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/*
* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004 Red Hat, Inc. All rights reserved.
*
* This file is part of LVM2.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU General Public License v.2.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "lib.h"
/*
* Initialise a list before use.
* The list head's next and previous pointers point back to itself.
*/
void list_init(struct list *head)
{
head->n = head->p = head;
}
/*
* Insert an element before 'head'.
* If 'head' is the list head, this adds an element to the end of the list.
*/
void list_add(struct list *head, struct list *elem)
{
assert(head->n);
elem->n = head;
elem->p = head->p;
head->p->n = elem;
head->p = elem;
}
/*
* Insert an element after 'head'.
* If 'head' is the list head, this adds an element to the front of the list.
*/
void list_add_h(struct list *head, struct list *elem)
{
assert(head->n);
elem->n = head->n;
elem->p = head;
head->n->p = elem;
head->n = elem;
}
/*
* Delete an element from its list.
* Note that this doesn't change the element itself - it may still be safe
* to follow its pointers.
*/
void list_del(struct list *elem)
{
elem->n->p = elem->p;
elem->p->n = elem->n;
}
/*
* Is the list empty?
*/
int list_empty(const struct list *head)
{
return head->n == head;
}
/*
* Is this the first element of the list?
*/
int list_start(const struct list *head, const struct list *elem)
{
return elem->p == head;
}
/*
* Is this the last element of the list?
*/
int list_end(const struct list *head, const struct list *elem)
{
return elem->n == head;
}
/*
* Return first element of the list or NULL if empty
*/
struct list *list_first(const struct list *head)
{
return (list_empty(head) ? NULL : head->n);
}
/*
* Return last element of the list or NULL if empty
*/
struct list *list_last(const struct list *head)
{
return (list_empty(head) ? NULL : head->p);
}
/*
* Return the previous element of the list, or NULL if we've reached the start.
*/
struct list *list_prev(const struct list *head, const struct list *elem)
{
return (list_start(head, elem) ? NULL : elem->p);
}
/*
* Return the next element of the list, or NULL if we've reached the end.
*/
struct list *list_next(const struct list *head, const struct list *elem)
{
return (list_end(head, elem) ? NULL : elem->n);
}
/*
* Return the number of elements in a list by walking it.
*/
unsigned int list_size(const struct list *head)
{
unsigned int s = 0;
const struct list *v;
list_iterate(v, head)
s++;
return s;
}
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