/*

  * 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.io.iterables;

 import org.apache.hadoop.mapreduce.InputSplit;

 import org.apache.hadoop.mapreduce.TaskAttemptContext;

 import java.io.IOException;

 import java.util.Iterator;

 /**

  * Reader for some kind of data.

  *

  * @param <T> Type of data which we are reading (can be vertex, edges, etc)

  */

 public interface GiraphReader<T> extends Iterator<T> {

   /**

    * Use the input split and context to setup reading.

    * Guaranteed to be called prior to any other function.

    *

    * @param inputSplit Input split to be used for reading.

    * @param context Context from the task.

    */

   void initialize(InputSplit inputSplit, TaskAttemptContext context) throws

       IOException, InterruptedException;

   /**

    * Close this {@link GiraphReader} to future operations.

    *

    * @throws IOException

    */

   void close() throws IOException;

   /**

    * How much of the input has the {@link GiraphReader} consumed i.e.

    * has been processed by?

    *

    * @return Progress from <code>0.0</code> to <code>1.0</code>.

    * @throws IOException

    * @throws InterruptedException

    */

   float getProgress() throws IOException, InterruptedException;

 }