Class CDeltaTimer

class CDeltaTimer : public CActive;

Description

A queue of timed events.

A timed event is a callback function encapsulated by a TDeltaTimerEntry object, and is intended to be called when the time interval represented by the event expires.

The queue itself is a TDeltaQue list. A timed event entry is added into a position in the queue that is determined by the time interval specified for that event. Although the time interval for a timed event is specified as an interval from the present moment, when added to the queue the implementation treats each event as having an interval from the previous timed event (or now).

CDeltaTimer is an active object, driven by an RTimer which is usually set to expire upon completion of the event at the head of the queue. If the time to the next event is too great or an event at the head of the queue has been removed, the timer may be set to expire prior to the event at the head of the queue (if any).

When the timer completes, the head of the queue is inspected to see whether the timed event at the head of the queue has expired. On expiry, the callback function represented by that timed event is called, and the timed event entry is removed from the queue. The queue then inspects further events for expiry, calling and removing them as necessary until either the queue is empty or there is an event in the future to wait for.

Note that the tick period is the minimum time interval for an event and the granularity of all timings using the queue. Note that in general, any event may be called back some time after it has expired and that specifically the duration of all events will at least be rounded up to a muliple of the tick period.

Derivation

• CBase - Base class for all classes to be instantiated on the heap

• CActive - The core class of the active object abstraction

• CDeltaTimer - A queue of timed events

Members

Defined in CDeltaTimer:
NewL(), NewL(), Queue(), QueueLong(), Remove()

Inherited from CActive:
Cancel(), Deque(), DoCancel(), EPriorityHigh, EPriorityIdle, EPriorityLow, EPriorityStandard, EPriorityUserInput, Extension_(), IsActive(), IsAdded(), Priority(), RunError(), RunL(), SetActive(), SetPriority(), TPriority, iStatus

Inherited from CBase:
Delete(), operator new()

See also:

• TDeltaTimerEntry
• TDeltaQue
• RTimer

static IMPORT_C CDeltaTimer *NewL(TInt aPriority);

Description

Creates a new timed event queue with the specified active object priority.

Parameters

TInt aPriority The priority of this active object.

Return value

CDeltaTimer * On successful return, a pointer to the queue of timed events.

static IMPORT_C CDeltaTimer *NewL(TInt aPriority, TTimeIntervalMicroSeconds32 aGranularity);

Description

Creates a new timed event queue with the specified active object priority, and the specified timer granularity.

Parameters

TInt aPriority The priority of this active object. TTimeIntervalMicroSeconds32 aGranularity Ignored. The resolution of the timer is the tick period.

Return value

CDeltaTimer * On successful return, a pointer to the queue of timed events.

virtual IMPORT_C void Queue(TTimeIntervalMicroSeconds32 aTimeInMicroSeconds, TDeltaTimerEntry &aEntry);

Description

Adds a new timed event entry into the timed event queue.

Parameters

TTimeIntervalMicroSeconds32 aTimeInMicroSeconds The interval from the present time when the timed event entry is to expire. TDeltaTimerEntry &aEntry The timed event entry encapsulating the call back that is to be called when this timed event entry expires.

virtual IMPORT_C void Remove(TDeltaTimerEntry &aEntry);

Description

Removes the specified timed event entry from the timer queue.

Parameters

TDeltaTimerEntry &aEntry The timed event entry.

IMPORT_C TInt QueueLong(TTimeIntervalMicroSeconds aTimeInMicroSeconds, TDeltaTimerEntry &aEntry);

Description

Adds a new timed event entry into the timed event queue.

Parameters

TTimeIntervalMicroSeconds aTimeInMicroSeconds The interval from the present time when the timed event entry is to expire. TDeltaTimerEntry &aEntry The timed event entry encapsulating the call back that is to be called when this timed event entry expires.

Return value

TInt KErrNone if sucessful, KErrOverflow if the interval is too great or negative.