Re: [Qemu-devel] [PATCH 3/6] range: add min/max operations on ranges

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

On Tue, Sep 10, 2013 at 11:35:54AM +0200, Igor Mammedov wrote:
> On Wed, 4 Sep 2013 13:48:35 +0300
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  include/qemu/range.h | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> > 
> > diff --git a/include/qemu/range.h b/include/qemu/range.h
> > index 4a0780d..1c688ca 100644
> > --- a/include/qemu/range.h
> > +++ b/include/qemu/range.h
> > @@ -17,6 +17,23 @@ struct Range {
> >      uint64_t end;   /* 1 + the last byte. 0 if range empty or ends at ~0x0LL. */
> >  };
> >  
> > +static inline void range_extend(Range *range, Range *extend_by)
> doc comment what it does pls.
> 
> > +{
> > +    if (!extend_by->begin && !extend_by->end) {
> > +        return;
> > +    }
> > +    if (!range->begin && !range->end) {
> > +        *range = *extend_by;
> > +        return;
> > +    }
> > +    if (range->begin > extend_by->begin) {
> > +        range->begin = extend_by->begin;
> > +    }
> > +    if (range->end - 1 < extend_by->end - 1) {
> (foo)->end could be 0 at this point leading to overflow when subtracted,
> is it intended to be so?

Absolutely - as the comment near this field definition states:
0 means region ends at ~0x0LL.


> > +        range->end = extend_by->end;
> > +    }
> > +}
> > +
> >  /* Get last byte of a range from offset + length.
> >   * Undefined for ranges that wrap around 0. */
> >  static inline uint64_t range_get_last(uint64_t offset, uint64_t len)
>