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

Quincey Koziol koziol at lbl.gov
Tue Sep 5 14:27:48 CDT 2017


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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