compression

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

>
>  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(......)
>  NXcompress(.......)
>  NXputdata(....)
>
>
>  which means that NXcompress only acts upon an open SDS.   
>
By the above sequence do i understand that you need to specify "NXcompress"
separately for each SDS that you write? If so, i think this may go against 
the philosophy of NXUwritedata which was introduced as the sequence of
"make,open,put"
was considered to be rather verbose for an average user and they would now
have to
double their code size with an extra "NXcompress" for each "NXUwritedata".
While
you certainly need to be able to control crompression on an SDS by SDS
basis, would
it also be a good idea to introduce a function to indicate the "default
comression" to
be used in the absense of an NXcompress? Something like

NXstatus NXsetdefault(int default_type, int default_setting)

called as   

  NXsetdefault(NX_COMPRESS, NX_COMPRESS_RLE)

and also define the symbol NX_COMPRESS_NONE to turn off compression?

Cheers,

Freddie