[NUT-devel] Incomplete description of checksum algorithm

[Rich Felker]

On Fri, Feb 17, 2006 at 03:31:04AM +0100, Michael Niedermayer wrote:
> Hi
> 
> On Thu, Feb 16, 2006 at 04:06:22PM -0500, Rich Felker wrote:
> > On Thu, Feb 16, 2006 at 07:47:49PM +0100, Michael Niedermayer wrote:
> > > > > personally i would simply include the forward ptr, so the all zero case would
> > > > > naturally be gone, if the others are against this then we must either use a 
> > > > 
> > > > Is there an all-zero case? As far as I can tell, there's no NUT packet
> > > > that's valid as all zeros, except possibly the very first
> > > > syncpoint/header pair in the file.
> > > 
> > > maybe, but having all zero packets with always matching checksum is risky, 
> > > we will have to check that no change we do might lead to legal all zero
> > > packets, and its also more tricky on the demuxer side (search for a packet 
> > > with matchig checksum vs. search for a packet we can parse with no errors 
> > > and which has a matching checksum)
> > 
> > Fine, IMO it's ok to include forward pointer, but what about
> > syncpoints? Do we really want to add another byte to them? :(
> 
> a compromise would be a flag in the main header for that, so as long as we
> havnt added any fields to syncpoints there wont be a forward ptr ...
> but personally i probably would simply unconditionally add the forward ptr

Well, I had another idea: having two separate startcodes for
syncpoints, one with extensibility and the other with minimal size.
However, somehow I doubt it's worth the added complexity in the
demuxer to support such nonsense..

Rich