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RepresentativeByteStructIterator 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  package org.apache.giraph.utils;
19  
20  import java.io.IOException;
21  import org.apache.hadoop.io.Writable;
22  
23  /**
24   * The objects provided by this iterator have lifetimes only until next() is
25   * called.  In that sense, the object provided is only a representative object.
26   *
27   * @param <T> Type that extends Writable that will be iterated
28   */
29  public abstract class RepresentativeByteStructIterator<T extends
30      Writable> extends ByteStructIterator<T> {
31    /** Representative writable */
32    private final T representativeWritable = createWritable();
33  
34    /**
35     * Wrap ExtendedDataInput in ByteArrayIterator
36     *
37     * @param extendedDataInput ExtendedDataInput
38     */
39    public RepresentativeByteStructIterator(ExtendedDataInput extendedDataInput) {
40      super(extendedDataInput);
41    }
42  
43    @Override
44    public T next() {
45      try {
46        representativeWritable.readFields(extendedDataInput);
47      } catch (IOException e) {
48        throw new IllegalStateException("next: readFields got IOException", e);
49      }
50      return representativeWritable;
51    }
52  }