/*

  * 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.DataOutput;

 /**

  * 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

  */

 public interface VertexIdMessageBytesIterator<I extends WritableComparable,

     M extends Writable> extends VertexIdDataIterator<I, M> {

   /**

    * Write the current message to an ExtendedDataOutput object

    *

    * @param dataOutput Where the current message will be written to

    */

   void writeCurrentMessageBytes(DataOutput dataOutput);

 }