1
//////////////////////////////////////////////////////////////////////
3
// JCSP ("CSP for Java") Libraries //
4
// Copyright (C) 1996-2008 Peter Welch and Paul Austin. //
5
// 2001-2004 Quickstone Technologies Limited. //
7
// This library is free software; you can redistribute it and/or //
8
// modify it under the terms of the GNU Lesser General Public //
9
// License as published by the Free Software Foundation; either //
10
// version 2.1 of the License, or (at your option) any later //
13
// This library is distributed in the hope that it will be //
14
// useful, but WITHOUT ANY WARRANTY; without even the implied //
15
// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR //
16
// PURPOSE. See the GNU Lesser General Public License for more //
19
// You should have received a copy of the GNU Lesser General //
20
// Public License along with this library; if not, write to the //
21
// Free Software Foundation, Inc., 59 Temple Place, Suite 330, //
22
// Boston, MA 02111-1307, USA. //
24
// Author contact: P.H.Welch@kent.ac.uk //
27
//////////////////////////////////////////////////////////////////////
29
package org.jcsp.lang;
31
import org.jcsp.util.*;
34
* This implements an any-to-one object channel with user-definable buffering,
35
* safe for use by many writers and one reader.
36
* <H2>Description</H2>
37
* <TT>BufferedAny2OneChannel</TT> implements an any-to-one object channel with
38
* user-definable buffering. It is safe for use by many writing processes
39
* but only one reader. Writing processes compete with each other to use
40
* the channel. Only the reader and one writer will
41
* actually be using the channel at any one time. This is taken care of by
42
* <TT>BufferedAny2OneChannel</TT> -- user processes just read from or write to it.
44
* The reading process may {@link Alternative <TT>ALT</TT>} on this channel.
45
* The writing process is committed (i.e. it may not back off).
47
* The constructor requires the user to provide
48
* the channel with a <I>plug-in</I> driver conforming to the
49
* {@link org.jcsp.util.ChannelDataStore <TT>ChannelDataStore</TT>}
50
* interface. This allows a variety of different channel semantics to be
51
* introduced -- including buffered channels of user-defined capacity
52
* (including infinite), overwriting channels (with various overwriting
54
* Standard examples are given in the <TT>org.jcsp.util</TT> package, but
55
* <I>careful users</I> may write their own.
57
* <H3><A NAME="Caution">Implementation Note and Caution</H3>
58
* <I>Fair</I> servicing of writers to this channel depends on the <I>fair</I>
59
* servicing of requests to enter a <TT>synchronized</TT> block (or method) by
60
* the underlying Java Virtual Machine (JVM). Java does not specify how threads
61
* waiting to synchronize should be handled. Currently, Sun's standard JDKs queue
62
* these requests - which is <I>fair</I>. However, there is at least one JVM
63
* that puts such competing requests on a stack - which is legal but <I>unfair</I>
64
* and can lead to infinite starvation. This is a problem for <I>any</I> Java system
65
* relying on good behaviour from <TT>synchronized</TT>, not just for these
66
* <I>any-1</I> channels.
68
* @see org.jcsp.lang.Alternative
69
* @see org.jcsp.lang.BufferedOne2OneChannel
70
* @see org.jcsp.lang.BufferedOne2AnyChannel
71
* @see org.jcsp.lang.BufferedAny2AnyChannel
72
* @see org.jcsp.util.ChannelDataStore
78
class BufferedAny2OneChannel extends Any2OneImpl
81
* Constructs a new BufferedAny2OneChannel with the specified ChannelDataStore.
83
* @param data The ChannelDataStore used to store the data for the channel
85
public BufferedAny2OneChannel(ChannelDataStore data)
87
super(new BufferedOne2OneChannel(data));