View Javadoc

1   /**
2    * Copyright The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one or more
5    * contributor license agreements. See the NOTICE file distributed with this
6    * work for additional information regarding copyright ownership. The ASF
7    * licenses this file to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance with the License.
9    * 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, WITHOUT
15   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
16   * License for the specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.apache.hadoop.hbase.io.hfile.bucket;
20  
21  import java.io.IOException;
22  import java.nio.ByteBuffer;
23  
24  import org.apache.hadoop.hbase.classification.InterfaceAudience;
25  import org.apache.hadoop.hbase.util.ByteBufferArray;
26  
27  /**
28   * IO engine that stores data on the memory using an array of ByteBuffers
29   * {@link ByteBufferArray}
30   */
31  @InterfaceAudience.Private
32  public class ByteBufferIOEngine implements IOEngine {
33  
34    private ByteBufferArray bufferArray;
35    private final long capacity;
36    private final boolean direct;
37  
38    /**
39     * Construct the ByteBufferIOEngine with the given capacity
40     * @param capacity
41     * @param direct true if allocate direct buffer
42     * @throws IOException
43     */
44    public ByteBufferIOEngine(long capacity, boolean direct)
45        throws IOException {
46      this.capacity = capacity;
47      this.direct = direct;
48      bufferArray = new ByteBufferArray(capacity, direct);
49    }
50  
51    @Override
52    public String toString() {
53      return "ioengine=" + this.getClass().getSimpleName() + ", capacity=" +
54        String.format("%,d", this.capacity) + ", direct=" + this.direct;
55    }
56  
57    /**
58     * Memory IO engine is always unable to support persistent storage for the
59     * cache
60     * @return false
61     */
62    @Override
63    public boolean isPersistent() {
64      return false;
65    }
66  
67    /**
68     * Transfers data from the buffer array to the given byte buffer
69     * @param dstBuffer the given byte buffer into which bytes are to be written
70     * @param offset The offset in the ByteBufferArray of the first byte to be
71     *          read
72     * @return number of bytes read
73     * @throws IOException
74     */
75    @Override
76    public int read(ByteBuffer dstBuffer, long offset) throws IOException {
77      assert dstBuffer.hasArray();
78      return bufferArray.getMultiple(offset, dstBuffer.remaining(), dstBuffer.array(),
79          dstBuffer.arrayOffset());
80    }
81  
82    /**
83     * Transfers data from the given byte buffer to the buffer array
84     * @param srcBuffer the given byte buffer from which bytes are to be read
85     * @param offset The offset in the ByteBufferArray of the first byte to be
86     *          written
87     * @throws IOException
88     */
89    @Override
90    public void write(ByteBuffer srcBuffer, long offset) throws IOException {
91      assert srcBuffer.hasArray();
92      bufferArray.putMultiple(offset, srcBuffer.remaining(), srcBuffer.array(),
93          srcBuffer.arrayOffset());
94    }
95  
96    /**
97     * No operation for the sync in the memory IO engine
98     */
99    @Override
100   public void sync() {
101 
102   }
103 
104   /**
105    * No operation for the shutdown in the memory IO engine
106    */
107   @Override
108   public void shutdown() {
109 
110   }
111 }