Add a filter to HighFive #978

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1. LauZanMo commented on Apr 14, 2024

   

   LauZanMo

   on Apr 14, 2024

   Last edited by LauZanMo

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   I spent some time clarifying the structure of PropertyList in HighFive and found it very easy to add filter on this basis.
   First, I need to declare and implement the Blosc class in H5PropertyList.hpp and H5PropertyList_misc.hpp, respectively. Just like this:

   # H5PropertyList.hpp
   
   /// \implements PropertyInterface
   class Blosc {
       public:
           explicit Blosc(unsigned level, unsigned shuffle, unsigned compressor);
   
       private:
           friend DataSetCreateProps;
           void apply(hid_t hid) const;
           unsigned _cd_values[7];
   };
   
   
   
   # H5PropertyList_misc.hpp
   
   inline Blosc::Blosc(unsigned int level, unsigned int shuffle, unsigned int compressor) {
       _cd_values[4] = level;
       _cd_values[5] = shuffle;
       _cd_values[6] = compressor;
   }
   
   inline void Blosc::apply(const hid_t hid) const {
       detail::h5p_set_blosc(hid, _cd_values);
   }

   Then, as for the specific implementation function ‘detail::h5p_set_blosc’, I refer to the implementation of hdf5_blosc: #https://github.com/Blosc/hdf5-blosc/blob/master/src/example.c#L57 just like this:

   # h5p_wrapper.hpp
   
   #include "blosc_filter.h"
   inline herr_t h5p_set_blosc(hid_t plist_id, const unsigned int *cd_values) {
       char *version, *date;
       if (register_blosc(&version, &date) < 0) {
           HDF5ErrMapper::ToException<PropertyException>("Blosc filter unavailable.");
       }
       
       herr_t err = H5Pset_filter(plist_id, FILTER_BLOSC, H5Z_FLAG_OPTIONAL, 7, cd_values);
       if (err < 0) {
           HDF5ErrMapper::ToException<PropertyException>("Error setting blosc property");
       }
       return err;
   }
   

   Of course I need to link hdf5-blosc dynamic library files:

   # root CMakeLists.txt
   # I install hdf5-blosc to the default path
   set(blosc_filter_DIR /usr/local/lib/) 
   target_link_libraries(HighFive INTERFACE blosc_filter)
   target_link_directories(HighFive INTERFACE /usr/local/include/)

   Finally I can write with blosc-filter!

   HighFive::DataSetCreateProps props;
   props.add(HighFive::Chunking({4,4}));
   props.add(HighFive::Blosc(4, 1, BLOSC_BLOSCLZ));
   // create dataset and write with this properties!

   
2. alkino commented on Apr 14, 2024

   

   alkino

   on Apr 14, 2024

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   Do you think you can propose a PR with that? It looks exactly what you should do to add your own filter.
3. LauZanMo commented on Apr 15, 2024

   

   LauZanMo

   on Apr 15, 2024

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   OK, I'll submit a PR soon.