content: /**
   * 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 com.aliyun.odps.io;
  
  import com.aliyun.odps.conf.Configuration;
  import com.aliyun.odps.utils.ReflectionUtils;
  
  import java.io.*;
  import java.lang.reflect.Array;
  import java.util.concurrent.atomic.AtomicReference;
  
  /**
   * A Writable for arrays containing instances of a class. The elements of this
   * writable must all be instances of the same class. If this writable will be
   * the input for a Reducer, you will need to create a subclass that sets the
   * value to be of the proper type.
   *
   * For example:
   * <code>
   * public class IntArrayWritable extends ArrayWritable {
   *   public IntArrayWritable() {
   *     super(IntWritable.class);
   *   }
   * }
   * </code>
   */
  public class ArrayWritable implements Writable {
  
    private AtomicReference<Configuration> conf;
    private Class<? extends Writable> valueClass;
    private Writable[] values;
  
    private ArrayWritable() {
      conf = new AtomicReference<Configuration>();
    }
  
    public ArrayWritable(Class<? extends Writable> valueClass) {
      this();
      if (valueClass == null) {
        throw new IllegalArgumentException("null valueClass");
      }
      this.valueClass = valueClass;
    }
  
    public ArrayWritable(Class<? extends Writable> valueClass, Writable[] values) {
      this(valueClass);
      this.values = values;
    }
  
    public Class getValueClass() {
      return valueClass;
    }
  
    public String[] toStrings() {
      String[] strings = new String[values.length];
      for (int i = 0; i < values.length; i++) {
        strings[i] = values[i].toString();
      }
      return strings;
    }
  
    public Object toArray() {
      Object result = Array.newInstance(valueClass, values.length);
      for (int i = 0; i < values.length; i++) {
        Array.set(result, i, values[i]);
      }
      return result;
    }
  
    public void set(Writable[] values) { this.values = values; }
  
    public Writable[] get() { return values; }
  
    public void readFields(DataInput in) throws IOException {
      values = new Writable[in.readInt()];          // construct values
      for (int i = 0; i < values.length; i++) {
        Writable value = ReflectionUtils.newInstance(valueClass, conf.get());
        value.readFields(in);                       // read a value
        values[i] = value;                          // store it in values
      }
    }
  
    public void write(DataOutput out) throws IOException {
      out.writeInt(values.length);                 // write values
      for (int i = 0; i < values.length; i++) {
        values[i].write(out);
      }
    }
  
  }
  