "pointer type mismatch in container_of()"); \
24 ((type *)(__mptr - offsetof(type, member))); })
25
26 #define LIST_POISON1 ((void *) 0x100)
27 #define LIST_POISON2 ((void *) 0x122)
28
29 /*
30 * Circular doubly linked list implementation.
31 *
32 * Some of the internal functions ("__xxx") are useful when
33 * manipulating whole lists rather than single entries, as
34 * sometimes we already know the next/prev entries and we can
35 * generate better code by using them directly rather than
36 * using the generic single-entry routines.
37 */
38
39 #define LIST_HEAD_INIT(name) { &(name), &(name) }
40
41 #define LIST_HEAD(name) \
42 struct list_head name = LIST_HEAD_INIT(name)
43
44 /**
45 * INIT_LIST_HEAD - Initialize a list_head structure
46 * @list: list_head structure to be initialized.
47 *
48 * Initializes the list_head to point to itself. If it is a list header,
49 * the result is an empty list.
50 */
51 static inline void INIT_LIST_HEAD(struct list_head *list)
52 {
53 list->next = list;
54 list->prev = list;
55 }
56
57 /*
58 * Insert a new entry between two known consecutive entries.
59 *
60 * This is only for internal list manipulation where we know
61 * the prev/next entries already!
62 */
63 static inline void __list_add(struct list_head *new,
64 struct list_head *prev,
65 struct list_head *next)
66 {
67 next->prev = new;
68 new->next = next;
69 new->prev = prev;
70 prev->next = new;
71 }
72
73 /**
74 * list_add - add a new entry
75 * @new: new entry to be added
76 * @head: list head to add it after
77 *
78 * Insert a new entry after the specified head.
79 * This is good for implementing stacks.
80 */
81 static inline void list_add(struct list_head *new, struct list_head *head)
82 {
83 __list_add(new, head, head->next);
84 }
85
86 /**
87 * list_add_tail - add a new entry
88 * @new: new entry to be added
89 * @head: list head to add it before
90 *
91 * Insert a new entry before the specified head.
92 * This is useful for implementing queues.
93 */
94 static inline void list_add_tail(struct list_head *new, struct list_head *head)
95 {
96 __list_add(new, head->prev, head);
97 }
98
99 /*
100 * Delete a list entry by making the prev/next entries
101 * point to each other.
102 *
103 * This is only for internal list manipulation where we know
104 * the prev/next entries already!
105 */
106 static inline void __list_del(struct list_head *prev, struct list_head *next)
107 {
108 next->prev = prev;
109 prev->next = next;
110 }
111
112 static inline void __list_del_entry(struct list_head *entry)
113 {
114 __list_del(entry->prev, entry->next);
115 }
116
117 /**
118 * list_del - deletes entry from list.
119 * @entry: the element to delete from the list.
120 * Note: list_empty() on entry does not return true after this, the entry is
121 * in an undefined state.
122 */
123 static inline void list_del(struct list_head *entry)
124 {
125 __list_del_entry(entry);
126 entry->next = LIST_POISON1;
127 entry->prev = LIST_POISON2;
128 }
129
130 /**
131 * list_move - delete from one list and add as another's head
132 * @list: the entry to move
133 * @head: the head that will precede our entry
134 */
135 static inline void list_move(struct list_head *list, struct list_head *head)
136 {
137 __list_del_entry(list);
138 list_add(list, head);
139 }
140
141 /**
142 * list_move_tail - delete from one list and add as another's tail
143 * @list: the entry to move
144 * @head: the head that will follow our entry
145 */
146 static inline void list_move_tail(struct list_head *list,
147 struct list_head *head)
148 {
149 __list_del_entry(list);
150 list_add_tail(list, head);
151 }
152
153 /**
154 * list_is_head - tests whether @list is the list @head
155 * @list: the entry to test
156 * @head: the head of the list
157 */
158 static inline int list_is_head(const struct list_head *list, const struct list_head *head)
159 {
160 return list == head;
161 }
162
163 /**
164 * list_empty - tests whether a list is empty
165 * @head: the list to test.
166 */
167 static inline int list_empty(const struct list_head *head)
168 {
169 return head->next == head;
170 }
171
172 /**
173 * list_entry - get the struct for this entry
174 * @ptr: the &struct list_head pointer.
175 * @type: the type of the struct this is embedded in.
176 * @member: the name of the list_head within the struct.
177 */
178 #define list_entry(ptr, type, member) \
179 container_of(ptr, type, member)
180
181 /**
182 * list_first_entry - get the first element from a list
183 * @ptr: the list head to take the element from.
184 * @type: the type of the struct this is embedded in.
185 * @member: the name of the list_head within the struct.
186 *
187 * Note, that list is expected to be not empty.
188 */
189 #define list_first_entry(ptr, type, member) \
190 list_entry((ptr)->next, type, member)
191
192 /**
193 * list_last_entry - get the last element from a list
194 * @ptr: the list head to take the element from.
195 * @type: the type of the struct this is embedded in.
196 * @member: the name of the list_head within the struct.
197 *
198 * Note, that list is expected to be not empty.
199 */
200 #define list_last_entry(ptr, type, member) \
201 list_entry((ptr)->prev, type, member)
202
203 /**
204 * list_next_entry - get the next element in list
205 * @pos: the type * to cursor
206 * @member: the name of the list_head within the struct.
207 */
208 #define list_next_entry(pos, member) \
209 list_entry((pos)->member.next, typeof(*(pos)), member)
210
211 /**
212 * list_prev_entry - get the prev element in list
213 * @pos: the type * to cursor
214 * @member: the name of the list_head within the struct.
215 */
216 #define list_prev_entry(pos, member) \
217 list_entry((pos)->member.prev, typeof(*(pos)), member)
218
219 /**
220 * list_entry_is_head - test if the entry points to the head of the list
221 * @pos: the type * to cursor
222 * @head: the head for your list.
223 * @member: the name of the list_head within the struct.
224 */
225 #define list_entry_is_head(pos, head, member) \
226 (&pos->member == (head))
227
228 /**
229 * list_for_each_entry - iterate over list of given type
230 * @pos: the type * to use as a loop cursor.
231 * @head: the head for your list.
232 * @member: the name of the list_head within the struct.
233 */
234 #define list_for_each_entry(pos, head, member) \
235 for (pos = list_first_entry(head, typeof(*pos), member); \
236 !list_entry_is_head(pos, head, member); \
237 pos = list_next_entry(pos, member))
238
239 /**
240 * list_for_each_entry_reverse - iterate backwards over list of given type.
241 * @pos: the type * to use as a loop cursor.
242 * @head: the head for your list.
243 * @member: the name of the list_head within the struct.
244 */
245 #define list_for_each_entry_reverse(pos, head, member) \
246 for (pos = list_last_entry(head, typeof(*pos), member); \
247 !list_entry_is_head(pos, head, member); \
248 pos = list_prev_entry(pos, member))
249
250 /**
251 * list_for_each_entry_safe - iterate over list of given type. Safe against removal of list entry
252 * @pos: the type * to use as a loop cursor.
253 * @n: another type * to use as temporary storage
254 * @head: the head for your list.
255 * @member: the name of the list_head within the struct.
256 */
257 #define list_for_each_entry_safe(pos, n, head, member) \
258 for (pos = list_first_entry(head, typeof(*pos), member), \
259 n = list_next_entry(pos, member); \
260 !list_entry_is_head(pos, head, member); \
261 pos = n, n = list_next_entry(n, member))
262
263 /*
264 * Double linked lists with a single pointer list head.
265 * Mostly useful for hash tables where the two pointer list head is
266 * too wasteful.
267 * You lose the ability to access the tail in O(1).
268 */
269
270 #define HLIST_HEAD_INIT { .first = NULL }
271
272 /**
273 * hlist_add_head - add a new entry at the beginning of the hlist
274 * @n: new entry to be added
275 * @h: hlist head to add it after
276 *
277 * Insert a new entry after the specified head.
278 * This is good for implementing stacks.
279 */
280 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
281 {
282 struct hlist_node *first = h->first;
283
284 n->next = first;
285 if (first)
286 first->pprev = &n->next;
287 h->first = n;
288 n->pprev = &h->first;
289 }
290
291 #define hlist_entry(ptr, type, member) container_of(ptr, type, member)
292
293 #define hlist_entry_safe(ptr, type, member) \
294 ({ typeof(ptr) ____ptr = (ptr); \
295 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
296 })
297
298 /**
299 * hlist_for_each_entry - iterate over list of given type
300 * @pos: the type * to use as a loop cursor.
301 * @head: the head for your list.
302 * @member: the name of the hlist_node within the struct.
303 */
304 #define hlist_for_each_entry(pos, head, member) \
305 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
306 pos; \
307 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
308
309 #endif /* LIST_H */
310
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