hash.h

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/* Copyright (C) 2006-2012 B.A.T.M.A.N. contributors:
 *
 * Simon Wunderlich, Marek Lindner
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA
 */

#ifndef _NET_BATMAN_ADV_HASH_H_
#define _NET_BATMAN_ADV_HASH_H_

#include <linux/list.h>

/* callback to a compare function.  should compare 2 element datas for their
 * keys, return 0 if same and not 0 if not same
 */
typedef int (*batadv_hashdata_compare_cb)(const struct hlist_node *,
                      const void *);

/* the hashfunction, should return an index
 * based on the key in the data of the first
 * argument and the size the second
 */
typedef uint32_t (*batadv_hashdata_choose_cb)(const void *, uint32_t);
typedef void (*batadv_hashdata_free_cb)(struct hlist_node *, void *);

struct batadv_hashtable {
    struct hlist_head *table;   /* the hashtable itself with the buckets */
    spinlock_t *list_locks;     /* spinlock for each hash list entry */
    uint32_t size;          /* size of hashtable */
};

/* allocates and clears the hash */
struct batadv_hashtable *batadv_hash_new(uint32_t size);

/* set class key for all locks */
void batadv_hash_set_lock_class(struct batadv_hashtable *hash,
                struct lock_class_key *key);

/* free only the hashtable and the hash itself. */
void batadv_hash_destroy(struct batadv_hashtable *hash);

/* remove the hash structure. if hashdata_free_cb != NULL, this function will be
 * called to remove the elements inside of the hash.  if you don't remove the
 * elements, memory might be leaked.
 */
static inline void batadv_hash_delete(struct batadv_hashtable *hash,
                      batadv_hashdata_free_cb free_cb,
                      void *arg)
{
    struct hlist_head *head;
    struct hlist_node *node, *node_tmp;
    spinlock_t *list_lock; /* spinlock to protect write access */
    uint32_t i;

    for (i = 0; i < hash->size; i++) {
        head = &hash->table[i];
        list_lock = &hash->list_locks[i];

        spin_lock_bh(list_lock);
        hlist_for_each_safe(node, node_tmp, head) {
            hlist_del_rcu(node);

            if (free_cb)
                free_cb(node, arg);
        }
        spin_unlock_bh(list_lock);
    }

    batadv_hash_destroy(hash);
}

static inline int batadv_hash_add(struct batadv_hashtable *hash,
                  batadv_hashdata_compare_cb compare,
                  batadv_hashdata_choose_cb choose,
                  const void *data,
                  struct hlist_node *data_node)
{
    uint32_t index;
    int ret = -1;
    struct hlist_head *head;
    struct hlist_node *node;
    spinlock_t *list_lock; /* spinlock to protect write access */

    if (!hash)
        goto out;

    index = choose(data, hash->size);
    head = &hash->table[index];
    list_lock = &hash->list_locks[index];

    spin_lock_bh(list_lock);

    hlist_for_each(node, head) {
        if (!compare(node, data))
            continue;

        ret = 1;
        goto unlock;
    }

    /* no duplicate found in list, add new element */
    hlist_add_head_rcu(data_node, head);

    ret = 0;

unlock:
    spin_unlock_bh(list_lock);
out:
    return ret;
}

/* removes data from hash, if found. returns pointer do data on success, so you
 * can remove the used structure yourself, or NULL on error .  data could be the
 * structure you use with just the key filled, we just need the key for
 * comparing.
 */
static inline void *batadv_hash_remove(struct batadv_hashtable *hash,
                       batadv_hashdata_compare_cb compare,
                       batadv_hashdata_choose_cb choose,
                       void *data)
{
    uint32_t index;
    struct hlist_node *node;
    struct hlist_head *head;
    void *data_save = NULL;

    index = choose(data, hash->size);
    head = &hash->table[index];

    spin_lock_bh(&hash->list_locks[index]);
    hlist_for_each(node, head) {
        if (!compare(node, data))
            continue;

        data_save = node;
        hlist_del_rcu(node);
        break;
    }
    spin_unlock_bh(&hash->list_locks[index]);

    return data_save;
}

#endif /* _NET_BATMAN_ADV_HASH_H_ */