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1   //******************************************************************************
2   //
3   // File:    SharedByteReductionBuf.java
4   // Package: edu.rit.mp.buf
5   // Unit:    Class edu.rit.mp.buf.SharedByteReductionBuf
6   //
7   // This Java source file is copyright (C) 2007 by Alan Kaminsky. All rights
8   // reserved. For further information, contact the author, Alan Kaminsky, at
9   // ark@cs.rit.edu.
10  //
11  // This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
12  // software; you can redistribute it and/or modify it under the terms of the GNU
13  // General Public License as published by the Free Software Foundation; either
14  // version 3 of the License, or (at your option) any later version.
15  //
16  // PJ is distributed in the hope that it will be useful, but WITHOUT ANY
17  // WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
18  // A PARTICULAR PURPOSE. See the GNU General Public License for more details.
19  //
20  // Linking this library statically or dynamically with other modules is making a
21  // combined work based on this library. Thus, the terms and conditions of the GNU
22  // General Public License cover the whole combination.
23  //
24  // As a special exception, the copyright holders of this library give you
25  // permission to link this library with independent modules to produce an
26  // executable, regardless of the license terms of these independent modules, and
27  // to copy and distribute the resulting executable under terms of your choice,
28  // provided that you also meet, for each linked independent module, the terms
29  // and conditions of the license of that module. An independent module is a module
30  // which is not derived from or based on this library. If you modify this library,
31  // you may extend this exception to your version of the library, but you are not
32  // obligated to do so. If you do not wish to do so, delete this exception
33  // statement from your version.
34  //
35  // A copy of the GNU General Public License is provided in the file gpl.txt. You
36  // may also obtain a copy of the GNU General Public License on the World Wide
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38  //
39  //******************************************************************************
40  package edu.rit.mp.buf;
41  
42  import java.nio.ByteBuffer;
43  
44  import edu.rit.mp.Buf;
45  import edu.rit.pj.reduction.ByteOp;
46  import edu.rit.pj.reduction.Op;
47  import edu.rit.pj.reduction.SharedByte;
48  
49  /**
50   * Class SharedByteReductionBuf provides a reduction buffer for class
51   * {@linkplain SharedByteBuf}.
52   *
53   * @author Alan Kaminsky
54   * @version 26-Oct-2007
55   */
56  class SharedByteReductionBuf
57          extends SharedByteBuf {
58  
59  // Hidden data members.
60      ByteOp myOp;
61  
62  // Exported constructors.
63      /**
64       * Construct a new byte item reduction buffer.
65       *
66       * @param item SharedByte object that wraps the item.
67       * @param op Binary operation.
68       * @exception NullPointerException (unchecked exception) Thrown if
69       * <code>op</code> is null.
70       */
71      public SharedByteReductionBuf(SharedByte item,
72              ByteOp op) {
73          super(item);
74          if (op == null) {
75              throw new NullPointerException("SharedByteReductionBuf(): op is null");
76          }
77          myOp = op;
78      }
79  
80  // Exported operations.
81      /**
82       * {@inheritDoc}
83       *
84       * Store the given item in this buffer. The item at index <code>i</code> in this
85       * buffer is combined with the given <code>item</code> using the binary
86       * operation.
87       * <P>
88       * The <code>put()</code> method must not block the calling thread; if it does,
89       * all message I/O in MP will be blocked.
90       */
91      public void put(int i,
92              byte item) {
93          myItem.reduce(item, myOp);
94      }
95  
96      /**
97       * {@inheritDoc}
98       *
99       * Create a buffer for performing parallel reduction using the given binary
100      * operation. The results of the reduction are placed into this buffer.
101      * @exception ClassCastException (unchecked exception) Thrown if this
102      * buffer's element data type and the given binary operation's argument data
103      * type are not the same.
104      */
105     public Buf getReductionBuf(Op op) {
106         throw new UnsupportedOperationException();
107     }
108 
109 // Hidden operations.
110     /**
111      * {@inheritDoc}
112      *
113      * Receive as many items as possible from the given byte buffer to this
114      * buffer. As the items are received, they are combined with the items in
115      * this buffer using the binary operation.
116      * <P>
117      * The <code>receiveItems()</code> method must not block the calling thread; if
118      * it does, all message I/O in MP will be blocked.
119      */
120     protected int receiveItems(int i,
121             int num,
122             ByteBuffer buffer) {
123         if (num >= 1 && buffer.remaining() >= 1) {
124             myItem.reduce(buffer.get(), myOp);
125             return 1;
126         } else {
127             return 0;
128         }
129     }
130 
131 }