Re: zero length attrributes...

• To: netcdf-hdf@xxxxxxxxxxxxxxxx
• Subject: Re: zero length attrributes...
• From: Quincey Koziol <koziol@xxxxxxxxxxxxx>
• Date: Wed, 12 Nov 2003 10:42:09 -0600 (CST)

Hi Ed,

> Quincey Koziol <koziol@xxxxxxxxxxxxx> writes:
> 
> >     What I was planning to do was to create empty dataspaces the same way we
> > create scalar dataspaces:
> >     scalar_space_id=H5Screate(H5S_SCALAR);  /* Create a scalar dataspace */
> > 
> > only use a new constant:
> >     empty_space_id=H5Screate(H5S_EMPTY);    /* Create an empty dataspace */
> > 
> >     Additionally, I think it would be a good idea to have two dataspaces 
> > that
> > are created by the library: H5S_SPACE_SCALAR and H5S_SPACE_EMPTY, which 
> > would
> > avoid the need for users to create these dataspaces (as outlined above) and
> > could be used directly in creating datasets or attributes:
> > 
> >     
> > dataset_id=H5Dcreate(fid,"/Dataset",H5T_NATIVE_INT,H5S_SPACE_EMPTY,H5P_DEFAULT);
> > 
> >     This would need support in the tools, the FORTRAN & C++ APIs, etc...
> > 
> >     Quincey
> > 
> > > Make sure that selections work sensibly:
> > > 
> > >     EMPTY AND SPACE = ??
> > >     EMPTY OR SPACE = ??
> > >     SPACE - EMPTY = SPACE
> > >     EMPTY - SPACE = ??
> > > 
> > > etc. 
> >     Hmm, you can't operate between two dataspaces, so these don't make any
> > sense.  Also, since there are no elements in the dataspace, there is no way
> > to perform I/O on an empty dataspace.
> > 
> >     Quincey
> 
> Quincey,
> 
> It sounds terrific to me, but don't forget that we also need to use
> this space for creating attributes, which currently are more
> restrictive than dataspaces.
    Yes, it'll work for attributes also.

        Quincey