Random hex number of given length in QT?

[jiveaxe]

Hi, I wonder if there is a way using plain QT to obtain a random hexadecimal number of any length. I found that it is possible to get 32 characters hex numbers with QUuid::createUuid() (removing {,},-), but what about for others lengths? I'm missing some qt feature or I have to use simple c++ routines?

Thanks,
Giuseppe

[ChrisW67]

For simple definitions of "random" you can use qsrand() and then qrand() to get 32, or fewer, bits at a time until you get sufficient bits. If you really want a hexadecimal string then stuff the bytes into a QByteArray and call QByteArray::toHex().

For any cryptographic purpose you want a better source of randomness and a cryptographic PRNG.


BTW: A UUID is not entirely random.

[jiveaxe]

Ok, I've followed qsrand()/qrand() way:

QTime time = QTime::currentTime();
qsrand((uint)time.msec());
 
...
 
QString Utils::getRandomHex(const int &length)
{
    QString randomHex;
 
    for(int i = 0; i < length; i++) {
        int n = qrand() % 16;
        randomHex.append(QString::number(n,16));
    }
 
    return randomHex;
}

QTime time = QTime::currentTime();
qsrand((uint)time.msec());

...

QString Utils::getRandomHex(const int &length)
{
    QString randomHex;

    for(int i = 0; i < length; i++) {
        int n = qrand() % 16;
        randomHex.append(QString::number(n,16));
    }

    return randomHex;
}

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