svn commit: r332072 - head/sys/sys

[Roger Pau Monné]

On Thu, Apr 05, 2018 at 09:32:57AM -0600, Ian Lepore wrote:
> On Thu, 2018-04-05 at 14:31 +0000, Roger Pau Monné wrote:
> > Author: royger
> > Date: Thu Apr  5 14:31:54 2018
> > New Revision: 332072
> > URL: https://svnweb.freebsd.org/changeset/base/332072
> > 
> > Log:
> >   introduce GiB and MiB macros
> >   
> >   This macros convert from GiB or MiB into bytes.
> >   
> >   Sponsored by: Citrix Systems R&D
> > 
> > Modified:
> >   head/sys/sys/param.h
> > 
> > Modified: head/sys/sys/param.h
> > ==============================================================================
> > --- head/sys/sys/param.h	Thu Apr  5 14:25:39 2018	(r332071)
> > +++ head/sys/sys/param.h	Thu Apr  5 14:31:54 2018	(r332072)
> > @@ -362,4 +362,8 @@ __END_DECLS
> >   */
> >  #define __PAST_END(array, offset) (((__typeof__(*(array)) *)(array))[offset])
> >  
> > +/* Unit conversion macros. */
> > +#define GiB(v) (v ## ULL << 30)
> > +#define MiB(v) (v ## ULL << 20)
> > +
> >  #endif	/* _SYS_PARAM_H_ */
> > 
> 
> These names don't make it clear whether the conversion is bytes->GiB or
> GiB->bytes.  The names seem way too generic for a public namespace in a
> file as heavily included behind your back as param.h is.
> 
> Also, this completely reasonable usage won't work, likely with
> confusing compile error messages:
> 
>   int bytes, gibytes;
>   ...
>   bytes = GiB(gibytes);

I find those helpful for their specific usage. I could introduce
static inline functions like:

size_t gb_to_bytes(size_t)...

But I assume this is also going to cause further discussion.

Roger.