branch-2.0.4-alpha/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/task/reduce/InMemoryWriter.java

/**
 * 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.mapreduce.task.reduce;

import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.BoundedByteArrayOutputStream;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.io.WritableUtils;
import org.apache.hadoop.mapred.IFile;
import org.apache.hadoop.mapred.IFileOutputStream;
import org.apache.hadoop.mapred.IFile.Writer;

@InterfaceAudience.Private
@InterfaceStability.Unstable
public class InMemoryWriter<K, V> extends Writer<K, V> {
  private DataOutputStream out;
  
  public InMemoryWriter(BoundedByteArrayOutputStream arrayStream) {
    super(null);
    this.out = 
      new DataOutputStream(new IFileOutputStream(arrayStream));
  }
  
  public void append(K key, V value) throws IOException {
    throw new UnsupportedOperationException
    ("InMemoryWriter.append(K key, V value");
  }
  
  public void append(DataInputBuffer key, DataInputBuffer value)
  throws IOException {
    int keyLength = key.getLength() - key.getPosition();
    if (keyLength < 0) {
      throw new IOException("Negative key-length not allowed: " + keyLength + 
                            " for " + key);
    }
    
    int valueLength = value.getLength() - value.getPosition();
    if (valueLength < 0) {
      throw new IOException("Negative value-length not allowed: " + 
                            valueLength + " for " + value);
    }

    WritableUtils.writeVInt(out, keyLength);
    WritableUtils.writeVInt(out, valueLength);
    out.write(key.getData(), key.getPosition(), keyLength); 
    out.write(value.getData(), value.getPosition(), valueLength); 
  }

  public void close() throws IOException {
    // Write EOF_MARKER for key/value length
    WritableUtils.writeVInt(out, IFile.EOF_MARKER);
    WritableUtils.writeVInt(out, IFile.EOF_MARKER);
    
    // Close the stream 
    out.close();
    out = null;
  }

}