Philip Withnall authored Aug 08, 2014 and Olivier Crête committed Aug 21, 2014

Previously, an EWOULDBLOCK return value from the low-level socket calls
(including PseudoTcpSocket) would be represented by a zero number of
bytes (or messages) read by the agent. This conflicts with the use of
zero to represent end of stream (EOS) for pseudo-TCP connections, where
the sender has indicated that they are not going to send any more bytes.

So, now use GError (G_IO_ERROR_WOULD_BLOCK) to represent EWOULDBLOCK,
just like the GSocket functions. Zero is reserved exclusively for if:
 • the number of requested bytes/messages is zero; or
 • reliable mode is enabled and EOS is reached.

This does change the documented behaviour of the NiceAgent send/recv
API, but only by allowing a new behaviour (returning zero) rather than
by changing an existing one, so it should be OK.