Finally process the Golay(24,12,8) parity bit.

AMBEFEC.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2010,2014,2016,2018 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2010,2014,2016,2018,2021 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 Mathias Weyland, HB9FRV
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -20,6 +20,7 @@
 #include "Golay24128.h"
 #include "Hamming.h"
 #include "AMBEFEC.h"
+#include "Utils.h"
 
 #include <cstdio>
 #include <cassert>
@@ -792,10 +793,12 @@ unsigned int CAMBEFEC::regenerateIMBE(unsigned char* bytes) const
 
 unsigned int CAMBEFEC::regenerateDStar(unsigned int& a, unsigned int& b) const
 {
+	bool valid;
+
 	unsigned int orig_a = a;
 	unsigned int orig_b = b;
 
-	unsigned int data = CGolay24128::decode24128(a);
+	unsigned int data = CGolay24128::decode24128(a, valid);
 
 	a = CGolay24128::encode24128(data);
 
@@ -804,35 +807,29 @@ unsigned int CAMBEFEC::regenerateDStar(unsigned int& a, unsigned int& b) const
 
 	b ^= p;
 
-	unsigned int datb = CGolay24128::decode24128(b);
+	unsigned int datb = CGolay24128::decode24128(b, valid);
 
 	b = CGolay24128::encode24128(datb);
 
 	b ^= p;
 
-	unsigned int errsA = 0U, errsB = 0U;
-
 	unsigned int v = a ^ orig_a;
-	while (v != 0U) {
-		v &= v - 1U;
-		errsA++;
-	}
+	unsigned int errsA = CUtils::countBits(v);
 
 	v = b ^ orig_b;
-	while (v != 0U) {
-		v &= v - 1U;
-		errsB++;
-	}
+	unsigned int errsB = CUtils::countBits(v);
 
 	return errsA + errsB;
 }
 
 unsigned int CAMBEFEC::regenerateDMR(unsigned int& a, unsigned int& b, unsigned int& c) const
 {
+	bool valid;
+
 	unsigned int orig_a = a;
 	unsigned int orig_b = b;
 
-	unsigned int data = CGolay24128::decode24128(a);
+	unsigned int data = CGolay24128::decode24128(a, valid);
 
 	a = CGolay24128::encode24128(data);
 
@@ -847,19 +844,11 @@ unsigned int CAMBEFEC::regenerateDMR(unsigned int& a, unsigned int& b, unsigned
 
 	b ^= p;
 
-	unsigned int errsA = 0U, errsB = 0U;
-
 	unsigned int v = a ^ orig_a;
-	while (v != 0U) {
-		v &= v - 1U;
-		errsA++;
-	}
+	unsigned int errsA = CUtils::countBits(v);
 
 	v = b ^ orig_b;
-	while (v != 0U) {
-		v &= v - 1U;
-		errsB++;
-	}
+	unsigned int errsB = CUtils::countBits(v);
 
 	if (errsA >= 4U || ((errsA + errsB) >= 6U && errsA >= 2U)) {
 		a = 0xF00292U;

Golay24128.cpp

@@ -1,9 +1,10 @@
 /*
- *   Copyright (C) 2010,2016 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2010,2016,2021 by Jonathan Naylor G4KLX
  *   Copyright (C) 2002 by Robert H. Morelos-Zaragoza. All rights reserved.
  */
 
 #include "Golay24128.h"
+#include "Utils.h"
 
 #include <cstdio>
 #include <cassert>
@@ -1089,20 +1090,23 @@ unsigned int CGolay24128::decode23127(unsigned int code)
 	return code >> 11;
 }
 
-unsigned int CGolay24128::decode24128(unsigned int code)
+unsigned int CGolay24128::decode24128(unsigned int input, bool& valid)
 {
-	return decode23127(code >> 1);
+	unsigned int syndrome = ::get_syndrome_23127(input >> 1);
+	unsigned int error_pattern = DECODING_TABLE_23127[syndrome] << 1;
+
+	unsigned int output = input ^ error_pattern;
+
+	valid = (CUtils::countBits(syndrome) < 3U) || !(CUtils::countBits(output) & 1);
+
+	return output >> 12;
 }
 
-unsigned int CGolay24128::decode24128(unsigned char* bytes)
+unsigned int CGolay24128::decode24128(unsigned char* bytes, bool& valid)
 {
 	assert(bytes != NULL);
 
-	unsigned int code = bytes[0U];
-	code <<= 8;
-	code |= bytes[1U];
-	code <<= 8;
-	code |= bytes[2U];
+	unsigned int code = (bytes[0U] << 16) | (bytes[1U] << 8) | (bytes[2U] << 0);
 
-	return decode23127(code >> 1);
+	return decode24128(code, valid);
 }

Golay24128.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2010,2016 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2010,2016,2021 by Jonathan Naylor G4KLX
  *
  *   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
@@ -25,8 +25,8 @@ class CGolay24128 {
 	static unsigned int encode24128(unsigned int data);
 
 	static unsigned int decode23127(unsigned int code);
-	static unsigned int decode24128(unsigned int code);
-	static unsigned int decode24128(unsigned char* bytes);
+	static unsigned int decode24128(unsigned int code, bool& valid);
+	static unsigned int decode24128(unsigned char* bytes, bool& valid);
 };
 
 #endif

M17Control.cpp

@@ -206,13 +206,14 @@ bool CM17Control::writeModem(unsigned char* data, unsigned int len)
 	}
 
 	if (m_rfState == RS_RF_LATE_ENTRY && data[0U] == TAG_DATA) {
-		unsigned int frag1, frag2, frag3, frag4;
-		CM17Utils::splitFragmentLICHFEC(data + 2U + M17_SYNC_LENGTH_BYTES, frag1, frag2, frag3, frag4);
+		bool valid1, valid2, valid3, valid4;
+		unsigned int lich1 = CGolay24128::decode24128(data + 2U + M17_SYNC_LENGTH_BYTES + 0U, valid1);
+		unsigned int lich2 = CGolay24128::decode24128(data + 2U + M17_SYNC_LENGTH_BYTES + 3U, valid2);
+		unsigned int lich3 = CGolay24128::decode24128(data + 2U + M17_SYNC_LENGTH_BYTES + 6U, valid3);
+		unsigned int lich4 = CGolay24128::decode24128(data + 2U + M17_SYNC_LENGTH_BYTES + 9U, valid4);
 
-		unsigned int lich1 = CGolay24128::decode24128(frag1);
-		unsigned int lich2 = CGolay24128::decode24128(frag2);
-		unsigned int lich3 = CGolay24128::decode24128(frag3);
-		unsigned int lich4 = CGolay24128::decode24128(frag4);
+		if (!valid1 || !valid2 || !valid3 || !valid4)
+			return false;
 
 		unsigned char lich[M17_LICH_FRAGMENT_LENGTH_BYTES];
 		CM17Utils::combineFragmentLICH(lich1, lich2, lich3, lich4, lich);
@@ -306,7 +307,7 @@ bool CM17Control::writeModem(unsigned char* data, unsigned int len)
 		unsigned int errors = 0U;
 		for (unsigned int i = 0U; i < (M17_FN_LENGTH_BYTES + M17_PAYLOAD_LENGTH_BYTES); i++) {
 			unsigned int offset = i + 2U + M17_SYNC_LENGTH_BYTES + M17_LICH_FRAGMENT_FEC_LENGTH_BYTES;
-			errors += countBits(rfData[offset] ^ data[offset]);
+			errors += CUtils::countBits(rfData[offset] ^ data[offset]);
 		}
 
 		LogDebug("M17, FN: %u, errs: %u/144 (%.1f%%)", m_rfFN & 0x7FU, errors, float(errors) / 1.44F);
@@ -785,17 +786,3 @@ void CM17Control::enable(bool enabled)
 
 	m_enabled = enabled;
 }
-
-unsigned int CM17Control::countBits(unsigned char byte)
-{
-	unsigned int count = 0U;
-
-	const unsigned char* p = &byte;
-
-	for (unsigned int i = 0U; i < 8U; i++) {
-		if (READ_BIT(p, i) != 0U)
-			count++;
-	}
-
-	return count;
-}

M17Control.h

@@ -92,8 +92,6 @@ class CM17Control {
 
 	bool checkCallsign(const std::string& source) const;
 
-	unsigned int countBits(unsigned char byte);
-
 	void writeEndRF();
 	void writeEndNet();
 

Utils.cpp

@@ -1,5 +1,5 @@
 /*
- *	Copyright (C) 2009,2014,2015,2016 Jonathan Naylor, G4KLX
+ *	Copyright (C) 2009,2014,2015,2016,2021 Jonathan Naylor, G4KLX
  *
  *	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
@@ -144,3 +144,15 @@ void CUtils::bitsToByteLE(const bool* bits, unsigned char& byte)
 	byte |= bits[6U] ? 0x40U : 0x00U;
 	byte |= bits[7U] ? 0x80U : 0x00U;
 }
+
+unsigned int CUtils::countBits(unsigned int v)
+{
+	unsigned int count = 0U;
+
+	while (v != 0U) {
+		v &= v - 1U;
+		count++;
+	}
+
+	return count;
+}

Utils.h

@@ -1,5 +1,5 @@
 /*
- *	Copyright (C) 2009,2014,2015 by Jonathan Naylor, G4KLX
+ *	Copyright (C) 2009,2014,2015,2021 by Jonathan Naylor, G4KLX
  *
  *	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
@@ -30,6 +30,8 @@ class CUtils {
 	static void bitsToByteBE(const bool* bits, unsigned char& byte);
 	static void bitsToByteLE(const bool* bits, unsigned char& byte);
 
+	static unsigned int countBits(unsigned int v);
+
 private:
 };
 

YSFFICH.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2016,2017,2019,2020 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2016,2017,2019,2020,2021 by Jonathan Naylor G4KLX
  *
  *   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
@@ -99,10 +99,14 @@ bool CYSFFICH::decode(const unsigned char* bytes)
 	unsigned char output[13U];
 	viterbi.chainback(output, 96U);
 
-	unsigned int b0 = CGolay24128::decode24128(output + 0U);
-	unsigned int b1 = CGolay24128::decode24128(output + 3U);
-	unsigned int b2 = CGolay24128::decode24128(output + 6U);
-	unsigned int b3 = CGolay24128::decode24128(output + 9U);
+	bool valid1, valid2, valid3, valid4;
+	unsigned int b0 = CGolay24128::decode24128(output + 0U, valid1);
+	unsigned int b1 = CGolay24128::decode24128(output + 3U, valid2);
+	unsigned int b2 = CGolay24128::decode24128(output + 6U, valid3);
+	unsigned int b3 = CGolay24128::decode24128(output + 9U, valid4);
+
+	if (!valid1 || !valid2 || !valid3 || !valid4)
+		return false;
 
 	m_fich[0U] = (b0 >> 4) & 0xFFU;
 	m_fich[1U] = ((b0 << 4) & 0xF0U) | ((b1 >> 8) & 0x0FU);