/*
 * Copyright (C) 2002 Free Software Foundation, Inc.
 * (originally part of the GNU C Library and Userspace RCU)
 * Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
 *
 * Copyright (C) 2009 Pierre-Marc Fournier
 * Conversion to RCU list.
 * Copyright (C) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * 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 library 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.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see
 * <http://www.gnu.org/licenses/>.
 */

#ifndef LIST_H
#define LIST_H

#include <stddef.h>

/*
 * The definitions of this file are adopted from those which can be
 * found in the Linux kernel headers to enable people familiar with the
 * latter find their way in these sources as well.
 */

/* Basic type for the double-link list. */
struct list_head {
	struct list_head *next, *prev;
};

/* avoid conflicts with BSD-only sys/queue.h */
#undef LIST_HEAD
/* Define a variable with the head and tail of the list. */
#define LIST_HEAD(name) struct list_head name = { &(name), &(name) }

/* Initialize a new list head. */
#define INIT_LIST_HEAD(ptr) (ptr)->next = (ptr)->prev = (ptr)

#define LIST_HEAD_INIT(name)              \
	{                                     \
		.next = &(name), .prev = &(name), \
	}

/* Add new element at the head of the list. */
static inline void list_add(struct list_head *newp, struct list_head *head)
{
	head->next->prev = newp;
	newp->next		 = head->next;
	newp->prev		 = head;
	head->next		 = newp;
}

/* Add new element at the tail of the list. */
static inline void list_add_tail(struct list_head *newp, struct list_head *head)
{
	head->prev->next = newp;
	newp->next		 = head;
	newp->prev		 = head->prev;
	head->prev		 = newp;
}

/* Remove element from list. */
static inline void __list_del(struct list_head *prev, struct list_head *next)
{
	next->prev = prev;
	prev->next = next;
}

/* Remove element from list. */
static inline void list_del(struct list_head *elem)
{
	__list_del(elem->prev, elem->next);
}

/* Remove element from list, initializing the element's list pointers. */
static inline void list_del_init(struct list_head *elem)
{
	list_del(elem);
	INIT_LIST_HEAD(elem);
}

/* Delete from list, add to another list as head. */
static inline void list_move(struct list_head *elem, struct list_head *head)
{
	__list_del(elem->prev, elem->next);
	list_add(elem, head);
}

/* Replace an old entry. */
static inline void list_replace(struct list_head *old, struct list_head *newp)
{
	newp->next		 = old->next;
	newp->prev		 = old->prev;
	newp->prev->next = newp;
	newp->next->prev = newp;
}

/* Join two lists. */
static inline void list_splice(struct list_head *add, struct list_head *head)
{
	/* Do nothing if the list which gets added is empty. */
	if (add != add->next) {
		add->next->prev	 = head;
		add->prev->next	 = head->next;
		head->next->prev = add->prev;
		head->next		 = add->next;
	}
}

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

static inline void list_replace_init(struct list_head *old,
									 struct list_head *newp)
{
	struct list_head *head = old->next;

	list_del(old);
	list_add_tail(newp, head);
	INIT_LIST_HEAD(old);
}

/**
 * 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, type, member) \
	((type *)((char *)(ptr)-offsetof(type, 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, type, member) \
	list_entry((ptr)->next, type, 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, type, member) list_entry((ptr)->prev, type, 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, typeof(*(pos)), member)

/**
 * __typed_list_for_each() - macro for making other typed for_each macros.
 * @Te:			list entry type.
 * @e:			entry.
 * @emember:	member of the entry structure that holds list_head.
 * @l:			list head to iterate over.
 * @lmember:	member of the list head structure that holds list_head.
 */
#define __typed_list_for_each(Te, e, emember, l, lmember)  \
	for (e = list_first_entry(&(l)->lmember, Te, emember); \
		 &e->emember != &(l)->lmember;                     \
		 e = list_entry(e->emember.next, Te, emember))

/**
 * 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; !list_is_head(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; !list_is_head(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; !list_is_head(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; !list_is_head(pos, (head)); \
		 pos = n, n = pos->prev)

/**
 * list_entry_is_head - test if the entry points to the head of the list
 * @pos:	the type * to cursor
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
#define list_entry_is_head(pos, head, member) (&pos->member == (head))

/**
 * 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, typeof(*pos), member); \
		 !list_entry_is_head(pos, head, member);             \
		 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, typeof(*pos), member), \
		n	 = list_next_entry(pos, member);                 \
		 !list_entry_is_head(pos, head, member);             \
		 pos = n, n = list_next_entry(n, member))

/*
 * This is exactly the same as a normal list_head, except that it can be
 * declared volatile (e.g., if you have a list that may be accessed from signal
 * handlers).
 */
struct volatile_list_head {
	volatile struct volatile_list_head *next, *prev;
};

#define VOLATILE_LIST_HEAD(name) \
	volatile struct volatile_list_head name = { &(name), &(name) }

static inline void __volatile_list_del(volatile struct volatile_list_head *prev,
									   volatile struct volatile_list_head *next)
{
	next->prev = prev;
	prev->next = next;
}

static inline void volatile_list_del(volatile struct volatile_list_head *elem)
{
	__volatile_list_del(elem->prev, elem->next);
}

static inline int volatile_list_empty(volatile struct volatile_list_head *head)
{
	return head == head->next;
}

static inline void volatile_list_add(volatile struct volatile_list_head *newp,
									 volatile struct volatile_list_head *head)
{
	head->next->prev = newp;
	newp->next		 = head->next;
	newp->prev		 = head;
	head->next		 = newp;
}

#endif /* LIST_H */