MessageBus handlers can now have one of four concurrency modes for the eventuality
of an event being raised whilst a previous event is still being processed. An additional
(optional) parameter is provided to the listen() functions to allow this to be selected
on a per event handler basis. The permissable options are:
MESSAGE_BUS_LISTENER_REENTRANT:
The event handler is fired with the new event, regardless of whether or not
a previous event is still be processed by that handler.
MESSAGE_BUS_LISTENER_QUEUE_IF_BUSY:
The new event is queued until such a time as the previous event has completed
execution. The new event is then processed. This option does not preclude the
processing of the new event by other event handlers.
MESSAGE_BUS_LISTENER_DROP_IF_BUSY:
The new event is dropped, and will never be processed the the event handler.
This option does not preclude the processing of the new event by other event handlers.
MESSAGE_BUS_LISTENER_NONBLOCKING:
The event handler is self-declaring that it never blocks. This flag is used purely
for optimisation, as it permits direct execution of the event hadnelr without inducing
any overhead from the scheduler.
In addition, the following minor revisions were made in this release:
* Cleanup of the #include dependencies contained in the microbit-dal .h files
* Bugfix to the scheduler block on event matching code.
* Introduced a MICROBIT_ID_ALERT MessageBus channel, for general purpose eventing using nonces.
This is the first commit of the microbit-dal on GitHub.
This repository contains the runtime, which is a light
weight operating system developed by Lancaster University.
Joe Finney