Blocking Master Example

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 ** Copyright (C) 2012 Denis Shienkov <denis.shienkov@gmail.com>
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 #include "masterthread.h"

 #include <QSerialPort>
 #include <QTime>

 MasterThread::MasterThread(QObject *parent) :
     QThread(parent)
 {
 }

 MasterThread::~MasterThread()
 {
     m_mutex.lock();
     m_quit = true;
     m_cond.wakeOne();
     m_mutex.unlock();
     wait();
 }

 void MasterThread::transaction(const QString &portName, int waitTimeout, const QString &request)
 {
     const QMutexLocker locker(&m_mutex);
     m_portName = portName;
     m_waitTimeout = waitTimeout;
     m_request = request;
     if (!isRunning())
         start();
     else
         m_cond.wakeOne();
 }

 void MasterThread::run()
 {
     bool currentPortNameChanged = false;

     m_mutex.lock();
     QString currentPortName;
     if (currentPortName != m_portName) {
         currentPortName = m_portName;
         currentPortNameChanged = true;
     }

     int currentWaitTimeout = m_waitTimeout;
     QString currentRequest = m_request;
     m_mutex.unlock();
     QSerialPort serial;

     if (currentPortName.isEmpty()) {
         emit error(tr("No port name specified"));
         return;
     }

     while (!m_quit) {
         if (currentPortNameChanged) {
             serial.close();
             serial.setPortName(currentPortName);

             if (!serial.open(QIODevice::ReadWrite)) {
                 emit error(tr("Can't open %1, error code %2")
                            .arg(m_portName).arg(serial.error()));
                 return;
             }
         }
         // write request
         const QByteArray requestData = currentRequest.toUtf8();
         serial.write(requestData);
         if (serial.waitForBytesWritten(m_waitTimeout)) {
             // read response
             if (serial.waitForReadyRead(currentWaitTimeout)) {
                 QByteArray responseData = serial.readAll();
                 while (serial.waitForReadyRead(10))
                     responseData += serial.readAll();

                 const QString response = QString::fromUtf8(responseData);
                 emit this->response(response);
             } else {
                 emit timeout(tr("Wait read response timeout %1")
                              .arg(QTime::currentTime().toString()));
             }
         } else {
             emit timeout(tr("Wait write request timeout %1")
                          .arg(QTime::currentTime().toString()));
         }
         m_mutex.lock();
         m_cond.wait(&m_mutex);
         if (currentPortName != m_portName) {
             currentPortName = m_portName;
             currentPortNameChanged = true;
         } else {
             currentPortNameChanged = false;
         }
         currentWaitTimeout = m_waitTimeout;
         currentRequest = m_request;
         m_mutex.unlock();
     }
 }