5.7 Opaque Type Introduction
NetCDF-4 added support for the opaque type. This is not supported in
classic or 64-bit offset files.
The opaque type is a type which is a collection of objects of a known
size. (And each object is the same size). Nothing is known to netCDF
about the contents of these blobs of data, except their size in bytes,
and the name of the type.
To use an opaque type, first define it with NF90_DEF_OPAQUE. If
encountering an enum type in a new data file, use NF90_INQ_OPAQUE
to learn it's name and size.
