Mimetype optimization

[Jakub Stachowski]

Dnia wtorek, 22 kwietnia 2008, David Faure napisał:
> On Tuesday 22 April 2008, Jakub Stachowski wrote:
> > Hello,
> >
> > profiling dolphin while opening /usr/bin shows that about 35% of time is
> > spent in QRegExp matching called by kmimefactory.cpp: matchFileName. This
> > function already contains optimizations: for some simple (but popular)
> > patterns like *.something or something* it uses direct comparision
> > instead of QRegExp big gun. It looks like:
> >    if (pattern like *.something && filename long enough to match the
> > pattern) compare directly;.
> > However for short names (lots of them in /usr/bin) it often falls back to
> > slow path. Attached patch changes is to:
> > if (pattern like *.something) {
> > 	if (filename not long enough to match) return false;
> > 	else compare directly;
> > }
> >
> > and detects patterns without wildcards (is checking for *,? and ]
> > enough?)
> >
> > Results (measured by callgrind):
> > Unpatched, for 179 calls to KMimeTypeFactory::findFromFileName
> > - 5554 calls to QRegExp::exactMatch, which accounts for 35% of CPU time
> >
> > Patched,  for 150 calls to KMimeTypeFactory::findFromFileName
> > - QRegExp matched 13 times.  findFromFileName takes 0.67% of CPU time
>
> Wow, excellent. Great find.
> If the kdecore/tests/kmimetypetest unit test still passes, please commit :)

Actually I get two failures (at lines 297 and 619, both related to *.doc) with 
and without the patch. But nothing changed, so I'm commiting.