giraph-core/src/main/java/org/apache/giraph/io/iterables/GiraphReader.java

/*
 * 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;
}