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List:       kde-devel
Subject:    Re: kdelibs/kfile
From:       Hans Petter Bieker <zerium () traad ! lavvu ! no>
Date:       1999-06-23 18:20:17
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On Wed, 23 Jun 1999, Stephan Kulow wrote:

> That's the problem with using QString. If you want to compare the
> first couple of characters, you have to create a complete new
> string and you make it way slower ;(

#include <qstring.h>
int main()
{
        QString a1("hei på deg");
        QString a2("hei på meg");
        int i;
        for (i = 0; i < 6400000; i++)
	        strcmp(a1.latin1(), a2.latin1());
}
...takes:
real    0m8.410s
user    0m8.211s
sys     0m0.067s

If I change "strcmp(a1.latin1(), a2.latin1());" to a1.compare(a2); or just
a1 == a2, it the results are:
real    0m22.573s
user    0m21.889s
sys     0m0.090s

If I change "a1 == a2" to "a1.lower() == a2.lower();", and just test 1/10,
the results are..:
real    0m28.776s
user    0m28.914s
sys     0m0.093s

> Perhaps QString should get far more operators to make this easier,
> for example instead of using qstring1.left(3) == qstring2.left(3)
> there could be qstring1.strncmp(qstring2, 3) or something like that...

Maybe... But why is QString::compare() so much slower than strcmp() in
the first place?

I tried to create my own compare():
bool compare( const QString &as, const QString &bs )
{
    if (as.length() != bs.length()) return false;
    const QChar *a = as.unicode();
    const QChar *b = bs.unicode();
    if (memcmp(a, b, as.length() * sizeof(QChar)) != 0)
        return false;
    return true;
}

That code seems to work, but uses only:
real    0m0.681s
user    0m1.562s
sys     0m0.062s

What am I missing?

> At least now we buy the price of having the possibility of showing
> cjk filenames with speed. 

cjk?

-bieker-

Benytt Dem av http://www.excite.no/, det gjør jeg!    -- Ich vermisse Kiel!
Oslo, Kongeriket Norge/Norwegiches Königreich/Monarchy of Norway, Europ[ae]

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