/* Doubly linked list macros compatible with Linux kernel's version

 * Copyright (c) 2015 by Takashi Iwai <tiwai@suse.de>

 *

 * This library is free software; you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as

 * published by the Free Software Foundation; either version 2.1 of

 * the License, or (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 */

#ifndef _LIST_H

#define _LIST_H

#include <stddef.h>

struct list_head {

	struct list_head *next;

	struct list_head *prev;

};

/* one-shot definition of a list head */

#define LIST_HEAD(x) \

	struct list_head x = { &x, &x }

/* initialize a list head explicitly */

static inline void INIT_LIST_HEAD(struct list_head *p)

{

	p->next = p->prev = p;

}

#define list_entry_offset(p, type, offset) \

	((type *)((char *)(p) - (offset)))

/* list_entry - retrieve the original struct from list_head

 * @p: list_head pointer

 * @type: struct type

 * @member: struct field member containing the list_head

 */

#define list_entry(p, type, member) \

	list_entry_offset(p, type, offsetof(type, member))

/* list_for_each - iterate over the linked list

 * @p: iterator, a list_head pointer variable

 * @list: list_head pointer containing the list

 */

#define list_for_each(p, list) \

	for (p = (list)->next; p != (list); p = p->next)

/* list_for_each_safe - iterate over the linked list, safe to delete

 * @p: iterator, a list_head pointer variable

 * @s: a temporary variable to keep the next, a list_head pointer, too

 * @list: list_head pointer containing the list

 */

#define list_for_each_safe(p, s, list) \

	for (p = (list)->next; s = p->next, p != (list); p = s)

/* list_add - prepend a list entry at the head

 * @p: the new list entry to add

 * @list: the list head

 */

static inline void list_add(struct list_head *p, struct list_head *list)

{

	struct list_head *first = list->next;

	p->next = first;

	first->prev = p;

	list->next = p;

	p->prev = list;

}

/* list_add_tail - append a list entry at the tail

 * @p: the new list entry to add

 * @list: the list head

 */

static inline void list_add_tail(struct list_head *p, struct list_head *list)

{

	struct list_head *last = list->prev;

	last->next = p;

	p->prev = last;

	p->next = list;

	list->prev = p;

}

/* list_insert - insert a new list entry between two known consecutive entries

 * @p: the new entry to be inserted between prev and next

 * @prev: the left-side entry

 * @next: the right-side entry

 */

static inline void list_insert(struct list_head *p,

			       struct list_head *prev,

			       struct list_head *next)

{

	next->prev = p;

	p->next = next;

	p->prev = prev;

	prev->next = p;

}

/* list_del - delete the given list entry */

static inline void list_del(struct list_head *p)

{

	p->prev->next = p->next;

	p->next->prev = p->prev;

}

/* list_empty - returns 1 if the given list is empty */

static inline int list_empty(const struct list_head *p)

{

	return p->next == p;

}

#endif /* _LIST_H */