Adds Galois 24/12/7 error correction and detection for use with P25 decoder.

src/bits/BitSetBuffer.java

@@ -19,9 +19,14 @@ package bits;
 
 import java.util.BitSet;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 public class BitSetBuffer extends BitSet
 {
-    private static final long serialVersionUID = 1L;
+	private final static Logger mLog = LoggerFactory.getLogger( BitSetBuffer.class );
+
+	private static final long serialVersionUID = 1L;
 
     /**
      * Logical (ie constructed) size of this bitset, despite the actual size of
@@ -524,4 +529,99 @@ public class BitSetBuffer extends BitSet
 
 		return buffer;
 	}
+	
+	/**
+	 * Left rotates the bits between start and end indices, number of places.
+	 */
+	public void rotateLeft( int places, int startIndex, int endIndex )
+	{
+		for( int x = 0; x < places; x++ )
+		{
+			rotateLeft( startIndex, endIndex );
+		}
+	}
+	
+	/**
+	 * Left rotates the bits between start and end and wraps the left-most
+	 * bit around to the end.
+	 */
+	public void rotateLeft( int startIndex, int endIndex )
+	{
+		boolean wrapBit = get( startIndex );
+		
+		for( int x = startIndex; x < endIndex; x++ )
+		{
+			if( get( x + 1 ) )
+			{
+				set( x );
+			}
+			else
+			{
+				clear( x );
+			}
+		}
+		
+		if( wrapBit )
+		{
+			set( endIndex );
+		}
+		else
+		{
+			clear( endIndex );
+		}
+	}
+
+	/**
+	 * Right rotates the bits between start and end indices, number of places.
+	 */
+	public void rotateRight( int places, int startIndex, int endIndex )
+	{
+		for( int x = 0; x < places; x++ )
+		{
+			rotateRight( startIndex, endIndex );
+		}
+	}
+	
+	/**
+	 * Right rotates the bits between start and end and wraps the right-most
+	 * bit around to the start.
+	 */
+	public void rotateRight( int startIndex, int endIndex )
+	{
+		boolean wrapBit = get( endIndex );
+		
+		for( int x = endIndex - 1; x >= startIndex; x-- )
+		{
+			if( get( x ) )
+			{
+				set( x + 1 );
+			}
+			else
+			{
+				clear( x + 1 );
+			}
+		}
+		
+		if( wrapBit )
+		{
+			set( startIndex );
+		}
+		else
+		{
+			clear( startIndex );
+		}
+	}
+	
+	/**
+	 * Performs exclusive or of the value against this bitset starting at the
+	 * offset position using width bits from the value.
+	 */
+	public void xor( int offset, int width, int value )
+	{
+		BitSetBuffer mask = new BitSetBuffer( this.size() );
+		
+		mask.load( offset, width, value );
+		
+		this.xor( mask );
+	}
 }

src/controller/activity/MessageActivityModel.java

@@ -52,9 +52,9 @@ public class MessageActivityModel extends AbstractTableModel
 	
 	private boolean mNewMessagesFirst = true;
 	
-	private FilterSet mMessageFilter;
+	private FilterSet<Message> mMessageFilter;
 	
-	public MessageActivityModel( FilterSet messageFilter )
+	public MessageActivityModel( FilterSet<Message> messageFilter )
 	{
 		mMessageFilter = messageFilter;
 	}
@@ -82,7 +82,7 @@ public class MessageActivityModel extends AbstractTableModel
 		});
 	}
 	
-	public FilterSet getMessageFilter()
+	public FilterSet<Message> getMessageFilter()
 	{
 		return mMessageFilter;
 	}

src/controller/activity/MessageActivityPanel.java

@@ -273,7 +273,7 @@ public class MessageActivityPanel extends JPanel implements ChannelEventListener
 								"[grow,fill][][]" ) );
 
 						@SuppressWarnings( "unchecked" )
-                        FilterSet<Message> filter = 
+                        FilterSet<Message> filter = (FilterSet<Message>)
 								mDisplayedChannel
 								.getProcessingChain().getChannelState()
 								.getMessageActivityModel().getMessageFilter();

src/crc/CRCP25.java

@@ -375,10 +375,7 @@ public class CRCP25
     public static long getLongChecksum( BitSetBuffer message, 
     				int crcStart, int crcLength )
     {
-    	int[] checksumIndexes = BitSetBuffer
+    	return message.getLong( crcStart, crcStart + crcLength );
-    			.getFieldIndexes( crcStart, crcLength, false );
-
-    	return message.getLong( checksumIndexes );
     }
 
 	/**
@@ -387,10 +384,7 @@ public class CRCP25
     public static int getIntChecksum( BitSetBuffer message, 
     				int crcStart, int crcLength )
     {
-    	int[] checksumIndexes = BitSetBuffer
+    	return message.getInt( crcStart, crcStart + crcLength );
-    			.getFieldIndexes( crcStart, crcLength, false );
-    	
-    	return message.getInt( checksumIndexes );
     }
 
     /**

src/crc/CRCUtil.java

@@ -50,12 +50,10 @@ public class CRCUtil
 			
 			message.set( x );
 			
-			message = decode( message, messageSize, polynomial, crcSize );
+			message = decode( message, 0, messageSize, polynomial, crcSize );
 			
 			long checksum = message.getLong( checksumIndexes );
 			
-			mLog.debug( "Index " + x + " Checksum:" + Long.toHexString( checksum ) );
-			
 			crcTable[ x ] = checksum;
 		}
 		
@@ -70,6 +68,48 @@ public class CRCUtil
 		return crcTable;
 	}
 
+	/**
+	 * Generates the checksum table and treats the final bit of each check value
+	 * as a parity bit that complies with the request parity argument.
+	 */
+	public static long[] generate( int messageSize,
+								   int crcSize,
+								   long polynomial,
+								   long initialFill,
+								   boolean includeCRCBitErrors,
+								   Parity parity )
+	{
+		long[] table = generate( messageSize, crcSize, polynomial, initialFill, 
+				includeCRCBitErrors );
+
+		if( parity == Parity.NONE )
+		{
+			return table;
+		}
+		else
+		{
+			for( int x = 0; x < table.length; x++ )
+			{
+				table[ x ] <<= 1;
+				
+				if( parity( table[ x ] ) != parity )
+				{
+					table[ x ] ^= 0x1;
+				}
+			}
+			
+			return table;
+		}
+	}
+	
+	public enum Parity{ EVEN, ODD, NONE };
+
+	/* Determines the parity (number of 1 bits) for the value */
+	public static Parity parity( long value ) 
+	{ 
+		return Long.bitCount( value ) % 2 == 0 ? Parity.EVEN : Parity.ODD;
+	} 
+	
 
 	/**
 	 * Performs binary division of the polynomial into the message for bits
@@ -91,14 +131,13 @@ public class CRCUtil
 	 * placed in the crc field which starts at index messageLength
 	 */
 	public static BitSetBuffer decode( BitSetBuffer message,
+									   int messageStart,
 									   int messageSize,
 									   long polynomial,
 									   int crcSize )
 	{
-		int MESSAGE_START = 0;
+		for (int i = message.nextSetBit( messageStart ); 
-		
+				 i >= messageStart && i < messageSize; 
-		for (int i = message.nextSetBit( MESSAGE_START ); 
-				 i >= MESSAGE_START && i < messageSize; 
 				 i = message.nextSetBit( i+1 ) )
 		{
 			BitSetBuffer polySet = new BitSetBuffer( crcSize + i + 1 );
@@ -115,17 +154,9 @@ public class CRCUtil
 	{
 		mLog.debug( "Starting" );
 
-		long polynomial = 0x104C11DB7l;
+		long polynomial = 0xC75l;
 
-//		String raw = "101111101110000000000000001101111110001100111100001110000111000011111111101010111011000011100100";
+		long[] table = generate( 12, 11, polynomial, 0x0, true, Parity.NONE );
-//		BitSetBuffer buffer = BitSetBuffer.load( raw );
-//		mLog.debug( "ORIG:" + buffer.toString() );
-//		BitSetBuffer processed = decode( buffer, 64, polynomial, 32 );
-//		mLog.debug( "PROC:" + processed.toString() );
-
-		long[] table = generate( 256, 32, 0x104C11DB7l, 0xFFFFFFFFl, true );
-		
-//		long[] table = generate( 80, 16, 0x11021l, 0xFFFFl, true );
 		mLog.debug( toCodeArray( table ) );
 		mLog.debug( "Finished" );
 	}

src/crc/Galois24.java

@@ -0,0 +1,174 @@
+package crc;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import bits.BitSetBuffer;
+
+/*******************************************************************************
+ *     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/>
+ *     -----------------------------------------------------------------------
+ *     Galois24 decoder based on Hank Wallace's tutorial/algorithm located at:
+ *     http://www.aqdi.com/golay.htm
+ ******************************************************************************/
+
+/**
+ * Galois 24/12/7 decoder
+ */
+public class Galois24
+{
+	private final static Logger mLog = LoggerFactory.getLogger( Galois24.class );
+
+	/**
+	 * Galois 24/12 checksums generated by:
+	 * 
+	 * CRCUtil.generate( 12, 11, 0xC75, 0x0, true );
+	 */
+	public static final int[] CHECKSUMS = new int[]
+	{
+	    0x63A, 0x31D, 0x7B4, 0x3DA, 0x1ED, 0x6CC, 0x366, 0x1B3, 
+	    0x6E3, 0x54B, 0x49F, 0x475, 0x400, 0x200, 0x100, 0x080, 
+	    0x040, 0x020, 0x010, 0x008, 0x004, 0x002, 0x001 
+	};
+
+	private static int calculateChecksum( BitSetBuffer message, int startIndex )
+	{
+		int calculated = 0; //Starting value
+
+		/* Iterate the set bits and XOR running checksum with lookup value */
+		for (int i = message.nextSetBit( startIndex ); 
+				 i >= startIndex && i < startIndex + 12; 
+				 i = message.nextSetBit( i+1 ) ) 
+		{
+			calculated ^= CHECKSUMS[ i - startIndex ];
+		}
+		
+		return calculated;
+	}
+	
+	public static boolean checkAndCorrect( BitSetBuffer message, int startIndex )
+	{
+		boolean parityError = message.cardinality() % 2 != 0;
+		
+		int syndrome = getSyndrome( message, startIndex );
+		
+		/* No errors */
+		if( syndrome == 0 )
+		{
+			if( parityError )
+			{
+				message.flip( startIndex + 23 );
+			}
+			
+			return true;
+		}
+
+		/* Get original message value */
+		int original = message.getInt( 0, 22 );
+		
+		int index = -1;
+		int syndromeWeight = 3;
+		int maskBit = 0;
+		int errors = 0;
+		
+		while( index < 23 )
+		{
+			if( index != -1 )
+			{
+				/* restore the previous flipped bit */
+				if( index > 0 )
+				{
+					message.flip( maskBit - 1 );
+				}
+				
+				message.flip( maskBit );
+				
+				syndromeWeight = 2;
+			}
+			
+			syndrome = getSyndrome( message, startIndex );
+			
+			if( syndrome > 0 )
+			{
+				for( int i = 0; i < 23; i++ )
+				{
+				
+					errors = Integer.bitCount( syndrome );
+					
+					if( errors <= syndromeWeight )
+					{
+						message.xor( 12, 11, syndrome );
+						
+						message.rotateRight( i, startIndex, startIndex + 22 );
+
+						if( index >= 0 )
+						{
+							errors ++;
+						}
+
+						int corrected = message.getInt( 0, 22 );
+						
+						if( Integer.bitCount( original ^ corrected ) > 3 )
+						{
+							return false;
+						}
+						
+						return true;
+					}
+					else
+					{
+						message.rotateLeft( startIndex, startIndex + 22 );
+						syndrome = getSyndrome( message, startIndex );
+					}
+				}
+				
+				index++;
+			}
+		}
+
+		return false;
+	}
+	
+	private static int getSyndrome( BitSetBuffer message, int startIndex )
+	{
+		int calculated = calculateChecksum( message, startIndex );
+		
+		int checksum = message.getInt( startIndex + 12, startIndex + 22 );
+
+		return ( checksum ^ calculated );
+	}
+	
+	public static void main( String[] args )
+	{
+		/* NID + TDULC message */
+		String msg = "0010011000001111100100110011000100111010000111010001000000000000000000000000000000000000000000000100101010010111000000000000000000000000000010010111101111111111000000000000000000000000000000000000000000000000000110001011100001111101010110111001001011010010101111010010000010110011101111111100100000010001111100011010010100001101111001111001100000111000";
+
+		BitSetBuffer message = BitSetBuffer.load( msg );
+
+		mLog.debug( "MSG: " + message.toString() );
+
+		int x = 64;
+		
+		while( x < msg.length() )
+		{
+			boolean passes = checkAndCorrect( message, x );
+
+			mLog.debug( "X:" + x + " Pass:" + passes );
+			x += 24;
+		}
+	}
+}