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.utils;
20
21 import org.apache.hadoop.io.WritableComparable;
22
23 import java.io.IOException;
24 import javax.annotation.concurrent.NotThreadSafe;
25
26 /**
27 * Special iterator that reuses vertex ids and data objects so that the
28 * lifetime of the object is only until next() is called.
29 *
30 * Vertex id ownership can be released if desired through
31 * releaseCurrentVertexId(). This optimization allows us to cut down
32 * on the number of objects instantiated and garbage collected.
33 *
34 * @param <I> vertexId type parameter
35 * @param <T> vertexData type parameter
36 */
37 @NotThreadSafe
38 public class ByteStructVertexIdDataIterator<I extends WritableComparable, T>
39 extends ByteStructVertexIdIterator<I> implements VertexIdDataIterator<I, T> {
40 /** VertexIdData to iterate over */
41 protected AbstractVertexIdData<I, T> vertexIdData;
42 /** Serialized size of the message object in bytestore */
43 protected int dataSize;
44 /** Current data. */
45 private T data;
46
47 /**
48 * Constructor
49 *
50 * @param vertexIdData vertexIdData
51 */
52 public ByteStructVertexIdDataIterator(
53 AbstractVertexIdData<I, T> vertexIdData) {
54 super(vertexIdData.extendedDataOutput, vertexIdData.getConf());
55 this.vertexIdData = vertexIdData;
56 }
57
58 @Override
59 public void next() {
60 if (vertexId == null) {
61 vertexId = vertexIdData.getConf().createVertexId();
62 }
63 if (data == null) {
64 data = vertexIdData.createData();
65 }
66 try {
67 vertexId.readFields(extendedDataInput);
68 int initial = extendedDataInput.getPos();
69 vertexIdData.readData(extendedDataInput, data);
70 dataSize = extendedDataInput.getPos() - initial;
71 } catch (IOException e) {
72 throw new IllegalStateException("next: IOException", e);
73 }
74 }
75
76 @Override
77 public int getCurrentDataSize() {
78 return dataSize;
79 }
80
81 @Override
82 public T getCurrentData() {
83 return data;
84 }
85
86 @Override
87 public T releaseCurrentData() {
88 T releasedData = data;
89 data = null;
90 return releasedData;
91 }
92 }