Add cds_list_empty

[urcu.git] / urcu / list.h

/*
 * Copyright (C) 2002 Free Software Foundation, Inc.
 * (originally part of the GNU C Library)
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef _CDS_LIST_H
#define _CDS_LIST_H	1

/* 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 cds_list_head
{
  struct cds_list_head *next;
  struct cds_list_head *prev;
};

/* Define a variable with the head and tail of the list.  */
#define CDS_LIST_HEAD(name) \
  struct cds_list_head name = { &(name), &(name) }

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

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

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


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

/* Remove element from list.  */
static inline void
cds_list_del (struct cds_list_head *elem)
{
  __cds_list_del (elem->prev, elem->next);
}

/* Remove element from list, initializing the element's list pointers. */
static inline void
cds_list_del_init (struct cds_list_head *elem)
{
	cds_list_del(elem);
	CDS_INIT_LIST_HEAD(elem);
}

/* delete from list, add to another list as head */
static inline void
cds_list_move (struct cds_list_head *elem, struct cds_list_head *head)
{
  __cds_list_del (elem->prev, elem->next);
  cds_list_add (elem, head);
}

/* replace an old entry.
 */
static inline void
cds_list_replace(struct cds_list_head *old, struct cds_list_head *_new)
{
	_new->next = old->next;
	_new->prev = old->prev;
	_new->prev->next = _new;
	_new->next->prev = _new;
}

/* Join two lists.  */
static inline void
cds_list_splice (struct cds_list_head *add, struct cds_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;
    }
}

/* Returns 1 if list is empty, 0 otherwise */
static inline
int cds_list_empty(struct cds_list_head *head)
{
	return head->next == head->prev;
}

/* Get typed element from list at a given position.  */
#define cds_list_entry(ptr, type, member) \
  ((type *) ((char *) (ptr) - (unsigned long) (&((type *) 0)->member)))


/* Get first entry from a list. */
#define cds_list_first_entry(head, type, member) \
	cds_list_entry((head)->next, type, member)


/* Iterate forward over the elements of the list.  */
#define cds_list_for_each(pos, head) \
  for (pos = (head)->next; pos != (head); pos = pos->next)


/* Iterate forward over the elements of the list.  */
#define cds_list_for_each_prev(pos, head) \
  for (pos = (head)->prev; pos != (head); pos = pos->prev)


/* Iterate backwards over the elements list.  The list elements can be
   removed from the list while doing this.  */
#define cds_list_for_each_prev_safe(pos, p, head) \
  for (pos = (head)->prev, p = pos->prev; \
       pos != (head); \
       pos = p, p = pos->prev)

#define cds_list_for_each_entry(pos, head, member)				\
	for (pos = cds_list_entry((head)->next, typeof(*pos), member);	\
	     &pos->member != (head);					\
	     pos = cds_list_entry(pos->member.next, typeof(*pos), member))

#define cds_list_for_each_entry_reverse(pos, head, member)			\
	for (pos = cds_list_entry((head)->prev, typeof(*pos), member);	\
	     &pos->member != (head);					\
	     pos = cds_list_entry(pos->member.prev, typeof(*pos), member))

#define cds_list_for_each_entry_safe(pos, p, head, member)			\
	for (pos = cds_list_entry((head)->next, typeof(*pos), member),	\
		     p = cds_list_entry(pos->member.next,typeof(*pos), member); \
	     &pos->member != (head);					\
	     pos = p, p = cds_list_entry(pos->member.next, typeof(*pos), member))

static inline int cds_list_empty(struct cds_list_head *head)
{
	return head == head->next;
}

static inline void cds_list_replace_init(struct cds_list_head *old,
				     struct cds_list_head *_new)
{
	struct cds_list_head *head = old->next;
	cds_list_del(old);
	cds_list_add_tail(_new, head);
	CDS_INIT_LIST_HEAD(old);
}

#endif	/* _CDS_LIST_H */