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/* Copyright (C) 2011 The Android Open Source Project
**
** This software is licensed under the terms of the GNU General Public
** License version 2, as published by the Free Software Foundation, and
** may be copied, distributed, and modified under those terms.
**
** This program 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 General Public License for more details.
*/
#ifndef _ANDROID_UTILS_LIST_H
#define _ANDROID_UTILS_LIST_H
#include <inttypes.h>
/* Encapsulates a double-linked, circular list.
* The list is organized in the following way:
* - List entries contain references to the next, and the previous entry in the
* list.
* - The list is circular, i.e. the "last" list entry references the "list head"
* in its 'next' reference, and the "list head" references the "last" entry in
* its 'previous' reference.
* - The list is empty if its 'next' and 'previous' references are addressing the
* head of the list.
*/
typedef struct ACList ACList;
struct ACList {
/* Next entry in the list */
ACList* next;
/* Previous entry in the list */
ACList* prev;
};
/* Initializes the list. */
AINLINED void
alist_init(ACList* list)
{
list->next = list->prev = list;
}
/* Checks if the list is empty. */
AINLINED int
alist_is_empty(const ACList* list)
{
return list->next == list;
}
/* Inserts an entry to the head of the list */
AINLINED void
alist_insert_head(ACList* list, ACList* entry)
{
ACList* const next = list->next;
entry->next = next;
entry->prev = list;
next->prev = entry;
list->next = entry;
}
/* Inserts an entry to the tail of the list */
AINLINED void
alist_insert_tail(ACList* list, ACList* entry)
{
ACList* const prev = list->prev;
entry->next = list;
entry->prev = prev;
prev->next = entry;
list->prev = entry;
}
/* Removes an entry from the list. NOTE: Entry must be in the list when this
* routine is called. */
AINLINED void
alist_remove(ACList* entry)
{
ACList* const next = entry->next;
ACList* const prev = entry->prev;
prev->next = next;
next->prev = prev;
entry->next = entry->prev = entry;
}
/* Returns an entry removed from the head of the list. If the list was empty,
* this routine returns NULL. */
AINLINED ACList*
alist_remove_head(ACList* list)
{
ACList* entry = NULL;
if (!alist_is_empty(list)) {
entry = list->next;
list->next = entry->next;
entry->next->prev = list;
entry->next = entry->prev = entry;
}
return entry;
}
/* Returns an entry removed from the tail of the list. If the list was empty,
* this routine returns NULL. */
AINLINED ACList*
alist_remove_tail(ACList* list)
{
ACList* entry = NULL;
if (!alist_is_empty(list)) {
entry = list->prev;
list->prev = entry->prev;
entry->prev->next = list;
entry->next = entry->prev = entry;
}
return entry;
}
#endif /* _ANDROID_UTILS_LIST_H */
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