001/* A base class for actors that transform an input stream into an output stream.
002
003 Copyright (c) 1998-2014 The Regents of the University of California.
004 All rights reserved.
005 Permission is hereby granted, without written agreement and without
006 license or royalty fees, to use, copy, modify, and distribute this
007 software and its documentation for any purpose, provided that the above
008 copyright notice and the following two paragraphs appear in all copies
009 of this software.
010
011 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
012 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
013 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
014 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
015 SUCH DAMAGE.
016
017 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
018 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
019 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
020 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
021 CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
022 ENHANCEMENTS, OR MODIFICATIONS.
023
024 PT_COPYRIGHT_VERSION_2
025 COPYRIGHTENDKEY
026
027 */
028package ptolemy.domains.pn.lib;
029
030import ptolemy.actor.lib.Transformer;
031import ptolemy.data.IntToken;
032import ptolemy.data.Token;
033import ptolemy.data.expr.Parameter;
034import ptolemy.data.type.BaseType;
035import ptolemy.kernel.CompositeEntity;
036import ptolemy.kernel.util.IllegalActionException;
037import ptolemy.kernel.util.NameDuplicationException;
038
039///////////////////////////////////////////////////////////////////
040//// Starver
041
042/**
043 On each firing, read at most one input token and send it
044 to the output port. When the number of output tokens that
045 have been produced reaches the value given by <i>limit</i>,
046 then do not produce any more outputs.  Subsequent input tokens
047 are consumed and discarded.
048
049 @author Edward A. Lee
050 @version $Id$
051 @since Ptolemy II 6.1
052 @Pt.ProposedRating Green (eal)
053 @Pt.AcceptedRating Red (cxh)
054 */
055public class Starver extends Transformer {
056    /** Construct an actor with the given container and name.
057     *  @param container The container.
058     *  @param name The name of this actor.
059     *  @exception IllegalActionException If the actor cannot be contained
060     *   by the proposed container.
061     *  @exception NameDuplicationException If the container already has an
062     *   actor with this name.
063     */
064    public Starver(CompositeEntity container, String name)
065            throws NameDuplicationException, IllegalActionException {
066        super(container, name);
067        limit = new Parameter(this, "limit");
068        limit.setTypeEquals(BaseType.INT);
069        limit.setExpression("1");
070    }
071
072    ///////////////////////////////////////////////////////////////////
073    ////                     ports and parameters                  ////
074
075    /** The limit on the number of tokens that can be transferred
076     *  from the input to the output.  This is an integer that
077     *  defaults to 1. If the value is negative, then there is no
078     *  limit.
079     */
080    public Parameter limit;
081
082    ///////////////////////////////////////////////////////////////////
083    ////                         public methods                    ////
084
085    /** Read at most one input token, and if the number of outputs
086     *  has not yet exceeded the value given by <i>limit</i>, then
087     *  produce that token on the output.
088     *  @exception IllegalActionException Not thrown in this base class.
089     */
090    @Override
091    public void fire() throws IllegalActionException {
092        super.fire();
093        Token token = null;
094        if (input.hasToken(0)) {
095            token = input.get(0);
096        }
097        int limitValue = ((IntToken) limit.getToken()).intValue();
098        if (token != null && (limitValue < 0 || _count < limitValue)) {
099            output.send(0, token);
100            _count++;
101        }
102    }
103
104    /** Initialize this actor by setting the count of outputs to zero.
105     *  @exception IllegalActionException If a derived class throws it.
106     */
107    @Override
108    public void initialize() throws IllegalActionException {
109        super.initialize();
110        _count = 0;
111    }
112
113    ///////////////////////////////////////////////////////////////////
114    ////                         public methods                    ////
115
116    /** The count of outputs that have been produced. */
117    private int _count;
118}