hashtable.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2/*
  3 * Statically sized hash table implementation
  4 * (C) 2012  Sasha Levin <levinsasha928@gmail.com>
  5 */
  6
  7#ifndef _LINUX_HASHTABLE_H
  8#define _LINUX_HASHTABLE_H
  9
 10#include <linux/list.h>
 11#include <linux/types.h>
 12#include <linux/kernel.h>
 13#include <linux/bitops.h>
 14#include <linux/hash.h>
 15#include <linux/log2.h>
 16
 17#define DEFINE_HASHTABLE(name, bits)						\
 18	struct hlist_head name[1 << (bits)] =					\
 19			{ [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }
 20
 21#define DECLARE_HASHTABLE(name, bits)                                   	\
 22	struct hlist_head name[1 << (bits)]
 23
 24#define HASH_SIZE(name) (ARRAY_SIZE(name))
 25#define HASH_BITS(name) ilog2(HASH_SIZE(name))
 26
 27/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
 28#define hash_min(val, bits)							\
 29	(sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits))
 30
 31static inline void __hash_init(struct hlist_head *ht, unsigned int sz)
 32{
 33	unsigned int i;
 34
 35	for (i = 0; i < sz; i++)
 36		INIT_HLIST_HEAD(&ht[i]);
 37}
 38
 39/**
 40 * hash_init - initialize a hash table
 41 * @hashtable: hashtable to be initialized
 42 *
 43 * Calculates the size of the hashtable from the given parameter, otherwise
 44 * same as hash_init_size.
 45 *
 46 * This has to be a macro since HASH_BITS() will not work on pointers since
 47 * it calculates the size during preprocessing.
 48 */
 49#define hash_init(hashtable) __hash_init(hashtable, HASH_SIZE(hashtable))
 50
 51/**
 52 * hash_add - add an object to a hashtable
 53 * @hashtable: hashtable to add to
 54 * @node: the &struct hlist_node of the object to be added
 55 * @key: the key of the object to be added
 56 */
 57#define hash_add(hashtable, node, key)						\
 58	hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])
 59
 60/**
 61 * hash_hashed - check whether an object is in any hashtable
 62 * @node: the &struct hlist_node of the object to be checked
 63 */
 64static inline bool hash_hashed(struct hlist_node *node)
 65{
 66	return !hlist_unhashed(node);
 67}
 68
 69static inline bool __hash_empty(struct hlist_head *ht, unsigned int sz)
 70{
 71	unsigned int i;
 72
 73	for (i = 0; i < sz; i++)
 74		if (!hlist_empty(&ht[i]))
 75			return false;
 76
 77	return true;
 78}
 79
 80/**
 81 * hash_empty - check whether a hashtable is empty
 82 * @hashtable: hashtable to check
 83 *
 84 * This has to be a macro since HASH_BITS() will not work on pointers since
 85 * it calculates the size during preprocessing.
 86 */
 87#define hash_empty(hashtable) __hash_empty(hashtable, HASH_SIZE(hashtable))
 88
 89/**
 90 * hash_del - remove an object from a hashtable
 91 * @node: &struct hlist_node of the object to remove
 92 */
 93static inline void hash_del(struct hlist_node *node)
 94{
 95	hlist_del_init(node);
 96}
 97
 98/**
 99 * hash_for_each - iterate over a hashtable
100 * @name: hashtable to iterate
101 * @bkt: integer to use as bucket loop cursor
102 * @obj: the type * to use as a loop cursor for each entry
103 * @member: the name of the hlist_node within the struct
104 */
105#define hash_for_each(name, bkt, obj, member)				\
106	for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
107			(bkt)++)\
108		hlist_for_each_entry(obj, &name[bkt], member)
109
110/**
111 * hash_for_each_safe - iterate over a hashtable safe against removal of
112 * hash entry
113 * @name: hashtable to iterate
114 * @bkt: integer to use as bucket loop cursor
115 * @tmp: a &struct used for temporary storage
116 * @obj: the type * to use as a loop cursor for each entry
117 * @member: the name of the hlist_node within the struct
118 */
119#define hash_for_each_safe(name, bkt, tmp, obj, member)			\
120	for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
121			(bkt)++)\
122		hlist_for_each_entry_safe(obj, tmp, &name[bkt], member)
123
124/**
125 * hash_for_each_possible - iterate over all possible objects hashing to the
126 * same bucket
127 * @name: hashtable to iterate
128 * @obj: the type * to use as a loop cursor for each entry
129 * @member: the name of the hlist_node within the struct
130 * @key: the key of the objects to iterate over
131 */
132#define hash_for_each_possible(name, obj, member, key)			\
133	hlist_for_each_entry(obj, &name[hash_min(key, HASH_BITS(name))], member)
134
135/**
136 * hash_for_each_possible_safe - iterate over all possible objects hashing to the
137 * same bucket safe against removals
138 * @name: hashtable to iterate
139 * @obj: the type * to use as a loop cursor for each entry
140 * @tmp: a &struct used for temporary storage
141 * @member: the name of the hlist_node within the struct
142 * @key: the key of the objects to iterate over
143 */
144#define hash_for_each_possible_safe(name, obj, tmp, member, key)	\
145	hlist_for_each_entry_safe(obj, tmp,\
146		&name[hash_min(key, HASH_BITS(name))], member)
147
148
149#endif