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Common functionality for HBase
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/**
 * 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;

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

import org.apache.hadoop.hbase.io.util.StreamUtils;
import org.apache.hadoop.hbase.util.ByteBufferUtils;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * When deal with OutputStream which is not ByteBufferWriter type, wrap it with this class. We will
 * have to write offheap ByteBuffer (DBB) data into the OS. This class is having a temp byte array
 * to which we can copy the DBB data for writing to the OS.
 * 

 * This is used while writing Cell data to WAL. In case of AsyncWAL, the OS created there is
 * ByteBufferWriter. But in case of FSHLog, the OS passed by DFS client, is not of type
 * ByteBufferWriter. We will need this temp solution until DFS client supports writing ByteBuffer
 * directly to the OS it creates.
 * 

 * Note: This class is not thread safe.
 */
@InterfaceAudience.Private
public class ByteBufferWriterOutputStream extends OutputStream
    implements ByteBufferWriter {

  private static final int TEMP_BUF_LENGTH = 4 * 1024;
  private final OutputStream os;
  private byte[] tempBuf = null;

  public ByteBufferWriterOutputStream(OutputStream os) {
    this.os = os;
  }

  @Override
  public void write(ByteBuffer b, int off, int len) throws IOException {
    byte[] buf = null;
    if (len > TEMP_BUF_LENGTH) {
      buf = new byte[len];
    } else {
      if (this.tempBuf == null) {
        this.tempBuf = new byte[TEMP_BUF_LENGTH];
      }
      buf = this.tempBuf;
    }
    ByteBufferUtils.copyFromBufferToArray(buf, b, off, 0, len);
    this.os.write(buf, 0, len);
  }

  @Override
  public void writeInt(int i) throws IOException {
    StreamUtils.writeInt(this.os, i);
  }

  @Override
  public void write(int b) throws IOException {
    this.os.write(b);
  }

  @Override
  public void write(byte b[], int off, int len) throws IOException {
    this.os.write(b, off, len);
  }

  @Override
  public void flush() throws IOException {
    this.os.flush();
  }

  @Override
  public void close() throws IOException {
    this.os.close();
  }
}