Updates pull request from Roman Tsypuk to convert the build system from

ant to gradle.  Removes linux and windows application launch scripts and
produces an executable jar with all resources included.

src/main/java/io/github/dsheirer/edac/Golay24.java

@@ -0,0 +1,167 @@
+package io.github.dsheirer.edac;
+
+import io.github.dsheirer.bits.BinaryMessage;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/*******************************************************************************
+ *     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 Golay24
+{
+	private final static Logger mLog = LoggerFactory.getLogger( Golay24.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( BinaryMessage 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;
+	}
+	
+	/**
+	 * Performs error detection and returns a corrected copy of the 24-bit
+	 * message that starts at the start index.
+	 * @param message - source message containing startIndex + 24 bits length
+	 * @param startIndex - start of the 24-bit galois 24 protected bit set
+	 * @return - corrected 24-bit galois value
+	 */
+	public static BinaryMessage checkAndCorrect( BinaryMessage 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 );
+			}
+
+			message.setCRC( CRC.PASSED );
+			
+			return message;
+		}
+
+		/* Get original message value */
+		int original = message.getInt( 0, 22 );
+		
+		int index = -1;
+		int syndromeWeight = 3;
+		int errors = 0;
+		
+		while( index < 23 )
+		{
+			if( index != -1 )
+			{
+				/* restore the previous flipped bit */
+				if( index > 0 )
+				{
+					message.flip( index - 1 );
+				}
+				
+				message.flip( index );
+				
+				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 )
+						{
+							message.setCRC( CRC.FAILED_CRC );
+							
+							return message;
+						}
+						
+						message.setCRC( CRC.PASSED );
+						
+						return message;
+					}
+					else
+					{
+						message.rotateLeft( startIndex, startIndex + 22 );
+						syndrome = getSyndrome( message, startIndex );
+					}
+				}
+				
+				index++;
+			}
+		}
+
+		message.setCRC( CRC.FAILED_CRC );
+		
+		return message;
+	}
+
+	private static int getSyndrome( BinaryMessage message, int startIndex )
+	{
+		int calculated = calculateChecksum( message, startIndex );
+		
+		int checksum = message.getInt( startIndex + 12, startIndex + 22 );
+
+		return ( checksum ^ calculated );
+	}
+}