001/* A merge actor for the DE domain.
002
003 Copyright (c) 1997-2018 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.de.lib;
029
030import java.util.LinkedList;
031import java.util.Queue;
032
033import ptolemy.data.BooleanToken;
034import ptolemy.data.Token;
035import ptolemy.data.expr.Parameter;
036import ptolemy.data.type.BaseType;
037import ptolemy.kernel.CompositeEntity;
038import ptolemy.kernel.util.IllegalActionException;
039import ptolemy.kernel.util.NameDuplicationException;
040import ptolemy.kernel.util.Workspace;
041
042///////////////////////////////////////////////////////////////////
043//// Merge
044
045/**
046 A timed merge actor for the DE domain. It merges a set of input signals
047 into a single output signal based on the order of the tags
048 associated with the events of signals. A tag is a tuple of a timestamp
049 (as an instance of Time) and a microstep or index (as non-negative integer).
050 Tags have a lexicographic order.
051 <p>
052 This actor has an input port (a multiport) and an output port
053 (a single port). The types of the ports are undeclared and will be
054 resolved by the type resolution mechanism, with the constraint that
055 the output type must be greater than or equal to the input type.
056 <p>
057 There is a boolean parameter <i>discardEvents</i> associated
058 with this actor, which decides how to handle simultaneously
059 available inputs.
060 <p>
061 If the <i>discardEvents</i> parameter is configured to true,
062 then each time this actor fires, it reads the first
063 available token from an input channel and send it to the output
064 port.  Then this actor discards all the remaining inputs in the rest of
065 channels.
066 <p>
067 If the <i>discardEvents</i> parameter is configured to false (the default),
068 then the handling of simultaneous events is a bit more subtle.
069 On each firing, it reads at most one input from each input channel
070 in the order of the channels and puts them on a queue to be produced
071 as an output. It then takes the first token (the oldest one) from the queue
072 and produces it on the output. If after this firing the queue is not empty,
073 then it requests a refiring at the current time.
074
075 @author Edward A. Lee, Haiyang Zheng
076 @version $Id$
077 @since Ptolemy II 0.4
078 @Pt.ProposedRating Green (hyzheng)
079 @Pt.AcceptedRating Green (hyzheng)
080 */
081public class Merge extends DETransformer {
082    /** Construct an actor in the specified container with the specified
083     *  name. Create ports and make the input port a multiport.
084     *  @param container The container.
085     *  @param name The name.
086     *  @exception NameDuplicationException If an actor
087     *   with an identical name already exists in the container.
088     *  @exception IllegalActionException If the actor cannot be contained
089     *   by the proposed container.
090     */
091    public Merge(CompositeEntity container, String name)
092            throws NameDuplicationException, IllegalActionException {
093        super(container, name);
094        input.setMultiport(true);
095
096        discardEvents = new Parameter(this, "discardEvents");
097        discardEvents.setExpression("false");
098        discardEvents.setTypeEquals(BaseType.BOOLEAN);
099
100        _attachText("_iconDescription",
101                "<svg>\n" + "<polygon points=\"-10,20 10,10 10,-10, -10,-20\" "
102                        + "style=\"fill:green\"/>\n" + "</svg>\n");
103    }
104
105    ///////////////////////////////////////////////////////////////////
106    ////                       ports and parameters                ////
107
108    /** A flag to indicate whether the input events can be discarded.
109     *  Its default value is false.
110     */
111    public Parameter discardEvents;
112
113    ///////////////////////////////////////////////////////////////////
114    ////                         public methods                    ////
115
116    /** Clone this actor into the specified workspace.
117     *  @param workspace The workspace for the cloned object.
118     *  @exception CloneNotSupportedException If cloned ports cannot have
119     *   as their container the cloned entity (this should not occur), or
120     *   if one of the attributes cannot be cloned.
121     *  @return A new ComponentEntity.
122     */
123    @Override
124    public Object clone(Workspace workspace) throws CloneNotSupportedException {
125        Merge newObject = (Merge) super.clone(workspace);
126        newObject._queue = null;
127        return newObject;
128    }
129
130    /** Read the first available tokens from an input channel and
131     *  send them to the output port. If the discardEvents parameter
132     *  is true, consume all the available tokens of the other channels
133     *  and discard them. Otherwise, if the other channels have tokens,
134     *  request a refiring at the current time to process them.
135     *  @exception IllegalActionException If there is no director, or
136     *  the input can not be read, or the output can not be sent.
137     */
138    @Override
139    public void fire() throws IllegalActionException {
140        super.fire();
141        boolean discard = ((BooleanToken) discardEvents.getToken())
142                .booleanValue();
143        boolean foundInput = false;
144
145        // If tokens can be discarded, this actor sends
146        // out the first available tokens only. It discards all
147        // remaining tokens from other input channels.
148        // Otherwise, this actor handles one channel at each firing
149        // and requests refiring at the current time to handle the
150        // the remaining channels that have tokens.
151        for (int i = 0; i < input.getWidth(); i++) {
152            if (input.hasNewToken(i)) {
153                // This output will be produced regardless of discard status.
154                if (!discard || !foundInput) {
155                    _queue.offer(input.get(i));
156                }
157                foundInput = true;
158            }
159        }
160        if (!_queue.isEmpty()) {
161            output.send(0, _queue.poll());
162            if (!_queue.isEmpty()) {
163                // Refiring the actor to handle the other tokens.
164                getDirector().fireAt(this, getDirector().getModelTime());
165            }
166        }
167    }
168
169    /** Initialize this actor by creating a new queue for pending outputs.
170     *  @exception IllegalActionException If a superclass throws it.
171     */
172    @Override
173    public void initialize() throws IllegalActionException {
174        super.initialize();
175        _queue = new LinkedList<Token>();
176    }
177
178    ///////////////////////////////////////////////////////////////////
179    //                        private variables                      //
180
181    // Queue of outputs to be produced.
182    private Queue<Token> _queue = null;
183}