/*

  * 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.giraph.utils;

 import java.io.DataInput;

 import java.io.DataOutput;

 import java.io.IOException;

 import java.lang.reflect.Array;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableFactories;

 import com.google.common.base.Preconditions;

 /**

  * A Writable for arrays containing instances of a class. The elements of this

  * writable must all be instances of the same class.

  *

  * @param <T> element type

  */

 public class ArrayWritable<T extends Writable> implements Writable {

   /** Element type class */

   private Class<T> valueClass;

   /** Array */

   private T[] values;

   /** Constructor */

   public ArrayWritable() {

   }

   /**

    * Constructor

    * @param valueClass Element type class

    * @param values Array of elements

    */

   public ArrayWritable(Class<T> valueClass, T[] values) {

     Preconditions.checkNotNull(valueClass,

         "valueClass cannot be null in ArrayWritable");

     this.valueClass = valueClass;

     this.values = values;

   }

   /**

    * Get element type class

    * @return element type class

    */

   public Class<T> getValueClass() {

     return valueClass;

   }

   /**

    * Set array

    * @param values array

    */

   public void set(T[] values) { this.values = values; }

   /**

    * Ger array

    * @return array

    */

   public T[] get() { return values; }

   @Override

   public void readFields(DataInput in) throws IOException {

     valueClass = WritableUtils.readClass(in);

     values = (T[]) Array.newInstance(valueClass, in.readInt());

     for (int i = 0; i < values.length; i++) {

       T value = (T) WritableFactories.newInstance(valueClass);

       value.readFields(in);                       // read a value

       values[i] = value;                          // store it in values

     }

   }

   @Override

   public void write(DataOutput out) throws IOException {

     Preconditions.checkNotNull(valueClass,

         "valueClass cannot be null in ArrayWritable");

     WritableUtils.writeClass(valueClass, out);

     out.writeInt(values.length);                 // write values

     for (int i = 0; i < values.length; i++) {

       values[i].write(out);

     }

   }

 }