Re: [Qemu-devel] [PATCH RFC 08/13] range: add Range structure

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, May 13, 2013 at 09:20:08PM +0100, Peter Maydell wrote:
> On 13 May 2013 21:01, Michael S. Tsirkin <mst@redhat.com> wrote:
> > Sometimes we need to pass ranges around, add a
> > handy structure for this purpose.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  include/qemu/range.h | 22 ++++++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> >
> > diff --git a/include/qemu/range.h b/include/qemu/range.h
> > index 3502372..4bcd346 100644
> > --- a/include/qemu/range.h
> > +++ b/include/qemu/range.h
> > @@ -1,6 +1,28 @@
> >  #ifndef QEMU_RANGE_H
> >  #define QEMU_RANGE_H
> >
> > +#include <inttypes.h>
> > +
> > +/*
> > + * Operations on 64 address ranges.
> 
> missing "bit" ?
> 
> > + * Notes:
> > + *   - ranges must not wrap around 0, but can include the last byte ~0x0LL.
> > + *   - this can not represent a full 0 to ~0x0LL range.
> > + */
> > +
> > +/* A structure representing a range of addresses. */
> > +struct Range {
> > +    uint64_t begin; /* First byte of the range, or 0 if empty. */
> > +    uint64_t end;   /* 1 + the last byte. 0 if range empty or ends at ~0x0LL. */
> > +};
> > +typedef struct Range Range;
> > +
> > +/* verify that range is not empty and does not overlap */
> 
> Doesn't overlap what?

I meant wrap around there.

> Why isn't an empty range valid?
> The struct definition above says it's OK.

Yes it's a bad name. Should be range_non_empty or something.

> > +{
> > +    return range->begin + 1 <= range->end;
> > +}
> 
> I note that memory.c defines its own concept of an AddrRange.
> 
> thanks
> -- PMM

Good point, maybe I'll reuse that or just use two 64 bit fields explicitly.

-- 
MST