Re: [PATCH 1/4] hashfile: allow skipping the hash function

From: Jeff King <peff@peff.net>
Date: Dec 8, 2022, 07:32 UTC
Message-ID: <Y5GTJuM3jNnStvsQ@coredump.intra.peff.net>
In-Reply-To: <221207.868rjiam86.gmgdl@evledraar.gmail.com>

On Wed, Dec 07, 2022 at 11:13:15PM +0100, Ævar Arnfjörð Bjarmason wrote:

Show 23 quoted lines

> > +	if (f->skip_hash)
> > +		memset(f->buffer, 0, the_hash_algo->rawsz);
> 
> Here you're hardcoding a new version of null_oid(), but we can use it
> instead. Perhaps:
> 	
> 	diff --git a/csum-file.c b/csum-file.c
> 	index 3243473c3d7..b54c4f66cbb 100644
> 	--- a/csum-file.c
> 	+++ b/csum-file.c
> 	@@ -63,11 +63,12 @@ int finalize_hashfile(struct hashfile *f, unsigned char *result,
> 	 		      enum fsync_component component, unsigned int flags)
> 	 {
> 	 	int fd;
> 	+	const struct object_id *const noid = null_oid();
> 	 
> 	 	hashflush(f);
> 	 
> 	 	if (f->skip_hash)
> 	-		memset(f->buffer, 0, the_hash_algo->rawsz);
> 	+		memcpy(f->buffer, noid, sizeof(*noid));
> 	 	else
> 	 		the_hash_algo->final_fn(f->buffer, &f->ctx);

I don't think that's quite right; the object_id struct has other stuff in it. You'd probably want:

  hashcpy(f->buffer, null_oid());

But I think we already have a helper to just do it directly:

  hashclr(f->buffer);

-Peff