xref: /aosp_15_r20/external/e2fsprogs/lib/blkid/list.h (revision 6a54128f25917bfc36a8a6e9d722c04a0b4641b6)

#if !defined(_BLKID_LIST_H) && !defined(LIST_HEAD_INIT)
#define _BLKID_LIST_H

#ifdef __cplusplus
extern "C" {
#endif

#ifdef HAVE_INTTYPES_H
#include <inttypes.h>
#else
#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif
#endif

#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 LIST_HEAD_INIT(name) { &(name), &(name) }

#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_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) \
	((type *)((char *)(ptr)-(unsigned long)(intptr_t)(&((type *)0)->member)))

/**
 * 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_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)

#undef _INLINE_

#ifdef __cplusplus
}
#endif

#endif /* _BLKID_LIST_H */