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util-linux/include/list.h

380 lines
9.4 KiB

/*
* 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_entry_is_first - tests whether is entry first in the list
* @entry: the entry to test.
* @head: the list to test.
*/
_INLINE_ int list_entry_is_first(struct list_head *entry, struct list_head *head)
{
return head->next == 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)
/**
* list_free - remove all entries from list and call freefunc()
* for each entry
* @head: the head for your list
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
* @freefunc: the list entry deallocator
*/
#define list_free(head, type, member, freefunc) \
do { \
struct list_head *__p, *__pnext; \
\
list_for_each_safe (__p, __pnext, (head)) { \
type *__elt = list_entry(__p, type, member); \
list_del(__p); \
freefunc(__elt); \
} \
} while (0)
_INLINE_ size_t list_count_entries(struct list_head *head)
{
struct list_head *pos;
size_t ct = 0;
list_for_each(pos, head)
ct++;
return ct;
}
#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 */