1 //******************************************************************************
2 //
3 // File: EmptyObjectBuf.java
4 // Package: edu.rit.mp.buf
5 // Unit: Class edu.rit.mp.buf.EmptyObjectBuf
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
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
47 /**
48 * Class EmptyObjectBuf provides an object buffer that contains no items for
49 * messages using the Message Protocol (MP). When a message is sent from an
50 * EmptyObjectBuf, the message item type is Object and the message length is 0.
51 * When a message is received into an EmptyObjectBuf, the message item type must
52 * be Object, but all items in the message are discarded.
53 *
54 * @author Alan Kaminsky
55 * @version 03-Jul-2008
56 */
57 public class EmptyObjectBuf
58 extends ObjectBuf<Object> {
59
60 // Exported constructors.
61 /**
62 * Construct a new empty object buffer.
63 */
64 public EmptyObjectBuf() {
65 super(0);
66 }
67
68 // Exported operations.
69 /**
70 * {@inheritDoc}
71 *
72 * Obtain the given item from this buffer.
73 * <P>
74 * The <code>get()</code> method must not block the calling thread; if it does,
75 * all message I/O in MP will be blocked.
76 */
77 public Object get(int i) {
78 throw new IndexOutOfBoundsException();
79 }
80
81 /**
82 * {@inheritDoc}
83 *
84 * Store the given item in this buffer.
85 * <P>
86 * The <code>put()</code> method must not block the calling thread; if it does,
87 * all message I/O in MP will be blocked.
88 */
89 public void put(int i,
90 Object item) {
91 throw new IndexOutOfBoundsException();
92 }
93
94 /**
95 * {@inheritDoc}
96 *
97 * Copy items from the given buffer to this buffer. The number of items
98 * copied is this buffer's length or <code>theSrc</code>'s length, whichever is
99 * smaller. If <code>theSrc</code> is this buffer, the <code>copy()</code> method
100 * does nothing.
101 * @exception ClassCastException (unchecked exception) Thrown if
102 * <code>theSrc</code>'s item data type is not the same as this buffer's item
103 * data type.
104 */
105 public void copy(Buf theSrc) {
106 }
107
108 /**
109 * {@inheritDoc}
110 *
111 * Create a buffer for performing parallel reduction using the given binary
112 * operation. The results of the reduction are placed into this buffer.
113 * <P>
114 * Operations performed on the returned reduction buffer have the same
115 * effect as operations performed on this buffer, except whenever a source
116 * item <I>S</I> is put into a destination item <I>D</I> in this buffer,
117 * <I>D</I> is set to <I>D op S</I>, that is, the reduction of <I>D</I> and
118 * <I>S</I> using the given binary operation (rather than just setting
119 * <I>D</I> to <I>S</I>).
120 * @exception ClassCastException (unchecked exception) Thrown if this
121 * buffer's element data type and the given binary operation's argument data
122 * type are not the same.
123 */
124 public Buf getReductionBuf(Op op) {
125 ObjectOp<?> objectop = (ObjectOp<?>) op;
126 return this;
127 }
128
129 }