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    Subject[RFC 1/4] hashtable: introduce a small and naive hashtable
    Date
    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>
    ---
    include/linux/hashtable.h | 46 +++++++++++++++++++++++++++++++++++++++++++++
    1 files changed, 46 insertions(+), 0 deletions(-)
    create mode 100644 include/linux/hashtable.h

    diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h
    new file mode 100644
    index 0000000..9b29fd1
    --- /dev/null
    +++ b/include/linux/hashtable.h
    @@ -0,0 +1,46 @@
    +#ifndef _LINUX_HASHTABLE_H
    +#define _LINUX_HASHTABLE_H
    +
    +#include <linux/list.h>
    +#include <linux/types.h>
    +#include <linux/kernel.h>
    +#include <linux/hash.h>
    +
    +#define DEFINE_HASHTABLE(name, bits) \
    + struct hlist_head name[1 << bits];
    +
    +#define HASH_BITS(name) (order_base_2(ARRAY_SIZE(name)))
    +#define HASH_SIZE(name) (1 << (HASH_BITS(name)))
    +
    +#define HASH_INIT(name) \
    +({ \
    + int __i; \
    + for (__i = 0 ; __i < HASH_SIZE(name) ; __i++) \
    + INIT_HLIST_HEAD(&name[__i]); \
    +})
    +
    +#define HASH_ADD(name, obj, key) \
    + hlist_add_head(obj, &name[ \
    + hash_long((unsigned long)key, HASH_BITS(name))]);
    +
    +#define HASH_GET(name, key, type, member, cmp_fn) \
    +({ \
    + struct hlist_node *__node; \
    + typeof(key) __key = key; \
    + type *__obj = NULL; \
    + hlist_for_each_entry(__obj, __node, &name[ \
    + hash_long((unsigned long) __key, \
    + HASH_BITS(name))], member) \
    + if (cmp_fn(__obj, __key)) \
    + break; \
    + __obj; \
    +})
    +
    +#define HASH_DEL(obj, member) \
    + hlist_del(&obj->member)
    +
    +#define HASH_FOR_EACH(bkt, node, name, obj, member) \
    + for (bkt = 0; bkt < HASH_SIZE(name); bkt++) \
    + hlist_for_each_entry(obj, node, &name[i], member)
    +
    +#endif
    --
    1.7.8.6


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