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1   //******************************************************************************
2   //
3   // File:    EmptySigned16BitIntegerBuf.java
4   // Package: edu.rit.mp.buf
5   // Unit:    Class edu.rit.mp.buf.EmptySigned16BitIntegerBuf
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.Signed16BitIntegerBuf;
46  import edu.rit.pj.reduction.IntegerOp;
47  import edu.rit.pj.reduction.Op;
48  
49  /**
50   * Class EmptySigned16BitIntegerBuf provides a signed 16-bit integer buffer that
51   * contains no items for messages using the Message Protocol (MP). When a
52   * message is sent from an EmptySigned16BitIntegerBuf, the message item type is
53   * signed 16-bit <code>int</code> and the message length is 0. When a message is
54   * received into an EmptySigned16BitIntegerBuf, the message item type must be
55   * signed 16-bit <code>int</code>, but all items in the message are discarded.
56   *
57   * @author Alan Kaminsky
58   * @version 19-Nov-2007
59   */
60  public class EmptySigned16BitIntegerBuf
61          extends Signed16BitIntegerBuf {
62  
63  // Exported constructors.
64      /**
65       * Construct a new empty signed 16-bit integer buffer.
66       */
67      public EmptySigned16BitIntegerBuf() {
68          super(0);
69      }
70  
71  // Exported operations.
72      /**
73       * {@inheritDoc}
74       *
75       * Obtain the given item from this buffer.
76       * <P>
77       * The <code>get()</code> method must not block the calling thread; if it does,
78       * all message I/O in MP will be blocked.
79       */
80      public int get(int i) {
81          throw new IndexOutOfBoundsException();
82      }
83  
84      /**
85       * {@inheritDoc}
86       *
87       * Store the given item in this buffer.
88       * <P>
89       * The <code>put()</code> method must not block the calling thread; if it does,
90       * all message I/O in MP will be blocked.
91       */
92      public void put(int i,
93              int item) {
94          throw new IndexOutOfBoundsException();
95      }
96  
97      /**
98       * {@inheritDoc}
99       *
100      * Copy items from the given buffer to this buffer. The number of items
101      * copied is this buffer's length or <code>theSrc</code>'s length, whichever is
102      * smaller. If <code>theSrc</code> is this buffer, the <code>copy()</code> method
103      * does nothing.
104      * @exception ClassCastException (unchecked exception) Thrown if
105      * <code>theSrc</code>'s item data type is not the same as this buffer's item
106      * data type.
107      */
108     public void copy(Buf theSrc) {
109     }
110 
111     /**
112      * {@inheritDoc}
113      *
114      * Create a buffer for performing parallel reduction using the given binary
115      * operation. The results of the reduction are placed into this buffer.
116      * <P>
117      * Operations performed on the returned reduction buffer have the same
118      * effect as operations performed on this buffer, except whenever a source
119      * item <I>S</I> is put into a destination item <I>D</I> in this buffer,
120      * <I>D</I> is set to <I>D op S</I>, that is, the reduction of <I>D</I> and
121      * <I>S</I> using the given binary operation (rather than just setting
122      * <I>D</I> to <I>S</I>).
123      * @exception ClassCastException (unchecked exception) Thrown if this
124      * buffer's element data type and the given binary operation's argument data
125      * type are not the same.
126      */
127     public Buf getReductionBuf(Op op) {
128         IntegerOp intop = (IntegerOp) op;
129         return this;
130     }
131 
132 // Hidden operations.
133     /**
134      * {@inheritDoc}
135      *
136      * Send as many items as possible from this buffer to the given byte buffer.
137      * <P>
138      * The <code>sendItems()</code> method must not block the calling thread; if it
139      * does, all message I/O in MP will be blocked.
140      */
141     protected int sendItems(int i,
142             ByteBuffer buffer) {
143         return 0;
144     }
145 
146     /**
147      * {@inheritDoc}
148      *
149      * Receive as many items as possible from the given byte buffer to this
150      * buffer.
151      * <P>
152      * The <code>receiveItems()</code> method must not block the calling thread; if
153      * it does, all message I/O in MP will be blocked.
154      */
155     protected int receiveItems(int i,
156             int num,
157             ByteBuffer buffer) {
158         return 0;
159     }
160 
161 }