hashtable: introduce a small and naive hashtable

/*

 * Statically sized hash table implementation

 * (C) 2012  Sasha Levin <levinsasha928@gmail.com>

 */

#ifndef _LINUX_HASHTABLE_H

#define _LINUX_HASHTABLE_H

#include <linux/list.h>

#include <linux/types.h>

#include <linux/kernel.h>

#include <linux/hash.h>

#include <linux/rculist.h>

#define DEFINE_HASHTABLE(name, bits)						\

	struct hlist_head name[1 << (bits)] =					\

			{ [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }

#define DECLARE_HASHTABLE(name, bits)                                   	\

	struct hlist_head name[1 << (bits)]

#define HASH_SIZE(name) (ARRAY_SIZE(name))

#define HASH_BITS(name) ilog2(HASH_SIZE(name))

/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */

#define hash_min(val, bits)							\

	(sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits))

static inline void __hash_init(struct hlist_head *ht, unsigned int sz)

{

	unsigned int i;

	for (i = 0; i < sz; i++)

		INIT_HLIST_HEAD(&ht[i]);

}

/**

 * hash_init - initialize a hash table

 * @hashtable: hashtable to be initialized

 *

 * Calculates the size of the hashtable from the given parameter, otherwise

 * same as hash_init_size.

 *

 * This has to be a macro since HASH_BITS() will not work on pointers since

 * it calculates the size during preprocessing.

 */

#define hash_init(hashtable) __hash_init(hashtable, HASH_SIZE(hashtable))

/**

 * hash_add - add an object to a hashtable

 * @hashtable: hashtable to add to

 * @node: the &struct hlist_node of the object to be added

 * @key: the key of the object to be added

 */

#define hash_add(hashtable, node, key)						\

	hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])

/**

 * hash_add_rcu - add an object to a rcu enabled hashtable

 * @hashtable: hashtable to add to

 * @node: the &struct hlist_node of the object to be added

 * @key: the key of the object to be added

 */

#define hash_add_rcu(hashtable, node, key)					\

	hlist_add_head_rcu(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])

/**

 * hash_hashed - check whether an object is in any hashtable

 * @node: the &struct hlist_node of the object to be checked

 */

static inline bool hash_hashed(struct hlist_node *node)

{

	return !hlist_unhashed(node);

}

static inline bool __hash_empty(struct hlist_head *ht, unsigned int sz)

{

	unsigned int i;

	for (i = 0; i < sz; i++)

		if (!hlist_empty(&ht[i]))

			return false;

	return true;

}

/**

 * hash_empty - check whether a hashtable is empty

 * @hashtable: hashtable to check

 *

 * This has to be a macro since HASH_BITS() will not work on pointers since

 * it calculates the size during preprocessing.

 */

#define hash_empty(hashtable) __hash_empty(hashtable, HASH_SIZE(hashtable))

/**

 * hash_del - remove an object from a hashtable

 * @node: &struct hlist_node of the object to remove

 */

static inline void hash_del(struct hlist_node *node)

{

	hlist_del_init(node);

}

/**

 * hash_del_rcu - remove an object from a rcu enabled hashtable

 * @node: &struct hlist_node of the object to remove

 */

static inline void hash_del_rcu(struct hlist_node *node)

{

	hlist_del_init_rcu(node);

}

/**

 * hash_for_each - iterate over a hashtable

 * @name: hashtable to iterate

 * @bkt: integer to use as bucket loop cursor

 * @node: the &struct list_head to use as a loop cursor for each entry

 * @obj: the type * to use as a loop cursor for each entry

 * @member: the name of the hlist_node within the struct

 */

#define hash_for_each(name, bkt, node, obj, member)				\

	for ((bkt) = 0, node = NULL; node == NULL && (bkt) < HASH_SIZE(name); (bkt)++)\

		hlist_for_each_entry(obj, node, &name[bkt], member)

/**

 * hash_for_each_rcu - iterate over a rcu enabled hashtable

 * @name: hashtable to iterate

 * @bkt: integer to use as bucket loop cursor

 * @node: the &struct list_head to use as a loop cursor for each entry

 * @obj: the type * to use as a loop cursor for each entry

 * @member: the name of the hlist_node within the struct

 */

#define hash_for_each_rcu(name, bkt, node, obj, member)				\

	for ((bkt) = 0, node = NULL; node == NULL && (bkt) < HASH_SIZE(name); (bkt)++)\

		hlist_for_each_entry_rcu(obj, node, &name[bkt], member)

/**

 * hash_for_each_safe - iterate over a hashtable safe against removal of

 * hash entry

 * @name: hashtable to iterate

 * @bkt: integer to use as bucket loop cursor

 * @node: the &struct list_head to use as a loop cursor for each entry

 * @tmp: a &struct used for temporary storage

 * @obj: the type * to use as a loop cursor for each entry

 * @member: the name of the hlist_node within the struct

 */

#define hash_for_each_safe(name, bkt, node, tmp, obj, member)			\

	for ((bkt) = 0, node = NULL; node == NULL && (bkt) < HASH_SIZE(name); (bkt)++)\

		hlist_for_each_entry_safe(obj, node, tmp, &name[bkt], member)

/**

 * hash_for_each_possible - iterate over all possible objects hashing to the

 * same bucket

 * @name: hashtable to iterate

 * @obj: the type * to use as a loop cursor for each entry

 * @node: the &struct list_head to use as a loop cursor for each entry

 * @member: the name of the hlist_node within the struct

 * @key: the key of the objects to iterate over

 */

#define hash_for_each_possible(name, obj, node, member, key)			\

	hlist_for_each_entry(obj, node,	&name[hash_min(key, HASH_BITS(name))], member)

/**

 * hash_for_each_possible_rcu - iterate over all possible objects hashing to the

 * same bucket in an rcu enabled hashtable

 * in a rcu enabled hashtable

 * @name: hashtable to iterate

 * @obj: the type * to use as a loop cursor for each entry

 * @node: the &struct list_head to use as a loop cursor for each entry

 * @member: the name of the hlist_node within the struct

 * @key: the key of the objects to iterate over

 */

#define hash_for_each_possible_rcu(name, obj, node, member, key)		\

	hlist_for_each_entry_rcu(obj, node, &name[hash_min(key, HASH_BITS(name))], member)

/**

 * hash_for_each_possible_safe - iterate over all possible objects hashing to the

 * same bucket safe against removals

 * @name: hashtable to iterate

 * @obj: the type * to use as a loop cursor for each entry

 * @node: the &struct list_head to use as a loop cursor for each entry

 * @tmp: a &struct used for temporary storage

 * @member: the name of the hlist_node within the struct

 * @key: the key of the objects to iterate over

 */

#define hash_for_each_possible_safe(name, obj, node, tmp, member, key)		\

	hlist_for_each_entry_safe(obj, node, tmp,				\

		&name[hash_min(key, HASH_BITS(name))], member)

#endif