list.h

#ifndef _LINUX_LIST_H
#define _LINUX_LIST_H

/*
 * include/linux/list.h
 * 
 * Simple doubly linked list implementation.
 *
 * Some of the internal functions ("__xxx") are useful when
 * manipulating whole lists rather than single entries, as
 * sometimes we already know the next/prev entries and we can
 * generate better code by using them directly rather than
 * using the generic single-entry routines.
 */
struct list_head {
	struct list_head *next, *prev;
};

#define LIST_POISON1	((void *)0x00100100)
#define LIST_POISON2	((void *)0x00200200)
#define LIST_HEAD_INIT(name) { &(name), &(name) }

#define LIST_HEAD(name) \
	struct list_head name = LIST_HEAD_INIT(name)

static inline void INIT_LIST_HEAD(struct list_head *list)
{
	list->next = list;
	list->prev = list;
}

/*
* Insert a new entry between two known consecutive entries.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
static inline void __list_add(struct list_head *new,
			      struct list_head *prev,
			      struct list_head *next)
{
	next->prev = new;
	new->next = next;
	new->prev = prev;
	prev->next = new;
}

/**
* list_add - add a new entry
* @new: new entry to be added
* @head: list head to add it after
*
* Insert a new entry after the specified head.
* This is good for implementing stacks.
*/
static inline void list_add(struct list_head *new, struct list_head *head)
{
	__list_add(new, head, head->next);
}

/**
* list_add_tail - add a new entry
* @new: new entry to be added
* @head: list head to add it before
*
* Insert a new entry before the specified head.
* This is useful for implementing queues.
*/
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
	__list_add(new, head->prev, head);
}

/*
* Delete a list entry by making the prev/next entries
* point to each other.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
	next->prev = prev;
	prev->next = next;
}

/**
* list_del - deletes entry from list.
* @entry: the element to delete from the list.
* Note: list_empty() on entry does not return true after this, the entry is
* in an undefined state.
*/
static inline void __list_del_entry(struct list_head *entry)
{
	__list_del(entry->prev, entry->next);
}

static inline void list_del(struct list_head *entry)
{
	__list_del_entry(entry);
	entry->next = LIST_POISON1;
	entry->prev = LIST_POISON2;
}

/**
* list_replace - replace old entry by new one
* @old : the element to be replaced
* @new : the new element to insert
*
* If @old was empty, it will be overwritten.
*/
static inline void list_replace(struct list_head *old,
				struct list_head *new)
{
	new->next = old->next;
	new->next->prev = new;
	new->prev = old->prev;
	new->prev->next = new;
}

static inline void list_replace_init(struct list_head *old,
				     struct list_head *new)
{
	list_replace(old, new);
	INIT_LIST_HEAD(old);
}

/**
* list_del_init - deletes entry from list and reinitialize it.
* @entry: the element to delete from the list.
*/
static inline void list_del_init(struct list_head *entry)
{
	__list_del_entry(entry);
	INIT_LIST_HEAD(entry);
}

/**
* list_move - delete from one list and add as another's head
* @list: the entry to move
* @head: the head that will precede our entry
*/
static inline void list_move(struct list_head *list, struct list_head *head)
{
	__list_del_entry(list);
	list_add(list, head);
}

/**
* list_move_tail - delete from one list and add as another's tail
* @list: the entry to move
* @head: the head that will follow our entry
*/
static inline void list_move_tail(struct list_head *list,
				  struct list_head *head)
{
	__list_del_entry(list);
	list_add_tail(list, head);
}

/**
* list_is_last - tests whether @list is the last entry in list @head
* @list: the entry to test
* @head: the head of the list
*/
static inline int list_is_last(const struct list_head *list,
			       const struct list_head *head)
{
	return list->next == head;
}

/**
* list_empty - tests whether a list is empty
* @head: the list to test.
*/
static inline int list_empty(const struct list_head *head)
{
	return head->next == head;
}

/**
* list_empty_careful - tests whether a list is empty and not being modified
* @head: the list to test
*
* Description:
* tests whether a list is empty _and_ checks that no other CPU might be
* in the process of modifying either member (next or prev)
*
* NOTE: using list_empty_careful() without synchronization
* can only be safe if the only activity that can happen
* to the list entry is list_del_init(). Eg. it cannot be used
* if another CPU could re-list_add() it.
*/
static inline int list_empty_careful(const struct list_head *head)
{
	struct list_head *next = head->next;
	return (next == head) && (next == head->prev);
}

/**
* list_rotate_left - rotate the list to the left
* @head: the head of the list
*/
static inline void list_rotate_left(struct list_head *head)
{
	struct list_head *first;

	if (!list_empty(head)) {
		first = head->next;
		list_move_tail(first, head);
	}
}

/**
* list_is_singular - tests whether a list has just one entry.
* @head: the list to test.
*/
static inline int list_is_singular(const struct list_head *head)
{
	return !list_empty(head) && (head->next == head->prev);
}

static inline void __list_cut_position(struct list_head *list,
				       struct list_head *head, struct list_head *entry)
{
	struct list_head *new_first = entry->next;
	list->next = head->next;
	list->next->prev = list;
	list->prev = entry;
	entry->next = list;
	head->next = new_first;
	new_first->prev = head;
}

/**
* list_cut_position - cut a list into two
* @list: a new list to add all removed entries
* @head: a list with entries
* @entry: an entry within head, could be the head itself
*	and if so we won't cut the list
*
* This helper moves the initial part of @head, up to and
* including @entry, from @head to @list. You should
* pass on @entry an element you know is on @head. @list
* should be an empty list or a list you do not care about
* losing its data.
*
*/
static inline void list_cut_position(struct list_head *list,
				     struct list_head *head, struct list_head *entry)
{
	if (list_empty(head))
		return;
	if (list_is_singular(head) &&
		(head->next != entry && head != entry))
		return;
	if (entry == head)
		INIT_LIST_HEAD(list);
	else
		__list_cut_position(list, head, entry);
}

static inline void __list_splice(const struct list_head *list,
				 struct list_head *prev,
				 struct list_head *next)
{
	struct list_head *first = list->next;
	struct list_head *last = list->prev;

	first->prev = prev;
	prev->next = first;

	last->next = next;
	next->prev = last;
}

/**
* list_splice - join two lists, this is designed for stacks
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
static inline void list_splice(const struct list_head *list,
			       struct list_head *head)
{
	if (!list_empty(list))
		__list_splice(list, head, head->next);
}

/**
* list_splice_tail - join two lists, each list being a queue
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
static inline void list_splice_tail(struct list_head *list,
				    struct list_head *head)
{
	if (!list_empty(list))
		__list_splice(list, head->prev, head);
}

/**
* list_splice_init - join two lists and reinitialise the emptied list.
* @list: the new list to add.
* @head: the place to add it in the first list.
*
* The list at @list is reinitialised
*/
static inline void list_splice_init(struct list_head *list,
				    struct list_head *head)
{
	if (!list_empty(list)) {
		__list_splice(list, head, head->next);
		INIT_LIST_HEAD(list);
	}
}

/**
* list_splice_tail_init - join two lists and reinitialise the emptied list
* @list: the new list to add.
* @head: the place to add it in the first list.
*
* Each of the lists is a queue.
* The list at @list is reinitialised
*/
static inline void list_splice_tail_init(struct list_head *list,
					 struct list_head *head)
{
	if (!list_empty(list)) {
		__list_splice(list, head->prev, head);
		INIT_LIST_HEAD(list);
	}
}

/**
* list_entry - get the struct for this entry
* @ptr:	the &struct list_head pointer.
* @type:	the type of the struct this is embedded in.
* @member:	the name of the list_head within the struct.
*/
#define list_entry(ptr, pos, member) \
	container_of_var(ptr, pos, member)

/**
* list_first_entry - get the first element from a list
* @ptr:	the list head to take the element from.
* @type:	the type of the struct this is embedded in.
* @member:	the name of the list_head within the struct.
*
* Note, that list is expected to be not empty.
*/
#define list_first_entry(ptr, pos, member) \
	list_entry((ptr)->next, pos, member)

/**
* list_last_entry - get the last element from a list
* @ptr:	the list head to take the element from.
* @type:	the type of the struct this is embedded in.
* @member:	the name of the list_head within the struct.
*
* Note, that list is expected to be not empty.
*/
#define list_last_entry(ptr, pos, member) \
	list_entry((ptr)->prev, pos, member)

/**
* list_next_entry - get the next element in list
* @pos:	the type * to cursor
* @member:	the name of the list_head within the struct.
*/
#define list_next_entry(pos, member) \
	list_entry((pos)->member.next, pos, member)

/**
* list_prev_entry - get the prev element in list
* @pos:	the type * to cursor
* @member:	the name of the list_head within the struct.
*/
#define list_prev_entry(pos, member) \
	list_entry((pos)->member.prev, pos, member)

/**
* list_for_each	-	iterate over a list
* @pos:	the &struct list_head to use as a loop cursor.
* @head:	the head for your list.
*/
#define list_for_each(pos, head) \
	for (pos = (head)->next; pos != (head); pos = pos->next)

/**
* list_for_each_prev	-	iterate over a list backwards
* @pos:	the &struct list_head to use as a loop cursor.
* @head:	the head for your list.
*/
#define list_for_each_prev(pos, head) \
	for (pos = (head)->prev; pos != (head); pos = pos->prev)

/**
* list_for_each_safe - iterate over a list safe against removal of list entry
* @pos:	the &struct list_head to use as a loop cursor.
* @n:		another &struct list_head to use as temporary storage
* @head:	the head for your list.
*/
#define list_for_each_safe(pos, n, head) \
	for (pos = (head)->next, n = pos->next; pos != (head); \
		pos = n, n = pos->next)

/**
* list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
* @pos:	the &struct list_head to use as a loop cursor.
* @n:		another &struct list_head to use as temporary storage
* @head:	the head for your list.
*/
#define list_for_each_prev_safe(pos, n, head) \
	for (pos = (head)->prev, n = pos->prev; \
	     pos != (head); \
	     pos = n, n = pos->prev)

/**
* list_for_each_entry	-	iterate over list of given type
* @pos:	the type * to use as a loop cursor.
* @head:	the head for your list.
* @member:	the name of the list_head within the struct.
*/
#define list_for_each_entry(pos, head, member)				\
	for (pos = list_first_entry(head, pos, member);	\
	     &pos->member != (head);					\
	     pos = list_next_entry(pos, member))

/**
* list_for_each_entry_reverse - iterate backwards over list of given type.
* @pos:	the type * to use as a loop cursor.
* @head:	the head for your list.
* @member:	the name of the list_head within the struct.
*/
#define list_for_each_entry_reverse(pos, head, member)			\
	for (pos = list_last_entry(head, pos, member);		\
	     &pos->member != (head); 					\
	     pos = list_prev_entry(pos, member))

/**
* list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
* @pos:	the type * to use as a start point
* @head:	the head of the list
* @member:	the name of the list_head within the struct.
*
* Prepares a pos entry for use as a start point in list_for_each_entry_continue().
*/
#define list_prepare_entry(pos, head, member) \
	((pos) ? : list_entry(head, pos, member))

/**
* list_for_each_entry_continue - continue iteration over list of given type
* @pos:	the type * to use as a loop cursor.
* @head:	the head for your list.
* @member:	the name of the list_head within the struct.
*
* Continue to iterate over list of given type, continuing after
* the current position.
*/
#define list_for_each_entry_continue(pos, head, member) 		\
	for (pos = list_next_entry(pos, member);			\
	     &pos->member != (head);					\
	     pos = list_next_entry(pos, member))

/**
* list_for_each_entry_continue_reverse - iterate backwards from the given point
* @pos:	the type * to use as a loop cursor.
* @head:	the head for your list.
* @member:	the name of the list_head within the struct.
*
* Start to iterate over list of given type backwards, continuing after
* the current position.
*/
#define list_for_each_entry_continue_reverse(pos, head, member)		\
	for (pos = list_prev_entry(pos, member);			\
	     &pos->member != (head);					\
	     pos = list_prev_entry(pos, member))

/**
* list_for_each_entry_from - iterate over list of given type from the current point
* @pos:	the type * to use as a loop cursor.
* @head:	the head for your list.
* @member:	the name of the list_head within the struct.
*
* Iterate over list of given type, continuing from current position.
*/
#define list_for_each_entry_from(pos, head, member) 			\
	for (; &pos->member != (head);					\
	     pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member)			\
	for (pos = list_first_entry(head, pos, member),	\
		n = list_next_entry(pos, member);			\
	     &pos->member != (head); 					\
	     pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_continue - continue list iteration safe against removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate over list of given type, continuing after current point,
 * safe against removal of list entry.
 */
#define list_for_each_entry_safe_continue(pos, n, head, member) 		\
	for (pos = list_next_entry(pos, member), 				\
		n = list_next_entry(pos, member);				\
	     &pos->member != (head);						\
	     pos = n, n = list_next_entry(n, member))

/**
* list_for_each_entry_safe_from - iterate over list from current point safe against removal
* @pos:	the type * to use as a loop cursor.
* @n:		another type * to use as temporary storage
* @head:	the head for your list.
* @member:	the name of the list_head within the struct.
*
* Iterate over list of given type from current point, safe against
* removal of list entry.
*/
#define list_for_each_entry_safe_from(pos, n, head, member) 			\
	for (n = list_next_entry(pos, member);					\
	     &pos->member != (head);						\
	     pos = n, n = list_next_entry(n, member))

/**
* list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
* @pos:	the type * to use as a loop cursor.
* @n:		another type * to use as temporary storage
* @head:	the head for your list.
* @member:	the name of the list_head within the struct.
*
* Iterate backwards over list of given type, safe against removal
* of list entry.
*/
#define list_for_each_entry_safe_reverse(pos, n, head, member)		\
	for (pos = list_last_entry(head, pos, member),		\
		n = list_prev_entry(pos, member);			\
	     &pos->member != (head); 					\
	     pos = n, n = list_prev_entry(n, member))

/**
* list_safe_reset_next - reset a stale list_for_each_entry_safe loop
* @pos:	the loop cursor used in the list_for_each_entry_safe loop
* @n:		temporary storage used in list_for_each_entry_safe
* @member:	the name of the list_head within the struct.
*
* list_safe_reset_next is not safe to use in general if the list may be
* modified concurrently (eg. the lock is dropped in the loop body). An
* exception to this is if the cursor element (pos) is pinned in the list,
* and list_safe_reset_next is called after re-taking the lock and before
* completing the current iteration of the loop body.
*/
#define list_safe_reset_next(pos, n, member)				\
	n = list_next_entry(pos, member)

#endif