/*******************************************************************************
 *     SDR Trunk 
 *     Copyright (C) 2014 Dennis Sheirer
 * 
 *     This program is free software: you can redistribute it and/or modify
 *     it under the terms of the GNU General Public License as published by
 *     the Free Software Foundation, either version 3 of the License, or
 *     (at your option) any later version.
 * 
 *     This program is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *     GNU General Public License for more details.
 * 
 *     You should have received a copy of the GNU General Public License
 *     along with this program.  If not, see <http://www.gnu.org/licenses/>
 ******************************************************************************/
package dsp;

import sample.Listener;

public class NRZDecoder implements Listener<Boolean>
{
	public final static boolean MODE_NORMAL = true;
	public final static boolean MODE_INVERTED = false;
	
	private Listener<Boolean> mListener;
	private boolean mMode = MODE_NORMAL;
	private boolean mPrevious;

	/**
	 * Non Return To Zero (NRZ) and NRZ Inverted (NRZ-I) Decoder.
	 * 
	 * Use default constructor for NRZ output.  Use the alternate constructor
	 * with the MODE_INVERTED argument for NRZ-I output.
	 * 
	 * Performs XOR of incoming bit with previous output and sends the result
	 * to the registered listener.  
	 */
	public NRZDecoder( boolean mode )
	{
		mMode = mode;
	}
	
	public NRZDecoder()
	{
		this( MODE_NORMAL );
	}
	
	public void dispose()
	{
		mListener = null;
	}

	@Override
    public void receive( Boolean bit )
    {
		boolean result = mPrevious ^ bit;
		
		if( mListener != null )
		{
			mListener.receive( mMode ? result : !result );
		}
		
		mPrevious = result;
    }

	public void setListener( Listener<Boolean> listener )
	{
		mListener = listener;
	}
	
	public void removeListener( Listener<Boolean> listener )
	{
		mListener = null;
	}
}