re: https://github.com/Unidata/netcdf-c/issues/2294
Ed Hartnett suggested that the netcdf library installation process
be extended to install the standard filters into a user specified
location. The user can then set HDF5_PLUGIN_PATH to that location.
This PR provides that capability using:
````
configure option: --with-plugin-dir=<absolute directory path>
cmake option: -DPLUGIN_INSTALL_DIR=<absolute directory path>
````
Currently, the following plugins are always installed, if
available: bzip2, zstd, blosc.
If NCZarr is enabled, then additional plugins are installed:
fletcher32, shuffle, deflate, szip.
Additionally, the necessary codec support is installed
for each of the above filters that is installed.
## Changes:
1. Cleanup handling of built-in bzip2.
2. Add documentation to docs/filters.md
3. Re-factor the NCZarr codec libraries
4. Add a test, although it can only be exercised after
the library is installed, so it cannot be used during
normal testing.
5. Cleanup use of HDF5_PLUGIN_PATH in the filter test cases.
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.
