re: Issue https://github.com/Unidata/netcdf-c/issues/2502
H/T Charlie Zender
* Fix NCZarr handling of endianness value NC_ENDIAN_NATIVE. This now matches how it is handled in libhdf5
* Fix NCZarr handling of char typed attribute with value "". This now matches how it is handled in libhdf5
* Add test for various char attribute values
* Change the mapping of NC_CHAR and NC_STRING to dtype; requires changing some test files also.
* Optimize the testing for NC_ENOTBUILT in NC_open.
* Turn off debugging left on accidentally
* Fix memory leak in tst_pnetcdf.c
* Fix blosc test
re: PR https://github.com/Unidata/netcdf-c/pull/2492
re: Issue https://github.com/Unidata/netcdf-c/issues/2494
This PR fixes some problems with the pull request https://github.com/Unidata/netcdf-c/pull/2492 in response to Issue https://github.com/Unidata/netcdf-c/issues/2494.
* Found and fixed more scalar handling problems and add a test case for scalars.
* Cleanup nczarr_test/run_string.sh test
* Document *_nczarr_default_maxstrlen* and *_nczarr_maxstrlen*.
* Support both "Nan" and *Nan* as being floating point constants
for attributes. It is unclear from the Zarr V2 spec if
unquoted *Nan* is legal or not, but support for reading.
Write the quoted versions when writing an attribute. Similar
for Infinity constants.
So NCZarr supports the following constants for use in Attributes
* *Nan*, "Nan", *-Nan*, "-Nan"
* *Nanf*, "Nanf", *-Nanf*, "-Nanf"
* *Infinity*, "Infinity", *-Infinity*, "-Infinity"
* *Infinityf*, "Infinityf", *-Infinityf*, "-Infinityf"
* re: https://github.com/Unidata/netcdf-c/pull/2278
* re: https://github.com/Unidata/netcdf-c/issues/2485
* re: https://github.com/Unidata/netcdf-c/issues/2474
This PR subsumes PR https://github.com/Unidata/netcdf-c/pull/2278.
Actually is a bit an omnibus covering several issues.
## PR https://github.com/Unidata/netcdf-c/pull/2278
Add support for the Zarr string type.
Zarr strings are restricted currently to be of fixed size.
The primary issue to be addressed is to provide a way for user to
specify the size of the fixed length strings. This is handled by providing
the following new attributes special:
1. **_nczarr_default_maxstrlen** —
This is an attribute of the root group. It specifies the default
maximum string length for string types. If not specified, then
it has the value of 64 characters.
2. **_nczarr_maxstrlen** —
This is a per-variable attribute. It specifies the maximum
string length for the string type associated with the variable.
If not specified, then it is assigned the value of
**_nczarr_default_maxstrlen**.
This PR also requires some hacking to handle the existing netcdf-c NC_CHAR
type, which does not exist in zarr. The goal was to choose numpy types for
both the netcdf-c NC_STRING type and the netcdf-c NC_CHAR type such that
if a pure zarr implementation read them, it would still work and an
NC_CHAR type would be handled by zarr as a string of length 1.
For writing variables and NCZarr attributes, the type mapping is as follows:
* "|S1" for NC_CHAR.
* ">S1" for NC_STRING && MAXSTRLEN==1
* ">Sn" for NC_STRING && MAXSTRLEN==n
Note that it is a bit of a hack to use endianness, but it should be ok since for
string/char, the endianness has no meaning.
For reading attributes with pure zarr (i.e. with no nczarr
atribute types defined), they will always be interpreted as of
type NC_CHAR.
## Issue: https://github.com/Unidata/netcdf-c/issues/2474
This PR partly fixes this issue because it provided more
comprehensive support for Zarr attributes that are JSON valued expressions.
This PR still does not address the problem in that issue where the
_ARRAY_DIMENSION attribute is incorrectly set. Than can only be
fixed by the creator of the datasets.
## Issue: https://github.com/Unidata/netcdf-c/issues/2485
This PR also fixes the scalar failure shown in this issue.
It generally cleans up scalar handling.
It also adds a note to the documentation describing that
NCZarr supports scalars while Zarr does not and also how
scalar interoperability is achieved.
## Misc. Other Changes
1. Convert the nczarr special attributes and keys to be all lower case. So "_NCZARR_ATTR" now used "_nczarr_attr. Support back compatibility for the upper case names.
2. Cleanup my too-clever-by-half handling of scalars in libnczarr.
## Overwriting
I think I solved the file overwrite problem by doing light name
mangling of the shared library names. With this change the probabilty
is very small that installing our filter wrappers in a directory will
overwrite code produced by others.
## Default Install Location
I have setup the --with-plugin-dir option default to install in
the following locations in order of preference
1. If HDF5_PLUGIN_PATH is defined (at build time remember), then the last directory in that path will be where the filter wrapper shared libraries will be installed.
2. Otherwise the default is "/usr/local/hdf5/lib/plugin" (on *nix*) or "%ALLUSERSPROFILE%\\hdf5\\lib\\plugin" for Windows or Mingw.
Currently, --with-plugin-dir is disabled by default.
I should note that even if I enable it by default, installing
netcdf-c will still not run "out of the box" because the hypothetical
naive user will not know which compressor libraries need to be
pre-installed before netcdf is installed. Nor will that user have any
way to find out what needs to be installed.
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.
