Re: Delitifier broken (Re: diff-core segfault)

On Mon, 12 Dec 2005, Junio C Hamano wrote:

Nicolas Pitre [off-list ref] writes:

quoted

I would say involving an empty blob with deltas _is_ the bug in the 
first place.  Please don't let that happen.

I agree with Nicolas.

Not all use of delta is to produce a pack.  An empty->empty
delta is a valid two byte \0\0 sequence, and I do not see any
reason to forbid it.  Although using such delta to represent
anything in a pack does *not* make any sense as you say, it
makes other callers simpler if they do not have to check if
from_len and to_len are empty before calling the delta code.

And you don't need to.

Do what pack-objects.c does: just call "diff_delta()" and check the result 
for NULL. If the result is NULL, then you have to do some special code, 
because that means that it's a full create or a full delete (or it's an 
unchanged empty file). Regardless, it really _is_ a special case, and it 
would be silly to generate a delta for it.

		Linus