compression

[Ray Osborn]

on 99/11/24 1:55 AM, Mark Koennecke at Mark.Koennecke at psi.ch wrote:

> 
> 
> High together,
> 
> The compression topic has come up recently again in the NeXus mailing
> lists. In order to solve this I propose the following additions to the
> NAPI:
>
> - three additional defines:
> NX_LZW, NX_RLE and NX_HUFF
> which indicate the compression type to use when storing data.
> 
> - an additional API function with the signature:
> 
> int NXcompress(NXhandle hfil, int compr_type);
> 
> hfil is the usual NeXus file handle, compr_type is one of the three
> defines for the compression type.
> 
> There is no need to bother about compression when reading data. (This is
> the way HDF deals with it) At the writing end the usage sequence would
> be:
> 
> NXopendata(......)
> NXcompres(.......)
> NXputdata(....)
> 
> which means that NXcompress only acts upon an open SDS.
> 

That seems like a very elegant solution.  Is the int return value
essentially of NXstatus type?  I know they are equivalent at the moment.

> 
> If I do not receive screams of pain and terror about this I will submit
> these changes to the NeXus repository on Friday, thereby incrementing
> the version number to 1.2.2.
> 

We should certainly increment the version number.  However, please could you
wait until I've updated the Fortran API's before we actually tag the
repository.  It might be an idea to call this version 1.3.0, and leave
1.3.1, 1.3.2 etc for minor bug fixes.  What do others think?

Thanks,
Ray
-- 
Dr Ray Osborn                Tel: +1 (630) 252-9011
Materials Science Division   Fax: +1 (630) 252-7777
Argonne National Laboratory  E-mail: ROsborn at anl.gov
Argonne, IL 60439-4845