/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jena.sdb.layout2.index;
import java.util.HashMap;
import java.util.Map;
import org.apache.jena.sdb.Store ;
/** Experimental : cache for int <=> node hash
*
*/
public class IndexCache
{
static int LIMIT = 10 ;
static private Map<Store, IndexCache> indexes = new HashMap<Store, IndexCache>() ;
public static IndexCache getIndexCache(Store store)
{
IndexCache idx = indexes.get(store) ;
if ( idx == null )
{
idx = new IndexCache() ;
indexes.put(store, idx) ;
}
return idx ;
}
// Finite cache?
// Use a reverse structure for cache mgt?
// cache.entrySet()
// Later : use Trove on basic types.
private Map<Long, Integer>cache = new HashMap<Long, Integer>() ;
private IndexCache() {}
public Integer get(Long hashCode)
{
Integer i = _get(hashCode) ;
if ( i == null )
{
i = fetch(hashCode) ;
insert(hashCode, i) ;
}
return i ;
}
private Integer _get(Long hashCode)
{
Integer idx = cache.get(hashCode) ;
if ( idx != null )
{
// Move to end of LRU list.
}
return idx ;
}
private Integer fetch(Long hashCode)
{
return -1 ;
}
private void insert(Long hashCode, Integer idx)
{
if ( cache.size() > LIMIT )
{
}
}
}