This PR started as an attempt to add unlimited dimensions to NCZarr.
It did that, but this exposed significant problems with test interference.
So this PR is mostly about fixing -- well mitigating anyway -- test
interference.
The problem of test interference is now documented in the document docs/internal.md.
The solutions implemented here are also describe in that document.
The solution is somewhat fragile but multiple cleanup mechanisms
are provided. Note that this feature requires that the
AWS command line utility must be installed.
## Unlimited Dimensions.
The existing NCZarr extensions to Zarr are modified to support unlimited dimensions.
NCzarr extends the Zarr meta-data for the ".zgroup" object to include netcdf-4 model extensions. This information is stored in ".zgroup" as dictionary named "_nczarr_group".
Inside "_nczarr_group", there is a key named "dims" that stores information about netcdf-4 named dimensions. The value of "dims" is a dictionary whose keys are the named dimensions. The value associated with each dimension name has one of two forms
Form 1 is a special case of form 2, and is kept for backward compatibility. Whenever a new file is written, it uses format 1 if possible, otherwise format 2.
* Form 1: An integer representing the size of the dimension, which is used for simple named dimensions.
* Form 2: A dictionary with the following keys and values"
- "size" with an integer value representing the (current) size of the dimension.
- "unlimited" with a value of either "1" or "0" to indicate if this dimension is an unlimited dimension.
For Unlimited dimensions, the size is initially zero, and as variables extend the length of that dimension, the size value for the dimension increases.
That dimension size is shared by all arrays referencing that dimension, so if one array extends an unlimited dimension, it is implicitly extended for all other arrays that reference that dimension.
This is the standard semantics for unlimited dimensions.
Adding unlimited dimensions required a number of other changes to the NCZarr code-base. These included the following.
* Did a partial refactor of the slice handling code in zwalk.c to clean it up.
* Added a number of tests for unlimited dimensions derived from the same test in nc_test4.
* Added several NCZarr specific unlimited tests; more are needed.
* Add test of endianness.
## Misc. Other Changes
* Modify libdispatch/ncs3sdk_aws.cpp to optionally support use of the
AWS Transfer Utility mechanism. This is controlled by the
```#define TRANSFER```` command in that file. It defaults to being disabled.
* Parameterize both the standard Unidata S3 bucket (S3TESTBUCKET) and the netcdf-c test data prefix (S3TESTSUBTREE).
* Fixed an obscure memory leak in ncdump.
* Removed some obsolete unit testing code and test cases.
* Uncovered a bug in the netcdf-c handling of big-endian floats and doubles. Have not fixed yet. See tst_h5_endians.c.
* Renamed some nczarr_tests testcases to avoid name conflicts with nc_test4.
* Modify the semantics of zmap\#ncsmap_write to only allow total rewrite of objects.
* Modify the semantics of zodom to properly handle stride > 1.
* Add a truncate operation to the libnczarr zmap code.
re: https://github.com/Unidata/netcdf-c/issues/2733
When addressing the above issue, I noticed that there was a disconnect
in NCZarr between nc_set_chunk_cache and nc_set_var_chunk cache.
Specifically, setting nc_set_chunk_cache had no impact on the per-variable cache parameters when nc_set_var_chunk_cache was not used.
So, modified the NCZarr code so that the per-variable cache parameters are set in this order (#1 is first choice):
1. The values set by nc_set_var_chunk_cache
2. The values set by nc_set_chunk_cache
3. The defaults set by configure.ac
re: PR https://github.com/Unidata/netcdf-c/pull/2716).
re: Issue https://github.com/Unidata/netcdf-c/issues/2189
The basic change is to make use of the fact that HDF5 automatically suppresses optional filters when an attempt is made to apply them to variable-length typed arrays.
This means that e.g. ncdump or nccopy will properly see meaningful data.
Note that if a filter is defined as HDF5 mandatory, then the corresponding variable will be suppressed and will be invisible to ncdump and nccopy.
This functionality is also propagated to NCZarr.
This PR makes some minor changes to PR https://github.com/Unidata/netcdf-c/pull/2716 as follows:
* Move the test for filter X variable-length from dfilter.c down into the dispatch table functions.
* Make all filters for HDF5 optional rather than mandatory so that the built-in HDF5 test for filter X variable-length will be invoked.
The test case for this was expanded to verify that the filters are defined, but suppressed.
re: PR https://github.com/Unidata/netcdf-c/pull/2655
This PR modifies the transient types PR so that all created
transient types are given a created unique name (within a
group). The form of the name is "_Anonymous<Class>NN". The class
is the user-defined type class: Enum, Compound, Opaque, or
Vlen. NN is an integer identifier to ensure uniqueness.
Additionally, this was applied to DAP/4 anonymous dimensions.
This also required some test baseline data changes.
The transient test case is modified to verify that the name exists.
re: Discussion https://github.com/Unidata/netcdf-c/discussions/2554
re: PR https://github.com/Unidata/netcdf-c/pull/2231
re: Issue https://github.com/Unidata/netcdf-c/issues/2189
After some discussion, the issue of applying filters on variables
whose type is not fixed size, was resolved as follows:
1. A call to nc_def_var_filter will ignore such filters, but will issue a log warning.
2. Loading (from an existing file) a variable whose type is not fixed-size and which has filters, will cause the variable to be suppressed.
This PR enforces those rules.
### Misc. Other changes
* Add a test case to test the vlen change.
* Make some minor clean-ups in various cmake and automake files.
* Remove unused test
The `FIND_PACKAGE` should not be called if the filter/compression library is not enabled. It was causing some inconsistencied in link libraries and CMake configure output...
