001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.io.hfile.bucket;
019
020import java.io.IOException;
021import java.nio.ByteBuffer;
022import org.apache.hadoop.hbase.io.hfile.Cacheable;
023import org.apache.hadoop.hbase.nio.ByteBuff;
024import org.apache.yetus.audience.InterfaceAudience;
025
026/**
027 * A class implementing IOEngine interface supports data services for {@link BucketCache}.
028 */
029@InterfaceAudience.Private
030public interface IOEngine {
031  /** Returns true if persistent storage is supported for the cache when shutdown */
032  boolean isPersistent();
033
034  /**
035   * IOEngine uses shared memory means, when reading Cacheable from it, those refers to the same
036   * memory area as used by the Engine for caching it.
037   * @return true when IOEngine using shared memory.
038   */
039  default boolean usesSharedMemory() {
040    return false;
041  }
042
043  /**
044   * Transfers data from IOEngine to a Cacheable object.
045   * @param be maintains an (offset,len,refCnt) inside.
046   * @return Cacheable which will wrap the NIO ByteBuffers from IOEngine.
047   * @throws IOException              when any IO error happen
048   * @throws IllegalArgumentException when the length of the ByteBuff read is less than 'len'
049   */
050  Cacheable read(BucketEntry be) throws IOException;
051
052  /**
053   * Transfers data from the given byte buffer to IOEngine
054   * @param srcBuffer the given byte buffer from which bytes are to be read
055   * @param offset    The offset in the IO engine where the first byte to be written
056   */
057  void write(ByteBuffer srcBuffer, long offset) throws IOException;
058
059  /**
060   * Transfers the data from the given MultiByteBuffer to IOEngine
061   * @param srcBuffer the given MultiBytebufffers from which bytes are to be read
062   * @param offset    the offset in the IO engine where the first byte to be written
063   */
064  void write(ByteBuff srcBuffer, long offset) throws IOException;
065
066  /**
067   * Sync the data to IOEngine after writing
068   */
069  void sync() throws IOException;
070
071  /**
072   * Shutdown the IOEngine
073   */
074  void shutdown();
075}