Merge pull request #1756 from brauner/2017-08-10/further_lxc_2.1_preparations

[mirror_lxc.git] / src / lxc / list.h

/*
 * lxc: linux Container library
 *
 * (C) Copyright IBM Corp. 2007, 2008
 *
 * Authors:
 * Daniel Lezcano <daniel.lezcano at free.fr>
 *
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef __LXC_LIST_H
#define __LXC_LIST_H

struct lxc_list {
	void *elem;
	struct lxc_list *next;
	struct lxc_list *prev;
};

#define lxc_init_list(l) { .next = l, .prev = l }

/*
 * Iterate through an lxc list. An example for an idiom would be:
 *
 * struct lxc_list *iterator;
 * type *tmp; // where "type" can be an int, char * etc.
 * lxc_list_for_each(iterator, list) {
 * 	  tmp = iterator->elem;
 *        // Do stuff with tmp.
 * }
 * free(iterator);
 */
#define lxc_list_for_each(__iterator, __list)				\
	for (__iterator = (__list)->next;				\
	     __iterator != __list;					\
	     __iterator = __iterator->next)

/*
 * Iterate safely through an lxc list. An example for an appropriate use case
 * would be:
 *
 * struct lxc_list *iterator;
 * lxc_list_for_each_safe(iterator, list, list->next) {
 * 	  tmp = iterator->elem;
 *        // Do stuff with tmp.
 * }
 * free(iterator);
 */
#define lxc_list_for_each_safe(__iterator, __list, __next)		\
	for (__iterator = (__list)->next, __next = __iterator->next;	\
	     __iterator != __list;					\
	     __iterator = __next, __next = __next->next)

/* Initalize list. */
static inline void lxc_list_init(struct lxc_list *list)
{
	list->elem = NULL;
	list->next = list->prev = list;
}

/* Add an element to a list. See lxc_list_add() and lxc_list_add_tail() for an
 * idiom. */
static inline void lxc_list_add_elem(struct lxc_list *list, void *elem)
{
	list->elem = elem;
}

/* Retrieve first element of list. */
static inline void *lxc_list_first_elem(struct lxc_list *list)
{
	return list->next->elem;
}

/* Retrieve last element of list. */
static inline void *lxc_list_last_elem(struct lxc_list *list)
{
	return list->prev->elem;
}

/* Determine if list is empty. */
static inline int lxc_list_empty(struct lxc_list *list)
{
	return list == list->next;
}

/* Workhorse to be called from lxc_list_add() and lxc_list_add_tail(). */
static inline void __lxc_list_add(struct lxc_list *new,
				  struct lxc_list *prev,
				  struct lxc_list *next)
{
	next->prev = new;
	new->next = next;
	new->prev = prev;
	prev->next = new;
}

/*
 * Idiom to add an element to the beginning of an lxc list:
 *
 *	struct lxc_list *tmp = malloc(sizeof(*tmp));
 *	if (tmp == NULL)
 *		return 1;
 *	lxc_list_add_elem(tmp, elem);
 *	lxc_list_add(list, tmp);
 */
static inline void lxc_list_add(struct lxc_list *head, struct lxc_list *list)
{
	__lxc_list_add(list, head, head->next);
}

/*
 * Idiom to add an element to the end of an lxc list:
 *
 *	struct lxc_list *tmp = malloc(sizeof(*tmp));
 *	if (tmp == NULL)
 *		return 1;
 *	lxc_list_add_elem(tmp, elem);
 *	lxc_list_add_tail(list, tmp);
 */
static inline void lxc_list_add_tail(struct lxc_list *head,
				     struct lxc_list *list)
{
	__lxc_list_add(list, head->prev, head);
}

/*
 * Idiom to free an lxc list:
 *
 * lxc_list_for_each_safe(iterator, list, list->next) {
 * 	  lxc_list_del(iterator);
 * 	  free(iterator);
 * }
 * free(iterator);
 */
static inline void lxc_list_del(struct lxc_list *list)
{
	struct lxc_list *next, *prev;

	next = list->next;
	prev = list->prev;
	next->prev = prev;
	prev->next = next;
}

/* Return length of the list. */
static inline size_t lxc_list_len(struct lxc_list *list)
{
	 size_t i = 0;
	 struct lxc_list *iter;
	 lxc_list_for_each(iter, list) {
		i++;
	 }

	 return i;
}

#endif