Encode/decode to binary file

jsulm

@Hollywood33 Then you want to write text. Because text editors (like the name suggests) only understand text. It wouldn't be a binary file. You would write 1 and 0 as characters:

QFile file("out.txt");
if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
    return;

QTextStream out(&file);
out << "010001100101110";

You need to understand the difference between text and binary. 0 as character in a text file is stored as ASCII number 48, 1 is 49. That means if you store 01 in a text file and open it in a hex editor you will see 4849 (or 0x30 0x31 as hex).

Hollywood33

@jsulm i know the difference between text and binary code.
I want to see 0&1's as UTF-8 text in *.txt file. What you have written is only writes text into file.

jsulm

@Hollywood33 '1' and '0' are same in ASCII and UTF-8 as far as I know...

J.Hilk

because I'm a good guy :-)

QString toBitString(const QVariant &v)
{
    QByteArray bytes = v.toByteArray();
    QString bitString;

    QChar Zero('0');
    QChar One('1');

    for(int y(0); y <bytes.size(); y++){
        for(int i(0); i < 8; i++){
            bool b = (bytes[y] >> i) & 1;
            bitString.append(b ? One:Zero);
        }
    }
    return bitString;
}

Edit:
Small edit in the code example, v.toByteArray().data() totally unnecessary!

Hollywood33

@J.Hilk It looks like what I need. It remains only to understand how to use it with QFileDialog.

mrjj

@Hollywood33
Hi
The docs shows how to use it.
http://doc.qt.io/qt-5/qfiledialog.html
It has sample :)

Cobra91151

@Hollywood33

Ok, here is the code how I would save it with QFileDialog class using @J-Hilk solution.

QString filters = "Text Documents (*.txt);;All files (*.*)";
QString filePath = QFileDialog::getSaveFileName(this, "Save binary file", qApp->applicationDirPath() + "/MyFile", filters, nullptr);

 if (!filePath.isEmpty()) {
      QFile *myFile = new QFile(filePath);
      myFile->open(QIODevice::WriteOnly);
      QTextStream myTextStream(myFile); //QTextStream is used because you want to save it in .txt file
      myTextStream << toBitString(QString("This is a test!"));
      myFile->close();
      myFile->deleteLater();
      QMessageBox::information(this, "Information", "Binary file is saved!", QMessageBox::Ok);
 }

mrjj

@Cobra91151
Hi
Just as a note.
There is really no need to new the QFile.
QFile myFile;
will work just as fine as it has no need to survive the scope/function.
but you do delete it so no leak but no real benefit :)

Cobra91151

@mrjj

Hi! Yes, you right, in this example better to use QFile myFile on the stack.

Hollywood33

@Cobra91151 can't build: nullptr is not declared in this scope;
tobitstring is not declared in this scope

mrjj

@Hollywood33
odd it dont know nullptr but you can use 0 (zero) or NULL instead
also just remove
myTextStream << toBitString(QString("This is a test!"));
--->
myTextStream << QString("This is a test!");

Cobra91151

@mrjj

The code - myTextStream << QString("This is a test!"); will write only text not bit representation as he wants. So it must be - myTextStream << toBitString(QString("This is a test!"));

Cobra91151

@Hollywood33

You must declare tobitstring function in the header (.h file) to use it. + Specify more info about your building process (Qt version, compiler, OS)?

Also, instead of nullptr, you can use - Q_NULLPTR macro or add the QString *selectedFilter as the parameter points to in the docs - QFileDialog.

Hollywood33

@mrjj it writes test text, no 0&1s.

I was told to read into QByteArray and then send it to stream:
QFile f("/Users/ro888.jpg");
f.open(QIODevice::ReadOnly);
QByteArray ba = f.readAll();
stream << ba;

So I have to update code in the following example using QByteArray:
How to do it?

void MainWindow::on_pushButton_3_clicked()
{
QFile file("/Users/file.bin");
if(file.open(QIODevice::WriteOnly))
{
QDataStream stream(&file);
stream. setVersion(QDataStream::Qt_4_2);
stream << QPointF(30, 30) << QImage("/Users/ro888.jpg");
if(stream.status() != QDataStream::Ok)
{
qDebug() << "Error";
}
}
file.close();
}

mrjj

@Hollywood33
Hi
Yes sorry my bad.
I missed that QString toBitString(const QVariant &v) was the function @J-Hilk provided :)
So place
QString toBitString(const QVariant &v) in .h and
the body in the cpp as @Cobra91151 says :)

mrjj

@Hollywood33
Hi
Yes using QDataStream will be a binary file.
You paths for the JPG files looks a bit odd but if you are sure they are valid then
should produce a truly binary file :)

Hollywood33

@Cobra91151 I'm on Qt 5.1.0, OS X 10.6.8
I added to header #include "tobitstring.h" - error: no such file or directory

Cobra91151

@Hollywood33 said in Encode/decode to binary file:

@Cobra91151 I'm on Qt 5.1.0, OS X 10.6.8
I added to header #include "tobitstring.h" - error: no such file or directory

You should add the prototype of the function to header file, not include it. Include works for additional files, not for functions!

For example:

test.h file:

public:
    explicit Test(QWidget *parent = 0);
    QString toBitString(const QVariant &v);
    ~Test();

It contains a constructor, prototype function and destructor.
And then put the body of the function in test.cpp file like this:

QString Test::toBitString(const QVariant &v)
{
    QByteArray bytes = v.toByteArray();
    QString bitString = "";

    QChar Zero('0');
    QChar One('1');

    for (int y(0); y <bytes.size(); y++){
        for (int i(0); i < 8; i++){
            bool b = (bytes[y] >> i) & 1;
            bitString.append(b ? One:Zero);
        }
    }

    return bitString;
}

Your class is - MainWindow, Test is just for testing purposes.

J.Hilk

@Cobra91151 I have to compliment your patience. *Thumbs up*

VRonin

You can simplify it:

QString Test::toBitString(const QVariant &v)
{
    const QByteArray bytes = v.toByteArray();
    QString bitString;
for(const char* singlebyte = bytes.begin();singlebyte != bytes.end();++singlebyte)
bitString.append(QString::number(*singlebyte,2));
    return bitString;
}

But still looks absolutely useless to me