On Fri, Sep 18, 2020 at 11:10:45AM -0400, Thomas Guyot-Sionnest wrote: > > So, my last point is the most important of the three. I'd expect > > something more along the lines of: > > > > 1. diff_fill_oid_info resolve the link to the pipe, and > > 2. index_path handles the resolved fd. > > > > ...but it looks like that is already what it's doing? I'm confused why > > this doesn't work as-is. > > So the idea is to checksum the data and write a valid oid. I'll see if > I can figure that out. Thanks for the hint though else I would likely > have gone with a buffer and memcmp. Your solution seems cleaner, and > there is a few other uses of oideq's that look dubious at best with > the case of null oids / buffered data so it's definitely a better > approach. You're generally better off not to compute the oid just to compare two buffers: - a byte-by-byte comparison can quit early as soon as it sees a difference, whereas computing two hashes has to cover each byte - even in the worst case that the byte comparison has to go all the way to the end, it's way faster than computing a sha1 So generally in the diff code we compare oids if we got them for free (from the index, or from a tree), but otherwise it's OK to have filespecs without the oid_valid flag set, and compare them byte-wise when necessary. And there something like: if (one->size == two->size && !memcmp(one->data, two->data, one->size)) is what you'd want. Note that filespecs may not have their data or size loaded yet, though. Looking at that part of builtin_diffstat(), I'm pretty sure that is possible here (see how later code calls diff_populate_filespec() to make sure it has data). OTOH, I guess if they're from stdin we'd always have the data (since we'd have no oid to load from), so it might be OK under that conditional. -Peff