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1   //******************************************************************************
2   //
3   // File:    SharedObjectBuf.java
4   // Package: edu.rit.mp.buf
5   // Unit:    Class edu.rit.mp.buf.SharedObjectBuf
6   //
7   // This Java source file is copyright (C) 2012 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
37  // Web at http://www.gnu.org/licenses/gpl.html.
38  //
39  //******************************************************************************
40  package edu.rit.mp.buf;
41  
42  import edu.rit.mp.Buf;
43  import edu.rit.mp.ObjectBuf;
44  import edu.rit.pj.reduction.ObjectOp;
45  import edu.rit.pj.reduction.Op;
46  import edu.rit.pj.reduction.SharedObject;
47  
48  /**
49   * Class SharedObjectBuf provides a buffer for a shared object item sent or
50   * received using the Message Protocol (MP). While an instance of class
51   * SharedObjectBuf may be constructed directly, normally you will use a factory
52   * method in class {@linkplain edu.rit.mp.ObjectBuf ObjectBuf}. See that class
53   * for further information.
54   *
55   * @param <T> Data type of the objects in the buffer.
56   * @author Alan Kaminsky
57   * @version 01-Apr-2012
58   */
59  @SuppressWarnings("unchecked")
60  public class SharedObjectBuf<T>
61          extends ObjectBuf<T> {
62  
63  // Hidden data members.
64      SharedObject<T> myItem;
65  
66  // Exported constructors.
67      /**
68       * Construct a new shared object buffer.
69       *
70       * @param item SharedObject object that wraps the item.
71       */
72      public SharedObjectBuf(SharedObject<T> item) {
73          super(1);
74          myItem = item;
75      }
76  
77  // Exported operations.
78      /**
79       * {@inheritDoc}
80       *
81       * Obtain the given item from this buffer.
82       * <P>
83       * The <code>get()</code> method must not block the calling thread; if it does,
84       * all message I/O in MP will be blocked.
85       */
86      public T get(int i) {
87          return myItem.get();
88      }
89  
90      /**
91       * Store the given item in this buffer.
92       * <P>
93       * The <code>put()</code> method must not block the calling thread; if it does,
94       * all message I/O in MP will be blocked.
95       *
96       * @param i Item index in the range 0 .. <code>length()</code>-1.
97       * @param item Item to be stored at index <code>i</code>.
98       */
99      public void put(int i,
100             T item) {
101         myItem.set(item);
102         mySerializedItems = null;
103     }
104 
105     /**
106      * {@inheritDoc}
107      *
108      * Create a buffer for performing parallel reduction using the given binary
109      * operation. The results of the reduction are placed into this buffer.
110      * @exception ClassCastException (unchecked exception) Thrown if this
111      * buffer's element data type and the given binary operation's argument data
112      * type are not the same.
113      */
114     public Buf getReductionBuf(Op op) {
115         return new SharedObjectReductionBuf<T>(myItem, (ObjectOp<T>) op, this);
116     }
117 
118 }