Performance problem with QFile.

[Abdeljalil]

I’m trying to calculate the hash of some disk image files (.iso)
so i have to read the entire file and store it in QByteArray to pass it later to QCryptographicHash::Hash
the problem is with reading performance, it takes a lot of time and the system freeze while using QFile::readAll() and storing it in byte array.
is there any solution to reduce the time and prevent the system form freezing?

[ecanela]

use the http://doc.qt.io/qt-4.8/QCryptographicHash::addData(), instead QCryptographicHash::hash(),

#include <QCryptographicHash>
#include <QFile>
#include <QDebug>
 
int main()
{
    QCryptographicHash crypto(QCryptographicHash::Md5);
    QFile file("linuxmint-16-xfce-dvd-64bit.iso");
 
    if ( !file.open(QFile::ReadOnly) ){
        qDebug() << "ERROR: cant read file";
    }
 
    qint64 size = 4 * 1024 * 1024; // segment of 4MB
    int iter = 0;
    while(!file.atEnd()){
        crypto.addData(file.read(size));
 
        ++iter;
        qDebug() << "iteration #" << iter
                 << " data offset; " << size*iter << "(bytes)" ;
    }
 
    QByteArray hash = crypto.result();
    qDebug() << hash.toHex();
    return true;
}

#include <QCryptographicHash>
#include <QFile>
#include <QDebug>

int main()
{
    QCryptographicHash crypto(QCryptographicHash::Md5);
    QFile file("linuxmint-16-xfce-dvd-64bit.iso");

    if ( !file.open(QFile::ReadOnly) ){
        qDebug() << "ERROR: cant read file";
    }

    qint64 size = 4 * 1024 * 1024; // segment of 4MB
    int iter = 0;
    while(!file.atEnd()){
        crypto.addData(file.read(size));

        ++iter;
        qDebug() << "iteration #" << iter
                 << " data offset; " << size*iter << "(bytes)" ;
    }

    QByteArray hash = crypto.result();
    qDebug() << hash.toHex();
    return true;
}

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i test this minimal example, only replace the filepath