net/batman-adv/hash.h

   1 /* Copyright (C) 2006-2014 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, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #ifndef _NET_BATMAN_ADV_HASH_H_
  19 #define _NET_BATMAN_ADV_HASH_H_
  20
  21 #include <linux/list.h>
  22
  23 /* callback to a compare function.  should compare 2 element datas for their
  24  * keys, return 0 if same and not 0 if not same
  25  */
  26 typedef int (*batadv_hashdata_compare_cb)(const struct hlist_node *,
  27                                           const void *);
  28
  29 /* the hashfunction, should return an index
  30  * based on the key in the data of the first
  31  * argument and the size the second
  32  */
  33 typedef uint32_t (*batadv_hashdata_choose_cb)(const void *, uint32_t);
  34 typedef void (*batadv_hashdata_free_cb)(struct hlist_node *, void *);
  35
  36 struct batadv_hashtable {
  37         struct hlist_head *table;   /* the hashtable itself with the buckets */
  38         spinlock_t *list_locks;     /* spinlock for each hash list entry */
  39         uint32_t size;              /* size of hashtable */
  40 };
  41
  42 /* allocates and clears the hash */
  43 struct batadv_hashtable *batadv_hash_new(uint32_t size);
  44
  45 /* set class key for all locks */
  46 void batadv_hash_set_lock_class(struct batadv_hashtable *hash,
  47                                 struct lock_class_key *key);
  48
  49 /* free only the hashtable and the hash itself. */
  50 void batadv_hash_destroy(struct batadv_hashtable *hash);
  51
  52 /* remove the hash structure. if hashdata_free_cb != NULL, this function will be
  53  * called to remove the elements inside of the hash.  if you don't remove the
  54  * elements, memory might be leaked.
  55  */
  56 static inline void batadv_hash_delete(struct batadv_hashtable *hash,
  57                                       batadv_hashdata_free_cb free_cb,
  58                                       void *arg)
  59 {
  60         struct hlist_head *head;
  61         struct hlist_node *node, *node_tmp;
  62         spinlock_t *list_lock; /* spinlock to protect write access */
  63         uint32_t i;
  64
  65         for (i = 0; i < hash->size; i++) {
  66                 head = &hash->table[i];
  67                 list_lock = &hash->list_locks[i];
  68
  69                 spin_lock_bh(list_lock);
  70                 hlist_for_each_safe(node, node_tmp, head) {
  71                         hlist_del_rcu(node);
  72
  73                         if (free_cb)
  74                                 free_cb(node, arg);
  75                 }
  76                 spin_unlock_bh(list_lock);
  77         }
  78
  79         batadv_hash_destroy(hash);
  80 }
  81
  82 /**
  83  *      batadv_hash_bytes - hash some bytes and add them to the previous hash
  84  *      @hash: previous hash value
  85  *      @data: data to be hashed
  86  *      @size: number of bytes to be hashed
  87  *
  88  *      Returns the new hash value.
  89  */
  90 static inline uint32_t batadv_hash_bytes(uint32_t hash, const void *data,
  91                                          uint32_t size)
  92 {
  93         const unsigned char *key = data;
  94         int i;
  95
  96         for (i = 0; i < size; i++) {
  97                 hash += key[i];
  98                 hash += (hash << 10);
  99                 hash ^= (hash >> 6);
 100         }
 101         return hash;
 102 }
 103
 104 /**
 105  *      batadv_hash_add - adds data to the hashtable
 106  *      @hash: storage hash table
 107  *      @compare: callback to determine if 2 hash elements are identical
 108  *      @choose: callback calculating the hash index
 109  *      @data: data passed to the aforementioned callbacks as argument
 110  *      @data_node: to be added element
 111  *
 112  *      Returns 0 on success, 1 if the element already is in the hash
 113  *      and -1 on error.
 114  */
 115 static inline int batadv_hash_add(struct batadv_hashtable *hash,
 116                                   batadv_hashdata_compare_cb compare,
 117                                   batadv_hashdata_choose_cb choose,
 118                                   const void *data,
 119                                   struct hlist_node *data_node)
 120 {
 121         uint32_t index;
 122         int ret = -1;
 123         struct hlist_head *head;
 124         struct hlist_node *node;
 125         spinlock_t *list_lock; /* spinlock to protect write access */
 126
 127         if (!hash)
 128                 goto out;
 129
 130         index = choose(data, hash->size);
 131         head = &hash->table[index];
 132         list_lock = &hash->list_locks[index];
 133
 134         spin_lock_bh(list_lock);
 135
 136         hlist_for_each(node, head) {
 137                 if (!compare(node, data))
 138                         continue;
 139
 140                 ret = 1;
 141                 goto unlock;
 142         }
 143
 144         /* no duplicate found in list, add new element */
 145         hlist_add_head_rcu(data_node, head);
 146
 147         ret = 0;
 148
 149 unlock:
 150         spin_unlock_bh(list_lock);
 151 out:
 152         return ret;
 153 }
 154
 155 /* removes data from hash, if found. returns pointer do data on success, so you
 156  * can remove the used structure yourself, or NULL on error .  data could be the
 157  * structure you use with just the key filled, we just need the key for
 158  * comparing.
 159  */
 160 static inline void *batadv_hash_remove(struct batadv_hashtable *hash,
 161                                        batadv_hashdata_compare_cb compare,
 162                                        batadv_hashdata_choose_cb choose,
 163                                        void *data)
 164 {
 165         uint32_t index;
 166         struct hlist_node *node;
 167         struct hlist_head *head;
 168         void *data_save = NULL;
 169
 170         index = choose(data, hash->size);
 171         head = &hash->table[index];
 172
 173         spin_lock_bh(&hash->list_locks[index]);
 174         hlist_for_each(node, head) {
 175                 if (!compare(node, data))
 176                         continue;
 177
 178                 data_save = node;
 179                 hlist_del_rcu(node);
 180                 break;
 181         }
 182         spin_unlock_bh(&hash->list_locks[index]);
 183
 184         return data_save;
 185 }
 186
 187 #endif /* _NET_BATMAN_ADV_HASH_H_ */