[Kst] readField() in a datasource

Nicholas Chapman nchapman at u.northwestern.edu
Mon Jun 23 15:32:58 UTC 2014

I had used the debugging in QtCreator which lead me to think there was
a problem.  However, after a weekend rest, I realized the problem was
partly operator error, and partly fitstable not handling cases where
only a subset of rows from a file should be read.  I can fix the
latter, but the former keeps cropping up. ;)


On 6/23/14, Brisset, Nicolas <nicolas.brisset at airbus.com> wrote:
> Dear Nicholas,
> My understanding is the same as yours regarding the expected arguments and
> the fact that frameCount should return the number of samples to read from
> the field. V is normally sized accordingly.
> I can't really help further here, other than suggesting you to use QtCreator
> to debug (in case you're not doing so already) as it is very convenient.
> What value does frameCount() return and which s and n args do you receive in
> readField()?
> Nicolas
> -----Ursprüngliche Nachricht-----
> Von: kst-bounces at kde.org [mailto:kst-bounces at kde.org] Im Auftrag von
> Nicholas Chapman
> Gesendet: Samstag, 21. Juni 2014 00:31
> An: kst
> Betreff: [Kst] readField() in a datasource
> Hi, I'm struggling with a bug with the FitsTable plugin.  I've discovered
> that on my mac, some Fits tables can't be read (Kst crashes), but those same
> files open fine on a different machine running linux.  Both are 64-bit.  My
> theory is that very long tables are causing the problem.  I would like some
> help understanding the
> readField() function in a datasource.  For example, from FitsTable:
> int FitsTableSource::readField(double *v, const QString& field, int s, int
> n) {
> My understanding is that v is the array which needs to have values added to
> it.  Kst will read v to then plot the data.  n is then the length of v,
> which has already been allocated by Kst.
> Is that correct?  If so, how does Kst know what the value of n should be for
> a given field?  I thought it was from the function, e.g.
> int FitsTableSource::frameCount(const QString& field) const {
> which should return the size of a given field.  If so, then I don't
> understand why the value of n passed to readField() is not the correct
> value.  I wonder if this is an int versus long int thing.
> Thanks,
> Nicholas Chapman
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