Re: [PATCH 02/20] write_reuse_object(): convert to new revindex API

On Tue, Jan 12, 2021 at 11:31:40AM -0500, Taylor Blau wrote:

quoted

quoted

+	datalen = pack_pos_to_offset(p, pos + 1) - offset;

This "pos + 1" means we may be looking one past the end of the array.
That's OK (at least for now), because our revindex always puts in an
extra dummy value exactly for computing these kinds of byte-distances.
That might be worth documenting in the API header.

Yeah, I made sure to document that when I was touching up the last
patch. FWIW, that's a behavior that we're going to carry over even when
the reverse index is stored on-disk (not by writing four extra bytes
into the .rev file, but by handling queries for pos == p->num_objects
separately.)

I think the only reason to look past the end like that is to compute the
size of the final entry. So we _could_ abstract that away from the
callers with a separate function like:

  off_t pack_pos_to_size(struct packed_git *p, uint32_t pos);

But as long as the behavior of passing p->num_objects is documented, I
do not mind overly mind spelling it one way or the other.

-Peff