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Viewing changes to src/org/jcsp/lang/CrewServer.java

  • Committer: Bazaar Package Importer
  • Author(s): Miguel Landaeta
  • Date: 2010-06-20 18:12:26 UTC
  • Revision ID: james.westby@ubuntu.com-20100620181226-8yg8d9rjjjiuy7oz
Tags: upstream-1.1-rc4
Import upstream version 1.1-rc4

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src/org/jcsp/lang/CrewServer.java
 
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    //////////////////////////////////////////////////////////////////////
 
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    //                                                                  //
 
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    //  JCSP ("CSP for Java") Libraries                                 //
 
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    //  Copyright (C) 1996-2008 Peter Welch and Paul Austin.            //
 
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    //                2001-2004 Quickstone Technologies Limited.        //
 
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    //                                                                  //
 
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    //  This library is free software; you can redistribute it and/or   //
 
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    //  modify it under the terms of the GNU Lesser General Public      //
 
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    //  License as published by the Free Software Foundation; either    //
 
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    //  version 2.1 of the License, or (at your option) any later       //
 
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    //  version.                                                        //
 
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    //                                                                  //
 
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    //  This library is distributed in the hope that it will be         //
 
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    //  useful, but WITHOUT ANY WARRANTY; without even the implied      //
 
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    //  warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR         //
 
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    //  PURPOSE. See the GNU Lesser General Public License for more     //
 
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    //  details.                                                        //
 
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    //                                                                  //
 
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    //  You should have received a copy of the GNU Lesser General       //
 
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    //  Public License along with this library; if not, write to the    //
 
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    //  Free Software Foundation, Inc., 59 Temple Place, Suite 330,     //
 
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    //  Boston, MA 02111-1307, USA.                                     //
 
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    //                                                                  //
 
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    //  Author contact: P.H.Welch@kent.ac.uk                             //
 
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    //                                                                  //
 
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    //                                                                  //
 
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    //////////////////////////////////////////////////////////////////////
 
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package org.jcsp.lang;
 
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/**
 
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 * @author P.H. Welch
 
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 */
 
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class CrewServer implements CSProcess
 
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{
 
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    public static final int READER = 0;
 
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    public static final int WRITER = 1;
 
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    private final AltingChannelInputInt request;
 
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    private final AltingChannelInputInt writerControl;
 
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    private final AltingChannelInputInt readerRelease;
 
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    ///TODO change this to use poisoning of the above channels, once poison is added
 
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    private final AltingChannelInputInt poison;
 
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   public CrewServer(final AltingChannelInputInt request,
 
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                     final AltingChannelInputInt writerControl,
 
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                     final AltingChannelInputInt readerRelease,
 
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                     final AltingChannelInputInt poison)
 
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   {
 
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       this.request = request;
 
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       this.writerControl = writerControl;
 
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       this.readerRelease = readerRelease;
 
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       this.poison = poison;
 
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   }
 
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    public void run()
 
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    {
 
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        int nReaders = 0;
 
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        final Alternative altMain =
 
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            new Alternative(new Guard[] {readerRelease, request, poison});
 
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        final int MAIN_READER_RELEASE = 0;
 
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        final int MAIN_REQUEST = 1;
 
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        final int MAIN_POISON = 2;
 
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        final Alternative altWriteComplete =
 
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            new Alternative(new Guard[] {writerControl, poison});
 
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        final int WC_WRITER_CONTROL = 0;
 
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        final int WC_POISON = 1;
 
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        final Alternative altReadComplete =
 
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            new Alternative(new Guard[] {readerRelease, poison});
 
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        final int RC_READER_RELEASE = 0;
 
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        final int RC_POISON = 1;
 
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        while (true)
 
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        {
 
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            // invariant : (nReaders is the number of current readers) and (there are no writers)
 
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            switch (altMain.priSelect())
 
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            {
 
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            case MAIN_READER_RELEASE:
 
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                readerRelease.read();
 
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                nReaders--;
 
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                break;
 
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            case MAIN_REQUEST:
 
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                switch (request.read())
 
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                {
 
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                case READER:
 
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                    nReaders++;
 
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                    break;
 
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                case WRITER:
 
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                    int n = nReaders; // tmp
 
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                    for (int i = 0; i < n; i++)
 
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                    {
 
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                        switch (altReadComplete.priSelect())
 
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                        {
 
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                        case RC_READER_RELEASE:
 
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                            readerRelease.read();
 
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                            nReaders--; // tmp
 
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                            break;
 
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                        case RC_POISON:
 
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                            poison.read(); // let the finalizer complete
 
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                            return;
 
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                        }
 
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                    }
 
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                    nReaders = 0;
 
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                    writerControl.read(); // let writer start writing
 
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                    switch (altWriteComplete.priSelect())
 
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                    {
 
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                    case WC_WRITER_CONTROL:
 
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                        writerControl.read(); // let writer finish writing
 
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                        break;
 
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                    case WC_POISON:
 
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                        poison.read(); // let the finalizer complete
 
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                        return;
 
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                    }
 
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                    break;
 
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                }
 
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                break;
 
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            case MAIN_POISON:
 
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                poison.read(); // let the finalizer complete
 
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                return;
 
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            }
 
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        }
 
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    }
 
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}