CPeriodic Class Reference

Protected constructor with priority.

Use this constructor to set the priority of the active object.

Classes derived from CPeriodic must define and provide a constructor through which the priority of the active object can be passed. Such a constructor can call CPeriodic's constructor in its constructor initialisation list.

Destructor.

Frees resources prior to destruction.

Allocates and constructs a CPeriodic object - non-leaving.

Specify a high priority so the callback function is scheduled as soon as possible after the timer events complete.

Allocates and constructs a CPeriodic object - leaving.

Specify a high priority so the callback function is scheduled as soon as possible after the timer events complete.

Handles an active object's request completion event.

A derived class must provide an implementation to handle the completed request. If appropriate, it may issue another request.

The function is called by the active scheduler when a request completion event occurs, i.e. after the active scheduler's WaitForAnyRequest() function completes.

Before calling this active object's RunL() function, the active scheduler has:

1. decided that this is the highest priority active object with a completed request

2. marked this active object's request as complete (i.e. the request is no longer outstanding)

RunL() runs under a trap harness in the active scheduler. If it leaves, then the active scheduler calls RunError() to handle the leave.

Note that once the active scheduler's Start() function has been called, all user code is run under one of the program's active object's RunL() or RunError() functions.

See also: CActiveScheduler::Start CActiveScheduler::Error CActiveScheduler::WaitForAnyRequest TRAPD

Starts generating periodic events.

The event calls the protected RunL() function, which in turn calls the function specified by aCallBack. The first event is generated after aDelay microseconds; subsequent events are generated regularly thereafter at intervals of anInterval microseconds.

The TCallBack contains a function pointer and a TAny* pointer. The function will be repeatedly called with the pointer as a parameter.

Once started, periodic events are generated until the CPeriodic object is destroyed.

Notes:

1. The callback function will be run as soon as possible after the initial delay, and after each period.

2. The callback may be delayed because the RunL() of another active object, with the deepest nesting-level active scheduler on the same thread, is running when the event occurs: this cannot be avoided, but can be minimised by making all RunL()s of short duration.

3. The callback may be delayed because other, higher-priority, active objects are scheduled instead. This can be avoided by giving the CPeriodic a very high priority.