Click tasks and timers

[Eddie Kohler]

Hi all,

This mail is about recent changes in the Click anonymous CVS repository.
We've changed both Timers and the way Click tasks are scheduled.

First, Timers. The change is simple: TimerHook callback functions used to
take an unsigned long argument; now they take (Timer *, void *).

     typedef void (*TimerHook)(Timer *, void *);

More significantly, tasks. Click tasks were previously synonymous with
elements -- an element could be placed on a router's task list, or not.
This had several problems: Every task had to be an element; each element
could correspond to only one task; every element had task-related space
overhead. This annoyed. So now, tasks are encapsulated in a separate class,
called Task. Elements that want to run as tasks must explicitly contain a
Task member. All scheduling-related functions, such as scheduled_next(),
scheduled(), set_max_tickets(), and so on, are now Task functions.

For example:

  class Unqueue : public Element { public:
    // ...
   private:
    // ...
    Task _task;
  };

  Unqueue::Unqueue()
    // must initialize the Task object to call this element as its callback
    : Element(1, 1), _task(this)
  { /* ... */ }

  int
  Unqueue::initialize(ErrorHandler *errh)
  {
    // must pass the Task to ScheduleInfo::join_scheduler
    ScheduleInfo::join_scheduler(this, &_task, errh);
    // ...
  }

  void
  Unqueue::uninitialize()
  {
    _task.unschedule();
  }

  void
  Unqueue::run_scheduled()
  {
    // ...  
    _task.reschedule();
  }

We've updated all the elements checked in to the MIT repository, but you
will need to update any elements you run yourselves. Hope this pleases. As
always, comments appreciated.

love,
ed