net/batman-adv/hash.h

   1 /*
   2  * Copyright (C) 2006-2011 B.A.T.M.A.N. contributors:
   3  *
   4  * Simon Wunderlich, Marek Lindner
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of version 2 of the GNU General Public
   8  * License as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  13  * General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  18  * 02110-1301, USA
  19  *
  20  */
  21
  22 #ifndef _NET_BATMAN_ADV_HASH_H_
  23 #define _NET_BATMAN_ADV_HASH_H_
  24
  25 #include <linux/list.h>
  26
  27 /* callback to a compare function.  should
  28  * compare 2 element datas for their keys,
  29  * return 0 if same and not 0 if not
  30  * same */
  31 typedef int (*hashdata_compare_cb)(const struct hlist_node *, const void *);
  32
  33 /* the hashfunction, should return an index
  34  * based on the key in the data of the first
  35  * argument and the size the second */
  36 typedef int (*hashdata_choose_cb)(const void *, int);
  37 typedef void (*hashdata_free_cb)(struct hlist_node *, void *);
  38
  39 struct hashtable_t {
  40         struct hlist_head *table;   /* the hashtable itself with the buckets */
  41         spinlock_t *list_locks;     /* spinlock for each hash list entry */
  42         int size;                   /* size of hashtable */
  43 };
  44
  45 /* allocates and clears the hash */
  46 struct hashtable_t *hash_new(int size);
  47
  48 /* free only the hashtable and the hash itself. */
  49 void hash_destroy(struct hashtable_t *hash);
  50
  51 /* remove the hash structure. if hashdata_free_cb != NULL, this function will be
  52  * called to remove the elements inside of the hash.  if you don't remove the
  53  * elements, memory might be leaked. */
  54 static inline void hash_delete(struct hashtable_t *hash,
  55                                hashdata_free_cb free_cb, void *arg)
  56 {
  57         struct hlist_head *head;
  58         struct hlist_node *node, *node_tmp;
  59         spinlock_t *list_lock; /* spinlock to protect write access */
  60         int i;
  61
  62         for (i = 0; i < hash->size; i++) {
  63                 head = &hash->table[i];
  64                 list_lock = &hash->list_locks[i];
  65
  66                 spin_lock_bh(list_lock);
  67                 hlist_for_each_safe(node, node_tmp, head) {
  68                         hlist_del_rcu(node);
  69
  70                         if (free_cb)
  71                                 free_cb(node, arg);
  72                 }
  73                 spin_unlock_bh(list_lock);
  74         }
  75
  76         hash_destroy(hash);
  77 }
  78
  79 /**
  80  *      hash_add - adds data to the hashtable
  81  *      @hash: storage hash table
  82  *      @compare: callback to determine if 2 hash elements are identical
  83  *      @choose: callback calculating the hash index
  84  *      @data: data passed to the aforementioned callbacks as argument
  85  *      @data_node: to be added element
  86  *
  87  *      Returns 0 on success, 1 if the element already is in the hash
  88  *      and -1 on error.
  89  */
  90
  91 static inline int hash_add(struct hashtable_t *hash,
  92                            hashdata_compare_cb compare,
  93                            hashdata_choose_cb choose,
  94                            const void *data, struct hlist_node *data_node)
  95 {
  96         int index, ret = -1;
  97         struct hlist_head *head;
  98         struct hlist_node *node;
  99         spinlock_t *list_lock; /* spinlock to protect write access */
 100
 101         if (!hash)
 102                 goto out;
 103
 104         index = choose(data, hash->size);
 105         head = &hash->table[index];
 106         list_lock = &hash->list_locks[index];
 107
 108         rcu_read_lock();
 109         __hlist_for_each_rcu(node, head) {
 110                 if (!compare(node, data))
 111                         continue;
 112
 113                 ret = 1;
 114                 goto err_unlock;
 115         }
 116         rcu_read_unlock();
 117
 118         /* no duplicate found in list, add new element */
 119         spin_lock_bh(list_lock);
 120         hlist_add_head_rcu(data_node, head);
 121         spin_unlock_bh(list_lock);
 122
 123         ret = 0;
 124         goto out;
 125
 126 err_unlock:
 127         rcu_read_unlock();
 128 out:
 129         return ret;
 130 }
 131
 132 /* removes data from hash, if found. returns pointer do data on success, so you
 133  * can remove the used structure yourself, or NULL on error .  data could be the
 134  * structure you use with just the key filled, we just need the key for
 135  * comparing. */
 136 static inline void *hash_remove(struct hashtable_t *hash,
 137                                 hashdata_compare_cb compare,
 138                                 hashdata_choose_cb choose, void *data)
 139 {
 140         size_t index;
 141         struct hlist_node *node;
 142         struct hlist_head *head;
 143         void *data_save = NULL;
 144
 145         index = choose(data, hash->size);
 146         head = &hash->table[index];
 147
 148         spin_lock_bh(&hash->list_locks[index]);
 149         hlist_for_each(node, head) {
 150                 if (!compare(node, data))
 151                         continue;
 152
 153                 data_save = node;
 154                 hlist_del_rcu(node);
 155                 break;
 156         }
 157         spin_unlock_bh(&hash->list_locks[index]);
 158
 159         return data_save;
 160 }
 161
 162 #endif /* _NET_BATMAN_ADV_HASH_H_ */