/*

  * 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.util.Iterator;

 import org.apache.hadoop.io.Writable;

 /**

  * This iterable is designed to deserialize a byte array on the fly to

  * provide new copies of writable objects when desired.  It does not reuse

  * objects, and instead creates a new one for every next().

  *

  * @param <T> Type that extends Writable that will be iterated

  */

 public abstract class ByteStructIterable<T extends Writable> implements

     Iterable<T> {

   /** Factory for data input */

   protected final Factory<? extends ExtendedDataInput> dataInputFactory;

   /**

    * Constructor

    *

    * @param dataInputFactory Factory for data inputs

    */

   public ByteStructIterable(

       Factory<? extends ExtendedDataInput> dataInputFactory) {

     this.dataInputFactory = dataInputFactory;

   }

   /**

    * Must be able to create the writable object

    *

    * @return New writable

    */

   protected abstract T createWritable();

   @Override

   public Iterator<T> iterator() {

     return new ByteStructIterator<T>(dataInputFactory.create()) {

       @Override

       protected T createWritable() {

         return ByteStructIterable.this.createWritable();

       }

     };

   }

 }