compression

[F.A.Akeroyd at rl.ac.uk]

>> The second thing to ponder is that you usually do not compress all data
items
>> in a NeXus file. Just the large ones such as the 64*64*512 counts array
at
>> SXD. Most data items in a NeXus files are single numbers and for those
>> compression would be nonsense. We end up with a little bit of extra code
for
>> the huge dataset.
>>

>I agree that this effectively rules out having a blanket default for every
>SDS.  We could possibly have two parameters, one defining the minimum size
>of SDS to be compressed (0 meaning no compression) and one to define the
>method of compression.  However, these should be part of the NXU utility
>routines (NXUsetcompress) rather than the core NX routines.  Mark's
solution
>fits into their philosophy perfectly.

That sounds a fair idea. My only other comment is that I personally prefer
having preprocessor symbols that say what they are about i.e.
NX_COMPRESS_NONE
rather than just NX_NONE etc. just in case a clash of words/meanings occurs
at a later stage.  

Cheers,

Freddie