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 */
26typedef 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 */
33typedef uint32_t (*batadv_hashdata_choose_cb)(const void *, uint32_t);
34typedef void (*batadv_hashdata_free_cb)(struct hlist_node *, void *);
35
36struct 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 */
43struct batadv_hashtable *batadv_hash_new(uint32_t size);
44
45/* set class key for all locks */
46void 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. */
50void 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 */
56static 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 */
90static 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 */
115static 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
149unlock:
150	spin_unlock_bh(list_lock);
151out:
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 */
160static 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_ */
188