How to enable compression support?

[dzenanz]

  xt::xzarr_file_system_store store(this->m_FileName); // version 2 file
  auto h = xt::get_zarr_hierarchy(store);
  //std::cout << "h.get_nodes " << h.get_nodes().dump(); // attempts to read non-existent file
  //std::cout << "h.get_children " << h.get_children("/").dump(); // attempts to read non-existent file
  std::cout << "h.get_array " << h.get_array("spectra"); // Unkown compressor type: blosc

Stepping through the code using debugger, I noticed that instance().m_builders only contains one entry: binary. As I had to specify the paths to zlib and blosc, I went back to CMake configurations, and noticed that xtensor-io has a few have settings so I enabled HAVE_Blosc, HAVE_GDAL and HAVE_ZLIB. After an incremental build of xtensor-io and xtensor-zarr, now instance().m_builders contains no entries. What am I doing wrong?

[davidbrochart]

You need to register the compressor first, like so:

xtensor-zarr/test/test_gcs.cpp

Line 22 in 90f0acf

xzarr_register_compressor<xzarr_gcs_store, xio_gzip_config>();

.

[dzenanz]

When I add that, I run into a link error: itkIOOMEZarrNGFF-5.3.lib(itkOMEZarrNGFFImageIO.obj) : error LNK2019: unresolved external symbol "void __cdecl xt::xzarr_register_compressor<class xt::xzarr_file_system_store,struct xt::xio_blosc_config>(void)" (??$xzarr_register_compressor@Vxzarr_file_system_store@xt@@Uxio_blosc_config@2@@xt@@YAXXZ) referenced in function "protected: __cdecl itk::OMEZarrNGFFImageIO::OMEZarrNGFFImageIO(void)" (??0OMEZarrNGFFImageIO@itk@@IEAA@XZ). This should not happen, as that procedure is templated. Do you have any suggestion? If it helps, my current code is here.

[davidbrochart]

I don't know, maybe @JohanMabille has some ideas?

[JohanMabille]

We have some precompiled instantiations of xzarr_register_compressor, maybe they prevent the ocmpiler from instantiating a new one?

Can you try adding this in your code before calling the register function (do not forget the declspec(dllexport/dllimport) if you need to use this instantitation in another library):

namespace xt
{
    template void xzarr_register_compressor<xzarr_file_system_store, xio_blosc_config>();
}

[dzenanz]

Yes, that did it. Perhaps it should be added to documentation? See #57.

[JohanMabille]

@dzenanz yes definitely. Would you like to open a PR?

[dzenanz]

I just added a new commit to #54.