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author | Sasha Levin <levinsasha928@gmail.com> | 2012-10-30 14:45:57 -0400 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-11-02 12:44:51 -0700 |
commit | d9b482c8ba1973a189f2d4c8175d405b87fbf2d7 (patch) | |
tree | 87d1f517365b7ec2113255fd537472d28b9697a4 /include | |
parent | c660b8f944f1815494a76935148571276fa47462 (diff) | |
download | linux-d9b482c8ba1973a189f2d4c8175d405b87fbf2d7.tar.bz2 |
hashtable: introduce a small and naive hashtable
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>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/hashtable.h | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h new file mode 100644 index 000000000000..227c62424f3c --- /dev/null +++ b/include/linux/hashtable.h @@ -0,0 +1,192 @@ +/* + * 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 |