1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, 13 * software distributed under the License is distributed on an 14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 15 * KIND, either express or implied. See the License for the 16 * specific language governing permissions and limitations 17 * under the License. 18 * 19 */ 20 package org.apache.directory.mavibot.btree; 21 22 23 import java.io.IOException; 24 25 import org.apache.directory.mavibot.btree.exception.EndOfFileExceededException; 26 27 28 /** 29 * A Value holder. As we may not store all the values in memory (except for an in-memory 30 * BTree), we will use a SoftReference to keep a reference to a Value, and if it's null, 31 * then we will load the Value from the underlying physical support, using the offset. 32 * 33 * @param <E> The type for the stored element (either a value or a page) 34 * @param <K> The type of the BTree key 35 * @param <V> The type of the BTree value 36 * 37 * @author <a href="mailto:labs@labs.apache.org">Mavibot labs Project</a> 38 */ 39 public interface ElementHolder<E, K, V> 40 { 41 /** 42 * Get back the element 43 * 44 * @param btree The Btree storing the element 45 * 46 * @return The stored element 47 */ 48 E getValue( BTree<K, V> btree ) throws EndOfFileExceededException, IOException; 49 }