net/batman-adv/hash.h

   1 /*
   2  * Copyright (C) 2006-2010 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)(void *, 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)(void *, int);
  37 typedef void (*hashdata_free_cb)(void *, void *);
  38
  39 struct element_t {
  40         void *data;             /* pointer to the data */
  41         struct hlist_node hlist;        /* bucket list pointer */
  42 };
  43
  44 struct hashtable_t {
  45         struct hlist_head *table;   /* the hashtable itself, with the buckets */
  46         int size;                   /* size of hashtable */
  47 };
  48
  49 /* allocates and clears the hash */
  50 struct hashtable_t *hash_new(int size);
  51
  52 /* free only the hashtable and the hash itself. */
  53 void hash_destroy(struct hashtable_t *hash);
  54
  55 /* remove the hash structure. if hashdata_free_cb != NULL, this function will be
  56  * called to remove the elements inside of the hash.  if you don't remove the
  57  * elements, memory might be leaked. */
  58 static inline void hash_delete(struct hashtable_t *hash,
  59                                hashdata_free_cb free_cb, void *arg)
  60 {
  61         struct hlist_head *head;
  62         struct hlist_node *walk, *safe;
  63         struct element_t *bucket;
  64         int i;
  65
  66         for (i = 0; i < hash->size; i++) {
  67                 head = &hash->table[i];
  68
  69                 hlist_for_each_safe(walk, safe, head) {
  70                         bucket = hlist_entry(walk, struct element_t, hlist);
  71                         if (free_cb)
  72                                 free_cb(bucket->data, arg);
  73
  74                         hlist_del(walk);
  75                         kfree(bucket);
  76                 }
  77         }
  78
  79         hash_destroy(hash);
  80 }
  81
  82 /* adds data to the hashtable. returns 0 on success, -1 on error */
  83 static inline int hash_add(struct hashtable_t *hash,
  84                            hashdata_compare_cb compare,
  85                            hashdata_choose_cb choose, void *data)
  86 {
  87         int index;
  88         struct hlist_head *head;
  89         struct hlist_node *walk, *safe;
  90         struct element_t *bucket;
  91
  92         if (!hash)
  93                 return -1;
  94
  95         index = choose(data, hash->size);
  96         head = &hash->table[index];
  97
  98         hlist_for_each_safe(walk, safe, head) {
  99                 bucket = hlist_entry(walk, struct element_t, hlist);
 100                 if (compare(bucket->data, data))
 101                         return -1;
 102         }
 103
 104         /* no duplicate found in list, add new element */
 105         bucket = kmalloc(sizeof(struct element_t), GFP_ATOMIC);
 106
 107         if (!bucket)
 108                 return -1;
 109
 110         bucket->data = data;
 111         hlist_add_head(&bucket->hlist, head);
 112
 113         return 0;
 114 }
 115
 116 /* removes data from hash, if found. returns pointer do data on success, so you
 117  * can remove the used structure yourself, or NULL on error .  data could be the
 118  * structure you use with just the key filled, we just need the key for
 119  * comparing. */
 120 static inline void *hash_remove(struct hashtable_t *hash,
 121                                 hashdata_compare_cb compare,
 122                                 hashdata_choose_cb choose, void *data)
 123 {
 124         size_t index;
 125         struct hlist_node *walk;
 126         struct element_t *bucket;
 127         struct hlist_head *head;
 128         void *data_save;
 129
 130         index = choose(data, hash->size);
 131         head = &hash->table[index];
 132
 133         hlist_for_each_entry(bucket, walk, head, hlist) {
 134                 if (compare(bucket->data, data)) {
 135                         data_save = bucket->data;
 136                         hlist_del(walk);
 137                         kfree(bucket);
 138                         return data_save;
 139                 }
 140         }
 141
 142         return NULL;
 143 }
 144
 145 /* finds data, based on the key in keydata. returns the found data on success,
 146  * or NULL on error */
 147 static inline void *hash_find(struct hashtable_t *hash,
 148                               hashdata_compare_cb compare,
 149                               hashdata_choose_cb choose, void *keydata)
 150 {
 151         int index;
 152         struct hlist_head *head;
 153         struct hlist_node *walk;
 154         struct element_t *bucket;
 155
 156         if (!hash)
 157                 return NULL;
 158
 159         index = choose(keydata , hash->size);
 160         head = &hash->table[index];
 161
 162         hlist_for_each(walk, head) {
 163                 bucket = hlist_entry(walk, struct element_t, hlist);
 164                 if (compare(bucket->data, keydata))
 165                         return bucket->data;
 166         }
 167
 168         return NULL;
 169 }
 170
 171 #endif /* _NET_BATMAN_ADV_HASH_H_ */