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1   //******************************************************************************
2   //
3   // File:    SharedSigned8BitIntegerBuf.java
4   // Package: edu.rit.mp.buf
5   // Unit:    Class edu.rit.mp.buf.SharedSigned8BitIntegerBuf
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.mp.Signed8BitIntegerBuf;
46  import edu.rit.pj.reduction.IntegerOp;
47  import edu.rit.pj.reduction.Op;
48  import edu.rit.pj.reduction.SharedInteger;
49  
50  /**
51   * Class SharedSigned8BitIntegerBuf provides a buffer for a shared signed 8-bit
52   * integer item sent or received using the Message Protocol (MP). While an
53   * instance of class SharedSigned8BitIntegerBuf may be constructed directly,
54   * normally you will use a factory method in class {@linkplain
55   * edu.rit.mp.Signed8BitIntegerBuf Signed8BitIntegerBuf}. See that class for
56   * further information.
57   *
58   * @author Alan Kaminsky
59   * @version 26-Oct-2007
60   */
61  public class SharedSigned8BitIntegerBuf
62          extends Signed8BitIntegerBuf {
63  
64  // Hidden data members.
65      SharedInteger myItem;
66  
67  // Exported constructors.
68      /**
69       * Construct a new shared signed 8-bit integer buffer.
70       *
71       * @param item SharedInteger object that wraps the item.
72       */
73      public SharedSigned8BitIntegerBuf(SharedInteger item) {
74          super(1);
75          myItem = item;
76      }
77  
78  // Exported operations.
79      /**
80       * {@inheritDoc}
81       *
82       * Obtain the given item from this buffer.
83       * <P>
84       * The <code>get()</code> method must not block the calling thread; if it does,
85       * all message I/O in MP will be blocked.
86       */
87      public int get(int i) {
88          return myItem.get();
89      }
90  
91      /**
92       * {@inheritDoc}
93       *
94       * Store the given item in this buffer.
95       * <P>
96       * The <code>put()</code> method must not block the calling thread; if it does,
97       * all message I/O in MP will be blocked.
98       */
99      public void put(int i,
100             int item) {
101         myItem.set(item);
102     }
103 
104     /**
105      * {@inheritDoc}
106      *
107      * Create a buffer for performing parallel reduction using the given binary
108      * operation. The results of the reduction are placed into this buffer.
109      * @exception ClassCastException (unchecked exception) Thrown if this
110      * buffer's element data type and the given binary operation's argument data
111      * type are not the same.
112      */
113     public Buf getReductionBuf(Op op) {
114         return new SharedSigned8BitIntegerReductionBuf(myItem, (IntegerOp) op);
115     }
116 
117 // Hidden operations.
118     /**
119      * {@inheritDoc}
120      *
121      * Send as many items as possible from this buffer to the given byte buffer.
122      * <P>
123      * The <code>sendItems()</code> method must not block the calling thread; if it
124      * does, all message I/O in MP will be blocked.
125      */
126     protected int sendItems(int i,
127             ByteBuffer buffer) {
128         if (buffer.remaining() >= 1) {
129             buffer.put((byte) myItem.get());
130             return 1;
131         } else {
132             return 0;
133         }
134     }
135 
136     /**
137      * {@inheritDoc}
138      *
139      * Receive as many items as possible from the given byte buffer to this
140      * buffer.
141      * <P>
142      * The <code>receiveItems()</code> method must not block the calling thread; if
143      * it does, all message I/O in MP will be blocked.
144      */
145     protected int receiveItems(int i,
146             int num,
147             ByteBuffer buffer) {
148         if (num >= 1 && buffer.remaining() >= 1) {
149             myItem.set(buffer.get());
150             return 1;
151         } else {
152             return 0;
153         }
154     }
155 
156 }