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Diffstat (limited to '')
| -rw-r--r-- | include/list.h | 340 |
1 files changed, 340 insertions, 0 deletions
diff --git a/include/list.h b/include/list.h new file mode 100644 index 0000000..f3ffc79 --- /dev/null +++ b/include/list.h @@ -0,0 +1,340 @@ +/* + * Copyright (C) 2008 Karel Zak <kzak@redhat.com> + * Copyright (C) 1999-2008 by Theodore Ts'o + * + * This file may be redistributed under the terms of the + * GNU Lesser General Public License. + * + * (based on list.h from e2fsprogs) + * Merge sort based on kernel's implementation. + */ + +#ifndef UTIL_LINUX_LIST_H +#define UTIL_LINUX_LIST_H + +#include "c.h" + +/* TODO: use AC_C_INLINE */ +#ifdef __GNUC__ +#define _INLINE_ static __inline__ +#else /* For Watcom C */ +#define _INLINE_ static inline +#endif + +/* + * Simple doubly linked list implementation. + * + * Some of the internal functions ("__xxx") are useful when + * manipulating whole lists rather than single entries, as + * sometimes we already know the next/prev entries and we can + * generate better code by using them directly rather than + * using the generic single-entry routines. + */ + +struct list_head { + struct list_head *next, *prev; +}; + +#define INIT_LIST_HEAD(ptr) do { \ + (ptr)->next = (ptr); (ptr)->prev = (ptr); \ +} while (0) + +/* + * Insert a new entry between two known consecutive entries. + * + * This is only for internal list manipulation where we know + * the prev/next entries already! + */ +_INLINE_ void __list_add(struct list_head * add, + struct list_head * prev, + struct list_head * next) +{ + next->prev = add; + add->next = next; + add->prev = prev; + prev->next = add; +} + +/** + * list_add - add a new entry + * @add: new entry to be added + * @head: list head to add it after + * + * Insert a new entry after the specified head. + * This is good for implementing stacks. + */ +_INLINE_ void list_add(struct list_head *add, struct list_head *head) +{ + __list_add(add, head, head->next); +} + +/** + * list_add_tail - add a new entry + * @add: new entry to be added + * @head: list head to add it before + * + * Insert a new entry before the specified head. + * This is useful for implementing queues. + */ +_INLINE_ void list_add_tail(struct list_head *add, struct list_head *head) +{ + __list_add(add, head->prev, head); +} + +/* + * Delete a list entry by making the prev/next entries + * point to each other. + * + * This is only for internal list manipulation where we know + * the prev/next entries already! + */ +_INLINE_ void __list_del(struct list_head * prev, + struct list_head * next) +{ + next->prev = prev; + prev->next = next; +} + +/** + * list_del - deletes entry from list. + * @entry: the element to delete from the list. + * + * list_empty() on @entry does not return true after this, @entry is + * in an undefined state. + */ +_INLINE_ void list_del(struct list_head *entry) +{ + __list_del(entry->prev, entry->next); +} + +/** + * list_del_init - deletes entry from list and reinitialize it. + * @entry: the element to delete from the list. + */ +_INLINE_ void list_del_init(struct list_head *entry) +{ + __list_del(entry->prev, entry->next); + INIT_LIST_HEAD(entry); +} + +/** + * list_empty - tests whether a list is empty + * @head: the list to test. + */ +_INLINE_ int list_empty(struct list_head *head) +{ + return head->next == head; +} + +/** + * list_entry_is_last - tests whether is entry last in the list + * @entry: the entry to test. + * @head: the list to test. + */ +_INLINE_ int list_entry_is_last(struct list_head *entry, struct list_head *head) +{ + return head->prev == entry; +} + +/** + * list_splice - join two lists + * @list: the new list to add. + * @head: the place to add it in the first list. + */ +_INLINE_ void list_splice(struct list_head *list, struct list_head *head) +{ + struct list_head *first = list->next; + + if (first != list) { + struct list_head *last = list->prev; + struct list_head *at = head->next; + + first->prev = head; + head->next = first; + + last->next = at; + at->prev = last; + } +} + +/** + * list_entry - get the struct for this entry + * @ptr: the &struct list_head pointer. + * @type: the type of the struct this is embedded in. + * @member: the name of the list_struct within the struct. + */ +#define list_entry(ptr, type, member) container_of(ptr, type, member) + +#define list_first_entry(head, type, member) \ + ((head) && (head)->next != (head) ? list_entry((head)->next, type, member) : NULL) + +#define list_last_entry(head, type, member) \ + ((head) && (head)->prev != (head) ? list_entry((head)->prev, type, member) : NULL) + +/** + * list_for_each - iterate over elements in a list + * @pos: the &struct list_head to use as a loop counter. + * @head: the head for your list. + */ +#define list_for_each(pos, head) \ + for (pos = (head)->next; pos != (head); pos = pos->next) + +/** + * list_for_each_backwardly - iterate over elements in a list in reverse + * @pos: the &struct list_head to use as a loop counter. + * @head: the head for your list. + */ +#define list_for_each_backwardly(pos, head) \ + for (pos = (head)->prev; pos != (head); pos = pos->prev) + +/** + * list_for_each_safe - iterate over elements in a list, but don't dereference + * pos after the body is done (in case it is freed) + * @pos: the &struct list_head to use as a loop counter. + * @pnext: the &struct list_head to use as a pointer to the next item. + * @head: the head for your list (not included in iteration). + */ +#define list_for_each_safe(pos, pnext, head) \ + for (pos = (head)->next, pnext = pos->next; pos != (head); \ + pos = pnext, pnext = pos->next) + +#define MAX_LIST_LENGTH_BITS 20 + +/* + * Returns a list organized in an intermediate format suited + * to chaining of merge() calls: null-terminated, no reserved or + * sentinel head node, "prev" links not maintained. + */ +_INLINE_ struct list_head *merge(int (*cmp)(struct list_head *a, + struct list_head *b, + void *data), + void *data, + struct list_head *a, struct list_head *b) +{ + struct list_head head, *tail = &head; + + while (a && b) { + /* if equal, take 'a' -- important for sort stability */ + if ((*cmp)(a, b, data) <= 0) { + tail->next = a; + a = a->next; + } else { + tail->next = b; + b = b->next; + } + tail = tail->next; + } + tail->next = a ? a : b; + return head.next; +} + +/* + * Combine final list merge with restoration of standard doubly-linked + * list structure. This approach duplicates code from merge(), but + * runs faster than the tidier alternatives of either a separate final + * prev-link restoration pass, or maintaining the prev links + * throughout. + */ +_INLINE_ void merge_and_restore_back_links(int (*cmp)(struct list_head *a, + struct list_head *b, + void *data), + void *data, + struct list_head *head, + struct list_head *a, struct list_head *b) +{ + struct list_head *tail = head; + + while (a && b) { + /* if equal, take 'a' -- important for sort stability */ + if ((*cmp)(a, b, data) <= 0) { + tail->next = a; + a->prev = tail; + a = a->next; + } else { + tail->next = b; + b->prev = tail; + b = b->next; + } + tail = tail->next; + } + tail->next = a ? a : b; + + do { + /* + * In worst cases this loop may run many iterations. + * Continue callbacks to the client even though no + * element comparison is needed, so the client's cmp() + * routine can invoke cond_resched() periodically. + */ + (*cmp)(tail->next, tail->next, data); + + tail->next->prev = tail; + tail = tail->next; + } while (tail->next); + + tail->next = head; + head->prev = tail; +} + + +/** + * list_sort - sort a list + * @head: the list to sort + * @cmp: the elements comparison function + * + * This function implements "merge sort", which has O(nlog(n)) + * complexity. + * + * The comparison function @cmp must return a negative value if @a + * should sort before @b, and a positive value if @a should sort after + * @b. If @a and @b are equivalent, and their original relative + * ordering is to be preserved, @cmp must return 0. + */ +_INLINE_ void list_sort(struct list_head *head, + int (*cmp)(struct list_head *a, + struct list_head *b, + void *data), + void *data) +{ + struct list_head *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists + -- last slot is a sentinel */ + size_t lev; /* index into part[] */ + size_t max_lev = 0; + struct list_head *list; + + if (list_empty(head)) + return; + + memset(part, 0, sizeof(part)); + + head->prev->next = NULL; + list = head->next; + + while (list) { + struct list_head *cur = list; + list = list->next; + cur->next = NULL; + + for (lev = 0; part[lev]; lev++) { + cur = merge(cmp, data, part[lev], cur); + part[lev] = NULL; + } + if (lev > max_lev) { + /* list passed to list_sort() too long for efficiency */ + if (lev >= ARRAY_SIZE(part) - 1) + lev--; + max_lev = lev; + } + part[lev] = cur; + } + + for (lev = 0; lev < max_lev; lev++) + if (part[lev]) + list = merge(cmp, data, part[lev], list); + + merge_and_restore_back_links(cmp, data, head, part[max_lev], list); +} + +#undef _INLINE_ + +#endif /* UTIL_LINUX_LIST_H */ |