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/**
* ARC
* an interface for Adaptive Replacement Caches
* Copyright 2009 by Michael Peter Christen, mc@yacy.net, Frankfurt a. M., Germany
* First released 29.08.2009 at http://yacy.net
*
* $LastChangedDate$
* $LastChangedRevision$
* $LastChangedBy$
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program in the file lgpl21.txt
* If not, see <http://www.gnu.org/licenses/>.
*/
package net.yacy.cora.storage;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
/**
* This is a simple cache using two generations of hashtables to store the content with a LFU strategy.
* The Algorithm is described in a slightly more complex version as Adaptive Replacement Cache, "ARC".
* For details see http://www.almaden.ibm.com/cs/people/dmodha/ARC.pdf
* or http://en.wikipedia.org/wiki/Adaptive_Replacement_Cache
* This version omits the ghost entry handling which is described in ARC, and keeps both cache levels
* at the same size.
*/
public interface ARC<K, V> extends Iterable<Map.Entry<K, V>> {
/**
* get the size of the ARC. this returns the sum of main and ghost cache
* @return the complete number of entries in the ARC cache
*/
public int size();
/**
* put a value to the cache.
* do not return a previous content value
* @param s
* @param v
*/
public void insert(K s, V v);
/**
* put a value to the cache if there was not an entry before
* do not return a previous content value
* @param s
* @param v
*/
public void insertIfAbsent(K s, V v);
/**
* put a value to the cache if there was not an entry before
* return a previous content value
* @param s
* @param v
* @return the value before inserting the new value
*/
public V putIfAbsent(K s, V v);
/**
* put a value to the cache.
* @param s
* @param v
*/
public V put(K s, V v);
/**
* get a value from the cache.
* @param s
* @return the value
*/
public V get(K s);
/**
* check if the map contains the value
* @param value
* @return the keys that have the given value
*/
public Collection<K> getKeys(V value);
/**
* check if the map contains the key
* @param key
* @return true if the map contains the key
*/
public boolean containsKey(K key);
/**
* remove an entry from the cache
* @param s
* @return the old value
*/
public V remove(K s);
/**
* clear the cache
*/
public void clear();
/**
* iterator implements the Iterable interface
* the method can easily be implemented using the entrySet method
*/
@Override
public Iterator<Map.Entry<K, V>> iterator();
/**
* Return a Set view of the mappings contained in this map.
* This method is the basis for all methods that are implemented
* by a AbstractMap implementation
*
* @return a set view of the mappings contained in this map
*/
public Set<Map.Entry<K, V>> entrySet();
/**
* a hash code for this ARC
* @return a hash code
*/
@Override
int hashCode();
}
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