[Nexus] problems with current stable of nxbrowse and nxdir

freddie.akeroyd at stfc.ac.uk freddie.akeroyd at stfc.ac.uk
Sat Sep 14 22:17:38 BST 2013

Hi Tobias,

I had a look at the files you sent me and the problem is indeed to do with attributes, but not with them being arrays - the NXgetnextattr() / NXgetattrinfo() functions did not agree on the attribute count of externally linked datasets. Some NeXus utilities (such as NXbrowse) repeatedly call NXgetnextattr() until it returns "no more attributes", these were working OK with external links; however utilities that call NXgetattrinfo() and then loop over NXgetnextattr() for the expected count (e.g. NXdir, NXtraverse) were rightly treating "no more attributes" as an error.

Another issue came to light when I loaded Eugen's example file into a few other NeXus utilities - one of the groups in the file (NexusConfigurationLogs) had no NeXus class attribute, and this caused problems similar to the attributes one above with calls to NXgetgroupinfo() / NXgetnextentry()    

I've now fixed both these issues on trunk http://trac.nexusformat.org/code/changeset/1914 and merged the changes back into the 4.3 branch - an updated source download is available at http://download.nexusformat.org/kits/snapshots.shtml



> -----Original Message-----
> From: nexus-bounces at nexusformat.org [mailto:nexus-
> bounces at nexusformat.org] On Behalf Of Tobias.Richter at diamond.ac.uk
> Sent: 10 September 2013 10:04
> To: nexus at nexusformat.org
> Subject: Re: [Nexus] problems with current stable of nxbrowse and nxdir
> I can confirm that we have failure on (some of) our files.
> My suspicion was that we have arrays as attributes, which for these utilities
> is unexpected.
> As I seem to be one of the last few to use command line tools on data files
> here, there wasn't enough push from clients to get this fixed.
> Regards,
> Tobias
> ________________________________________
> From: nexus-bounces at nexusformat.org [nexus-
> bounces at nexusformat.org] on behalf of Wintersberger, Eugen
> [eugen.wintersberger at desy.de]
> Sent: 10 September 2013 09:54
> To: nexus at nexusformat.org
> Subject: [Nexus] problems with current stable of nxbrowse and nxdir
> Hi folks
>   I got some reports that nxbrowse and nxdir do not work with the Nexus
> files we produce here at DESY. I can confirm this on my Debian system
> where libnexus0 is installed in version 4.2.1.
> I suspect that this still has a problem that we are using variable
> length strings and thus cannot read attribute data correctly. I have
> attached a file for testing. By the way can someone may have a look at
> the file if we got it at least a bit right ;)
> @Benjamin - this file does not collect non-standard fields into
> NXcollection as we discussed in Warwick. However, our new setups do. I
> am still working on the draft for a kind of 'best-practice' paper and I
> hope I can submit it to this mailing list this week.
> regards
>   Eugen
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