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//////////////////////////////////////////////////////////////////////
// //
// JCSP ("CSP for Java") Libraries //
// Copyright (C) 1996-2008 Peter Welch and Paul Austin. //
// 2001-2004 Quickstone Technologies Limited. //
// //
// This library is free software; you can redistribute it and/or //
// modify it under the terms of the GNU Lesser General Public //
// License as published by the Free Software Foundation; either //
// version 2.1 of the License, or (at your option) any later //
// version. //
// //
// This library is distributed in the hope that it will be //
// useful, but WITHOUT ANY WARRANTY; without even the implied //
// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR //
// PURPOSE. See the GNU Lesser General Public License for more //
// details. //
// //
// You should have received a copy of the GNU Lesser General //
// Public License along with this library; if not, write to the //
// Free Software Foundation, Inc., 59 Temple Place, Suite 330, //
// Boston, MA 02111-1307, USA. //
// //
// Author contact: P.H.Welch@kent.ac.uk //
// //
// //
//////////////////////////////////////////////////////////////////////
package org.jcsp.lang;
import org.jcsp.util.*;
/**
* This implements an any-to-any object channel with user-definable buffering,
* safe for use by many writers and many readers.
* <H2>Description</H2>
* <TT>BufferedOne2AnyChannel</TT> implements a one-to-any object channel with
* user-definable buffering. It is safe for use by any number of reading
* processes but ony one writer. Reading processes compete with each other
* to use the channel. Only one reader and the writer will actually be using
* the channel at any one time. This is taken care of by
* <TT>BufferedOne2AnyChannel</TT> -- user processes just read from or write to it.
* <P>
* <I>Please note that this is a safely shared channel and not
* a multicaster. Currently, multicasting has to be managed by
* writing active processes (see {@link org.jcsp.plugNplay.DynamicDelta}
* for an example of broadcasting).</I>
* <P>
* All reading processes and writing processes commit to the channel
* (i.e. may not back off). This means that the reading processes
* <I>may not</I> {@link Alternative <TT>ALT</TT>} on this channel.
* <P>
* The constructor requires the user to provide
* the channel with a <I>plug-in</I> driver conforming to the
* {@link org.jcsp.util.ChannelDataStore <TT>ChannelDataStore</TT>}
* interface. This allows a variety of different channel semantics to be
* introduced -- including buffered channels of user-defined capacity
* (including infinite), overwriting channels (with various overwriting
* policies) etc..
* Standard examples are given in the <TT>org.jcsp.util</TT> package, but
* <I>careful users</I> may write their own.
*
* <H3><A NAME="Caution">Implementation Note and Caution</H3>
* <I>Fair</I> servicing of readers to this channel depends on the <I>fair</I>
* servicing of requests to enter a <TT>synchronized</TT> block (or method) by
* the underlying Java Virtual Machine (JVM). Java does not specify how threads
* waiting to synchronize should be handled. Currently, Sun's standard JDKs queue
* these requests - which is <I>fair</I>. However, there is at least one JVM
* that puts such competing requests on a stack - which is legal but <I>unfair</I>
* and can lead to infinite starvation. This is a problem for <I>any</I> Java system
* relying on good behaviour from <TT>synchronized</TT>, not just for these
* <I>1-any</I> channels.
*
* @see org.jcsp.lang.BufferedOne2OneChannel
* @see org.jcsp.lang.BufferedOne2AnyChannel
* @see org.jcsp.lang.BufferedAny2AnyChannel
* @see org.jcsp.util.ChannelDataStore
*
* @author P.D. Austin
* @author P.H. Welch
*/
class BufferedOne2AnyChannel extends One2AnyImpl
{
/**
* Constructs a new BufferedOne2AnyChannel with the specified ChannelDataStore.
*
* @param data The ChannelDataStore used to store the data for the channel
*/
public BufferedOne2AnyChannel(ChannelDataStore data)
{
super(new BufferedOne2OneChannel(data));
}
}
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