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Diffstat (limited to 'lib/util/dlinklist.h')
| -rw-r--r-- | lib/util/dlinklist.h | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/lib/util/dlinklist.h b/lib/util/dlinklist.h new file mode 100644 index 0000000..49a135a --- /dev/null +++ b/lib/util/dlinklist.h @@ -0,0 +1,198 @@ +/* + 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 */ |