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F4KXL_DStarGateway/Common/NMEASentenceCollector.cpp

142 lines
4.1 KiB

/*
* Copyright (C) 2010,2012,2018 by Jonathan Naylor G4KLX
* Copyright (C) 2021-2022 by Geoffrey Merck F4FXL / KC3FRA
*
* 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 2 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, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <string.h>
#include <cassert>
#include <boost/algorithm/string.hpp>
#include "NMEASentenceCollector.h"
#include "StringUtils.h"
#include "Log.h"
#include "APRSUtils.h"
CNMEASentenceCollector::CNMEASentenceCollector(const std::string& sentence) :
CSentenceCollector(SLOW_DATA_TYPE_GPS, sentence, '\x0A')
{
}
bool CNMEASentenceCollector::isValidSentence(const std::string& sentence)
{
return isValidNMEA(sentence);
}
bool CNMEASentenceCollector::isValidNMEA(const std::string& nmea)
{
if(nmea.empty() || nmea[0] != '$')
return false;
auto posStar = nmea.find_last_of('*');
if(posStar == 0U || posStar == std::string::npos)
return false;
auto csum = calcXOR(nmea);
auto csumStr = CStringUtils::string_format("%02X", csum);
auto expctedCSumStr = nmea.substr(posStar + 1, 2U);
auto res = ::strcasecmp(expctedCSumStr.c_str(), csumStr.c_str()) == 0;
return res;
}
unsigned char CNMEASentenceCollector::calcXOR(const std::string& nmea)
{
unsigned char res = 0U;
if(!nmea.empty()) {
unsigned int i = nmea[0] == '$' ? 1U : 0U; //skip $ if it is there
while(i < nmea.length())
{
if(nmea[i] != '*') {
res ^= (unsigned char)nmea[i];
}
else {
break;
}
i++;
}
}
return res;
}
unsigned int CNMEASentenceCollector::getDataInt(unsigned char * data, unsigned int length)
{
if(data == nullptr || length == 0U)
return 0U;
std::string aprsFrame;
if(!getDataInt(aprsFrame))
return 0U;
auto aprsFrameLen = aprsFrame.length();
if(length < aprsFrameLen) {
CLog::logDebug("Not enough space to copy NMEA APRS frame");
return 0U;
}
for(unsigned int i = 0U; i < aprsFrameLen; i++){
data[i] = aprsFrame[i];
}
return aprsFrameLen;
}
bool CNMEASentenceCollector::getDataInt(std::string& data)
{
if(getMyCall1().empty() || getSentence().empty())
return false;
data.clear();
auto nmea = getSentence();
fixUpNMEATimeStamp(nmea);
std::string fromCall = getMyCall1();
CAPRSUtils::dstarCallsignToAPRS(fromCall);
// 20230425 Fix for https://github.com/F4FXL/DStarGateway/issues/33
size_t hyphenIndex = fromCall.find('-');
if(hyphenIndex != std::string::npos) {
fromCall = fromCall.substr(0, hyphenIndex);
}
std::string aprsFrame(fromCall);
aprsFrame.append("-5>GPS30,DSTAR*:")
.append(nmea);
data.assign(aprsFrame);
return true;
}
// When set on manual position Icom radios send 000000.00 as NMEA timestamps
// this is a dirty hack to correct this issue. Actually I am not sure about APRS
// software being peeky about this except APRS.fi
void CNMEASentenceCollector::fixUpNMEATimeStamp(std::string& nmea)
{
auto posStar = nmea.find_last_of('*');
if(posStar != std::string::npos)
nmea = nmea.substr(0, posStar);
time_t now;
::time(&now);
struct tm* tm = ::gmtime(&now);
auto timeStamp = CStringUtils::string_format(",%02d%02d%02d.00,", tm->tm_hour, tm->tm_min, tm->tm_sec);
boost::replace_all(nmea, ",000000.00,", timeStamp);
//recalculate checksum
nmea = CStringUtils::string_format("%s*%02x", nmea.c_str(), calcXOR(nmea));
}

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