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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include "modbusclient.h"
// The read response must contain the start address (quint16), the byte count
// (quint8) and at least one register value (quint16).
static constexpr int ReadHeaderSize {3};
static constexpr int MinimumReadResponseSize {ReadHeaderSize + 2}; // 2 payload bytes
// The response must contain the start address (quint16) and the number of
// registers written (quint16).
static constexpr int WriteResponseSize {4};
ModbusClient::ModbusClient(QObject *parent)
: QModbusTcpClient(parent)
{
QModbusResponse::registerDataSizeCalculator(CustomRead, [](const QModbusResponse &response) {
if (!response.isValid())
return -1;
if (response.dataSize() < MinimumReadResponseSize)
return -1;
return ReadHeaderSize + quint8(response.data().at(ReadHeaderSize - 1));
});
QModbusResponse::registerDataSizeCalculator(CustomWrite, [](const QModbusResponse &response) {
if (!response.isValid())
return -1;
return (response.dataSize() != WriteResponseSize ? -1 : WriteResponseSize);
});
}
//! [process_custom_read]
static bool collateBytes(const QModbusPdu &response, QModbusDataUnit *data)
{
if (response.dataSize() < MinimumReadResponseSize)
return false;
quint16 address; quint8 byteCount;
response.decodeData(&address, &byteCount);
if (byteCount % 2 != 0)
return false;
if (data) {
QDataStream stream(response.data().remove(0, 3));
QList<quint16> values;
const quint8 itemCount = byteCount / 2;
for (int i = 0; i < itemCount; i++) {
quint16 tmp;
stream >> tmp;
values.append(tmp);
}
*data = {QModbusDataUnit::HoldingRegisters, address, values};
}
return true;
}
//! [process_custom_read]
//! [process_custom_write]
static bool collateMultipleValues(const QModbusPdu &response, QModbusDataUnit *data)
{
if (response.dataSize() != WriteResponseSize)
return false;
quint16 address, count;
response.decodeData(&address, &count);
if (count < 1 || count > 10)
return false;
if (data)
*data = {QModbusDataUnit::HoldingRegisters, address, count};
return true;
}
//! [process_custom_write]
//! [private_response]
bool ModbusClient::processPrivateResponse(const QModbusResponse &response, QModbusDataUnit *data)
{
if (!response.isValid())
return QModbusClient::processPrivateResponse(response, data);
if (CustomRead == response.functionCode())
return collateBytes(response, data);
if (CustomWrite == response.functionCode())
return collateMultipleValues(response, data);
return QModbusClient::processPrivateResponse(response, data);
}
//! [private_response]