sdrtrunk/src/main/java/io/github/dsheirer/bits/MultiSyncPatternMatcher.java

/*
 *
 *  * ******************************************************************************
 *  * Copyright (C) 2014-2020 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 io.github.dsheirer.bits;

import io.github.dsheirer.dsp.symbol.ISyncDetectListener;
import org.apache.commons.lang3.Validate;
import org.apache.commons.math3.util.FastMath;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.List;

/**
 * Multi-Sync pattern matcher.  Accepts multiple sync detector objects for
 * comparision against the incoming bit stream.
 *
 * Note: works for sync patterns up to 63 bits (integer size - 1 ) long.
 * If a 64 bit or larger sync pattern is applied, then the wrapping feature
 * of the Long.rotate methods will wrap the MSB around to the LSB and
 * corrupt the matching value.
 */
public class MultiSyncPatternMatcher
{
    private final static Logger mLog = LoggerFactory.getLogger(MultiSyncPatternMatcher.class);

    private ISyncDetectListener mSyncDetectListener;
    private int mSyncLossThreshold;
    private int mBitCount;
    private List<ISyncProcessor> mSyncProcessors = new ArrayList<ISyncProcessor>();

    private long mBits = 0;
    private long mMask = 0;

    public MultiSyncPatternMatcher(ISyncDetectListener syncDetectListener, int syncLossThreshold, int syncSize)
    {
        mSyncDetectListener = syncDetectListener;
        mSyncLossThreshold = syncLossThreshold;
        Validate.isTrue(syncSize < 64);

        //Setup a bit mask of all ones the length of the sync pattern
        mMask = (long)((FastMath.pow(2, syncSize)) - 1);
    }

    public void dispose()
    {
        mSyncProcessors.clear();
    }

    /**
     * Processes two bits before checking sync processors for a match.
     */
    public void receive(boolean bit1, boolean bit2)
    {
        mBits = Long.rotateLeft(mBits, 1);

        mBits &= mMask;

        if(bit1)
        {
            mBits += 1;
        }

        mBits = Long.rotateLeft(mBits, 1);

        mBits &= mMask;

        if(bit2)
        {
            mBits += 1;
        }

        mBitCount += 2;

        for(ISyncProcessor processor : mSyncProcessors)
        {
            if(processor.checkSync(mBits))
            {
                mBitCount = 0;
            }
        }

        if(mBitCount > mSyncLossThreshold)
        {
            mSyncDetectListener.syncLost(mBitCount);
            mBitCount = 0;
        }
    }

    /**
     * Returns the number of bit errors for the current value against the sync pattern.
     * @return
     */
    public long getCurrentValue()
    {
        return mBits;
    }

    /**
     * Processes one bit before checking sync processors for a match.
     */
    public void receive(boolean bit)
    {
        mBits = Long.rotateLeft(mBits, 1);

        mBits &= mMask;

        if(bit)
        {
            mBits += 1;
        }

        for(ISyncProcessor processor : mSyncProcessors)
        {
            processor.checkSync(mBits);
        }
    }

    /**
     * Adds a sync processor to receive the bit stream.
     */
    public void add(ISyncProcessor processor)
    {
        mSyncProcessors.add(processor);
    }
}