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 }