001/* Lempel-Ziv decoder.
002
003 Copyright (c) 2004-2014 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.actor.lib.comm;
029
030import java.util.LinkedList;
031
032import ptolemy.actor.lib.Transformer;
033import ptolemy.data.BooleanToken;
034import ptolemy.data.IntToken;
035import ptolemy.data.Token;
036import ptolemy.data.expr.Parameter;
037import ptolemy.data.type.BaseType;
038import ptolemy.kernel.CompositeEntity;
039import ptolemy.kernel.util.IllegalActionException;
040import ptolemy.kernel.util.NameDuplicationException;
041
042///////////////////////////////////////////////////////////////////
043//// Lempel-Ziv decoder.
044
045/**
046 Lempel-Ziv decoder.
047
048 @see LempelZivCoder
049 @author Ye Zhou
050 @version $Id$
051 @since Ptolemy II 4.1
052 @Pt.ProposedRating Red (zhouye)
053 @Pt.AcceptedRating Red (cxh)
054 */
055public class LempelZivDecoder extends Transformer {
056    /** Construct an actor with the given container and name.
057     *  The output and trigger ports are also constructed.
058     *  @param container The container.
059     *  @param name The name of this actor.
060     *  @exception IllegalActionException If the entity cannot be contained
061     *   by the proposed container.
062     *  @exception NameDuplicationException If the container already has an
063     *   actor with this name.
064     */
065    public LempelZivDecoder(CompositeEntity container, String name)
066            throws NameDuplicationException, IllegalActionException {
067        super(container, name);
068
069        // Declare port types.
070        input.setTypeEquals(BaseType.INT);
071        new Parameter(input, "tokenConsumptionRate", new IntToken(2));
072        output.setTypeEquals(BaseType.BOOLEAN);
073    }
074
075    /** Decode the Lempel-Ziv code while generating the decode book.
076     *  The decode book should be same as the code book of the
077     *  corresponding Lempel-Ziv encoder.
078     *  @exception IllegalActionException if the input is not a decodable
079     *  Lempel-Ziv code.
080     */
081    @Override
082    public void fire() throws IllegalActionException {
083        super.fire();
084        Token[] inputToken = input.get(0, 2);
085        int oldPhase = ((IntToken) inputToken[0]).intValue();
086        int bit = ((IntToken) inputToken[1]).intValue();
087        String current = (String) _decodeBook.get(oldPhase);
088
089        if (bit == 0) {
090            current = current + "0";
091        } else if (bit == 1) {
092            current = current + "1";
093        } else {
094            throw new IllegalActionException(this,
095                    "This is not a valid Lempel-Ziv code.");
096        }
097
098        _decodeBook.add(current);
099
100        for (int i = 0; i < current.length(); i++) {
101            if (current.charAt(i) == '0') {
102                output.send(0, new BooleanToken(false));
103            } else {
104                output.send(0, new BooleanToken(true));
105            }
106        }
107    }
108
109    /** initialize the actor by creating a decode book that only
110     *  contains one empty string "".
111     *  @exception IllegalActionException If thrown by a super class.
112     */
113    @Override
114    public void initialize() throws IllegalActionException {
115        super.initialize();
116        _decodeBook = new LinkedList();
117        _decodeBook.add("");
118    }
119
120    ///////////////////////////////////////////////////////////////////
121    ////                         private variables                 ////
122    // The Lempel-Ziv decode book.
123    private LinkedList _decodeBook;
124}