tree 51f21da8d0ca289d2de6fdca39b50a13a6394f12
parent 687c6e70eaab87169f1623e8cc0f7273ef041c52
author QUICHE team <quiche-dev@google.com> 1564437991 -0700
committer Copybara-Service <copybara-worker@google.com> 1564509791 -0700

Create a QuartcMultiplexer which separates streams and datagrams into channels.

QuartcMultiplexer effectively reorganizes the calls and callbacks for
QuartcSession into three categories:
 - Per-channel send events
 - Per-channel receive events
 - Session-wide events that are not multiplexed

QuartcMultiplexer works at a low level to hide streams and messages from other
senders and receivers.  It consists of a core multiplexer object which interacts
with the QuartcEndpoint/Session, a channel sender which handles outgoing data,
and a channel receiver which handles incoming data.

The sender has a specific channel id, specified on creation.  A channel writes
this channel id in a varint form at the start of each new stream or datagram it
sends.

The multiplexer intercepts all the callbacks for incoming streams and datagrams.
It reads a varint from the start of each stream or datagram to identify the
channel id.  It then looks up a receiver for that channel and delegates the
stream or datagram to that receiver.

A default receiver may be registered to handle all streams or datagrams not
assigned to a specific receiver.  This allows endpoints to dispatch unhandled
data to a catch-all, or to await incoming data before registering a specific
receiver.  The latter may be useful to in conjunction with some forms of
negotiation; eg. when certain ranges of channel ids are allocated to different
protocols, but it is unknown which protocol will be used at startup.

gfe-relnote: n/a (quartc only)
PiperOrigin-RevId: 260588723
Change-Id: I4a3b815b48c4f825c47bc60b0b3fd76d4e3614a5