1 /**
2 *
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20 package org.apache.hadoop.hbase.io.hfile;
21
22 import java.nio.ByteBuffer;
23
24 import org.apache.hadoop.classification.InterfaceAudience;
25 import org.apache.hadoop.hbase.io.HeapSize;
26
27 /**
28 * Cacheable is an interface that allows for an object to be cached. If using an
29 * on heap cache, just use heapsize. If using an off heap cache, Cacheable
30 * provides methods for serialization of the object.
31 *
32 * Some objects cannot be moved off heap, those objects will return a
33 * getSerializedLength() of 0.
34 *
35 */
36 @InterfaceAudience.Private
37 public interface Cacheable extends HeapSize {
38 /**
39 * Returns the length of the ByteBuffer required to serialized the object. If the
40 * object cannot be serialized, it should also return 0.
41 *
42 * @return int length in bytes of the serialized form.
43 */
44
45 int getSerializedLength();
46
47 /**
48 * Serializes its data into destination.
49 */
50 void serialize(ByteBuffer destination);
51
52 /**
53 * Returns CacheableDeserializer instance which reconstructs original object from ByteBuffer.
54 *
55 * @return CacheableDeserialzer instance.
56 */
57 CacheableDeserializer<Cacheable> getDeserializer();
58
59 /**
60 * @return the block type of this cached HFile block
61 */
62 BlockType getBlockType();
63
64 }