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hashtable: introduce a small and naive hashtable

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This hashtable implementation is using hlist buckets to provide a simple
hashtable to prevent it from getting reimplemented all over the kernel.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
[ Merging this now, so that subsystems can start applying Sasha's
  patches that use this   - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sasha Levin 2012-10-30 14:45:57 -04:00 committed by Linus Torvalds
parent c660b8f944
commit d9b482c8ba
1 changed files with 192 additions and 0 deletions
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include/linux/hashtable.h Normal file
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/*
* 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