linux/include/linux/list_nulls.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_LIST_NULLS_H
#define _LINUX_LIST_NULLS_H

#include <linux/poison.h>
#include <linux/const.h>

/*
 * Special version of lists, where end of list is not a NULL pointer,
 * but a 'nulls' marker, which can have many different values.
 * (up to 2^31 different values guaranteed on all platforms)
 *
 * In the standard hlist, termination of a list is the NULL pointer.
 * In this special 'nulls' variant, we use the fact that objects stored in
 * a list are aligned on a word (4 or 8 bytes alignment).
 * We therefore use the last significant bit of 'ptr' :
 * Set to 1 : This is a 'nulls' end-of-list marker (ptr >> 1)
 * Set to 0 : This is a pointer to some object (ptr)
 */

struct hlist_nulls_head { … };

struct hlist_nulls_node { … };
#define NULLS_MARKER(value) …
#define INIT_HLIST_NULLS_HEAD(ptr, nulls) …

#define hlist_nulls_entry(ptr, type, member) …

#define hlist_nulls_entry_safe(ptr, type, member) …
/**
 * ptr_is_a_nulls - Test if a ptr is a nulls
 * @ptr: ptr to be tested
 *
 */
static inline int is_a_nulls(const struct hlist_nulls_node *ptr)
{ … }

/**
 * get_nulls_value - Get the 'nulls' value of the end of chain
 * @ptr: end of chain
 *
 * Should be called only if is_a_nulls(ptr);
 */
static inline unsigned long get_nulls_value(const struct hlist_nulls_node *ptr)
{ … }

/**
 * hlist_nulls_unhashed - Has node been removed and reinitialized?
 * @h: Node to be checked
 *
 * Not that not all removal functions will leave a node in unhashed state.
 * For example, hlist_del_init_rcu() leaves the node in unhashed state,
 * but hlist_nulls_del() does not.
 */
static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h)
{ … }

/**
 * hlist_nulls_unhashed_lockless - Has node been removed and reinitialized?
 * @h: Node to be checked
 *
 * Not that not all removal functions will leave a node in unhashed state.
 * For example, hlist_del_init_rcu() leaves the node in unhashed state,
 * but hlist_nulls_del() does not.  Unlike hlist_nulls_unhashed(), this
 * function may be used locklessly.
 */
static inline int hlist_nulls_unhashed_lockless(const struct hlist_nulls_node *h)
{ … }

static inline int hlist_nulls_empty(const struct hlist_nulls_head *h)
{ … }

static inline void hlist_nulls_add_head(struct hlist_nulls_node *n,
					struct hlist_nulls_head *h)
{ … }

static inline void __hlist_nulls_del(struct hlist_nulls_node *n)
{ … }

static inline void hlist_nulls_del(struct hlist_nulls_node *n)
{ … }

/**
 * hlist_nulls_for_each_entry	- iterate over list of given type
 * @tpos:	the type * to use as a loop cursor.
 * @pos:	the &struct hlist_node to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the hlist_node within the struct.
 *
 */
#define hlist_nulls_for_each_entry(tpos, pos, head, member) …

/**
 * hlist_nulls_for_each_entry_from - iterate over a hlist continuing from current point
 * @tpos:	the type * to use as a loop cursor.
 * @pos:	the &struct hlist_node to use as a loop cursor.
 * @member:	the name of the hlist_node within the struct.
 *
 */
#define hlist_nulls_for_each_entry_from(tpos, pos, member) …

#endif