Dimension Scales in C++ interface?

HDF5 Library C++ Users' Group
1

Does the HDF5 C++ API have an interface for creating and reading dimension scales?

I have been trying to use the C++ API, but, I suspect this may force me over the the C API. I understand it has more flexibility.

Thanks,
Mike

PS I’d be interested in knowing the support available for dimension scales in h5cpp as well.

2

If you are looking for flexibility without trade offs you might want to give a try to H5CPP an HDF5 header only interface for modern C++. From your point the most interesting feature is seamless integration/conversion from/to HDF5 CAPI hid_t descriptors.

The project embraces most HDF5 CAPI functionality and extends it with high performance packet table implementation. The only requirement is to link against: -lhdf5 -lz -ldl -lm.

From the HDF5 dimension scales documentation there are only a few calls which you can pass h5::ds_t dataset descriptor either by static_cast<hid_t>( ds ) or directly using H5CPP automatic conversion capabilities. If you have any problems getting working feel free to shoot me a line.

debian/ubuntu/rpm packages are here as well as the LLVM based source cod transformation tool. While other OS-s are not yet supported windows and mac are conformed to work. Just copy the include files into your project directory.

best wishes: steven

3

Steven,

I saw your presentation a couple of weeks ago on this. Your library looks really solid and if I were to move to one, it is the one I would use. For the moment I’m trying to get this done without adding an additional library, though (even though the templates are quite lightweight, easy to add). My next iteration, I may incorporate the templates.

Others,

Maybe someone has other ideas? What about mixing the C interface and the C++ interface - I’ve already gotten the code half written in the original C++ interface, and I’d had to have to go back and re-write (though that would be cleanest, I expect, for consistency).

Best Regards,
Mike

4

Hello Mike,

The C++ API offers wrappers for only a subset of the main C library and, unfortunately, dimension scales are not part of that subset at this time. If you’d like to continue using the C++ API but need some features that are not yet available, you can use the those features from the C library passing in the correct identifiers via the member function getId().

Thank you,

Binh-Minh

5

Hi Bihn-Minh,

I started using the C API and getId() from the C++ created items. That worked out well. I have written dimension scales to the file (confirmed with HDF Compass).

But, now I am trying to read them back in a general way. I don’t understand how H5DSIterate is supposed to work - though it seems like it should be that. All I really want is to get the id of the Dimension Scale dataset from the parent dataset, something like

dsid = H5Dget_datascale( did, indx )

is it possible to do this? Maybe I need to get that from the Data Space? I expect I could also just go to the DIMENSION_LIST attribute and get it from there. Alternately, I could explicitly add DIMENSION_LABELS, and use them as names of the variable which are the dimension scales, but, that seems a bit artificial.

Thanks for the help.

Best Regards,
Mike

6

Hi again, Mike (after 2yrs!)

I’m sorry that I didn’t see your message then. I hope you were able to get the id of the Dimension Scale dataset from the parent dataset and resolve the issue.

Binh-Minh