IOEngine.java example

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/**
 * Copyright The Apache Software Foundation
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package org.apache.hadoop.hbase.io.hfile.bucket;

import java.io.IOException;
import java.nio.ByteBuffer;

import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.io.hfile.Cacheable;
import org.apache.hadoop.hbase.io.hfile.CacheableDeserializer;
import org.apache.hadoop.hbase.nio.ByteBuff;

/**
 * A class implementing IOEngine interface supports data services for
 * {@link BucketCache}.
 */
@InterfaceAudience.Private
public interface IOEngine {
  /**
   * @return true if persistent storage is supported for the cache when shutdown
   */
  boolean isPersistent();

  /**
   * Transfers data from IOEngine to a Cacheable object.
   * @param length How many bytes to be read from the offset
   * @param offset The offset in the IO engine where the first byte to be read
   * @param deserializer The deserializer to be used to make a Cacheable from the data.
   * @return Cacheable
   * @throws IOException
   * @throws RuntimeException when the length of the ByteBuff read is less than 'len'
   */
  Cacheable read(long offset, int length, CacheableDeserializer<Cacheable> deserializer)
      throws IOException;

  /**
   * Transfers data from the given byte buffer to IOEngine
   * @param srcBuffer the given byte buffer from which bytes are to be read
   * @param offset The offset in the IO engine where the first byte to be
   *          written
   * @throws IOException
   */
  void write(ByteBuffer srcBuffer, long offset) throws IOException;

  /**
   * Transfers the data from the given MultiByteBuffer to IOEngine
   * @param srcBuffer the given MultiBytebufffers from which bytes are to be read
   * @param offset the offset in the IO engine where the first byte to be written
   * @throws IOException
   */
  void write(ByteBuff srcBuffer, long offset) throws IOException;

  /**
   * Sync the data to IOEngine after writing
   * @throws IOException
   */
  void sync() throws IOException;

  /**
   * Shutdown the IOEngine
   */
  void shutdown();
}