/* Unix SMB/CIFS implementation. some simple double linked list macros Copyright (C) Andrew Tridgell 1998-2010 This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. 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. You should have received a copy of the GNU General Public License along with this program. If not, see . */ /* 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 ((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) /* 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 */