Program freeze when try to get MD5 of files

[saeid0034]

i use this code (i dont know if its right or not)

QString loc40 = "/file/test.pak";
    QFuture<QString> future40 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc40);
    QString pakchunk40 = future40.result();

but program freeze again

[SGaist]

As explained in the result documentation, it will block if the computation is not done. Use QFutureWatcher with signals and slots to properly make things asynchronous.

[saeid0034]

@SGaist The computation is done
Because the outputs are correct after the program exits From freeze, the only problem is program freeze, no matter how i try, and i sure problem coming from MD5 Generation

[saeid0034]

i test Q In my code

    QFutureWatcher<void>* watcher = new QFutureWatcher<void>();
    connect(watcher, SIGNAL(finished()), this, SLOT(Md5_gen()));
    watcher->setFuture(future33);

It is wrong or ok?
i dont know how add my function to slot, i just put my md5 function name on it

[saeid0034]

here is my full code for now

QString Md5_gen(QString const &s)
{
    QString pakchunk_Md5;
    QCryptographicHash crypto(QCryptographicHash::Md5);
    QFile pakchunk(QDir::currentPath() + s);
    if (pakchunk.open(QIODevice::ReadOnly))
    {
        while(!pakchunk.atEnd()){
        crypto.addData(pakchunk.read(8192));
        }
    } else
    {
        qDebug() << "Can't open file.";
        pakchunk_Md5 = "nofile";
        return pakchunk_Md5;
    }
    pakchunk_Md5 = crypto.result().toHex();
    return pakchunk_Md5;
}

MainWindow2::MainWindow2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow2)
{
    ui->setupUi(this);
}

MainWindow2::~MainWindow2()
{
    delete ui;
}

void MainWindow2::on_pushButton_clicked()
{
    int file_ok = 0;

    QFutureWatcher<void>* watcher = new QFutureWatcher<void>();
    connect(watcher, SIGNAL(finished()), this, SLOT(Md5_gen()));
    //file pak33
    QString loc33 = "/SM/test.pak";
    QFuture<QString> future33 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc33);
    QString pakchunk33 = future33.result();
    watcher->setFuture(future33);
    qDebug() << pakchunk33;
    if (pakchunk33 == "f7002d4419cd235a87746715ba6fb2ea")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label_8->setText("OK");
        ui->label_8->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk33 == "nofile")
    {
        qDebug() << "no file found";
        ui->label_8->setText("not found");
        ui->label_8->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label_8->setText("wrong");
        ui->label_8->setStyleSheet("QLabel { color : red; }");
    }

    //file pak34
    QString loc34 = "/SM/test2.pak";
    QFuture<QString> future34 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc34);
    QString pakchunk34 = future34.result();
    qDebug() << pakchunk34;
    watcher->setFuture(future34);
    if (pakchunk34 == "64c77598586b6c3cb60beed0b0750620")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label->setText("OK");
        ui->label->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk34 == "nofile")
    {
        qDebug() << "no file found";
        ui->label->setText("not found");
        ui->label->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label->setText("wrong");
        ui->label->setStyleSheet("QLabel { color : red; }");
    }

    //file pak35
    QString loc35 = "/SM/test3.pak";
    QFuture<QString> future35 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc35);
    QString pakchunk35 = future35.result();
    watcher->setFuture(future35);
    qDebug() << pakchunk35;
    if (pakchunk35 == "ee53f7a7656a32b5278c460baec46f16")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label_7->setText("OK");
        ui->label_7->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk35 == "nofile")
    {
        qDebug() << "no file found";
        ui->label_7->setText("not found");
        ui->label_7->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label_7->setText("wrong");
        ui->label_7->setStyleSheet("QLabel { color : red; }");
    }
}

can anyone please help me find the problem

[saeid0034]

its fully fixed by adding qApp->processEvents(); to MD5 while

[SGaist]

You do realise that your code is wrong in terms of offloading the work ? As I already wrote: result will be blocking if the computation is not finished.

The idea is to use the watcher so you let the computation run and in the slot connected to your QFutureWatcher you run your UI updates.

What you have here is mostly the same code as before, but more complicated, since you are blocking your event loop with your calls to result.

[aha_1980]

Hi @saeid0034,

its fully fixed by adding qApp->processEvents(); to MD5 while

For sure not! Please don't use processEvents() if you don't know what you are doing!

Regards

[saeid0034]

@SGaist i don't know how correctly use QFutureWatcher in my code...
As you can see in my full cod in above im add QFutureWatcher to my cod, is it wrong?
Can you please guide me to how do this?

[aha_1980]

Hi @saeid0034,

As @SGaist already said, calling result() when the future is not done yet will block your event loop.

You should call result() in the slot connected to finished().

Regards

[saeid0034]

@aha_1980 thanks for information
problem is i dont know much about working with slots and QFutureWatcher
can you please say to me i need to do what with this code?

QString Md5_gen(QString const &s)
{
    QString pakchunk_Md5;
    QCryptographicHash crypto(QCryptographicHash::Md5);
    QFile pakchunk(QDir::currentPath() + s);
    if (pakchunk.open(QIODevice::ReadOnly))
    {
        while(!pakchunk.atEnd()){
        crypto.addData(pakchunk.read(8192));
        }
    } else
    {
        qDebug() << "Can't open file.";
        pakchunk_Md5 = "nofile";
        return pakchunk_Md5;
    }
    pakchunk_Md5 = crypto.result().toHex();
    return pakchunk_Md5;
}

MainWindow2::MainWindow2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow2)
{
    ui->setupUi(this);
}

MainWindow2::~MainWindow2()
{
    delete ui;
}

void MainWindow2::on_pushButton_clicked()
{
    int file_ok = 0;

    QFutureWatcher<void>* watcher = new QFutureWatcher<void>();
    connect(watcher, SIGNAL(finished()), this, SLOT(Md5_gen()));
    //file pak33
    QString loc33 = "/SM/test.pak";
    QFuture<QString> future33 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc33);
    QString pakchunk33 = future33.result();
    watcher->setFuture(future33);
    qDebug() << pakchunk33;
    if (pakchunk33 == "f7002d4419cd235a87746715ba6fb2ea")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label_8->setText("OK");
        ui->label_8->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk33 == "nofile")
    {
        qDebug() << "no file found";
        ui->label_8->setText("not found");
        ui->label_8->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label_8->setText("wrong");
        ui->label_8->setStyleSheet("QLabel { color : red; }");
    }

    //file pak34
    QString loc34 = "/SM/test2.pak";
    QFuture<QString> future34 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc34);
    QString pakchunk34 = future34.result();
    qDebug() << pakchunk34;
    watcher->setFuture(future34);
    if (pakchunk34 == "64c77598586b6c3cb60beed0b0750620")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label->setText("OK");
        ui->label->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk34 == "nofile")
    {
        qDebug() << "no file found";
        ui->label->setText("not found");
        ui->label->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label->setText("wrong");
        ui->label->setStyleSheet("QLabel { color : red; }");
    }

    //file pak35
    QString loc35 = "/SM/test3.pak";
    QFuture<QString> future35 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc35);
    QString pakchunk35 = future35.result();
    watcher->setFuture(future35);
    qDebug() << pakchunk35;
    if (pakchunk35 == "ee53f7a7656a32b5278c460baec46f16")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label_7->setText("OK");
        ui->label_7->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk35 == "nofile")
    {
        qDebug() << "no file found";
        ui->label_7->setText("not found");
        ui->label_7->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label_7->setText("wrong");
        ui->label_7->setStyleSheet("QLabel { color : red; }");
    }
}

[aha_1980]

Hi @saeid0034,

see e.g. this example.

Regards

[saeid0034]

@aha_1980 thanks, with this example gui run better, but on big file (1.5GB >) gui still freeze for some sec! what i need to do?

[Christian Ehrlicher]

@saeid0034 said in Program freeze when try to get MD5 of files:

what i need to do?

fix your code to properly run the task in a separate thread.

[saeid0034]

@Christian-Ehrlicher my code

main.cpp

#include "user_def.h"
#include "mainwindow2.h"
#include...

QString Md5_gen(QString const &s)
{
    QString pakchunk_Md5;
    QCryptographicHash crypto(QCryptographicHash::Md5);
    QFile pakchunk("D:/Games/TDPA - Man of Medan" + s);
    if (pakchunk.open(QIODevice::ReadOnly))
    {
        while(!pakchunk.atEnd()){
        crypto.addData(pakchunk.read(8192));
        }
    } else
    {
        qDebug() << "Can't open file.";
        pakchunk_Md5 = "nofile";
        return pakchunk_Md5;
    }
    pakchunk_Md5 = crypto.result().toHex();
    return pakchunk_Md5;
}

int main(int argc, char *argv[]) {
  QApplication a(argc, argv);

  a.setStyle(new DarkStyle);

  FramelessWindow framelessWindow;
  framelessWindow.setWindowIcon(a.style()->standardIcon(QStyle::SP_DesktopIcon));

  MainWindow *mainWindow = new MainWindow;

  framelessWindow.setContent(mainWindow);
  framelessWindow.show();

  return a.exec();
}

user_def.h

#ifndef USER_DEF_H
#define USER_DEF_H
#include <QString>

QString Md5_gen(QString const &s);

#endif // USER_DEF_H

mainwindow2.h

#ifndef MAINWINDOW2_H
#define MAINWINDOW2_H

#include <QMainWindow>
#include <QtConcurrentRun>
#include <QFuture>
#include <QFutureWatcher>
#include <QThread>
#include <QThreadPool>
#include "user_def.h"

namespace Ui {
class MainWindow2;
}

class MainWindow2 : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow2(QWidget *parent = nullptr);
    ~MainWindow2();

public slots:
      void run_thread();
      void displayFinishedBox();

private slots:
    void on_pushButton_clicked();

    void on_pushButton_2_clicked();

    void on_radioButton_2_clicked();

    void on_radioButton_4_clicked();

    void on_radioButton_3_clicked();

    void on_radioButton_clicked();

private:
    Ui::MainWindow2 *ui;
    QFutureWatcher<QString> *watcher;
    QFuture<QString> *future;
};

#endif // MAINWINDOW2_H

mainwindow2.cpp

#include...

MainWindow2::MainWindow2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow2)
{
    ui->setupUi(this);
    connect(ui->pushButton, &QPushButton::clicked,
               this, &MainWindow2::run_thread);


    // display a message box when the calculation has finished

    future = new QFuture<QString>;
    watcher = new QFutureWatcher<QString>;

    connect(watcher, SIGNAL(finished()),
            this, SLOT(displayFinishedBox()));

}

MainWindow2::~MainWindow2()
{
    delete ui;
}

void MainWindow2::run_thread()
{
    int file_ok = 0;
    //file pak33
    QString loc33 = "/SM/test1.pak";
    QFuture<QString> future33 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc33);
    watcher->setFuture(future33);
    QString pakchunk33 = future33.result();

    qDebug() << pakchunk33;
    if (pakchunk33 == "f7002d4419cd235a87746715ba6fb2ea")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label_8->setText("OK");
        ui->label_8->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk33 == "nofile")
    {
        qDebug() << "no file found";
        ui->label_8->setText("not found");
        ui->label_8->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label_8->setText("wrong");
        ui->label_8->setStyleSheet("QLabel { color : red; }");
    }
    ui->progressBar->setValue(12);

    //file pak34
    QString loc34 = "/SM/test2.pak";
    QFuture<QString> future34 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc34);
    watcher->setFuture(future34);
    QString pakchunk34 = future34.result();
    qDebug() << pakchunk34;

    if (pakchunk34 == "64c77598586b6c3cb60beed0b0750620")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label->setText("OK");
        ui->label->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk34 == "nofile")
    {
        qDebug() << "no file found";
        ui->label->setText("not found");
        ui->label->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label->setText("wrong");
        ui->label->setStyleSheet("QLabel { color : red; }");
    }
    ui->progressBar->setValue(25);

    //file pak35
    QString loc35 = "/SM/test3.pak";
    QFuture<QString> future35 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc35);
    watcher->setFuture(future35);
    QString pakchunk35 = future35.result();

    qDebug() << pakchunk35;
    if (pakchunk35 == "ee53f7a7656a32b5278c460baec46f16")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label_7->setText("OK");
        ui->label_7->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk35 == "nofile")
    {
        qDebug() << "no file found";
        ui->label_7->setText("not found");
        ui->label_7->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label_7->setText("wrong");
        ui->label_7->setStyleSheet("QLabel { color : red; }");
    }
    ui->progressBar->setValue(38);

    /*Some other code*/

i dont know what is problem on this code

[Christian Ehrlicher]

@saeid0034 said in Program freeze when try to get MD5 of files:

i dont know what is problem on this code

You don't read the post from others:

As @SGaist already said, calling result() when the future is not done yet will block your event loop.

[saeid0034]

@Christian-Ehrlicher i follow

@aha_1980 said in Program freeze when try to get MD5 of files:

see e.g. this example.

example, i read QtConcurrent doc and try to use it with watcher but after all i dont have any luck

[Christian Ehrlicher]

The example shows you exactly how to use it. Post some code of your try when you follow the example.

[SGaist]

@saeid0034 said in Program freeze when try to get MD5 of files:

@Christian-Ehrlicher i follow

@aha_1980 said in Program freeze when try to get MD5 of files:

see e.g. this example.

example, i read QtConcurrent doc and try to use it with watcher but after all i dont have any luck

You just added a watcher to your code, as already written several times: stop using result right after your run calls.

[JonB]

@saeid0034 said in Program freeze when try to get MD5 of files:

QFuture<QString> future33 = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc33);
watcher->setFuture(future33);
QString pakchunk33 = future33.result();

I am not saying anything that @SGaist & @Christian-Ehrlicher have not said already, but perhaps this will clarify.

Examine these three adjacent lines in your code:

1. First line sets off the computation to run concurrently in another thread. It ha started now, but (probably) not finished.
2. Second line places a "watcher" on the thread/result, to notify when it does finish. Thread is still running.
3. Third line wants the result from the thread. so it stops/blocks on that line until the thread finishes and the result is available. Code does not proceed from that line now, till the thread is done.

It's line #3 that you cannot afford to put where it is currently. The code which needs to read the result of the thread must not be executed till the thread is ready to deliver it, which will come in a slot on the watcher. Your code which works with the computed result belongs there. This is how you should rewrite your code.

Or, if you have let it start and done some stuff of your own here, and then you get "fed up" of waiting and have nothing else to do, you might at that point call future33.result(). But be aware that if you call it anywhere while the thread has not yet finished you will block on the call till it does. And that will stop your calling thread from doing anything else till it arrives, including servicing the main event loop which is what keeps your Qt UI responsive.