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ByteStructIterable 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.util.Iterator;
21  import org.apache.hadoop.io.Writable;
22  
23  /**
24   * This iterable is designed to deserialize a byte array on the fly to
25   * provide new copies of writable objects when desired.  It does not reuse
26   * objects, and instead creates a new one for every next().
27   *
28   * @param <T> Type that extends Writable that will be iterated
29   */
30  public abstract class ByteStructIterable<T extends Writable> implements
31      Iterable<T> {
32    /** Factory for data input */
33    protected final Factory<? extends ExtendedDataInput> dataInputFactory;
34  
35    /**
36     * Constructor
37     *
38     * @param dataInputFactory Factory for data inputs
39     */
40    public ByteStructIterable(
41        Factory<? extends ExtendedDataInput> dataInputFactory) {
42      this.dataInputFactory = dataInputFactory;
43    }
44  
45    /**
46     * Must be able to create the writable object
47     *
48     * @return New writable
49     */
50    protected abstract T createWritable();
51  
52    @Override
53    public Iterator<T> iterator() {
54      return new ByteStructIterator<T>(dataInputFactory.create()) {
55        @Override
56        protected T createWritable() {
57          return ByteStructIterable.this.createWritable();
58        }
59      };
60    }
61  }