hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/java/org/apache/hadoop/mapred/nativetask/util/SizedWritable.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.mapred.nativetask.util;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.util.ReflectionUtils;

@InterfaceAudience.Private
public class SizedWritable<T> {
  public static final int INVALID_LENGTH = -1;

  public int length = INVALID_LENGTH;
  public Writable v;

  public SizedWritable(Class<?> klass) {
    if (null != klass) {
      v = (Writable) ReflectionUtils.newInstance(klass, null);
    }
    length = INVALID_LENGTH;
  }

  public void readFields(DataInputBuffer key) throws IOException {
    if (null != key) {
      this.v.readFields(key);
      this.length = INVALID_LENGTH;
    } else {
      throw new IOException("input key is null");
    }

  }

  public void reset(T w) {
    this.v = (Writable) w;
    this.length = INVALID_LENGTH;
  }
}