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/*
* Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "list.h"
#include <assert.h>
/* Initializes 'list' as an empty list. */
void
list_init(struct list *list)
{
list->next = list->prev = list;
}
/* Initializes 'list' with pointers that will (probably) cause segfaults if
* dereferenced and, better yet, show up clearly in a debugger. */
void
list_poison(struct list *list)
{
memset(list, 0xcc, sizeof *list);
}
/* Inserts 'elem' just before 'before'. */
void
list_insert(struct list *before, struct list *elem)
{
elem->prev = before->prev;
elem->next = before;
before->prev->next = elem;
before->prev = elem;
}
/* Removes elements 'first' though 'last' (exclusive) from their current list,
then inserts them just before 'before'. */
void
list_splice(struct list *before, struct list *first, struct list *last)
{
if (first == last)
return;
last = last->prev;
/* Cleanly remove 'first'...'last' from its current list. */
first->prev->next = last->next;
last->next->prev = first->prev;
/* Splice 'first'...'last' into new list. */
first->prev = before->prev;
last->next = before;
before->prev->next = first;
before->prev = last;
}
/* Inserts 'elem' at the beginning of 'list', so that it becomes the front in
'list'. */
void
list_push_front(struct list *list, struct list *elem)
{
list_insert(list->next, elem);
}
/* Inserts 'elem' at the end of 'list', so that it becomes the back in
* 'list'. */
void
list_push_back(struct list *list, struct list *elem)
{
list_insert(list, elem);
}
/* Puts 'elem' in the position currently occupied by 'position'.
* Afterward, 'position' is not part of a list. */
void
list_replace(struct list *element, const struct list *position)
{
element->next = position->next;
element->next->prev = element;
element->prev = position->prev;
element->prev->next = element;
}
/* Adjusts pointers around 'list' to compensate for 'list' having been moved
* around in memory (e.g. as a consequence of realloc()).
*
* This always works if 'list' is a member of a list, or if 'list' is the head
* of a non-empty list. It fails badly, however, if 'list' is the head of an
* empty list; just use list_init() in that case. */
void
list_moved(struct list *list)
{
list->prev->next = list->next->prev = list;
}
/* Removes 'elem' from its list and returns the element that followed it.
Undefined behavior if 'elem' is not in a list. */
struct list *
list_remove(struct list *elem)
{
elem->prev->next = elem->next;
elem->next->prev = elem->prev;
return elem->next;
}
/* Removes the front element from 'list' and returns it. Undefined behavior if
'list' is empty before removal. */
struct list *
list_pop_front(struct list *list)
{
struct list *front = list->next;
list_remove(front);
return front;
}
/* Removes the back element from 'list' and returns it.
Undefined behavior if 'list' is empty before removal. */
struct list *
list_pop_back(struct list *list)
{
struct list *back = list->prev;
list_remove(back);
return back;
}
/* Returns the front element in 'list_'.
Undefined behavior if 'list_' is empty. */
struct list *
list_front(const struct list *list_)
{
struct list *list = (struct list *) list_;
assert(!list_is_empty(list));
return list->next;
}
/* Returns the back element in 'list_'.
Undefined behavior if 'list_' is empty. */
struct list *
list_back(const struct list *list_)
{
struct list *list = (struct list *) list_;
assert(!list_is_empty(list));
return list->prev;
}
/* Returns the number of elements in 'list'.
Runs in O(n) in the number of elements. */
size_t
list_size(const struct list *list)
{
const struct list *e;
size_t cnt = 0;
for (e = list->next; e != list; e = e->next)
cnt++;
return cnt;
}
/* Returns true if 'list' is empty, false otherwise. */
bool
list_is_empty(const struct list *list)
{
return list->next == list;
}
/* Returns true if 'list' has exactly 1 element, false otherwise. */
bool
list_is_singleton(const struct list *list)
{
return list_is_short(list) && !list_is_empty(list);
}
/* Returns true if 'list' has 0 or 1 elements, false otherwise. */
bool
list_is_short(const struct list *list)
{
return list->next == list->prev;
}
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