/*

  * 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.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import java.io.IOException;

 import javax.annotation.concurrent.NotThreadSafe;

 /**

  * Special iterator that reuses vertex ids and messages bytes 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.  Messages

  * can only be copied to an ExtendedDataOutput object

  *

  * @param <I> vertexId type parameter

  * @param <M> message type parameter

  */

 @NotThreadSafe

 public abstract class ByteStructVertexIdMessageBytesIterator<I

   extends WritableComparable, M extends Writable>

   extends ByteStructVertexIdDataIterator<I, M>

   implements VertexIdMessageBytesIterator<I, M> {

   /** Last message offset */

   protected int messageOffset = -1;

   /** Number of bytes in the last message */

   protected int messageBytes = -1;

   /**

    * Constructor with vertexIdData

    *

    * @param vertexIdData vertexIdData

    */

   public ByteStructVertexIdMessageBytesIterator(

     AbstractVertexIdData<I, M> vertexIdData) {

     super(vertexIdData);

   }

   /**

    * Moves to the next element in the iteration.

    */

   @Override

   public void next() {

     if (vertexId == null) {

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

     }

     try {

       vertexId.readFields(extendedDataInput);

       messageBytes = extendedDataInput.readInt();

       messageOffset = extendedDataInput.getPos();

       if (extendedDataInput.skipBytes(messageBytes) != messageBytes) {

         throw new IllegalStateException("next: Failed to skip " +

             messageBytes);

       }

     } catch (IOException e) {

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

     }

   }

 }