Append/Prepend QString to QByteArray

[ermustaqbal]

Hi,

I have a question about QByteArray.

assume that i have a source like this

QByteArray ba;
 
    QString inName = QFileDialog::getOpenFileName(this, "Load a file");
    QFile *fileIn = new QFile(inName);
    fileIn->open(QIODevice::ReadOnly);
 
 
    ba = fileIn->readAll();

QByteArray ba;

    QString inName = QFileDialog::getOpenFileName(this, "Load a file");
    QFile *fileIn = new QFile(inName);
    fileIn->open(QIODevice::ReadOnly);


    ba = fileIn->readAll();

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"ba" is a QByteArray, i want to append QString after ba. How can i do that? because when i use QByteArray::append() i can't see anything change, and after i try to write ba as a file again, it is still the same like before.

Thanks in advanced,


ps: my file is binary(video) file

[mcosta]

can you post your code???

[ermustaqbal]

can you post your code???

QByteArray ba;
 
    QString inName = QFileDialog::getOpenFileName(this, "Load a file");
    QFile *fileIn = new QFile(inName);
    fileIn->open(QIODevice::ReadOnly);
 
 
    ba = fileIn->readAll();
    qDebug() << ba;
    qDebug() << ba.length();
    fileIn->close();
 
    QByteArray acba = ba;
    QString key = "thisisakey";
    acba = acba.append(key);
    qDebug() << acba; //i hope here will go "thisisakey" appended
 
    QString outName = QFileDialog::getSaveFileName(this, "Save a file");
    QFile *fileOut = new QFile(outName);
    fileOut->open(QIODevice::WriteOnly);
 
    fileOut->write(acba); // i will fail save the same file as before because i have append it with key, 
                                   // but the result it is success, and it means there is no change.
    fileOut->flush();
    fileOut->close();

QByteArray ba;

    QString inName = QFileDialog::getOpenFileName(this, "Load a file");
    QFile *fileIn = new QFile(inName);
    fileIn->open(QIODevice::ReadOnly);


    ba = fileIn->readAll();
    qDebug() << ba;
    qDebug() << ba.length();
    fileIn->close();

    QByteArray acba = ba;
    QString key = "thisisakey";
    acba = acba.append(key);
    qDebug() << acba; //i hope here will go "thisisakey" appended

    QString outName = QFileDialog::getSaveFileName(this, "Save a file");
    QFile *fileOut = new QFile(outName);
    fileOut->open(QIODevice::WriteOnly);

    fileOut->write(acba); // i will fail save the same file as before because i have append it with key, 
                                   // but the result it is success, and it means there is no change.
    fileOut->flush();
    fileOut->close();

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[wysota]

What does acba.size() return after line 15 compared to its result before this line?

[ermustaqbal]

What does acba.size() return after line 15 compared to its result before this line?

wysota after i print it out i have something like this :

before append: 26246026
after append: 26246036

it means the key succesfully appended?

---

Added after 54 minutes:

Hohoho got it, thanks wysota you make me think about size ... thanks a lot ...

[mcosta]

size increeased of 10 (size of "thisisakey");

This code works for me.

QByteArray ba ("1234567890");
qDebug () << ba;
 
ba = ba.append(QString("Hello World"));
qDebug () << ba;

QByteArray ba ("1234567890");
qDebug () << ba;

ba = ba.append(QString("Hello World"));
qDebug () << ba;

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If your file is a binary one, writing on console is wrong because at the first 0x00 byte the output will be truncated.