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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.classification.InterfaceAudience;
25  
26  /**
27   * A class implementing IOEngine interface could support data services for
28   * {@link BucketCache}.
29   */
30  @InterfaceAudience.Private
31  public interface IOEngine {
32  
33    /**
34     * @return true if persistent storage is supported for the cache when shutdown
35     */
36    boolean isPersistent();
37  
38    /**
39     * Transfers data from IOEngine to the given byte buffer
40     * @param dstBuffer the given byte buffer into which bytes are to be written
41     * @param offset The offset in the IO engine where the first byte to be read
42     * @return number of bytes read
43     * @throws IOException
44     */
45    int read(ByteBuffer dstBuffer, long offset) throws IOException;
46  
47    /**
48     * Transfers data from the given byte buffer to IOEngine
49     * @param srcBuffer the given byte buffer from which bytes are to be read
50     * @param offset The offset in the IO engine where the first byte to be
51     *          written
52     * @throws IOException
53     */
54    void write(ByteBuffer srcBuffer, long offset) throws IOException;
55  
56    /**
57     * Sync the data to IOEngine after writing
58     * @throws IOException
59     */
60    void sync() throws IOException;
61  
62    /**
63     * Shutdown the IOEngine
64     */
65    void shutdown();
66  }