Create abstract class for all VCI events

[jdgeddes]

Currently when executing, depositing and destroying a VCI event a switch statement is used to determine what function should be called, all with similar parameters. To make it easier for managing VCI events, create an abstract class that has a vtable of callback functions that will be called at the appropriate times.

Also, any refactoring of the code that can be done should, so if possible these VCI events should have their own files for implementation.

[robgjansen]

I was thinking all events in shadow would follow the same pattern instead of having event "subtypes". This means the non-vci events (DTIMER, SIMOP, TICKTOCK) would also be refactored to extend the abstract class.

Or would it be better to differentiate "virtual" communication events (i.e. one node creating an event for itself or for another) from "physical" communication events (i.e. one process or thread creates events for another process or thread)?
Thoughts?

[jdgeddes]

It seems that it is definitely possible to have just one abstract event class which is used both for virtual and physics events. However, there would seem to be quite a few variables that would just be used by the VCI events, and I would think having two separate abstract classes would allow for easier expansion for events that needed to be added to either the physical or virtual event class, especially if they differed in some major way.

For now I'll just go ahead and create a separate abstract class for non-vci events, but if at any point it's decided that it's better to have just one abstract class, it should be a relatively easy to make that change.

[robgjansen]

Any part of this that may not have been done will be cleaned up during the re-write of the threading engine.