QFile - Row Count Problem

kingsta

Hi guys

I have datas in txt file. I want to count how many rows are in the txt file.

data_num.txt
@
10 15,2
12,1 42
...
@

@
...
QFile file("datas/data_num.txt");
...
QTextStream in(&file);
...
int rowSize;
while( !in.atEnd()){
rowSize++;
}
@

When I debuged the program, I guess I got endless loop. Because my program is waiting something and It crash. Why doesn't the while loop stop?

andre

Because inside your loop, you are not doing any file reading. You should read a line per loop iteration.

kingsta

[quote author="Andre" date="1364563689"]Because inside your loop, you are not doing any file reading. You should read a line per loop iteration.[/quote]

Okey. I changed the code but now I cant get the datas from txt. Because "in" locations is atEnd?

@ QString a;
while( !in.atEnd()){
a = in.readLine();
rowSize++;
}

...
QString data1, data2;

for(int i=0; !in.atEnd(); i++) {
in >> data1 >> data2;

    accTableColumn1[i] = data1.toDouble();
    accTableColumn2[i] = data2.toDouble();

}
@

andre

Why don't you combine the two operations in a single loop? That would be much more efficient...

kingsta

I know but there are some codes in second loop which need rowSize.

andre

Really? There is no way around that?
Note that reading the input file twice is much slower than iterating over an in-memory structure again to adapt some values...

But if you insist: how about you simply move the position back to the beginning of the file after you have measured the number of rows? QIODevice::seek should be what you are looking for there.

kingsta

Yes, you right. I should change my code a little. By the way I fix the error with seek() func. Thanks for quick help:)

@ QString a;
while( !in.atEnd()){
a = in.readLine();
rowSize++;
}
in.seek(0);
...@