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1   /**
2    * Copyright 2011 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  
21  package org.apache.hadoop.hbase.io.hfile;
22  
23  import java.nio.ByteBuffer;
24  import org.apache.hadoop.hbase.io.HeapSize;
25  
26  /**
27   * Cacheable is an interface that allows for an object to be cached. If using an
28   * on heap cache, just use heapsize. If using an off heap cache, Cacheable
29   * provides methods for serialization of the object.
30   *
31   * Some objects cannot be moved off heap, those objects will return a
32   * getSerializedLength() of 0.
33   *
34   */
35  public interface Cacheable extends HeapSize {
36    /**
37     * Returns the length of the ByteBuffer required to serialized the object. If the
38     * object cannot be serialized, it should also return 0.
39     *
40     * @return int length in bytes of the serialized form.
41     */
42  
43    public int getSerializedLength();
44  
45    /**
46     * Serializes its data into destination.
47     */
48    public void serialize(ByteBuffer destination);
49  
50    /**
51     * Returns CacheableDeserializer instance which reconstructs original object from ByteBuffer.
52     *
53     * @return CacheableDeserialzer instance.
54     */
55    public CacheableDeserializer<Cacheable> getDeserializer();
56  }