Re: [PATCH] Update packfile transfer protocol documentation

From: Shawn O. Pearce <spearce@spearce.org>
Date: Nov 4, 2009, 01:18 UTC
Message-ID: <20091104011802.GE10505@spearce.org>
In-Reply-To: <7vljinnllj.fsf@alter.siamese.dyndns.org>

Junio C Hamano <gitster@pobox.com> wrote:

Show 6 quoted lines

> "Shawn O. Pearce" <spearce@spearce.org> writes:
> > I don't think we ever send an empty packet.  If we have no data to
> > send, why the hell did we create the packet header?
> 
> Oh, I do not disagree that it is pointless, but the example that followed
> the part we are discussing also had "0004".  I think it is Ok to allow it.

If its pointless, why encourage it?  Why not discourage it with SHOULD NOT?

Show 12 quoted lines

> The original intent of packet_flush() was that everything else could be
> kept buffered in-core without going to write() until packet_flush() is
> called.  The protocol was defined in a way that we won't wait for
> listening a response from the other end to an earlier message we "sent"
> with packet_write() but haven't called packet_flush() yet hence could
> still be in our buffer.  We still have this comment:
> 
>     /*
>      * If we buffered things up above (we don't, but we should),
>      * we'd flush it here
>      */
>     void packet_flush(int fd)

The smart-http series causes fetch-pack to buffer.  :-)

> And once we start buffering, allowing "0004" packet_write() wouldn't even
> be a problem; it can be optimized out in the buffering layer.

Sure, but can't packet_write just return early without write() if format_packet returned 4 (aka vsnprintf returned 0)?

-- 
Shawn.