nc_inq_var_szip() fails before enddef for szip filter

[edwardhartnett]

This is a pretty minor issue, but it stands in the way of several other szip issues.

When setting the szip filter (with nc_def_var_filter() or nc_def_var_szip()), subsequent calls to nc_inq_var_szip() before enddef will fail to find that szip is set. From test_szip.c:

    szip_params[0] = H5_SZIP_NN_OPTION_MASK;
    szip_params[1] = H5_SZIP_MAX_PIXELS_PER_BLOCK_IN;
    { int stat = nc_def_var_filter(ncid, varid, HDF5_FILTER_SZIP, 2, szip_params);
       if(stat) {
         fprintf(stderr,"XXX: %d %s\b",stat,nc_strerror(stat));
         ERR;
       }
    }
    if(nc_inq_var_szip(ncid, varid, &options_mask_in, &pixels_per_block_in)) ERR;
    if(!(options_mask_in & H5_SZIP_NN_OPTION_MASK)) ERR;

I added the last two lines of code, and the second fails, because of this code in nc_inq_var_szip() (in dvarinq.c):

    if(id != H5Z_FILTER_SZIP || nparams != 4) 
         return NC_EFILTER; /* not szip or bad # params */ 

The problem is that szip has only 2 parameters until it is set by HDF5, then the number becomes 4. ;-)

Once enddef happens, the filter info is written to the dataset on disk, and from then on, nc_inq_var_szip() works correctly.

I will have a fix up shortly.