001/* Huffman 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 ptolemy.data.ArrayToken;
031import ptolemy.data.BooleanToken;
032import ptolemy.data.Token;
033import ptolemy.data.type.ArrayType;
034import ptolemy.data.type.BaseType;
035import ptolemy.kernel.CompositeEntity;
036import ptolemy.kernel.util.IllegalActionException;
037import ptolemy.kernel.util.InternalErrorException;
038import ptolemy.kernel.util.NameDuplicationException;
039import ptolemy.kernel.util.Workspace;
040
041///////////////////////////////////////////////////////////////////
042//// HuffmanCoder
043
044/**
045 Given a probability distribution and the corresponding alphabet,
046 decode the input using Huffman code and send the result to the output
047 port. Its base class HuffmanBasic generates the code book.
048 The decoder simply decode the input according to this code book.
049
050 @see HuffmanBasic
051 @see HuffmanCoder
052 @author Ye Zhou
053 @version $Id$
054 @since Ptolemy II 4.1
055 @Pt.ProposedRating Red (zhouye)
056 @Pt.AcceptedRating Red (cxh)
057 */
058public class HuffmanDecoder extends HuffmanBasic {
059    /** Construct an actor with the given container and name.
060     *  The output and trigger ports are also constructed.
061     *  @param container The container.
062     *  @param name The name of this actor.
063     *  @exception IllegalActionException If the entity cannot be contained
064     *   by the proposed container.
065     *  @exception NameDuplicationException If the container already has an
066     *   actor with this name.
067     */
068    public HuffmanDecoder(CompositeEntity container, String name)
069            throws NameDuplicationException, IllegalActionException {
070        super(container, name);
071
072        // Declare port types.
073        output.setTypeAtLeast(ArrayType.elementType(alphabet));
074        input.setTypeEquals(BaseType.BOOLEAN);
075    }
076
077    ///////////////////////////////////////////////////////////////////
078    ////                         public methods                    ////
079
080    /** Clone the actor into the specified workspace. This calls the
081     *  base class and then creates new ports and parameters.
082     *  @param workspace The workspace for the new object.
083     *  @return A new actor.
084     *  @exception CloneNotSupportedException If a derived class contains
085     *   an attribute that cannot be cloned.
086     */
087    @Override
088    public Object clone(Workspace workspace) throws CloneNotSupportedException {
089        HuffmanDecoder newObject = (HuffmanDecoder) super.clone(workspace);
090        try {
091            newObject.output
092                    .setTypeAtLeast(ArrayType.elementType(newObject.alphabet));
093        } catch (IllegalActionException e) {
094            // Should have been caught before.
095            throw new InternalErrorException(e);
096        }
097        return newObject;
098    }
099
100    /** Generate the Huffman codebook for the given <i>pmf</i>, and
101     *  encode the input into booleans and send them to the output port.
102     *  @exception IllegalActionException If the input is not a decodable code.
103     */
104    @Override
105    public void fire() throws IllegalActionException {
106        super.fire();
107
108        ArrayToken alphabetArrayToken = (ArrayToken) alphabet.getToken();
109        Token[] alphabetTokens = new Token[_pmf.length];
110
111        for (int i = 0; i < _pmf.length; i++) {
112            alphabetTokens[i] = alphabetArrayToken.getElement(i);
113        }
114
115        // Get the input token. Ready for output.
116        if (!input.hasToken(0) && !_code.equals("")) {
117            throw new IllegalActionException(this,
118                    "This is not a decodable code.");
119        }
120
121        BooleanToken inputToken = (BooleanToken) input.get(0);
122
123        if (inputToken.booleanValue()) {
124            _code = _code + "1";
125        } else {
126            _code = _code + "0";
127        }
128
129        // Find the codeword in the code book.
130        for (int i = 0; i < _pmf.length; i++) {
131            if (_code.equals(_codeBook[i])) {
132                output.send(0, alphabetTokens[i]);
133                _code = "";
134                break;
135            }
136        }
137    }
138
139    /** Initialize the actor. set the current input string to be empty.
140     */
141    @Override
142    public void initialize() throws IllegalActionException {
143        super.initialize();
144        _code = "";
145    }
146
147    ///////////////////////////////////////////////////////////////////
148    ////                         private variables                 ////
149    // The current input string, concatenated by input booleans.
150    private String _code = "";
151}