/*

  * 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.giraph.conf.ImmutableClassesGiraphConfiguration;

 import org.apache.hadoop.io.WritableComparable;

 /**

  * Common implementation for VertexIdEdgeIterator, VertexIdMessageIterator

  * and VertexIdMessageBytesIterator.

  *

  * @param <I> Vertex id

  */

 public abstract class ByteStructVertexIdIterator<I extends WritableComparable>

   implements VertexIdIterator<I> {

   /** Reader of the serialized edges */

   protected final ExtendedDataInput extendedDataInput;

   /** Current vertex id */

   protected I vertexId;

   /**

    * Constructor.

    *

    * @param extendedDataOutput Extended data output

    * @param conf Configuration

    */

   public ByteStructVertexIdIterator(

     ExtendedDataOutput extendedDataOutput,

     ImmutableClassesGiraphConfiguration<I, ?, ?> conf) {

     if (extendedDataOutput != null && conf != null) {

       extendedDataInput = conf.createExtendedDataInput(extendedDataOutput);

     } else {

       throw new IllegalStateException("Cannot instantiate vertexIdIterator " +

         "with null arguments");

     }

   }

   @Override

   public boolean hasNext() {

     return !extendedDataInput.endOfInput();

   }

   @Override

   public I getCurrentVertexId() {

     return vertexId;

   }

   @Override

   public I releaseCurrentVertexId() {

     I releasedVertexId = vertexId;

     vertexId = null;

     return releasedVertexId;

   }

 }