From 00e8a4da8cf0d7dba8cc4b0da28ea0f12dcf6b36 Mon Sep 17 00:00:00 2001 From: "Luis R. Rodriguez" Date: Wed, 6 Aug 2008 13:28:54 -0700 Subject: list.h: add list_cut_position() This adds list_cut_position() which lets you cut a list into two lists given a pivot in the list. Signed-off-by: Luis R. Rodriguez Signed-off-by: John W. Linville --- include/linux/list.h | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) (limited to 'include/linux/list.h') diff --git a/include/linux/list.h b/include/linux/list.h index a886f27a118..1d109e2ef0a 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -214,6 +214,46 @@ static inline int list_is_singular(const struct list_head *head) return !list_empty(head) && (head->next == head->prev); } +static inline void __list_cut_position(struct list_head *list, + struct list_head *head, struct list_head *entry) +{ + struct list_head *new_first = entry->next; + list->next = head->next; + list->next->prev = list; + list->prev = entry; + entry->next = list; + head->next = new_first; + new_first->prev = head; +} + +/** + * list_cut_position - cut a list into two + * @list: a new list to add all removed entries + * @head: a list with entries + * @entry: an entry within head, could be the head itself + * and if so we won't cut the list + * + * This helper moves the initial part of @head, up to and + * including @entry, from @head to @list. You should + * pass on @entry an element you know is on @head. @list + * should be an empty list or a list you do not care about + * losing its data. + * + */ +static inline void list_cut_position(struct list_head *list, + struct list_head *head, struct list_head *entry) +{ + if (list_empty(head)) + return; + if (list_is_singular(head) && + (head->next != entry && head != entry)) + return; + if (entry == head) + INIT_LIST_HEAD(list); + else + __list_cut_position(list, head, entry); +} + static inline void __list_splice(const struct list_head *list, struct list_head *prev, struct list_head *next) -- cgit v1.2.3