Re: [PATCH v5 05/15] pkt-line: add packet_write_gently_fmt()

On Wed, Aug 10, 2016 at 04:10:02PM +0200, Lars Schneider wrote:

quoted

On 10 Aug 2016, at 15:43, Jeff King [off-list ref] wrote:

On Wed, Aug 10, 2016 at 03:04:01PM +0200, larsxschneider@gmail.com wrote:

quoted

+int packet_write_gently_fmt(int fd, const char *fmt, ...)
+{
+	static struct strbuf buf = STRBUF_INIT;
+	va_list args;
+
+	strbuf_reset(&buf);
+	va_start(args, fmt);
+	format_packet(1, &buf, fmt, args);
+	va_end(args);
+	packet_trace(buf.buf + 4, buf.len - 4, 1);
+	return (write_in_full(fd, buf.buf, buf.len) == buf.len ? 0 : -1);
+}

Could the end of this function just be:

 return packet_write_gently(fd, buf.buf, buf.len);

? I guess we'd prefer to avoid that, because it incurs an extra
memmove() of the data.

I don't think the memmove would be that expensive. However, format_packet()
already creates the packet_header and packet_write_gently would do the same
again, no?

Yeah, I think you would want extra refactoring to have a shared common
function. I took a stab at it, but the result ends up pretty ugly; the
amount of boilerplate exceeds the duplication here (the really nasty
thing is that format_packet() is hard to split up, because the part you
want to switch out is in the middle, but it needs to keep some context
between the start and the end. In a higher level language you'd pass it
a callback to fill in the strbuf in the middle, but in C that just ends
up horrible).

quoted

Similarly, I'd think this could share code with the non-gentle form
(which should be able to just call this and die() if returns an error).
Though sometimes the va_list transformation makes that awkward.

Yeah, the code duplication annoyed me, too. va_list was the reason I did it
that way. Do you think that is something that needs to be addressed in the
series?

No, I don't think it needs to be. It's just a case of making sure that
the internals don't grow too crufty and unmanageable for future
maintainability.

-Peff