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/*
Unix SMB/CIFS implementation.
some simple double linked list macros
Copyright (C) Andrew Tridgell 1998-2010
** NOTE! The following LGPL license applies to this file (*dlinklist.h).
** This does NOT imply that all of Samba is released under the LGPL
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 3 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, see <http://www.gnu.org/licenses/>.
*/
/* To use these macros you must have a structure containing a next and
prev pointer */
#ifndef _DLINKLIST_H
#define _DLINKLIST_H
/*
February 2010 - changed list format to have a prev pointer from the
list head. This makes DLIST_ADD_END() O(1) even though we only have
one list pointer.
The scheme is as follows:
1) with no entries in the list:
list_head == NULL
2) with 1 entry in the list:
list_head->next == NULL
list_head->prev == list_head
3) with 2 entries in the list:
list_head->next == element2
list_head->prev == element2
element2->prev == list_head
element2->next == NULL
4) with N entries in the list:
list_head->next == element2
list_head->prev == elementN
elementN->prev == element{N-1}
elementN->next == NULL
This allows us to find the tail of the list by using
list_head->prev, which means we can add to the end of the list in
O(1) time
*/
/*
add an element at the front of a list
*/
#define DLIST_ADD(list, p) \
do { \
if (!(list)) { \
(p)->prev = (list) = (p); \
(p)->next = NULL; \
} else { \
(p)->prev = (list)->prev; \
(list)->prev = (p); \
(p)->next = (list); \
(list) = (p); \
} \
} while (0)
/*
remove an element from a list
Note that the element doesn't have to be in the list. If it
isn't then this is a no-op
*/
#define DLIST_REMOVE(list, p) \
do { \
if ((p) == (list)) { \
if ((p)->next) (p)->next->prev = (p)->prev; \
(list) = (p)->next; \
} else if ((p)->prev && (list) && (p) == (list)->prev) { \
(p)->prev->next = NULL; \
(list)->prev = (p)->prev; \
} else { \
if ((p)->prev) (p)->prev->next = (p)->next; \
if ((p)->next) (p)->next->prev = (p)->prev; \
} \
if ((p) != (list)) (p)->next = (p)->prev = NULL; \
} while (0)
/*
find the head of the list given any element in it.
Note that this costs O(N), so you should avoid this macro
if at all possible!
*/
#define DLIST_HEAD(p, result_head) \
do { \
(result_head) = (p); \
while (DLIST_PREV(result_head)) (result_head) = (result_head)->prev; \
} while(0)
/* return the last element in the list */
#define DLIST_TAIL(list) ((list)?(list)->prev:NULL)
/* return the previous element in the list. */
#define DLIST_PREV(p) (((p)->prev && (p)->prev->next != NULL)?(p)->prev:NULL)
/* insert 'p' after the given element 'el' in a list. If el is NULL then
this is the same as a DLIST_ADD() */
#define DLIST_ADD_AFTER(list, p, el) \
do { \
if (!(list) || !(el)) { \
DLIST_ADD(list, p); \
} else { \
(p)->prev = (el); \
(p)->next = (el)->next; \
(el)->next = (p); \
if ((p)->next) (p)->next->prev = (p); \
if ((list)->prev == (el)) (list)->prev = (p); \
}\
} while (0)
/*
add to the end of a list.
*/
#define DLIST_ADD_END(list, p) \
do { \
if (!(list)) { \
DLIST_ADD(list, p); \
} else { \
DLIST_ADD_AFTER(list, p, (list)->prev); \
} \
} while (0)
/* promote an element to the front of a list */
#define DLIST_PROMOTE(list, p) \
do { \
DLIST_REMOVE(list, p); \
DLIST_ADD(list, p); \
} while (0)
/*
demote an element to the end of a list.
*/
#define DLIST_DEMOTE(list, p) \
do { \
DLIST_REMOVE(list, p); \
DLIST_ADD_END(list, p); \
} while (0)
/*
* like DLIST_DEMOTE(), but optimized
* for short lists with 0, 1 or 2 elements
*/
#define DLIST_DEMOTE_SHORT(list, p) \
do { \
if ((list) == NULL) { \
/* no reason to demote, just add */ \
DLIST_ADD(list, p); \
} else if ((list)->prev == (p)) { \
/* optimize if p is last */ \
} else if ((list) == (p)) { \
/* optimize if p is first */ \
(list)->prev->next = (p); \
(list) = (p)->next; \
(p)->next = NULL; \
} else { \
DLIST_DEMOTE(list, p); \
} \
} while (0)
/*
concatenate two lists - putting all elements of the 2nd list at the
end of the first list.
*/
#define DLIST_CONCATENATE(list1, list2) \
do { \
if (!(list1)) { \
(list1) = (list2); \
} else { \
(list1)->prev->next = (list2); \
if (list2) { \
void *_tmplist = (void *)(list1)->prev; \
(list1)->prev = (list2)->prev; \
(list2)->prev = _tmplist; \
} \
} \
} while (0)
#endif /* _DLINKLIST_H */
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