/*

  * 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 org.apache.hadoop.io.WritableComparable;

 import java.io.IOException;

 import javax.annotation.concurrent.NotThreadSafe;

 /**

  * Special iterator that reuses vertex ids and data objects so that the

  * lifetime of the object is only until next() is called.

  *

  * Vertex id ownership can be released if desired through

  * releaseCurrentVertexId().  This optimization allows us to cut down

  * on the number of objects instantiated and garbage collected.

  *

  * @param <I> vertexId type parameter

  * @param <T> vertexData type parameter

  */

 @NotThreadSafe

 public class ByteStructVertexIdDataIterator<I extends WritableComparable, T>

   extends ByteStructVertexIdIterator<I> implements VertexIdDataIterator<I, T> {

   /** VertexIdData to iterate over */

   protected AbstractVertexIdData<I, T> vertexIdData;

   /** Serialized size of the message object in bytestore */

   protected int dataSize;

   /** Current data. */

   private T data;

   /**

    * Constructor

    *

    * @param vertexIdData vertexIdData

    */

   public ByteStructVertexIdDataIterator(

     AbstractVertexIdData<I, T> vertexIdData) {

     super(vertexIdData.extendedDataOutput, vertexIdData.getConf());

     this.vertexIdData = vertexIdData;

   }

   @Override

   public void next() {

     if (vertexId == null) {

       vertexId = vertexIdData.getConf().createVertexId();

     }

     if (data == null) {

       data = vertexIdData.createData();

     }

     try {

       vertexId.readFields(extendedDataInput);

       int initial = extendedDataInput.getPos();

       vertexIdData.readData(extendedDataInput, data);

       dataSize = extendedDataInput.getPos() - initial;

     } catch (IOException e) {

       throw new IllegalStateException("next: IOException", e);

     }

   }

   @Override

   public int getCurrentDataSize() {

     return dataSize;

   }

   @Override

   public T getCurrentData() {

     return data;

   }

   @Override

   public T releaseCurrentData() {

     T releasedData = data;

     data = null;

     return releasedData;

   }

 }