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36 
37 #ifndef QMODBUSADU_P_H
38 #define QMODBUSADU_P_H
39 
40 #include <QtSerialBus/qmodbuspdu.h>
41 
42 //
43 //  W A R N I N G
44 //  -------------
45 //
46 // This file is not part of the Qt API. It exists purely as an
47 // implementation detail. This header file may change from version to
48 // version without notice, or even be removed.
49 //
50 // We mean it.
51 //
52 
53 QT_BEGIN_NAMESPACE
54 
55 class QModbusSerialAdu
56 {
57 public:
58     enum Type {
59         Ascii,
60         Rtu
61     };
62 
QModbusSerialAdu(Type type,const QByteArray & data)63     inline QModbusSerialAdu(Type type, const QByteArray &data)
64         : m_type(type), m_data(data), m_rawData(data)
65     {
66         if (m_type == Ascii)
67             m_data = QByteArray::fromHex(m_data.mid(1, m_data.size() - 3));
68     }
69 
size()70     inline int size() const {
71         if (m_type == Ascii)
72             return m_data.size() - 1; // one byte, LRC
73         return m_data.size() - 2; // two bytes, CRC
74     }
data()75     inline QByteArray data() const { return m_data.left(size()); }
76 
rawSize()77     inline int rawSize() const { return m_rawData.size(); }
rawData()78     inline QByteArray rawData() const { return m_rawData; }
79 
serverAddress()80     inline int serverAddress() const {
81         Q_ASSERT_X(!m_data.isEmpty(), "QModbusAdu::serverAddress()", "Empty ADU.");
82         return quint8(m_data.at(0));
83     }
84 
pdu()85     inline QModbusPdu pdu() const {
86         Q_ASSERT_X(!m_data.isEmpty(), "QModbusAdu::pdu()", "Empty ADU.");
87         return QModbusPdu(QModbusPdu::FunctionCode(m_data.at(1)), m_data.mid(2, size() - 2));
88     }
89 
90     template <typename T>
91     auto checksum() const -> decltype(T()) {
92         Q_ASSERT_X(!m_data.isEmpty(), "QModbusAdu::checksum()", "Empty ADU.");
93         if (m_type == Ascii)
94             return quint8(m_data[m_data.size() - 1]);
95         return quint16(quint8(m_data[m_data.size() - 2]) << 8 | quint8(m_data[m_data.size() - 1]));
96     }
97 
matchingChecksum()98     inline bool matchingChecksum() const {
99         Q_ASSERT_X(!m_data.isEmpty(), "QModbusAdu::matchingChecksum()", "Empty ADU.");
100         if (m_type == Ascii)
101             return QModbusSerialAdu::calculateLRC(data(), size()) == checksum<quint8>();
102         return QModbusSerialAdu::calculateCRC(data(), size()) == checksum<quint16>();
103     }
104 
105     /*!
106         \internal
107         \fn quint8 QModbusSerialAdu::calculateLRC(const char *data, qint32 len)
108 
109         Returns the LRC checksum of the first \a len bytes of \a data. The checksum is independent
110         of the byte order (endianness).
111     */
calculateLRC(const char * data,qint32 len)112     inline static quint8 calculateLRC(const char *data, qint32 len)
113     {
114         quint32 lrc = 0;
115         while (len--)
116             lrc += *data++;
117         return -(quint8(lrc));
118     }
119 
120     /*!
121         \internal
122         \fn quint16 QModbusSerialAdu::calculateCRC(const char *data, qint32 len) const
123 
124         Returns the CRC checksum of the first \a len bytes of \a data.
125 
126         \note The code used by the function was generated with pycrc. There is no copyright assigned
127         to the generated code, however, the author of the script requests to show the line stating
128         that the code was generated by pycrc (see implementation).
129     */
calculateCRC(const char * data,qint32 len)130     inline static quint16 calculateCRC(const char *data, qint32 len)
131     {
132         // Generated by pycrc v0.8.3, https://pycrc.org
133         // Width = 16, Poly = 0x8005, XorIn = 0xffff, ReflectIn = True,
134         // XorOut = 0x0000, ReflectOut = True, Algorithm = bit-by-bit-fast
135 
136         quint16 crc = 0xFFFF;
137         while (len--) {
138             const quint8 c = *data++;
139             for (qint32 i = 0x01; i & 0xFF; i <<= 1) {
140                 bool bit = crc & 0x8000;
141                 if (c & i)
142                     bit = !bit;
143                 crc <<= 1;
144                 if (bit)
145                     crc ^= 0x8005;
146             }
147             crc &= 0xFFFF;
148         }
149         crc = crc_reflect(crc & 0xFFFF, 16) ^ 0x0000;
150         return (crc >> 8) | (crc << 8); // swap bytes
151     }
152 
153     inline static QByteArray create(Type type, int serverAddress, const QModbusPdu &pdu,
154                                     char delimiter = '\n') {
155         QByteArray result;
156         QDataStream out(&result, QIODevice::WriteOnly);
157         out << quint8(serverAddress) << pdu;
158 
159         if (type == Ascii) {
160             out << calculateLRC(result, result.size());
161             return ":" + result.toHex() + "\r" + delimiter;
162         } else {
163             out << calculateCRC(result, result.size());
164         }
165         return result;
166     }
167 
168 private:
crc_reflect(quint16 data,qint32 len)169     inline static quint16 crc_reflect(quint16 data, qint32 len)
170     {
171         // Generated by pycrc v0.8.3, https://pycrc.org
172         // Width = 16, Poly = 0x8005, XorIn = 0xffff, ReflectIn = True,
173         // XorOut = 0x0000, ReflectOut = True, Algorithm = bit-by-bit-fast
174 
175         quint16 ret = data & 0x01;
176         for (qint32 i = 1; i < len; i++) {
177             data >>= 1;
178             ret = (ret << 1) | (data & 0x01);
179         }
180         return ret;
181     }
182 
183 private:
184     Type m_type = Rtu;
185     QByteArray m_data;
186     QByteArray m_rawData;
187 };
188 
189 QT_END_NAMESPACE
190 
191 #endif // QMODBUSADU_P_H
192