[vlc-devel] [PATCH 04/10] vlc_tick: add helper function for explicit nanosecond to/from vlc_tick_t conversion

[Romain Vimont]

On Fri, Jun 22, 2018 at 03:27:27PM +0200, Romain Vimont wrote:
> On Fri, Jun 22, 2018 at 02:53:21PM +0200, Steve Lhomme wrote:
> > ---
> >  include/vlc_tick.h | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/include/vlc_tick.h b/include/vlc_tick.h
> > index 66cf8ecf687..bf037087510 100644
> > --- a/include/vlc_tick.h
> > +++ b/include/vlc_tick.h
> > @@ -73,6 +73,16 @@ static inline int64_t ms_from_vlc_tick(vlc_tick_t vtk)
> >      return vtk / (CLOCK_FREQ / 1000);
> >  }
> >  
> > +static inline vlc_tick_t vlc_tick_from_ns(int64_t nano)
> > +{
> > +    return nano / (INT64_C(1000000000) / CLOCK_FREQ);
> > +}
> > +
> > +static inline int64_t ns_from_vlc_tick(vlc_tick_t vtk)
> > +{
> > +    return vtk * INT64_C(1000000000) / CLOCK_FREQ;
> 
> Should compute division first, to avoid overflow (UB) if vtk > 2^64/10^9
> ticks, which is about 5 hours.

Fix: if vtk > 2^63/10^9 ticks, which is about 2h30.

> 
> > +}
> > +
> >  /*****************************************************************************
> >   * MSTRTIME_MAX_SIZE: maximum possible size of mstrtime
> >   *****************************************************************************
> > -- 
> > 2.17.0
> > 
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