1 //******************************************************************************
2 //
3 // File: ByteItemBuf.java
4 // Package: edu.rit.mp.buf
5 // Unit: Class edu.rit.mp.buf.ByteItemBuf
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
49 /**
50 * Class ByteItemBuf provides a buffer for a single byte item sent or received
51 * using the Message Protocol (MP). While an instance of class ByteItemBuf may
52 * be constructed directly, normally you will use a factory method in class
53 * {@linkplain edu.rit.mp.ByteBuf ByteBuf}. See that class for further
54 * information.
55 *
56 * @author Alan Kaminsky
57 * @version 25-Oct-2007
58 */
59 public class ByteItemBuf
60 extends ByteBuf {
61
62 // Exported data members.
63 /**
64 * Byte item to be sent or received.
65 */
66 public byte item;
67
68 // Exported constructors.
69 /**
70 * Construct a new byte item buffer.
71 */
72 public ByteItemBuf() {
73 super(1);
74 }
75
76 /**
77 * Construct a new byte item buffer with the given initial value.
78 *
79 * @param item Initial value of the {@link #item} field.
80 */
81 public ByteItemBuf(byte item) {
82 super(1);
83 this.item = item;
84 }
85
86 // Exported operations.
87 /**
88 * {@inheritDoc}
89 *
90 * Obtain the given item from this buffer.
91 * <P>
92 * The <code>get()</code> method must not block the calling thread; if it does,
93 * all message I/O in MP will be blocked.
94 */
95 public byte get(int i) {
96 return this.item;
97 }
98
99 /**
100 * {@inheritDoc}
101 *
102 * Store the given item in this buffer.
103 * <P>
104 * The <code>put()</code> method must not block the calling thread; if it does,
105 * all message I/O in MP will be blocked.
106 */
107 public void put(int i,
108 byte item) {
109 this.item = item;
110 }
111
112 /**
113 * {@inheritDoc}
114 *
115 * Create a buffer for performing parallel reduction using the given binary
116 * operation. The results of the reduction are placed into this buffer.
117 * @exception ClassCastException (unchecked exception) Thrown if this
118 * buffer's element data type and the given binary operation's argument data
119 * type are not the same.
120 */
121 public Buf getReductionBuf(Op op) {
122 return new ByteItemReductionBuf(this, (ByteOp) op);
123 }
124
125 // Hidden operations.
126 /**
127 * {@inheritDoc}
128 *
129 * Send as many items as possible from this buffer to the given byte buffer.
130 * <P>
131 * The <code>sendItems()</code> method must not block the calling thread; if it
132 * does, all message I/O in MP will be blocked.
133 */
134 protected int sendItems(int i,
135 ByteBuffer buffer) {
136 if (buffer.remaining() >= 1) {
137 buffer.put(this.item);
138 return 1;
139 } else {
140 return 0;
141 }
142 }
143
144 /**
145 * {@inheritDoc}
146 *
147 * Receive as many items as possible from the given byte buffer to this
148 * buffer.
149 * <P>
150 * The <code>receiveItems()</code> method must not block the calling thread; if
151 * it does, all message I/O in MP will be blocked.
152 */
153 protected int receiveItems(int i,
154 int num,
155 ByteBuffer buffer) {
156 if (num >= 1 && buffer.remaining() >= 1) {
157 this.item = buffer.get();
158 return 1;
159 } else {
160 return 0;
161 }
162 }
163
164 }