net/batman-adv/hash.h

   1 /* Copyright (C) 2006-2013 B.A.T.M.A.N. contributors:
   2  *
   3  * Simon Wunderlich, Marek Lindner
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 2 of the GNU General Public
   7  * License as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA
  18  */
  19
  20 #ifndef _NET_BATMAN_ADV_HASH_H_
  21 #define _NET_BATMAN_ADV_HASH_H_
  22
  23 #include <linux/list.h>
  24
  25 /* callback to a compare function.  should compare 2 element datas for their
  26  * keys, return 0 if same and not 0 if not same
  27  */
  28 typedef int (*batadv_hashdata_compare_cb)(const struct hlist_node *,
  29                                           const void *);
  30
  31 /* the hashfunction, should return an index
  32  * based on the key in the data of the first
  33  * argument and the size the second
  34  */
  35 typedef uint32_t (*batadv_hashdata_choose_cb)(const void *, uint32_t);
  36 typedef void (*batadv_hashdata_free_cb)(struct hlist_node *, void *);
  37
  38 struct batadv_hashtable {
  39         struct hlist_head *table;   /* the hashtable itself with the buckets */
  40         spinlock_t *list_locks;     /* spinlock for each hash list entry */
  41         uint32_t size;              /* size of hashtable */
  42 };
  43
  44 /* allocates and clears the hash */
  45 struct batadv_hashtable *batadv_hash_new(uint32_t size);
  46
  47 /* set class key for all locks */
  48 void batadv_hash_set_lock_class(struct batadv_hashtable *hash,
  49                                 struct lock_class_key *key);
  50
  51 /* free only the hashtable and the hash itself. */
  52 void batadv_hash_destroy(struct batadv_hashtable *hash);
  53
  54 /* remove the hash structure. if hashdata_free_cb != NULL, this function will be
  55  * called to remove the elements inside of the hash.  if you don't remove the
  56  * elements, memory might be leaked.
  57  */
  58 static inline void batadv_hash_delete(struct batadv_hashtable *hash,
  59                                       batadv_hashdata_free_cb free_cb,
  60                                       void *arg)
  61 {
  62         struct hlist_head *head;
  63         struct hlist_node *node, *node_tmp;
  64         spinlock_t *list_lock; /* spinlock to protect write access */
  65         uint32_t i;
  66
  67         for (i = 0; i < hash->size; i++) {
  68                 head = &hash->table[i];
  69                 list_lock = &hash->list_locks[i];
  70
  71                 spin_lock_bh(list_lock);
  72                 hlist_for_each_safe(node, node_tmp, head) {
  73                         hlist_del_rcu(node);
  74
  75                         if (free_cb)
  76                                 free_cb(node, arg);
  77                 }
  78                 spin_unlock_bh(list_lock);
  79         }
  80
  81         batadv_hash_destroy(hash);
  82 }
  83
  84 /**
  85  *      batadv_hash_bytes - hash some bytes and add them to the previous hash
  86  *      @hash: previous hash value
  87  *      @data: data to be hashed
  88  *      @size: number of bytes to be hashed
  89  *
  90  *      Returns the new hash value.
  91  */
  92 static inline uint32_t batadv_hash_bytes(uint32_t hash, const void *data,
  93                                          uint32_t size)
  94 {
  95         const unsigned char *key = data;
  96         int i;
  97
  98         for (i = 0; i < size; i++) {
  99                 hash += key[i];
 100                 hash += (hash << 10);
 101                 hash ^= (hash >> 6);
 102         }
 103         return hash;
 104 }
 105
 106 /**
 107  *      batadv_hash_add - adds data to the hashtable
 108  *      @hash: storage hash table
 109  *      @compare: callback to determine if 2 hash elements are identical
 110  *      @choose: callback calculating the hash index
 111  *      @data: data passed to the aforementioned callbacks as argument
 112  *      @data_node: to be added element
 113  *
 114  *      Returns 0 on success, 1 if the element already is in the hash
 115  *      and -1 on error.
 116  */
 117 static inline int batadv_hash_add(struct batadv_hashtable *hash,
 118                                   batadv_hashdata_compare_cb compare,
 119                                   batadv_hashdata_choose_cb choose,
 120                                   const void *data,
 121                                   struct hlist_node *data_node)
 122 {
 123         uint32_t index;
 124         int ret = -1;
 125         struct hlist_head *head;
 126         struct hlist_node *node;
 127         spinlock_t *list_lock; /* spinlock to protect write access */
 128
 129         if (!hash)
 130                 goto out;
 131
 132         index = choose(data, hash->size);
 133         head = &hash->table[index];
 134         list_lock = &hash->list_locks[index];
 135
 136         spin_lock_bh(list_lock);
 137
 138         hlist_for_each(node, head) {
 139                 if (!compare(node, data))
 140                         continue;
 141
 142                 ret = 1;
 143                 goto unlock;
 144         }
 145
 146         /* no duplicate found in list, add new element */
 147         hlist_add_head_rcu(data_node, head);
 148
 149         ret = 0;
 150
 151 unlock:
 152         spin_unlock_bh(list_lock);
 153 out:
 154         return ret;
 155 }
 156
 157 /* removes data from hash, if found. returns pointer do data on success, so you
 158  * can remove the used structure yourself, or NULL on error .  data could be the
 159  * structure you use with just the key filled, we just need the key for
 160  * comparing.
 161  */
 162 static inline void *batadv_hash_remove(struct batadv_hashtable *hash,
 163                                        batadv_hashdata_compare_cb compare,
 164                                        batadv_hashdata_choose_cb choose,
 165                                        void *data)
 166 {
 167         uint32_t index;
 168         struct hlist_node *node;
 169         struct hlist_head *head;
 170         void *data_save = NULL;
 171
 172         index = choose(data, hash->size);
 173         head = &hash->table[index];
 174
 175         spin_lock_bh(&hash->list_locks[index]);
 176         hlist_for_each(node, head) {
 177                 if (!compare(node, data))
 178                         continue;
 179
 180                 data_save = node;
 181                 hlist_del_rcu(node);
 182                 break;
 183         }
 184         spin_unlock_bh(&hash->list_locks[index]);
 185
 186         return data_save;
 187 }
 188
 189 #endif /* _NET_BATMAN_ADV_HASH_H_ */