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EdgeInputFormat xref
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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.giraph.io;
20  
21  import org.apache.hadoop.io.Writable;
22  import org.apache.hadoop.io.WritableComparable;
23  import org.apache.hadoop.mapreduce.InputSplit;
24  import org.apache.hadoop.mapreduce.TaskAttemptContext;
25  
26  import java.io.IOException;
27  
28  /**
29   * Input format for reading single edges.  Provides access to
30   * ImmutableClassesGiraphConfiguration.
31   *
32   * It's guaranteed that whatever parameters are set in the configuration are
33   * also going to be available in all method arguments related to this input
34   * format (context in getSplits and createEdgeReader; methods invoked on
35   * EdgeReader). So if backing input format relies on some parameters from
36   * configuration, you can safely set them for example in
37   * {@link #setConf(org.apache.giraph.conf.ImmutableClassesGiraphConfiguration)}.
38   *
39   * @param <I> Vertex id
40   * @param <E> Edge data
41   */
42  public abstract class EdgeInputFormat<I extends WritableComparable,
43      E extends Writable> extends GiraphInputFormat<I, Writable, E> {
44    /**
45     * Create an edge reader for a given split. The framework will call
46     * {@link EdgeReader#initialize(InputSplit, TaskAttemptContext)} before
47     * the split is used.
48     *
49     * @param split the split to be read
50     * @param context the information about the task
51     * @return a new record reader
52     * @throws IOException
53     */
54    public abstract EdgeReader<I, E> createEdgeReader(
55        InputSplit split,
56        TaskAttemptContext context) throws IOException;
57  }