[PATCH] diff: rewrite V2. -1005 bytes

[Denys Vlasenko]

On Thursday 14 January 2010 18:20, Matheus Izvekov wrote:
> > takes less than one second with current bbox diff:
> > 
> > # PATH="$PATH" time ./mkdiff
> > Command exited with non-zero status 1
> > real    0m 0.94s
> > user    0m 0.54s
> > sys     0m 0.40s
> > 
> > but new one takes 14 times longer:
> > 
> > # PATH=".:$PATH" time ./mkdiff
> > Command exited with non-zero status 1
> > real    0m 14.32s
> > user    0m 8.45s
> > sys     0m 5.83s
> 
> After a round of profiling, what I can see is that almost all of that
> performance hit comes from reusing the diff machinery to compare binary
> files. After adding back the old code which skipped those, that
> performance is regained.
> 
> Maybe that was not a good idea after all.
> 
> Maybe the code cmp uses to compare files could be moved to libbb, and I
> could reuse that?

I looked at cmp code. It's too big and too slow (since it needs to handle
-s -and -l). I guess it's better to write up separate code.
It should be trivial - two largish reads from both files + memcpy, right?
--
vda