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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-one object channel with user-definable buffering,
* safe for use by many writers and one reader.
* <H2>Description</H2>
* <TT>BufferedAny2OneChannel</TT> implements an any-to-one object channel with
* user-definable buffering. It is safe for use by many writing processes
* but only one reader. Writing processes compete with each other to use
* the channel. Only the reader and one writer will
* actually be using the channel at any one time. This is taken care of by
* <TT>BufferedAny2OneChannel</TT> -- user processes just read from or write to it.
* <P>
* The reading process may {@link Alternative <TT>ALT</TT>} on this channel.
* The writing process is committed (i.e. it may not back off).
* <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 writers 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>any-1</I> channels.
*
* @see org.jcsp.lang.Alternative
* @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 BufferedAny2OneChannel extends Any2OneImpl
{
/**
* Constructs a new BufferedAny2OneChannel with the specified ChannelDataStore.
*
* @param data The ChannelDataStore used to store the data for the channel
*/
public BufferedAny2OneChannel(ChannelDataStore data)
{
super(new BufferedOne2OneChannel(data));
}
}
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