4 * Simple doubly linked list implementation.
6 * Some of the internal functions ("__xxx") are useful when
7 * manipulating whole lists rather than single entries, as
8 * sometimes we already know the next/prev entries and we can
9 * generate better code by using them directly rather than
10 * using the generic single-entry routines.
13 #define prefetch(a) ((void)a)
16 struct list_head *next, *prev;
19 typedef struct list_head list_t;
21 #define LIST_HEAD_INIT(name) { &(name), &(name) }
23 #define LIST_HEAD(name) \
24 struct list_head name = LIST_HEAD_INIT(name)
26 #define INIT_LIST_HEAD(ptr) do { \
27 (ptr)->next = (ptr); (ptr)->prev = (ptr); \
31 * Insert a new entry between two known consecutive entries.
33 * This is only for internal list manipulation where we know
34 * the prev/next entries already!
36 static inline void __list_add(struct list_head * new,
37 struct list_head * prev,
38 struct list_head * next)
47 * list_add - add a new entry
48 * @new: new entry to be added
49 * @head: list head to add it after
51 * Insert a new entry after the specified head.
52 * This is good for implementing stacks.
54 static inline void list_add(struct list_head *new, struct list_head *head)
56 __list_add(new, head, head->next);
60 * list_add_tail - add a new entry
61 * @new: new entry to be added
62 * @head: list head to add it before
64 * Insert a new entry before the specified head.
65 * This is useful for implementing queues.
67 static inline void list_add_tail(struct list_head *new, struct list_head *head)
69 __list_add(new, head->prev, head);
73 * Delete a list entry by making the prev/next entries
74 * point to each other.
76 * This is only for internal list manipulation where we know
77 * the prev/next entries already!
79 static inline void __list_del(struct list_head * prev, struct list_head * next)
86 * list_del - deletes entry from list.
87 * @entry: the element to delete from the list.
88 * Note: list_empty on entry does not return true after this, the entry is in an undefined state.
90 static inline void list_del(struct list_head *entry)
92 __list_del(entry->prev, entry->next);
96 * list_del_init - deletes entry from list and reinitialize it.
97 * @entry: the element to delete from the list.
99 static inline void list_del_init(struct list_head *entry)
101 __list_del(entry->prev, entry->next);
102 INIT_LIST_HEAD(entry);
106 #ifndef list_for_each_entry
108 * list_move - delete from one list and add as another's head
109 * @list: the entry to move
110 * @head: the head that will precede our entry
112 static inline void list_move(struct list_head *list, struct list_head *head)
114 __list_del(list->prev, list->next);
115 list_add(list, head);
119 * list_move_tail - delete from one list and add as another's tail
120 * @list: the entry to move
121 * @head: the head that will follow our entry
123 static inline void list_move_tail(struct list_head *list,
124 struct list_head *head)
126 __list_del(list->prev, list->next);
127 list_add_tail(list, head);
131 #ifndef _LINUX_LIST_H
132 #define _LINUX_LIST_H
134 * list_empty - tests whether a list is empty
135 * @head: the list to test.
137 static inline int list_empty(struct list_head *head)
139 return head->next == head;
142 static inline void __list_splice(struct list_head *list,
143 struct list_head *head)
145 struct list_head *first = list->next;
146 struct list_head *last = list->prev;
147 struct list_head *at = head->next;
157 * list_splice - join two lists
158 * @list: the new list to add.
159 * @head: the place to add it in the first list.
161 static inline void list_splice(struct list_head *list, struct list_head *head)
163 if (!list_empty(list))
164 __list_splice(list, head);
168 * list_splice_init - join two lists and reinitialise the emptied list.
169 * @list: the new list to add.
170 * @head: the place to add it in the first list.
172 * The list at @list is reinitialised
174 static inline void list_splice_init(struct list_head *list,
175 struct list_head *head)
177 if (!list_empty(list)) {
178 __list_splice(list, head);
179 INIT_LIST_HEAD(list);
184 * list_entry - get the struct for this entry
185 * @ptr: the &struct list_head pointer.
186 * @type: the type of the struct this is embedded in.
187 * @member: the name of the list_struct within the struct.
189 #define list_entry(ptr, type, member) \
190 ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
193 * list_for_each - iterate over a list
194 * @pos: the &struct list_head to use as a loop counter.
195 * @head: the head for your list.
197 #define list_for_each(pos, head) \
198 for (pos = (head)->next, prefetch(pos->next); pos != (head); \
199 pos = pos->next, prefetch(pos->next))
202 * list_for_each_prev - iterate over a list in reverse order
203 * @pos: the &struct list_head to use as a loop counter.
204 * @head: the head for your list.
206 #define list_for_each_prev(pos, head) \
207 for (pos = (head)->prev, prefetch(pos->prev); pos != (head); \
208 pos = pos->prev, prefetch(pos->prev))
211 * list_for_each_safe - iterate over a list safe against removal of list entry
212 * @pos: the &struct list_head to use as a loop counter.
213 * @n: another &struct list_head to use as temporary storage
214 * @head: the head for your list.
216 #define list_for_each_safe(pos, n, head) \
217 for (pos = (head)->next, n = pos->next; pos != (head); \
218 pos = n, n = pos->next)
222 #ifndef list_for_each_entry
224 * list_for_each_entry - iterate over list of given type
225 * @pos: the type * to use as a loop counter.
226 * @head: the head for your list.
227 * @member: the name of the list_struct within the struct.
229 #define list_for_each_entry(pos, head, member) \
230 for (pos = list_entry((head)->next, typeof(*pos), member), \
231 prefetch(pos->member.next); \
232 &pos->member != (head); \
233 pos = list_entry(pos->member.next, typeof(*pos), member), \
234 prefetch(pos->member.next))
237 #ifndef list_for_each_entry_safe
239 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
240 * @pos: the type * to use as a loop counter.
241 * @n: another type * to use as temporary storage
242 * @head: the head for your list.
243 * @member: the name of the list_struct within the struct.
245 #define list_for_each_entry_safe(pos, n, head, member) \
246 for (pos = list_entry((head)->next, typeof(*pos), member), \
247 n = list_entry(pos->member.next, typeof(*pos), member); \
248 &pos->member != (head); \
249 pos = n, n = list_entry(n->member.next, typeof(*n), member))