[Hdf-forum] HDF lib incompatible with HDF file spec?

Krug, Markus markus.krug at hm.edu
Wed Sep 6 10:44:57 CDT 2017


Hi Quincey,

looking forward to get your results of the file analysis.

Best Regards
Markus

-----Ursprüngliche Nachricht-----
Von: Hdf-forum [mailto:hdf-forum-bounces at lists.hdfgroup.org] Im Auftrag von Quincey Koziol
Gesendet: Dienstag, 5. September 2017 21:28
An: HDF Users Discussion List <hdf-forum at lists.hdfgroup.org>
Betreff: Re: [Hdf-forum] HDF lib incompatible with HDF file spec?

Indeed.  :-)   I don’t have time to look into Markus’s file today, but I will take a look tomorrow and see what the best course of action is.

	Quincey



> On Sep 5, 2017, at 2:22 PM, Latham, Robert J. <robl at mcs.anl.gov> wrote:
> 
> On Tue, 2017-09-05 at 17:21 +0000, Miller, Mark C. wrote:
>> Hmm. If I understand you, you have written code that you believe 
>> produces an HDF5 file according to the 3.0 file version 
>> specification, https://support.hdfgroup.org/HDF5/doc/H5.format.html
>> but nevertheless does NOT use the HDF5 library to do it. Furthermore, 
>> where 'extended padding' is concerned, your implementation does 
>> business differently than the HDF5 implementation.
>> 
>> You can prove HDF5 tools will *read* the file ok. But, in a read- 
>> modify-write scenario, the file is getting corrupted by HDF5 library 
>> due to the difference in how the two implementations handle the 
>> extended padding -- a feature that you explain is '...not defined at 
>> all -- not even recommended'.
>> 
>> Is that about right?
>> 
>> If so, it does indeed sound like a potential issue in the file format 
>> specification for HDF5.
>> 
>> Your scenario sounds like a super useful test case...does a wholly 
>> independent implementation produce a file the HDF5 library can 
>> "handle"?
> 
> Over in Parallel-NetCDF land a few years back, we took, um, a "rather 
> aggressive interpretation" of the NetCDF spec with respect to 
> alignment and then opend a bug with Unidata when their tools did not 
> follow the rules as written.
> 
> As Mark observes, it was a productive exercise in keeping both 
> implementations honest.
> 
> ==rob
> 
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