3 * Simple doubly linked list implementation.
5 * Some of the internal functions ("__xxx") are useful when
6 * manipulating whole lists rather than single entries, as
7 * sometimes we already know the next/prev entries and we can
8 * generate better code by using them directly rather than
9 * using the generic single-entry routines.
12 #define prefetch(a) ((void)a)
15 struct list_head *next, *prev;
18 typedef struct list_head list_t;
20 #define LIST_HEAD_INIT(name) { &(name), &(name) }
22 #define LIST_HEAD(name) \
23 struct list_head name = LIST_HEAD_INIT(name)
25 #define INIT_LIST_HEAD(ptr) do { \
26 (ptr)->next = (ptr); (ptr)->prev = (ptr); \
30 * Insert a new entry between two known consecutive entries.
32 * This is only for internal list manipulation where we know
33 * the prev/next entries already!
35 static inline void __list_add(struct list_head * new,
36 struct list_head * prev,
37 struct list_head * next)
46 * list_add - add a new entry
47 * @new: new entry to be added
48 * @head: list head to add it after
50 * Insert a new entry after the specified head.
51 * This is good for implementing stacks.
53 static inline void list_add(struct list_head *new, struct list_head *head)
55 __list_add(new, head, head->next);
59 * list_add_tail - add a new entry
60 * @new: new entry to be added
61 * @head: list head to add it before
63 * Insert a new entry before the specified head.
64 * This is useful for implementing queues.
66 static inline void list_add_tail(struct list_head *new, struct list_head *head)
68 __list_add(new, head->prev, head);
72 * Delete a list entry by making the prev/next entries
73 * point to each other.
75 * This is only for internal list manipulation where we know
76 * the prev/next entries already!
78 static inline void __list_del(struct list_head * prev, struct list_head * next)
85 * list_del - deletes entry from list.
86 * @entry: the element to delete from the list.
87 * Note: list_empty on entry does not return true after this, the entry is in an undefined state.
89 static inline void list_del(struct list_head *entry)
91 __list_del(entry->prev, entry->next);
95 * list_del_init - deletes entry from list and reinitialize it.
96 * @entry: the element to delete from the list.
98 static inline void list_del_init(struct list_head *entry)
100 __list_del(entry->prev, entry->next);
101 INIT_LIST_HEAD(entry);
105 #ifndef list_for_each_entry
107 * list_move - delete from one list and add as another's head
108 * @list: the entry to move
109 * @head: the head that will precede our entry
111 static inline void list_move(struct list_head *list, struct list_head *head)
113 __list_del(list->prev, list->next);
114 list_add(list, head);
118 * list_move_tail - delete from one list and add as another's tail
119 * @list: the entry to move
120 * @head: the head that will follow our entry
122 static inline void list_move_tail(struct list_head *list,
123 struct list_head *head)
125 __list_del(list->prev, list->next);
126 list_add_tail(list, head);
130 #ifndef _LINUX_LIST_H
131 #define _LINUX_LIST_H
133 * list_empty - tests whether a list is empty
134 * @head: the list to test.
136 static inline int list_empty(struct list_head *head)
138 return head->next == head;
141 static inline void __list_splice(struct list_head *list,
142 struct list_head *head)
144 struct list_head *first = list->next;
145 struct list_head *last = list->prev;
146 struct list_head *at = head->next;
156 * list_splice - join two lists
157 * @list: the new list to add.
158 * @head: the place to add it in the first list.
160 static inline void list_splice(struct list_head *list, struct list_head *head)
162 if (!list_empty(list))
163 __list_splice(list, head);
167 * list_splice_init - join two lists and reinitialise the emptied list.
168 * @list: the new list to add.
169 * @head: the place to add it in the first list.
171 * The list at @list is reinitialised
173 static inline void list_splice_init(struct list_head *list,
174 struct list_head *head)
176 if (!list_empty(list)) {
177 __list_splice(list, head);
178 INIT_LIST_HEAD(list);
183 * list_entry - get the struct for this entry
184 * @ptr: the &struct list_head pointer.
185 * @type: the type of the struct this is embedded in.
186 * @member: the name of the list_struct within the struct.
188 #define list_entry(ptr, type, member) \
189 ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
192 * list_for_each - iterate over a list
193 * @pos: the &struct list_head to use as a loop counter.
194 * @head: the head for your list.
196 #define list_for_each(pos, head) \
197 for (pos = (head)->next, prefetch(pos->next); pos != (head); \
198 pos = pos->next, prefetch(pos->next))
201 * list_for_each_prev - iterate over a list in reverse order
202 * @pos: the &struct list_head to use as a loop counter.
203 * @head: the head for your list.
205 #define list_for_each_prev(pos, head) \
206 for (pos = (head)->prev, prefetch(pos->prev); pos != (head); \
207 pos = pos->prev, prefetch(pos->prev))
210 * list_for_each_safe - iterate over a list safe against removal of list entry
211 * @pos: the &struct list_head to use as a loop counter.
212 * @n: another &struct list_head to use as temporary storage
213 * @head: the head for your list.
215 #define list_for_each_safe(pos, n, head) \
216 for (pos = (head)->next, n = pos->next; pos != (head); \
217 pos = n, n = pos->next)
221 #ifndef list_for_each_entry
223 * list_for_each_entry - iterate over list of given type
224 * @pos: the type * to use as a loop counter.
225 * @head: the head for your list.
226 * @member: the name of the list_struct within the struct.
228 #define list_for_each_entry(pos, head, member) \
229 for (pos = list_entry((head)->next, typeof(*pos), member), \
230 prefetch(pos->member.next); \
231 &pos->member != (head); \
232 pos = list_entry(pos->member.next, typeof(*pos), member), \
233 prefetch(pos->member.next))
236 #ifndef list_for_each_entry_safe
238 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
239 * @pos: the type * to use as a loop counter.
240 * @n: another type * to use as temporary storage
241 * @head: the head for your list.
242 * @member: the name of the list_struct within the struct.
244 #define list_for_each_entry_safe(pos, n, head, member) \
245 for (pos = list_entry((head)->next, typeof(*pos), member), \
246 n = list_entry(pos->member.next, typeof(*pos), member); \
247 &pos->member != (head); \
248 pos = n, n = list_entry(n->member.next, typeof(*n), member))