Qt: Is QHttp's get function thread safe? - c++

Question

I have the following code:
class USBCamCaptureThread : public QThread
{
Q_OBJECT
void run() {
while (!threadQuit){
mutex.lock();
bytes.clear();
buffer->reset();
Request = http->get (url->path(),buffer););
mutex.unlock();
MG::SLEEP::msleep(250);
}
}
public:
USBCamCaptureThread(){
QFile file("setting_files/cameraIP.txt");
QString line = "192.168.1.5:80"; //default value
if(file.open(QIODevice::ReadOnly)) {
QTextStream in(&file);
line = in.readLine();
}
file.close();
url = new QUrl(line);
http = new QHttp(this);
buffer = new QBuffer(&bytes);
threadQuit = false;
imageReaded = true;
open(0);
}
~USBCamCaptureThread(){
}
public slots:
void Finished(int requestId, bool error){
QImage localImage;
mutex.lock();
localImage.loadFromData(bytes);
mutex.unlock();
QImg = localImage;
emit signalUSBImageRead();
}
bool open(int camID){
buffer->open(QIODevice::WriteOnly);
http->setHost(url->host());
connect(http, SIGNAL(requestFinished(int, bool)),this, SLOT(Finished(int, bool)));
return true;
}
Note that the run() is in a worker thread and the Finished() is in the main thread.
My question is: since the documentation says the QHttp get function is "The function does not block; instead, it returns immediately. The request is scheduled, and its execution is performed asynchronously."
Is it possible that when the requestFinished is emitted and Finished() is triggered, it happens that the run() function has the mutex and therefore the QBytearray bytes.clear() is called and when Finished() got the mutex, there is nothing to be loaded from the QBytearray bytes?
Furthermore, if the process of http->get() is scheduled to be processed later, does that mean its operation on buffer is no longer protected by the mutex?