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.hbase.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 return 0. 41 * 42 * @return int length in bytes of the serialized form or 0 if the object cannot be cached. 43 */ 44 int getSerializedLength(); 45 46 /** 47 * Serializes its data into destination. 48 * @param destination Where to serialize to 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 }