LempelZivCoder.java example

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ptii-master
/* Lempel-Ziv encoder.

 Copyright (c) 2004-2008 The Regents of the University of California.
 All rights reserved.
 Permission is hereby granted, without written agreement and without
 license or royalty fees, to use, copy, modify, and distribute this
 software and its documentation for any purpose, provided that the above
 copyright notice and the following two paragraphs appear in all copies
 of this software.

 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
 SUCH DAMAGE.

 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
 CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
 ENHANCEMENTS, OR MODIFICATIONS.

 PT_COPYRIGHT_VERSION_2
 COPYRIGHTENDKEY

 */
package ptolemy.actor.lib.comm;

import java.util.LinkedList;

import ptolemy.actor.lib.Transformer;
import ptolemy.data.BooleanToken;
import ptolemy.data.IntToken;
import ptolemy.data.type.BaseType;
import ptolemy.kernel.CompositeEntity;
import ptolemy.kernel.util.IllegalActionException;
import ptolemy.kernel.util.NameDuplicationException;

//////////////////////////////////////////////////////////////////////////
//// LempelZivCoder

/**
 Lempel-Ziv encoder.

 @author Ye Zhou
 @version $Id$
 @since Ptolemy II 4.1
 @Pt.ProposedRating Red (zhouye)
 @Pt.AcceptedRating Red (cxh)
 */
public class LempelZivCoder extends Transformer {
    /** Construct an actor with the given container and name.
     *  The output and trigger ports are also constructed.
     *  @param container The container.
     *  @param name The name of this actor.
     *  @exception IllegalActionException If the entity cannot be contained
     *   by the proposed container.
     *  @exception NameDuplicationException If the container already has an
     *   actor with this name.
     */
    public LempelZivCoder(CompositeEntity container, String name)
            throws NameDuplicationException, IllegalActionException {
        super(container, name);

        // Declare port types.
        input.setTypeEquals(BaseType.BOOLEAN);
        output.setTypeEquals(BaseType.INT);
    }

    /** Encode the input into Lempel-Ziv code while generating the
     *  code book.
     *  @exception IllegalActionException if the super class throws it.
     */
    public void fire() throws IllegalActionException {
        super.fire();
        if (input.hasToken(0)) {
            boolean inputValue = ((BooleanToken) input.get(0)).booleanValue();
            _current = _current + (inputValue ? "1" : "0");

            int index = _codeBook.indexOf(_current);

            if (index == -1) {
                output.send(0, new IntToken(_previousIndex));
                output.send(0, new IntToken(inputValue ? 1 : 0));
                _codeBook.add(_current);
                _current = "";
                _previousIndex = 0;
            } else {
                _previousIndex = index;
            }
        } /*else if (_current != "") {
                              // FIXME: This part of output can not be produced.
                              // The last few input booleans can not be encoded and produced.
                              // The input probably should be a string or frame of booleans.
                              // I.e., the actor knows whether the current input is the last
                              // input token, probably by giving a parameter to specify the
                              // length of the input.
                              int length = _current.length();
                              _previousIndex =
                              _codeBook.indexOf(_current.substring(0, length - 2));
                              output.send(0, new IntToken(_previousIndex));
                              if (_current.endsWith("1")) {
                              output.send(0, new IntToken(1));
                              } else {
                              output.send(0, new IntToken(0));
                              }
                              }*/
    }

    /** Initialize the actor by creating the code book containing
     *  only one empty string "".
     */
    public void initialize() {
        _codeBook = new LinkedList();
        _codeBook.add("");
        _current = "";
        _previousIndex = 0;
    }

    ///////////////////////////////////////////////////////////////////
    ////                         private variables                 ////
    // The Lempel-Ziv code book.
    private LinkedList _codeBook;

    // The current string, concatenated by the inputs.
    private String _current;

    // The index of the previous string in the code book.
    // current string is previous string appended by "1" or "0",
    // depending on whether the current input is true or false.
    private int _previousIndex = 0;
}