"Shawn O. Pearce" <spearce@xxxxxxxxxxx> writes:
>> > +A pkt-line with a length field of 0 ("0000"), called a flush-pkt,
>> > +is a special case and MUST be handled differently than an empty
>> > +pkt-line ("0004").
>>
>> ...especially that this sentence makes it sound as if it is perfectly
>> normal to send "0004" for "an empty line" (and I've always thought that is
>> Ok), I am quite puzzled by that "SHOULD NOT".
>
> 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.
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)
And once we start buffering, allowing "0004" packet_write() wouldn't even
be a problem; it can be optimized out in the buffering layer.
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