1 //******************************************************************************
2 //
3 // File: SharedByteBuf.java
4 // Package: edu.rit.mp.buf
5 // Unit: Class edu.rit.mp.buf.SharedByteBuf
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 java.nio.ByteBuffer;
43
44 import edu.rit.mp.Buf;
45 import edu.rit.mp.ByteBuf;
46 import edu.rit.pj.reduction.ByteOp;
47 import edu.rit.pj.reduction.Op;
48 import edu.rit.pj.reduction.SharedByte;
49
50 /**
51 * Class SharedByteBuf provides a buffer for a multiple thread safe byte item
52 * sent or received using the Message Protocol (MP). While an instance of class
53 * SharedByteBuf may be constructed directly, normally you will use a factory
54 * method in class {@linkplain edu.rit.mp.ByteBuf ByteBuf}. See that class for
55 * further information.
56 *
57 * @author Alan Kaminsky
58 * @version 26-Oct-2007
59 */
60 public class SharedByteBuf
61 extends ByteBuf {
62
63 // Hidden data members.
64 SharedByte myItem;
65
66 // Exported constructors.
67 /**
68 * Construct a new shared byte buffer.
69 *
70 * @param item SharedByte object that wraps the item.
71 */
72 public SharedByteBuf(SharedByte 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 byte get(int i) {
87 return myItem.get();
88 }
89
90 /**
91 * {@inheritDoc}
92 *
93 * Store the given item in this buffer.
94 * <P>
95 * The <code>put()</code> method must not block the calling thread; if it does,
96 * all message I/O in MP will be blocked.
97 */
98 public void put(int i,
99 byte item) {
100 myItem.set(item);
101 }
102
103 /**
104 * {@inheritDoc}
105 *
106 * Create a buffer for performing parallel reduction using the given binary
107 * operation. The results of the reduction are placed into this buffer.
108 * @exception ClassCastException (unchecked exception) Thrown if this
109 * buffer's element data type and the given binary operation's argument data
110 * type are not the same.
111 */
112 public Buf getReductionBuf(Op op) {
113 return new SharedByteReductionBuf(myItem, (ByteOp) op);
114 }
115
116 // Hidden operations.
117 /**
118 * {@inheritDoc}
119 *
120 * Send as many items as possible from this buffer to the given byte buffer.
121 * <P>
122 * The <code>sendItems()</code> method must not block the calling thread; if it
123 * does, all message I/O in MP will be blocked.
124 */
125 protected int sendItems(int i,
126 ByteBuffer buffer) {
127 if (buffer.remaining() >= 1) {
128 buffer.put(myItem.get());
129 return 1;
130 } else {
131 return 0;
132 }
133 }
134
135 /**
136 * {@inheritDoc}
137 *
138 * Receive as many items as possible from the given byte buffer to this
139 * buffer.
140 * <P>
141 * The <code>receiveItems()</code> method must not block the calling thread; if
142 * it does, all message I/O in MP will be blocked.
143 */
144 protected int receiveItems(int i,
145 int num,
146 ByteBuffer buffer) {
147 if (num >= 1 && buffer.remaining() >= 1) {
148 myItem.set(buffer.get());
149 return 1;
150 } else {
151 return 0;
152 }
153 }
154
155 }