Qt Program freeze when try to get MD5 of files

Question

Hi im using this code for generate MD5 of files in QT

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;
}

I need to Generate MD5 of 8 Big file with this code (1.5GB>) Problem is When i press button to start Generate MD5, GUI Freeze until all MD5 generated
Im Test QFuture, QFutureWatcher, QtConcurrent in this way, But no luck GUi still freeze every time

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();

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*/

can anybody say what is my problem and how can i fix it?

edit 1

I edit my code in this way it working good without freeze gui in term of coding this code is standard?

mainwindow2.cpp

MainWindow2::MainWindow2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow2)
{
    ui->setupUi(this);
    connect(ui->pushButton_3, &QPushButton::clicked, this, &MainWindow2::MD5_thread_1);

    future = new QFuture<QString>;
    watcher1 = new QFutureWatcher<QString>;
    watcher2 = new QFutureWatcher<QString>;
    watcher3 = new QFutureWatcher<QString>;

    connect(watcher1, &QFutureWatcher<QString>::finished, this, &MainWindow2::MD5_thread_2);
    connect(watcher2, &QFutureWatcher<QString>::finished, this, &MainWindow2::MD5_thread_3);
    connect(watcher3, &QFutureWatcher<QString>::finished, this, &MainWindow2::MD5_thread_4);
    //some other code
}

void MainWindow2::MD5_thread_1()
{
    ui->pushButton->setEnabled(false);
    ui->pushButton->setText("procces started");
    ui->pushButton->setStyleSheet("QPushButton { color : white; background-color: rgb(73, 80, 93); }");
    ui->label->setText("checking");
    ui->label_2->setText("checking");
    ui->label_3->setText("checking");
    ui->label_4->setText("checking");
    ui->label_5->setText("checking");
    ui->label_6->setText("checking");
    ui->label_7->setText("checking");
    ui->label_8->setText("checking");
    ui->label_14->setText("waiting for end of check");
    ui->progressBar->setRange(0, 100);
    ui->progressBar_2->setRange(0, 100);
    ui->progressBar->setValue(0);
    ui->progressBar_2->setValue(0);

    //file pak33
    QString loc33 = "/SMG0/editor.pak";
    *future= QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc33);
    watcher1->setFuture(*future);
}

void MainWindow2::MD5_thread_2()
{
    QString pakchunk33 = future->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);
    watcher1->deleteLater();

    //file pak34
    QString loc34 = "/SMG0/2Editor.pak";
    *future = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc34);
    watcher2->setFuture(*future);
}

void MainWindow2::MD5_thread_3()
{
    QString pakchunk34 = future->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);
    watcher2->deleteLater();

    //file pak35
    QString loc35 = "/SMG0/3Editor.pak";
    *future = QtConcurrent::run(QThreadPool::globalInstance(), Md5_gen, loc35);
    watcher3->setFuture(*future);
}


void MainWindow2::core_install
{
    QString pakchunk35 = future->result();

    qDebug() << pakchunk40;
    if (pakchunk40 == "49e0440340044f424caeb82bade1301f")
    {
        qDebug() << "OK";
        file_ok++;
        ui->label_2->setText("OK");
        ui->label_2->setStyleSheet("QLabel { color : green; }");
    } else if (pakchunk40 == "nofile")
    {
        qDebug() << "no file found";
        ui->label_2->setText("not found");
        ui->label_2->setStyleSheet("QLabel { color : red; }");
    } else
    {
        qDebug() << "file is diffrent";
        ui->label_2->setText("wrong");
        ui->label_2->setStyleSheet("QLabel { color : red; }");
    }
    ui->progressBar->setValue(100);
    watcher3->deleteLater();

    //check if game is okey or not
    if (file_ok == 8)
    {
        ui->label_14->setText("O");
        ui->label_14->setStyleSheet("QLabel { color : green; }");
    } else
    {
        ui->label_14->setText("X");
        ui->label_14->setStyleSheet("QLabel { color : red; }");
    }
}

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 MD5_thread_1();
      void MD5_thread_2();
      void MD5_thread_3();
      void core_install();

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> *watcher1;
    QFutureWatcher<QString> *watcher2;
    QFutureWatcher<QString> *watcher3;
    QFuture<QString> *future;
    int file_ok = 0;
};

#endif // MAINWINDOW2_H

Answer 1

The result method blocks your UI thread, making the whole concurrent / future dance useless.

Create a watcher per future and link its finished signal to a lambda that passes both the filename and the contents of the result to a onHashCalculated method on your window. In that method you can check if the hash matches one of your predefined hashes, and update the UI.

Alternatively, move your current run_thread function to a separate QObject that runs on a separate thread, and have it emit a hashCalculated(name, hash) signal that your mainwindow subscribes to using a onHashCalculated slot similar to the one I described above.

Here is code for a HashChecker that encapsulates both approaches.

Note the static QMap that maps filenames to hashes, the way doneFile is chained to checkDone.

enum class Status { Ok, NotOk, Missing };

class HashChecker : public QObject {
    Q_OBJECT

public:
    QMap<QString, Status> done;

    HashChecker(QObject *parent = nullptr) : QObject(parent) {
        QObject::connect(this, &HashChecker::doneFile, this, &HashChecker::checkDone);
    }

    inline static const QMap<QString, QString> hashes = {
        {"/SM/test1.pak", "f7002d4419cd235a87746715ba6fb2ea"},
        {"/SM/test2.pak", "64c77598586b6c3cb60beed0b0750620"},
        {"/SM/test3.pak", "ee53f7a7656a32b5278c460baec46f16"},
    };

signals:
    void finished();
    void doneFile(const QString& fname, Status s);

private slots:
    void checkDone(const QString& fname, Status s) {
        done[fname] = s;
        if (done.size() == hashes.size())
            emit finished();
    }

public slots:
    void check_parallel() {
        for (auto it = hashes.cbegin(); it != hashes.cend(); it++) {
            auto fname = it.key();
            auto hash = it.value();

            QFuture<Status> fut = QtConcurrent::run(do_hash, fname, hash);
            QFutureWatcher<Status> *fw = new QFutureWatcher<Status>(this);
            fw->setFuture(fut);
            QObject::connect(fw, &QFutureWatcher<Status>::finished, this,
                    [=]() {
                    fw->deleteLater();
                    emit doneFile(fname, fut.result());
            });
        }
    }

    void check_sequential() {
        for (auto it = hashes.cbegin(); it != hashes.cend(); it++) {
            auto fname = it.key();
            auto hash = it.value();

            auto result = do_hash(fname, hash);
            emit doneFile(fname, result);
        }
    }
};

If you want to check files in parallel:

HashChecker *hc = new HashChecker();
QObject::connect(hc, &HashChecker::doneFile, this, &MainWindow2::onHashCalculated);
hc->check_parallel();

Sequential in a different thread is almost the same:

QThread *t = new QThread(this);
HashChecker *hc = new HashChecker();
hc->moveToThread(t);
QObject::connect(t, &QThread::started, hc, &HashChecker::check_sequential);
QObject::connect(hc, &HashChecker::doneFile, this, &MainWindow2::onHashCalculated);
QObject::connect(hc, &HashChecker::finished, t, &QThread::quit);
t->start();