Re: [hybi] Framing take IV

On Tue, Aug 3, 2010 at 9:13 PM, Ian Hickson <ian@hixie.ch> wrote:

> On Tue, 3 Aug 2010, Scott Ferguson wrote:
> > Ian Hickson wrote:
> > > On Tue, 3 Aug 2010, Scott Ferguson wrote:
> > > > >   I agree. I can't see any benefit to fragmentation over a
> > > > > variable-size length field for an initial version without
> > > > > multiplexing. If the variable-size length field is well-designed,
> > > > > then in the common case where the message size is small it will
> > > > > only cost one extra branch to read the length. In the rare case
> > > > > where the message size is large, a variable-size length is easier
> > > > > to deal with than reassembling fragments, and easier on the
> > > > > sending side too.
> > > >
> > > > Some of us don't have infinite memory when sending messages.
> > >
> > > Why do you need infinite memory?
> >
> > Because we don't know the length of dynamically produced content until
> > the dynamic process is complete. That's why HTTP added chunking.
>
> Is this a common case we should expect? What are the use cases for this?
>
> If this is a rare occurence, then it's probably simplest to support this
> at the application layer - nothing stops anyone from having a subprotocol
> that defines the first byte/character of each message as being a
> "has continuation" byte.
>
> If this is a common occurance, then we'll be able to tell when people find
> themselves often implementing this at the application layer, and then we
> can easily add it at the WebSocket layer at that time (in a few months).
> We don't need to reserve bits specifically for it today.
>
>
We're adding a voice input capability, and we want to start sending the
user's voice up as soon as they start speaking, without waiting for the
recording to be finished so that we can start backend processing. Yes, we
could probably break it into multiple messages, but given that semantically
it's a single message, this is a case where we would want to start sending
data before knowing its length. Ditto for hooking up a video camera and
sending that data to some sort of web service.

> --
> Ian Hickson               U+1047E                )\._.,--....,'``.    fL
> http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
> Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
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