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F4KXL_DStarGateway/RSMS1AMessageBuilder.cpp

86 lines
2.5 KiB

/*
* 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 "RSMS1AMessageBuilder.h"
#include "StringUtils.h"
std::vector<char> CRSMS1AMessageBuilder::m_charsToEscape = {-17, 0, 17, 19, -2, -25, 26, -3, -1, 36, 13, 44};
void CRSMS1AMessageBuilder::buildMessage(std::string& message, const std::string& sender, const std::string& recipient, const std::string body)
{
std::string bodyTmp(body);
auto bodyCrc = calculateBodyCRC(body);
bodyTmp.push_back(bodyCrc);
escapeBody(bodyTmp, std::string(bodyTmp));
std::string header = CStringUtils::string_format("%s,%s,0011", sender.c_str(), recipient.c_str());
char c1, c2;
calcMsgIcomCRC(header, c1, c2);
header.push_back(c1);
header.push_back(c2);
message = "$$Msg," + header + bodyTmp + '\n';
}
char CRSMS1AMessageBuilder::calculateBodyCRC(const std::string& body)
{
if(body.length() == 1)
return body[0];
int num = 0;
for(auto c : body) {
num += c;
}
return (char)((num & 255) /*- 128*/);
}
void CRSMS1AMessageBuilder::escapeBody(std::string output, const std::string& body)
{
output.clear();
for(char c : body) {
if(std::find(m_charsToEscape.begin(), m_charsToEscape.end(), c) != m_charsToEscape.end()) {
output.push_back(-17);
}
output.push_back(c);
}
}
void CRSMS1AMessageBuilder::calcMsgIcomCRC(const std::string& msg, char& c1, char& c2)
{
int num = 0;
for(unsigned int i = 0U; i < msg.length(); i++) {
num += msg[i];
}
c1 = doWhatever((char)((num >> 4) & 15));
c2 = doWhatever((char)(num & 15));
}
char CRSMS1AMessageBuilder::doWhatever(char b2) {
int i;
int i2 = b2 & 255;
if (i2 >= 0 && i2 <= 9) {
i = b2 + 48;
} else if (10 > i2 || i2 > 15) {
return 0;
} else {
i = b2 + 55;
}
return (char) i;
}

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