Re: [PATCH v2] midx: use buffered I/O to talk to pack-objects

[Jeff King <peff@peff.net>]

On Wed, Aug 12, 2020 at 01:31:58PM -0700, Junio C Hamano wrote:

> Junio C Hamano <gitster@pobox.com> writes:
> 
> > René Scharfe <l.s.r@web.de> writes:
> >
> >>  		nth_midxed_object_oid(&oid, m, i);
> >> -		xwrite(cmd.in, oid_to_hex(&oid), the_hash_algo->hexsz);
> >> -		xwrite(cmd.in, "\n", 1);
> >> +		fprintf(cmd_in, "%s\n", oid_to_hex(&oid));
> >
> > I do think it is silly to send an object name and terminating LF in
> > two different system calls per object.
> >
> > The original uses xwrite() so that it does not have to worry about
> > having to restart interrupted system calls and such.
> 
> Oops.  There is not much in "and such".  xwrite() only restarts but
> the caller must deal with truncated write, which the original does
> not do.

Yeah, so I think the new code should be an improvement there, because it
will eventually retry the write when the buffer fills, or when we
eventually flush on close (my "everything written by the time we hit
fflush()" in the previous mail really should have been "...by the time
we hit fclose()").  Maybe another reason to use stdio. :)

The original also doesn't handle "real" errors at all (stuff besides
EINTR, etc). Nor does the rewrite. I guess it's unlikely to see a write
error here that doesn't also involve pack-objects returning a non-zero
exit code.

-Peff