I am looking for some advice on the best way to implement an internal timeout in an asynchronous state machine using the Boost Statechart library. My project requires an asynchronous state machine that multiple threads can queue events to. The asynchronous state machine will react to events and execute callback functions that are registered on creation of the state machine. So far, this hasn't been a problem, but I have hit a bit of a roadblock when handling timeouts. I need my asynchronous state machine class to start a timer in a certain reaction method, when this timer expires I need the scheduler to queue a timeout event. Basically, the timer will act as an interrupt, when it expires I need a timeout event to be immediately queued to the state machine event queue.

Since asynchronous state machines are created and managed by a scheduler class (in my case boost::statechart::fifo_scheduler<>) how can I get the asynchronous state machine to queue a timeout event? If possible, I would like to encapsulate this timeout functionality, so client code that uses my derived asynchronous state machine does not have to deal with managing timeouts.

My first thought is to have the asynchronous state machine class create a thread when the timer is started. The thread will continually check if the timer has expired and if it has, will queue a timeout event. The issue with this approach is that  I would need to pass the scheduler and state machine handler to the thread function in order to queue the event. Obviously, the state machine does not have access to these objects and I am unsure if this is a safe approach.

Any suggestions or help with this matter would be greatly appreciated! This is my first post to the mailing list so I hope this is the right arena for my question.

Thanks,

John Buonassisi