Re: libxdiff and patience diff

> On Tue, 4 Nov 2008, Pierre Habouzit wrote:
> 
> > Hi Davide,
> > 
> > I've been working tonight, trying to make libxdiff support the patience
> > diff algorithm, but I've totally failed, because I _thought_ I
> > understood what xdl_split was doing, but it appears I don't.
> > 
> > 
> > [ For the readers playing at home, the patience diff algorithm is
> >   explained after my sig. ]
> > 
> > 
> > What I did is to:
> > (1) add a flag to the xenv in xdl_split that says that I want a
> >     patience "split".
> > (2) Then in xdl_split, if that bit is set, I compute the longest common
> >     subsequence from the patience diff.
> > (3) for each split it computes I call xdl_recs_cmp on that interval.
> > 
> > 
> > What I thought it would achieve is that I force some boundaries at which
> > libxdiff _must_ resync. Though, it seems that for some reason it doesn't
> > work, probably because the "ha" stuff and the boundaries absolutely
> > don't work the way I thought it did.
> > 
> > So where is the place I should do that ? I suspect it should be
> > partly in xprepare.c but I'm a bit stuck right now.
> > 
> > 
> > Any pointer on how the stuff in xprepare.c and xdiffi.c work would help
> > greatly, it's really not self-evident to me :)
> 
> What makes you think it'd self-evident to me? :)
> Seriously, I forgot stuff I wrote the last month, this is way beyond my 
> memory limits.
> You definitely need to look at xprepare.c, especially at xdl_trim_ends() 
> and xdl_cleanup_records(). Lines are re-arranged in indexes, and this 
> might screw up your logic if you're not prepared for it.
> What xdl_split() does, is find the start of an LCS and return the 
> coordinate. Then xdl_recs_cmp() does the box reducing (first two "for" 
> loops) and different-lines marking (first and second "if").