Qt - QStringList to QByteArray

Question

What is the most efficient way of converting QStringList to QByteArray?

I have found many examples of similar conversions but never the one I needed or were just needlessly too complicated.

---

The code sanitize a string input and then convert it to QByteArray. I am struggling with the latter part.

void MainWindow::on_suicideButton_clicked()
{
    QString input = ui->lineEdit->text();
    try{
        if(ui->lineEdit->text().contains("0x")||ui->lineEdit->text().contains(",")||ui->lineEdit->text().contains("-"))
        {
            input = input.replace("0x","");
            if (input.contains(',')) input = input.replace(",", "");
            // QString trim = input.trimmed();
            // input = trim;//.split(',', ' ', '-');
            QStringList inputArray = input.split('-');
            QByteArray output = inputArray;
        }
        //printf("%s\n", input);

        ui->lineEdit->setText(input);
    }
    catch (const std::bad_alloc &) {input = " ";}
}

QStringList inputArray = input.split('-'); is important (or at least I believe it to be so), as I would need to split the bytes into separate chunks in order to perform various operations on them.

---

Here is an example, in order for you to see what kind of operations I would like to do:

char MainWindow::checkSum(QByteArray &b)
{
    char val = 0x00;
    char i;
    foreach (i, b)
    {
       val ^= i;
    }

    return val;
}

Answer 1

How about a QDataStream to serialize the string list?

// Fill the data buffer
QByteArray data;
QStringList list{"foo", "bar", "foobar"};
QDataStream dataStreamWrite(&data, QIODevice::WriteOnly);
dataStreamWrite << list;

// Do whatever you want with the raw data

// And if you want to convert it back to a QStringList
QDataStream dataStreamRead(data);
QStringList list2;
dataStreamRead >> list2;

Answer 2

You can simply apply QByteArray::append(const QString &str) for each string in your list. Docs says it will automatically convert string:

Appends the string str to this byte array. The Unicode data is converted into 8-bit characters using QString::toUtf8().

So you can write something like this:

QByteArray output;

// inputArray - your QStringList
foreach (const QString &str, inputArray)
{
    output.append(str);
}

But if you don't want default conversation you can append strings converted to const char * as stated in the same docs:

You can disable this function by defining QT_NO_CAST_TO_ASCII when you compile your applications. You then need to call QString::toUtf8() (or QString::toLatin1() or QString::toLocal8Bit()) explicitly if you want to convert the data to const char *.

And do something like this:

output.append(str.toUtf8()); // or str.toLatin1() or str.toLocal8Bit()

Edit 1

Just found that you can also use += instead of append() :

output += str;

This would behave the same way as append() as said here.

Answer 3

If I understand correctly, you will have to join the strings with a separator of your choice, then have to use one of the QString functions to convert to QByteArray depending on the QStrings encoding

QStringList strlist; //Let's assume there's a value in there

QChar separator = ''; //Any QChar or QString you want to use to separate the QStringList
strlist.join(separator).toLocal8Bit(); //8 bit
strlist.join(separator).toUtf8(); //UTF-8
strlist.join(separator).toLatin1(); //Latin

Edit 1 to fit your code

if(input.contains("0x")||input.contains(",")||input.contains("-"))
{
    //Just replace the chars you don't cant, then convert back to QByteArray
    input = input.replace("0x","");
    input = input.replace(",", "");
    input = input.replace("-", "");
    QByteArray output = input.toLocal8Bit();
}

Edit 2 with QStringList

if(input.contains("0x")||input.contains(",")||input.contains("-"))
{
    //Just replace the chars you don't cant, then convert back to QByteArray
    input = input.replace("0x","");
    input = input.replace(",", "");
    QStringList inputArray = input.Split('-');

    //Do what you want with your list
    //...

    //Converts it back
    QByteArray output = inputArray.join('').toLocal8Bit();
}

I cannot test the code right now, so there might be a typo

Answer 4

As dydil also answered, you can use QDataStream.

For example:

QByteArray serialize(QStringList data)
{
    QByteArray byteArray;
    QDataStream out(&byteArray, QIODevice::WriteOnly);
    out << data;
    return byteArray;
}

void deserialize(QByteArray byteArray, QStringList *data)
{
    QDataStream in(&byteArray, QIODevice::ReadOnly);
    in >> *data;
}