QFile and setTextMode

[lyuts]

Hi, guys.

I was just experimenting with QFile and reading a random file line by line and got this question. Here is what i tried

#include <QFile>
#include <QStringList>
 
#include <QtDebug>
 
int main(int argc, char *argv[])
{
    QStringList list;
 
    list << "Makefile";
 
    QList<QString>::const_iterator it;
 
    for (it = list.begin(); it != list.end(); ++it) {
 
        QFile file((*it));
        //file.setTextModeEnabled(true);
 
        if (file.open(QFile::ReadOnly)) {
 
            char buf[1024];
 
            while ( 0 < file.readLine(buf, sizeof(buf)) ) {
                qDebug() << buf;
            }
 
            file.close();
 
        } else {
            qDebug() << "main> Unable to open file " << (*it);
        }
    }
 
    return 0;
}

#include <QFile>
#include <QStringList>

#include <QtDebug>

int main(int argc, char *argv[])
{
    QStringList list;

    list << "Makefile";

    QList<QString>::const_iterator it;

    for (it = list.begin(); it != list.end(); ++it) {

        QFile file((*it));
        //file.setTextModeEnabled(true);

        if (file.open(QFile::ReadOnly)) {

            char buf[1024];

            while ( 0 < file.readLine(buf, sizeof(buf)) ) {
                qDebug() << buf;
            }

            file.close();

        } else {
            qDebug() << "main> Unable to open file " << (*it);
        }
    }

    return 0;
}

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Note that setTextMode is commented.

The i run the program and see the file printed line by line and it is ok.

But, if uncomment setTextMode line, compile this program and run it again i always get this error:

QFile::open: File (Makefile) already open

QFile::open: File (Makefile) already open

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As far as i know the setTextMode set to true takes care of end-of-line conversion only.

Why does this happen?

Thanks.

[roxton]

Try to avoid setTextModeEnabled() and open the file in a text mode:

if (file.open(QIODevice::ReadOnly | QIODevice::Text))

if (file.open(QIODevice::ReadOnly | QIODevice::Text))

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[lyuts]

Thanks.
I know that this way works, but it is very interesting to know the reason of that behavior with setTextMode.

[sophister]

I have run your codes on my computer, and I face the same problem.
Learning……
Good luck!

[mcosta]

I suppose you must use QIODevice::setTextModeEnabled on a opened File

[sophister]

if we use QIODevice::setTextModeEnabled on an opened file, the status of the file cannot be shown on the screen. There is no difference between set this true and false.

[mcosta]

From Qt Documentation

void QIODevice::setTextModeEnabled ( bool enabled )

If enabled is true, this function sets the Text flag on the device; otherwise the Text flag is removed. This feature is useful for classes that provide custom end-of-line handling on a QIODevice.

seems that you can use the function to customize end of line handling for QIODevice subclass