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sdrangel/sdrbase/util/dsc.cpp

973 lines
29 KiB
C++

///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2023 Jon Beniston, M7RCE <jon@beniston.com> //
// //
// 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 as 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 V3 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/>. //
///////////////////////////////////////////////////////////////////////////////////
#include <QDebug>
#include "util/dsc.h"
#include "util/popcount.h"
// "short" strings are meant to be compatible with YaDDNet
QMap<DSCMessage::FormatSpecifier, QString> DSCMessage::m_formatSpecifierStrings = {
{GEOGRAPHIC_CALL, "Geographic call"},
{DISTRESS_ALERT, "Distress alert"},
{GROUP_CALL, "Group call"},
{ALL_SHIPS, "All ships"},
{SELECTIVE_CALL, "Selective call"},
{AUTOMATIC_CALL, "Automatic call"}
};
QMap<DSCMessage::FormatSpecifier, QString> DSCMessage::m_formatSpecifierShortStrings = {
{GEOGRAPHIC_CALL, "AREA"},
{DISTRESS_ALERT, "DIS"},
{GROUP_CALL, "GRP"},
{ALL_SHIPS, "ALL"},
{SELECTIVE_CALL, "SEL"},
{AUTOMATIC_CALL, "AUT"}
};
QMap<DSCMessage::Category, QString> DSCMessage::m_categoryStrings = {
{ROUTINE, "Routine"},
{SAFETY, "Safety"},
{URGENCY, "Urgency"},
{DISTRESS, "Distress"}
};
QMap<DSCMessage::Category, QString> DSCMessage::m_categoryShortStrings = {
{ROUTINE, "RTN"},
{SAFETY, "SAF"},
{URGENCY, "URG"},
{DISTRESS, "DIS"}
};
QMap<DSCMessage::FirstTelecommand, QString> DSCMessage::m_telecommand1Strings = {
{F3E_G3E_ALL_MODES_TP, "F3E (FM speech)/G3E (phase modulated speech) all modes telephony"},
{F3E_G3E_DUPLEX_TP, "F3E (FM speech)/G3E (phase modulated speech) duplex telephony"},
{POLLING, "Polling"},
{UNABLE_TO_COMPLY, "Unable to comply"},
{END_OF_CALL, "End of call"},
{DATA, "Data"},
{J3E_TP, "J3E (SSB) telephony"},
{DISTRESS_ACKNOWLEDGEMENT, "Distress acknowledgement"},
{DISTRESS_ALERT_RELAY, "Distress alert relay"},
{F1B_J2B_TTY_FEC, "F1B (FSK) J2B (FSK via SSB) TTY FEC"},
{F1B_J2B_TTY_AQR, "F1B (FSK) J2B (FSK via SSB) TTY AQR"},
{TEST, "Test"},
{POSITION_UPDATE, "Position update"},
{NO_INFORMATION, "No information"}
};
QMap<DSCMessage::FirstTelecommand, QString> DSCMessage::m_telecommand1ShortStrings = {
{F3E_G3E_ALL_MODES_TP, "F3E/G3E"},
{F3E_G3E_DUPLEX_TP, "F3E/G3E, Duplex TP"},
{POLLING, "POLL"},
{UNABLE_TO_COMPLY, "UNABLE TO COMPLY"},
{END_OF_CALL, "EOC"},
{DATA, "DATA"},
{J3E_TP, "J3E TP"},
{DISTRESS_ACKNOWLEDGEMENT, "DISTRESS ACK"},
{DISTRESS_ALERT_RELAY, "DISTRESS RELAY"},
{F1B_J2B_TTY_FEC, "F1B/J2B TTY-FEC"},
{F1B_J2B_TTY_AQR, "F1B/J2B TTY-ARQ"},
{TEST, "TEST"},
{POSITION_UPDATE, "POSUPD"},
{NO_INFORMATION, "NOINF"}
};
QMap<DSCMessage::SecondTelecommand, QString> DSCMessage::m_telecommand2Strings = {
{NO_REASON, "No reason"},
{CONGESTION, "Congestion at switching centre"},
{BUSY, "Busy"},
{QUEUE, "Queue indication"},
{BARRED, "Station barred"},
{NO_OPERATOR, "No operator available"},
{OPERATOR_UNAVAILABLE, "Operator temporarily unavailable"},
{EQUIPMENT_DISABLED, "Equipment disabled"},
{UNABLE_TO_USE_CHANNEL, "Unable to use proposed channel"},
{UNABLE_TO_USE_MODE, "Unable to use proposed mode"},
{NOT_PARTIES_TO_CONFLICT, "Ships and aircraft of States not parties to an armed conflict"},
{MEDICAL_TRANSPORTS, "Medical transports"},
{PAY_PHONE, "Pay-phone/public call office"},
{FAX, "Facsimile"},
{NO_INFORMATION_2, "No information"}
};
QMap<DSCMessage::SecondTelecommand, QString> DSCMessage::m_telecommand2ShortStrings = {
{NO_REASON, "NO REASON GIVEN"},
{CONGESTION, "CONGESTION AT MARITIME CENTRE"},
{BUSY, "BUSY"},
{QUEUE, "QUEUE INDICATION"},
{BARRED, "STATION BARRED"},
{NO_OPERATOR, "NO OPERATOR AVAILABLE"},
{OPERATOR_UNAVAILABLE, "OPERATOR TEMPORARILY UNAVAILABLE"},
{EQUIPMENT_DISABLED, "EQUIPMENT DISABLED"},
{UNABLE_TO_USE_CHANNEL, "UNABLE TO USE PROPOSED CHANNEL"},
{UNABLE_TO_USE_MODE, "UNABLE TO USE PROPOSED MODE"},
{NOT_PARTIES_TO_CONFLICT, "SHIPS/AIRCRAFT OF STATES NOT PARTIES TO ARMED CONFLICT"},
{MEDICAL_TRANSPORTS, "MEDICAL TRANSPORTS"},
{PAY_PHONE, "PAY-PHONE/PUBLIC CALL OFFICE"},
{FAX, "FAX/DATA ACCORDING ITU-R M1081"},
{NO_INFORMATION_2, "NOINF"}
};
QMap<DSCMessage::DistressNature, QString> DSCMessage::m_distressNatureStrings = {
{FIRE, "Fire, explosion"},
{FLOODING, "Flooding"},
{COLLISION, "Collision"},
{GROUNDING, "Grounding"},
{LISTING, "Listing"},
{SINKING, "Sinking"},
{ADRIFT, "Adrift"},
{UNDESIGNATED, "Undesignated"},
{ABANDONING_SHIP, "Abandoning ship"},
{PIRACY, "Piracy, armed attack"},
{MAN_OVERBOARD, "Man overboard"},
{EPIRB, "EPIRB"}
};
QMap<DSCMessage::EndOfSignal, QString> DSCMessage::m_endOfSignalStrings = {
{REQ, "Req ACK"},
{ACK, "ACK"},
{EOS, "EOS"}
};
QMap<DSCMessage::EndOfSignal, QString> DSCMessage::m_endOfSignalShortStrings = {
{REQ, "REQ"},
{ACK, "ACK"},
{EOS, "EOS"}
};
DSCMessage::DSCMessage(const QByteArray& data, QDateTime dateTime) :
m_dateTime(dateTime),
m_data(data)
{
decode(data);
}
QString DSCMessage::toString(const QString separator) const
{
QStringList s;
s.append(QString("Format specifier: %1").arg(formatSpecifier()));
if (m_hasAddress) {
s.append(QString("Address: %1").arg(m_address));
}
if (m_hasCategory) {
s.append(QString("Category: %1").arg(category()));
}
s.append(QString("Self Id: %1").arg(m_selfId));
if (m_hasTelecommand1) {
s.append(QString("Telecommand 1: %1").arg(telecommand1(m_telecommand1)));
}
if (m_hasTelecommand2) {
s.append(QString("Telecommand 2: %1").arg(telecommand2(m_telecommand2)));
}
if (m_hasDistressId) {
s.append(QString("Distress Id: %1").arg(m_distressId));
}
if (m_hasDistressNature)
{
s.append(QString("Distress nature: %1").arg(distressNature(m_distressNature)));
s.append(QString("Distress coordinates: %1").arg(m_position));
}
else if (m_hasPosition)
{
s.append(QString("Position: %1").arg(m_position));
}
if (m_hasFrequency1) {
s.append(QString("RX Frequency: %1Hz").arg(m_frequency1));
}
if (m_hasChannel1) {
s.append(QString("RX Channel: %1").arg(m_channel1));
}
if (m_hasFrequency2) {
s.append(QString("TX Frequency: %1Hz").arg(m_frequency2));
}
if (m_hasChannel2) {
s.append(QString("TX Channel: %1").arg(m_channel2));
}
if (m_hasNumber) {
s.append(QString("Phone Number: %1").arg(m_number));
}
if (m_hasTime) {
s.append(QString("Time: %1").arg(m_time.toString()));
}
if (m_hasSubsequenceComms) {
s.append(QString("Subsequent comms: %1").arg(telecommand1(m_subsequenceComms)));
}
return s.join(separator);
}
QString DSCMessage::toYaddNetFormat(const QString& id, qint64 frequency) const
{
QStringList s;
// rx_id
s.append(QString("[%1]").arg(id));
// rx_freq
float frequencyKHZ = frequency / 1000.0f;
s.append(QString("%1").arg(frequencyKHZ, 0, 'f', 1));
// fmt
s.append(formatSpecifier(true));
// to
if (m_hasAddress)
{
if (m_formatSpecifier == GEOGRAPHIC_CALL)
{
char ns = m_addressLatitude >= 0 ? 'N' : 'S';
char ew = m_addressLongitude >= 0 ? 'E' : 'W';
int lat = abs(m_addressLatitude);
int lon = abs(m_addressLongitude);
s.append(QString("AREA %2%1%6=>%4%1 %3%1%7=>%5%1")
.arg(QChar(0xb0)) // degree
.arg(lat, 2, 10, QChar('0'))
.arg(lon, 3, 10, QChar('0'))
.arg(m_addressLatAngle, 2, 10, QChar('0'))
.arg(m_addressLonAngle, 2, 10, QChar('0'))
.arg(ns)
.arg(ew));
}
else
{
s.append(m_address);
}
}
else
{
s.append("");
}
// cat
s.append(category(true));
// from
s.append(m_selfId);
// tc1
if (m_hasTelecommand1) {
s.append(telecommand1(m_telecommand1, true));
} else {
s.append("--");
}
// tc2
if (m_hasTelecommand2) {
s.append(telecommand2(m_telecommand2, true));
} else {
s.append("--");
}
// distress fields don't appear to be used!
// freq
if (m_hasFrequency1 && m_hasFrequency2) {
s.append(QString("%1/%2KHz").arg(m_frequency1/1000.0, 7, 'f', 1, QChar('0')).arg(m_frequency2/1000.0, 7, 'f', 1, QChar('0')));
} else if (m_hasFrequency1) {
s.append(QString("%1KHz").arg(m_frequency1/1000.0, 7, 'f', 1, QChar('0')));
} else if (m_hasFrequency2) {
s.append(QString("%1KHz").arg(m_frequency2/1000.0, 7, 'f', 1, QChar('0')));
} else if (m_hasChannel1 && m_hasChannel2) {
s.append(QString("%1/%2").arg(m_channel1).arg(m_channel2));
} else if (m_hasChannel1) {
s.append(QString("%1").arg(m_channel1));
} else if (m_hasChannel2) {
s.append(QString("%1").arg(m_channel2));
} else {
s.append("--");
}
// pos
if (m_hasPosition) {
s.append(m_position); // FIXME: Format??
} else {
s.append("--"); // Sometimes this is " -- ". in YaDD Why?
}
// eos
s.append(endOfSignal(m_eos, true));
// ecc
s.append(QString("ECC %1 %2").arg(m_calculatedECC).arg(m_eccOk ? "OK" : "ERR"));
return s.join(";");
}
QString DSCMessage::formatSpecifier(bool shortString) const
{
if (shortString)
{
if (m_formatSpecifierShortStrings.contains(m_formatSpecifier)) {
return m_formatSpecifierShortStrings[m_formatSpecifier];
} else {
return QString("UNK/ERR").arg(m_formatSpecifier);
}
}
else
{
if (m_formatSpecifierStrings.contains(m_formatSpecifier)) {
return m_formatSpecifierStrings[m_formatSpecifier];
} else {
return QString("Unknown (%1)").arg(m_formatSpecifier);
}
}
}
QString DSCMessage::category(bool shortString) const
{
if (shortString)
{
if (m_categoryShortStrings.contains(m_category)) {
return m_categoryShortStrings[m_category];
} else {
return QString("UNK/ERR").arg(m_category);
}
}
else
{
if (!m_hasCategory) {
return "N/A";
} else if (m_categoryStrings.contains(m_category)) {
return m_categoryStrings[m_category];
} else {
return QString("Unknown (%1)").arg(m_category);
}
}
}
QString DSCMessage::telecommand1(FirstTelecommand telecommand, bool shortString)
{
if (shortString)
{
if (m_telecommand1ShortStrings.contains(telecommand)) {
return m_telecommand1ShortStrings[telecommand];
} else {
return QString("UNK/ERR").arg(telecommand);
}
}
else
{
if (m_telecommand1Strings.contains(telecommand)) {
return m_telecommand1Strings[telecommand];
} else {
return QString("Unknown (%1)").arg(telecommand);
}
}
}
QString DSCMessage::telecommand2(SecondTelecommand telecommand, bool shortString)
{
if (shortString)
{
if (m_telecommand2ShortStrings.contains(telecommand)) {
return m_telecommand2ShortStrings[telecommand];
} else {
return QString("UNK/ERR").arg(telecommand);
}
}
else
{
if (m_telecommand2Strings.contains(telecommand)) {
return m_telecommand2Strings[telecommand];
} else {
return QString("Unknown (%1)").arg(telecommand);
}
}
}
QString DSCMessage::distressNature(DistressNature nature)
{
if (m_distressNatureStrings.contains(nature)) {
return m_distressNatureStrings[nature];
} else {
return QString("Unknown (%1)").arg(nature);
}
}
QString DSCMessage::endOfSignal(EndOfSignal eos, bool shortString)
{
if (shortString)
{
if (m_endOfSignalShortStrings.contains(eos)) {
return m_endOfSignalShortStrings[eos];
} else {
return QString("UNK/ERR").arg(eos);
}
}
else
{
if (m_endOfSignalStrings.contains(eos)) {
return m_endOfSignalStrings[eos];
} else {
return QString("Unknown (%1)").arg(eos);
}
}
}
QString DSCMessage::symbolsToDigits(const QByteArray data, int startIdx, int length)
{
QString s;
for (int i = 0; i < length; i++)
{
QString digits = QString("%1").arg((int)data[startIdx+i], 2, 10, QChar('0'));
s = s.append(digits);
}
return s;
}
QString DSCMessage::formatCoordinates(int latitude, int longitude)
{
QString lat, lon;
if (latitude >= 0) {
lat = QString("%1%2N").arg(latitude).arg(QChar(0xb0));
} else {
lat = QString("%1%2S").arg(-latitude).arg(QChar(0xb0));
}
if (longitude >= 0) {
lon = QString("%1%2E").arg(longitude).arg(QChar(0xb0));
} else {
lon = QString("%1%2W").arg(-longitude).arg(QChar(0xb0));
}
return QString("%1 %2").arg(lat).arg(lon);
}
void DSCMessage::decode(const QByteArray& data)
{
int idx = 0;
// Format specifier
m_formatSpecifier = (FormatSpecifier) data[idx++];
m_formatSpecifierMatch = m_formatSpecifier == data[idx++];
// Address and category
if (m_formatSpecifier != DISTRESS_ALERT)
{
if (m_formatSpecifier != ALL_SHIPS)
{
m_address = symbolsToDigits(data, idx, 5);
idx += 5;
m_hasAddress = true;
if (m_formatSpecifier == SELECTIVE_CALL)
{
m_address = formatAddress(m_address);
}
else if (m_formatSpecifier == GEOGRAPHIC_CALL)
{
// Address definines a geographic rectangle. We have NW coord + 2 angles
QChar azimuthSector = m_address[0];
m_addressLatitude = m_address[1].digitValue() * 10 + m_address[2].digitValue(); // In degrees
m_addressLongitude = m_address[3].digitValue() * 100 + m_address[4].digitValue() * 10 + m_address[5].digitValue(); // In degrees
switch (azimuthSector.toLatin1())
{
case '0': // NE
break;
case '1': // NW
m_addressLongitude = -m_addressLongitude;
break;
case '2': // SE
m_addressLatitude = -m_addressLatitude;
break;
case '3': // SW
m_addressLongitude = -m_addressLongitude;
m_addressLatitude = -m_addressLatitude;
break;
default:
break;
}
m_addressLatAngle = m_address[6].digitValue() * 10 + m_address[7].digitValue();
m_addressLonAngle = m_address[8].digitValue() * 10 + m_address[9].digitValue();
int latitude2 = m_addressLatitude + m_addressLatAngle;
int longitude2 = m_addressLongitude + m_addressLonAngle;
/*m_address = QString("Lat %2%1 Lon %3%1 %4%5%6%1 %4%7%8%1")
.arg(QChar(0xb0)) // degree
.arg(m_addressLatitude)
.arg(m_addressLongitude)
.arg(QChar(0x0394)) // delta
.arg(QChar(0x03C6)) // phi
.arg(m_addressLatAngle)
.arg(QChar(0x03BB)) // lambda
.arg(m_addressLonAngle);*/
m_address = QString("%1 - %2")
.arg(formatCoordinates(m_addressLatitude, m_addressLongitude))
.arg(formatCoordinates(latitude2, longitude2));
}
}
else
{
m_hasAddress = false;
}
m_category = (Category) data[idx++];
m_hasCategory = true;
}
else
{
m_hasAddress = false;
m_hasCategory = true;
}
// Self Id
m_selfId = symbolsToDigits(data, idx, 5);
m_selfId = formatAddress(m_selfId);
idx += 5;
// Telecommands
if (m_formatSpecifier != DISTRESS_ALERT)
{
m_telecommand1 = (FirstTelecommand) data[idx++];
m_hasTelecommand1 = true;
if (m_category != DISTRESS) // Not Distress Alert Ack / Relay
{
m_telecommand2 = (SecondTelecommand) data[idx++];
m_hasTelecommand2 = true;
}
else
{
m_hasTelecommand2 = false;
}
}
else
{
m_hasTelecommand1 = false;
m_hasTelecommand2 = false;
}
// ID of source of distress for relays and acks
if (m_hasCategory && m_category == DISTRESS)
{
m_distressId = symbolsToDigits(data, idx, 5);
m_distressId = formatAddress(m_distressId);
idx += 5;
m_hasDistressId = true;
}
else
{
m_hasDistressId = false;
}
if (m_formatSpecifier == DISTRESS_ALERT)
{
m_distressNature = (DistressNature) data[idx++];
m_position = formatCoordinates(symbolsToDigits(data, idx, 5));
idx += 5;
m_hasDistressNature = true;
m_hasPosition = true;
m_hasFrequency1 = false;
m_hasChannel1 = false;
m_hasFrequency2 = false;
m_hasChannel2 = false;
}
else if (m_hasCategory && (m_category != DISTRESS))
{
m_hasDistressNature = false;
// Frequency or position
if (data[idx] == 55)
{
// Position 6
m_position = formatCoordinates(symbolsToDigits(data, idx, 5));
idx += 5;
m_hasPosition = true;
m_hasFrequency1 = false;
m_hasChannel1 = false;
m_hasFrequency2 = false;
m_hasChannel2 = false;
}
else
{
m_hasPosition = false;
// Frequency
m_frequency1 = 0;
decodeFrequency(data, idx, m_frequency1, m_channel1);
m_hasFrequency1 = m_frequency1 != 0;
m_hasChannel1 = !m_channel1.isEmpty();
if (m_formatSpecifier != AUTOMATIC_CALL)
{
m_frequency2 = 0;
decodeFrequency(data, idx, m_frequency2, m_channel2);
m_hasFrequency2 = m_frequency2 != 0;
m_hasChannel2 = !m_channel2.isEmpty();
}
else
{
m_hasFrequency2 = false;
m_hasChannel2 = false;
}
}
}
else
{
m_hasDistressNature = false;
m_hasPosition = false;
m_hasFrequency1 = false;
m_hasChannel1 = false;
m_hasFrequency2 = false;
m_hasChannel2 = false;
}
if (m_formatSpecifier == AUTOMATIC_CALL)
{
signed char oddEven = data[idx++];
int len = data.size() - idx - 2; // EOS + ECC
m_number = symbolsToDigits(data, idx, len);
idx += len;
if (oddEven == 105) { // Is number an odd number?
m_number = m_number.mid(1); // Drop leading digit (which should be a 0)
}
m_hasNumber = true;
}
else
{
m_hasNumber = false;
}
// Time
if ( (m_formatSpecifier == DISTRESS_ALERT)
|| (m_hasCategory && (m_category == DISTRESS))
//|| (m_formatSpecifier == SELECTIVE_CALL) && (m_category == SAFETY) && (m_telecommand1 == POSITION_UPDATE) && (m_telecommand2 == 126) && (m_frequency == pos4))
)
{
// 8 8 8 8 for no time
QString time = symbolsToDigits(data, idx, 2);
if (time != "8888")
{
m_time = QTime(time.left(2).toInt(), time.right(2).toInt());
m_hasTime = true;
}
else
{
m_hasTime = false;
}
// FIXME: Convert to QTime?
}
else
{
m_hasTime = false;
}
// Subsequent communications
if ((m_formatSpecifier == DISTRESS_ALERT) || (m_hasCategory && (m_category == DISTRESS)))
{
m_subsequenceComms = (FirstTelecommand)data[idx++];
m_hasSubsequenceComms = true;
}
else
{
m_hasSubsequenceComms = false;
}
m_eos = (EndOfSignal) data[idx++];
m_ecc = data[idx++];
checkECC(data);
// Indicate message as being invalid if any unexpected data, too long, or ECC didn't match
if ( m_formatSpecifierStrings.contains(m_formatSpecifier)
&& (!m_hasCategory || (m_hasCategory && m_categoryStrings.contains(m_category)))
&& (!m_hasTelecommand1 || (m_hasTelecommand1 && m_telecommand1Strings.contains(m_telecommand1)))
&& (!m_hasTelecommand2 || (m_hasTelecommand2 && m_telecommand2Strings.contains(m_telecommand2)))
&& (!m_hasDistressNature || (m_hasDistressNature && m_distressNatureStrings.contains(m_distressNature)))
&& m_endOfSignalStrings.contains(m_eos)
&& (!data.contains(-1))
&& (data.size() < DSCDecoder::m_maxBytes)
&& m_eccOk
) {
m_valid = true;
} else {
m_valid = false;
}
}
void DSCMessage::checkECC(const QByteArray& data)
{
m_calculatedECC = 0;
// Only use one format specifier and one EOS
for (int i = 1; i < data.size() - 1; i++) {
m_calculatedECC ^= data[i];
}
m_eccOk = m_calculatedECC == m_ecc;
}
void DSCMessage::decodeFrequency(const QByteArray& data, int& idx, int& frequency, QString& channel)
{
// No frequency information is indicated by 126 repeated 3 times
if ((data[idx] == 126) && (data[idx+1] == 126) && (data[idx+2] == 126))
{
idx += 3;
return;
}
// Extract frequency digits
QString s = symbolsToDigits(data, idx, 3);
idx += 3;
if (s[0] == '4')
{
s = s.append(symbolsToDigits(data, idx, 1));
idx++;
}
if ((s[0] == '0') || (s[0] == '1') || (s[0] == '2'))
{
frequency = s.toInt() * 100;
}
else if (s[0] == '3')
{
channel = "CH" + s.mid(1); // HF/MF
}
else if (s[0] == '4')
{
frequency = s.mid(1).toInt() * 10; // Frequency in multiples of 10Hz
}
else if (s[0] == '9')
{
channel = "CH" + s.mid(2) + "VHF"; // VHF
}
}
QString DSCMessage::formatAddress(const QString &address) const
{
// First 9 digits should be MMSI
// Last digit should always be 0, except for ITU-R M.1080, which allows 10th digit to specify different equipement on same vessel
if (address.right(1) == "0") {
return address.left(9);
} else {
return QString("%1-%2").arg(address.left(9)).arg(address.right(1));
}
}
QString DSCMessage::formatCoordinates(const QString& coords)
{
if (coords == "9999999999")
{
return "Not available";
}
else
{
QChar quadrant = coords[0];
QString latitude = QString("%1%3%2\'")
.arg(coords.mid(1, 2))
.arg(coords.mid(3, 2))
.arg(QChar(0xb0));
QString longitude = QString("%1%3%2\'")
.arg(coords.mid(1, 3))
.arg(coords.mid(4, 2))
.arg(QChar(0xb0));
switch (quadrant.toLatin1())
{
case '0':
latitude = latitude.append('N');
longitude = longitude.append('E');
break;
case '1':
latitude = latitude.append('N');
longitude = longitude.append('W');
break;
case '2':
latitude = latitude.append('S');
longitude = longitude.append('E');
break;
case '3':
latitude = latitude.append('S');
longitude = longitude.append('W');
break;
}
return QString("%1 %2").arg(latitude).arg(longitude);
}
}
// Doesn't include 125 111 125 as these will have be detected already, in DSDDemodSink
const signed char DSCDecoder::m_expectedSymbols[] = {
110,
125, 109,
125, 108,
125, 107,
125, 106
};
int DSCDecoder::m_maxBytes = 40; // Max bytes in any message
void DSCDecoder::init(int offset)
{
if (offset == 0)
{
m_state = FILL_DX;
}
else
{
m_phaseIdx = offset;
m_state = PHASING;
}
m_idx = 0;
m_errors = 0;
m_bytes = QByteArray();
m_eos = false;
}
bool DSCDecoder::decodeSymbol(signed char symbol)
{
bool ret = false;
switch (m_state)
{
case PHASING:
// Check if received phasing signals are as expected
if (symbol != m_expectedSymbols[9-m_phaseIdx]) {
m_errors++;
}
m_phaseIdx--;
if (m_phaseIdx == 0) {
m_state = FILL_DX;
}
break;
case FILL_DX:
// Fill up buffer
m_buf[m_idx++] = symbol;
if (m_idx == BUFFER_SIZE)
{
m_state = RX;
m_idx = 0;
}
else
{
m_state = FILL_RX;
}
break;
case FILL_RX:
if ( ((m_idx == 1) && (symbol != 106))
|| ((m_idx == 2) && (symbol != 105))
)
{
m_errors++;
}
m_state = FILL_DX;
break;
case RX:
{
signed char a = selectSymbol(m_buf[m_idx], symbol);
if (DSCMessage::m_endOfSignalStrings.contains((DSCMessage::EndOfSignal) a)) {
m_state = DX_EOS;
} else {
m_state = DX;
}
if (m_bytes.size() > m_maxBytes)
{
ret = true;
m_state = NO_EOS;
}
}
break;
case DX:
// Save received character in buffer
m_buf[m_idx] = symbol;
m_idx = (m_idx + 1) % BUFFER_SIZE;
m_state = RX;
break;
case DX_EOS:
// Save, EOS symbol
m_buf[m_idx] = symbol;
m_idx = (m_idx + 1) % BUFFER_SIZE;
m_state = RX_EOS;
break;
case RX_EOS:
selectSymbol(m_buf[m_idx], symbol);
m_state = DONE;
ret = true;
break;
case DONE:
case NO_EOS:
break;
}
return ret;
}
// Reverse order of bits in a byte
unsigned char DSCDecoder::reverse(unsigned char b)
{
b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
return b;
}
// Convert 10 bits to a symbol
// Returns -1 if error detected
signed char DSCDecoder::bitsToSymbol(unsigned int bits)
{
signed char data = reverse(bits >> 3) >> 1;
int zeros = 7-popcount(data);
int expectedZeros = bits & 0x7;
if (zeros == expectedZeros) {
return data;
} else {
return -1;
}
}
// Decode 10-bits to symbols then remove errors using repeated symbols
bool DSCDecoder::decodeBits(int bits)
{
signed char symbol = bitsToSymbol(bits);
//qDebug() << "Bits2sym: " << Qt::hex << bits << Qt::hex << symbol;
return decodeSymbol(symbol);
}
// Select time diversity symbol without errors
signed char DSCDecoder::selectSymbol(signed char dx, signed char rx)
{
signed char s;
if (dx != -1)
{
s = dx; // First received character has no detectable error
if (dx != rx) {
m_errors++;
}
}
else if (rx != -1)
{
s = rx; // Second received character has no detectable error
m_errors++;
}
else
{
s = '*'; // Both received characters have errors
m_errors += 2;
}
m_bytes.append(s);
return s;
}