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list.h

#ifndef _LINUX_LIST_H
#define _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.
 */

00014 struct list_head {
  struct list_head *next, *prev;
};

#define LIST_HEAD_INIT(name) { &(name), &(name) }

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

#define INIT_LIST_HEAD(ptr) do { \
      (ptr)->next = (ptr); (ptr)->prev = (ptr); \
} while (0)

/*
 * 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(struct list_head *entry)
{
  __list_del(entry->prev, entry->next);
  entry->next = (void *) 0;
  entry->prev = (void *) 0;
}

/**
 * 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->prev, entry->next);
  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(list->prev, list->next);
  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(list->prev, list->next);
  list_add_tail(list, head);
}

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

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

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

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

/**
 * list_splice - join two lists
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void
list_splice(struct list_head *list, struct list_head *head)
{
  if (!list_empty(list))
    __list_splice(list, 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);
    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_struct within the struct.
 */
#define list_entry(ptr, type, member) \
      ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

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

#endif

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