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