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re: Discussion https://github.com/Unidata/netcdf-c/discussions/2214 The primary change is to support so-called "standard filters". A standard filter is one that is defined by the following netcdf-c API: ```` int nc_def_var_XXX(int ncid, int varid, size_t nparams, unsigned* params); int nc_inq_var_XXXX(int ncid, int varid, int* usefilterp, unsigned* params); ```` So for example, zstandard would be a standard filter by defining the functions *nc_def_var_zstandard* and *nc_inq_var_zstandard*. In order to define these functions, we need a new dispatch function: ```` int nc_inq_filter_avail(int ncid, unsigned filterid); ```` This function, combined with the existing filter API can be used to implement arbitrary standard filters using a simple code pattern. Note that I would have preferred that this function return a list of all available filters, but HDF5 does not support that functionality. So this PR implements the dispatch function and implements the following standard functions: + bzip2 + zstandard + blosc Specific test cases are also provided for HDF5 and NCZarr. Over time, other specific standard filters will be defined. ## Primary Changes * Add nc_inq_filter_avail() to netcdf-c API. * Add standard filter implementations to test use of *nc_inq_filter_avail*. * Bump the dispatch table version number and add to all the relevant dispatch tables (libsrc, libsrcp, etc). * Create a program to invoke nc_inq_filter_avail so that it is accessible to shell scripts. * Cleanup szip support to properly support szip when HDF5 is disabled. This involves detecting libsz separately from testing if HDF5 supports szip. * Integrate shuffle and fletcher32 into the existing filter API. This means that, for example, nc_def_var_fletcher32 is now a wrapper around nc_def_var_filter. * Extend the Codec defaulting to allow multiple default shared libraries. ## Misc. Changes * Modify configure.ac/CMakeLists.txt to look for the relevant libraries implementing standard filters. * Modify libnetcdf.settings to list available standard filters (including deflate and szip). * Add CMake test modules to locate libbz2 and libzstd. * Cleanup the HDF5 memory manager function use in the plugins. * remove unused file include//ncfilter.h * remove tests for the HDF5 memory operations e.g. H5allocate_memory. * Add flag to ncdump to force use of _Filter instead of _Deflate or _Shuffle or _Fletcher32. Used for testing. |
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