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 /* remove element if you already found the element you want to delete and don't
  53  * need the overhead to find it again with hash_remove().  But usually, you
  54  * don't want to use this function, as it fiddles with hash-internals. */
  55 void *hash_remove_element(struct hashtable_t *hash, struct element_t *elem);
  56
  57 /* free only the hashtable and the hash itself. */
  58 void hash_destroy(struct hashtable_t *hash);
  59
  60 /* remove the hash structure. if hashdata_free_cb != NULL, this function will be
  61  * called to remove the elements inside of the hash.  if you don't remove the
  62  * elements, memory might be leaked. */
  63 static inline void hash_delete(struct hashtable_t *hash,
  64                                hashdata_free_cb free_cb, void *arg)
  65 {
  66         struct hlist_head *head;
  67         struct hlist_node *walk, *safe;
  68         struct element_t *bucket;
  69         int i;
  70
  71         for (i = 0; i < hash->size; i++) {
  72                 head = &hash->table[i];
  73
  74                 hlist_for_each_safe(walk, safe, head) {
  75                         bucket = hlist_entry(walk, struct element_t, hlist);
  76                         if (free_cb)
  77                                 free_cb(bucket->data, arg);
  78
  79                         hlist_del(walk);
  80                         kfree(bucket);
  81                 }
  82         }
  83
  84         hash_destroy(hash);
  85 }
  86
  87 /* adds data to the hashtable. returns 0 on success, -1 on error */
  88 static inline int hash_add(struct hashtable_t *hash,
  89                            hashdata_compare_cb compare,
  90                            hashdata_choose_cb choose, void *data)
  91 {
  92         int index;
  93         struct hlist_head *head;
  94         struct hlist_node *walk, *safe;
  95         struct element_t *bucket;
  96
  97         if (!hash)
  98                 return -1;
  99
 100         index = choose(data, hash->size);
 101         head = &hash->table[index];
 102
 103         hlist_for_each_safe(walk, safe, head) {
 104                 bucket = hlist_entry(walk, struct element_t, hlist);
 105                 if (compare(bucket->data, data))
 106                         return -1;
 107         }
 108
 109         /* no duplicate found in list, add new element */
 110         bucket = kmalloc(sizeof(struct element_t), GFP_ATOMIC);
 111
 112         if (!bucket)
 113                 return -1;
 114
 115         bucket->data = data;
 116         hlist_add_head(&bucket->hlist, head);
 117
 118         return 0;
 119 }
 120
 121 /* removes data from hash, if found. returns pointer do data on success, so you
 122  * can remove the used structure yourself, or NULL on error .  data could be the
 123  * structure you use with just the key filled, we just need the key for
 124  * comparing. */
 125 static inline void *hash_remove(struct hashtable_t *hash,
 126                                 hashdata_compare_cb compare,
 127                                 hashdata_choose_cb choose, void *data)
 128 {
 129         size_t index;
 130         struct hlist_node *walk;
 131         struct element_t *bucket;
 132         struct hlist_head *head;
 133         void *data_save;
 134
 135         index = choose(data, hash->size);
 136         head = &hash->table[index];
 137
 138         hlist_for_each_entry(bucket, walk, head, hlist) {
 139                 if (compare(bucket->data, data)) {
 140                         data_save = bucket->data;
 141                         hlist_del(walk);
 142                         kfree(bucket);
 143                         return data_save;
 144                 }
 145         }
 146
 147         return NULL;
 148 }
 149
 150 /* finds data, based on the key in keydata. returns the found data on success,
 151  * or NULL on error */
 152 static inline void *hash_find(struct hashtable_t *hash,
 153                               hashdata_compare_cb compare,
 154                               hashdata_choose_cb choose, void *keydata)
 155 {
 156         int index;
 157         struct hlist_head *head;
 158         struct hlist_node *walk;
 159         struct element_t *bucket;
 160
 161         if (!hash)
 162                 return NULL;
 163
 164         index = choose(keydata , hash->size);
 165         head = &hash->table[index];
 166
 167         hlist_for_each(walk, head) {
 168                 bucket = hlist_entry(walk, struct element_t, hlist);
 169                 if (compare(bucket->data, keydata))
 170                         return bucket->data;
 171         }
 172
 173         return NULL;
 174 }
 175
 176 #endif /* _NET_BATMAN_ADV_HASH_H_ */