/* Copyright (C) 2006-2014 B.A.T.M.A.N. contributors:

   *
   * Simon Wunderlich, Marek Lindner
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of version 2 of the GNU General Public
   * License as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License

   * along with this program; if not, see <http://www.gnu.org/licenses/>.

   */
  
  #ifndef _NET_BATMAN_ADV_HASH_H_
  #define _NET_BATMAN_ADV_HASH_H_
  
  #include <linux/list.h>

  /* callback to a compare function.  should compare 2 element datas for their
   * keys, return 0 if same and not 0 if not same
   */

  typedef int (*batadv_hashdata_compare_cb)(const struct hlist_node *,
  					  const void *);

  
  /* the hashfunction, should return an index
   * based on the key in the data of the first

   * argument and the size the second
   */

  typedef uint32_t (*batadv_hashdata_choose_cb)(const void *, uint32_t);
  typedef void (*batadv_hashdata_free_cb)(struct hlist_node *, void *);

  struct batadv_hashtable {

  	struct hlist_head *table;   /* the hashtable itself with the buckets */
  	spinlock_t *list_locks;     /* spinlock for each hash list entry */

  	uint32_t size;		    /* size of hashtable */

  };
  
  /* allocates and clears the hash */

  struct batadv_hashtable *batadv_hash_new(uint32_t size);

  /* set class key for all locks */

  void batadv_hash_set_lock_class(struct batadv_hashtable *hash,

  				struct lock_class_key *key);

  /* free only the hashtable and the hash itself. */

  void batadv_hash_destroy(struct batadv_hashtable *hash);

  
  /* remove the hash structure. if hashdata_free_cb != NULL, this function will be
   * called to remove the elements inside of the hash.  if you don't remove the

   * elements, memory might be leaked.
   */

  static inline void batadv_hash_delete(struct batadv_hashtable *hash,
  				      batadv_hashdata_free_cb free_cb,
  				      void *arg)

  {
  	struct hlist_head *head;

  	struct hlist_node *node, *node_tmp;

  	spinlock_t *list_lock; /* spinlock to protect write access */

  	uint32_t i;

  
  	for (i = 0; i < hash->size; i++) {
  		head = &hash->table[i];

  		list_lock = &hash->list_locks[i];

  		spin_lock_bh(list_lock);

  		hlist_for_each_safe(node, node_tmp, head) {
  			hlist_del_rcu(node);

  			if (free_cb)
  				free_cb(node, arg);

  		}

  		spin_unlock_bh(list_lock);

  	}

  	batadv_hash_destroy(hash);

  }

  /**

   *	batadv_hash_bytes - hash some bytes and add them to the previous hash
   *	@hash: previous hash value
   *	@data: data to be hashed
   *	@size: number of bytes to be hashed
   *
   *	Returns the new hash value.
   */

  static inline uint32_t batadv_hash_bytes(uint32_t hash, const void *data,

  					 uint32_t size)
  {
  	const unsigned char *key = data;
  	int i;
  
  	for (i = 0; i < size; i++) {
  		hash += key[i];
  		hash += (hash << 10);
  		hash ^= (hash >> 6);
  	}
  	return hash;
  }
  
  /**

   *	batadv_hash_add - adds data to the hashtable

   *	@hash: storage hash table
   *	@compare: callback to determine if 2 hash elements are identical
   *	@choose: callback calculating the hash index
   *	@data: data passed to the aforementioned callbacks as argument
   *	@data_node: to be added element
   *
   *	Returns 0 on success, 1 if the element already is in the hash
   *	and -1 on error.
   */

  static inline int batadv_hash_add(struct batadv_hashtable *hash,
  				  batadv_hashdata_compare_cb compare,
  				  batadv_hashdata_choose_cb choose,

  				  const void *data,
  				  struct hlist_node *data_node)

  {

  	uint32_t index;
  	int ret = -1;

  	struct hlist_head *head;

  	struct hlist_node *node;

  	spinlock_t *list_lock; /* spinlock to protect write access */

  
  	if (!hash)

  		goto out;

  
  	index = choose(data, hash->size);
  	head = &hash->table[index];

  	list_lock = &hash->list_locks[index];

  	spin_lock_bh(list_lock);
  
  	hlist_for_each(node, head) {

  		if (!compare(node, data))
  			continue;

  		ret = 1;

  		goto unlock;

  	}
  
  	/* no duplicate found in list, add new element */

  	hlist_add_head_rcu(data_node, head);

  	ret = 0;

  unlock:
  	spin_unlock_bh(list_lock);

  out:
  	return ret;

  }
  
  /* removes data from hash, if found. returns pointer do data on success, so you
   * can remove the used structure yourself, or NULL on error .  data could be the
   * structure you use with just the key filled, we just need the key for

   * comparing.
   */

  static inline void *batadv_hash_remove(struct batadv_hashtable *hash,
  				       batadv_hashdata_compare_cb compare,
  				       batadv_hashdata_choose_cb choose,
  				       void *data)

  {

  	uint32_t index;

  	struct hlist_node *node;

  	struct hlist_head *head;

  	void *data_save = NULL;

  
  	index = choose(data, hash->size);
  	head = &hash->table[index];

  	spin_lock_bh(&hash->list_locks[index]);

  	hlist_for_each(node, head) {
  		if (!compare(node, data))
  			continue;
  
  		data_save = node;
  		hlist_del_rcu(node);
  		break;

  	}

  	spin_unlock_bh(&hash->list_locks[index]);

  	return data_save;

  }

  #endif /* _NET_BATMAN_ADV_HASH_H_ */