P25 - added Header Data Unit (HDU) error detection and correction with Golay(18,6,8) and ReedSolomon(36,20,17).

src/edac/Golay18.java

@@ -0,0 +1,54 @@
+package edac;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import bits.BinaryMessage;
+
+/*******************************************************************************
+ *     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
+ ******************************************************************************/
+
+/**
+ * Golay 18/6/8 decoder.  Uses the Golay24 edac class to perform edac on Golay
+ * 18 messages by treating the Golay 18 message as a Golay 24 message with the 
+ * left-most 6 bits set to zero.
+ */
+public class Golay18
+{
+	private final static Logger mLog = LoggerFactory.getLogger( Golay18.class );
+
+	/**
+	 * Performs error detection and correction.
+	 */
+	public static void checkAndCorrect( BinaryMessage message, int startIndex )
+	{
+		int value = message.getInt( startIndex, startIndex + 17 );
+
+		BinaryMessage temp = new BinaryMessage( 24 );
+		temp.load( 6, 18, value );
+
+		BinaryMessage corrected = Golay24.checkAndCorrect( temp, 0 );
+
+		int correctedValue = corrected.getInt( 6, 23 );
+		
+		message.load( startIndex, 18, correctedValue );
+	}
+}

src/edac/Golay23.java

@@ -14,7 +14,7 @@ public class Golay23
 	};
 
 	/**
-	 * Implements Golay(23,11,7) error detection and correction.  Returns the
+	 * Implements Golay(23,12,7) error detection and correction.  Returns the
 	 * number of detected errors.  If the error count is less than or equal to
 	 * the max correctable errors (3), then the error bits are corrected.  
 	 * Otherwise the message is left intact and an error count greater than 3

src/edac/ReedSolomon_63_47_17.java

@@ -18,12 +18,12 @@ package edac;
  *     along with this program.  If not, see <http://www.gnu.org/licenses/>
  ******************************************************************************/
 
-public class ReedSolomon_24_12_13 extends BerlekempMassey_63
+public class ReedSolomon_63_47_17 extends BerlekempMassey_63
 {
 	/**
 	 * Reed-Solomon RS(24,12,13) decoder
 	 */
-	public ReedSolomon_24_12_13()
+	public ReedSolomon_63_47_17()
     {
 		/* TT = 6 = maximum correctable bit errors */
 	    super( 6 );