/* copy from linux kernel list */

#ifndef _HAIL_LIST_H_
#define _HAIL_LIST_H_

struct hail_list_head {
	struct hail_list_head *next, *prev;
};

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

#define HAIL_LIST_HEAD(name) \
	struct hail_list_head name = HAIL_LIST_HEAD_INIT(name)

#define INIT_HAIL_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 hail_list manipulation where we know
 * the prev/next entries already!
 */
static __inline__ void __hail_list_add(struct hail_list_head * new,
	struct hail_list_head * prev,
	struct hail_list_head * next)
{
	next->prev = new;
	new->next = next;
	new->prev = prev;
	prev->next = new;
}

/**
 * hail_list_add - add a new entry
 * @new: new entry to be added
 * @head: hail_list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
static __inline__ void hail_list_add(struct hail_list_head *new, struct hail_list_head *head)
{
	__hail_list_add(new, head, head->next);
}

/**
 * hail_list_add_tail - add a new entry
 * @new: new entry to be added
 * @head: hail_list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 */
static __inline__ void hail_list_add_tail(struct hail_list_head *new, struct hail_list_head *head)
{
	__hail_list_add(new, head->prev, head);
}

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

/**
 * hail_list_del - deletes entry from hail_list.
 * @entry: the element to delete from the hail_list.
 * Note: hail_list_empty on entry does not return true after this, the entry is in an undefined state.
 */
static __inline__ void hail_list_del(struct hail_list_head *entry)
{
	__hail_list_del(entry->prev, entry->next);
	entry->next = entry->prev = 0;
}

/**
 * hail_list_del_init - deletes entry from hail_list and reinitialize it.
 * @entry: the element to delete from the hail_list.
 */
static __inline__ void hail_list_del_init(struct hail_list_head *entry)
{
	__hail_list_del(entry->prev, entry->next);
	INIT_HAIL_LIST_HEAD(entry); 
}

/**
 * hail_list_empty - tests whether a hail_list is empty
 * @head: the hail_list to test.
 */
static __inline__ int hail_list_empty(struct hail_list_head *head)
{
	return head->next == head;
}

/**
 * hail_list_splice - join two hail_lists
 * @hail_list: the new hail_list to add.
 * @head: the place to add it in the first hail_list.
 */
static __inline__ void hail_list_splice(struct hail_list_head *hail_list, struct hail_list_head *head)
{
	struct hail_list_head *first = hail_list->next;

	if (first != hail_list) {
		struct hail_list_head *last = hail_list->prev;
		struct hail_list_head *at = head->next;

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

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

/**
 * hail_list_entry - get the struct for this entry
 * @ptr:	the &struct hail_list_head pointer.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the hail_list_struct within the struct.
 */
#define hail_list_entry(ptr, type, member) \
	((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

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

#endif /* _HAIL_LIST_H_ */