QP/C++  5.9.5
QP::QTimeEvt Class Reference

Time Event class. More...

#include <qf.h>

Inheritance diagram for QP::QTimeEvt:
QP::QEvt

Public Member Functions

 QTimeEvt (QActive *const act, enum_t const sgnl, uint_fast8_t const tickRate=static_cast< uint_fast8_t >(0))
 The Time Event constructor. More...
 
void armX (QTimeEvtCtr const nTicks, QTimeEvtCtr const interval=static_cast< QTimeEvtCtr >(0))
 Arm a time event (one shot or periodic) for event posting. More...
 
bool disarm (void)
 Disarm a time event. More...
 
bool rearm (QTimeEvtCtr const nTicks)
 Rearm a time event. More...
 
QTimeEvtCtr ctr (void) const
 Get the current value of the down-counter of a time event. More...
 

Friends

class QF
 

Additional Inherited Members

- Public Attributes inherited from QP::QEvt
QSignal sig
 signal of the event instance
 
uint8_t poolId_
 pool ID (0 for static event)
 
uint8_t volatile refCtr_
 reference counter
 

Detailed Description

Time Event class.

Description
Time events are special QF events equipped with the notion of time passage. The basic usage model of the time events is as follows. An active object allocates one or more QTimeEvt objects (provides the storage for them). When the active object needs to arrange for a timeout, it arms one of its time events to fire either just once (one-shot) or periodically. Each time event times out independently from the others, so a QF application can make multiple parallel timeout requests (from the same or different active objects). When QF detects that the appropriate moment has arrived, it inserts the time event directly into the recipient's event queue. The recipient then processes the time event just like any other event.

Time events, as any other QF events derive from the QP::QEvt base class. Typically, you will use a time event as-is, but you can also further derive more specialized time events from it by adding some more data members and/or specialized functions that operate on the specialized time events.

Internally, the armed time events are organized into a bi-directional linked list. This linked list is scanned in every invocation of the QP::QF::tickX_() function. Only armed (timing out) time events are in the list, so only armed time events consume CPU cycles.
Note
QF manages the time events in the macro TICK_X(), which must be called periodically, eitehr from a clock tick ISR, or from a task level.
In this version of QF QTimeEvt objects should not be allocated dynamically from event pools. Currently, QF will not correctly recycle the dynamically allocated Time Events.

Definition at line 363 of file qf.h.

Constructor & Destructor Documentation

◆ QTimeEvt()

QP::QTimeEvt::QTimeEvt ( QActive *const  act,
enum_t const  sgnl,
uint_fast8_t const  tickRate = static_cast<uint_fast8_t>(0) 
)

The Time Event constructor.

Description
When creating a time event, you must commit it to a specific active object act, tick rate tickRate and event signal sgnl. You cannot change these attributes later.
Parameters
[in]actpointer to the active object associated with this time event. The time event will post itself to this AO.
[in]sgnlsignal to associate with this time event.
[in]tickRatesystem tick rate to associate with this time event.
Precondition
The signal must be valid and the tick rate in range

Definition at line 225 of file qf_time.cpp.

Member Function Documentation

◆ armX()

void QP::QTimeEvt::armX ( QTimeEvtCtr const  nTicks,
QTimeEvtCtr const  interval = static_cast<QTimeEvtCtr>(0) 
)

Arm a time event (one shot or periodic) for event posting.

Description
Arms a time event to fire in a specified number of clock ticks and with a specified interval. If the interval is zero, the time event is armed for one shot ('one-shot' time event). The time event gets directly posted (using the FIFO policy) into the event queue of the host active object.
Parameters
[in]nTicksnumber of clock ticks (at the associated rate) to rearm the time event with.
[in]intervalinterval (in clock ticks) for periodic time event.
Note
After posting, a one-shot time event gets automatically disarmed while a periodic time event (interval != 0) is automatically re-armed.
A time event can be disarmed at any time by calling QP::QTimeEvt::disarm(). Also, a time event can be re-armed to fire in a different number of clock ticks by calling the QP::QTimeEvt::rearm() function.
Usage
The following example shows how to arm a one-shot time event from a state machine of an active object:
namespace DPP {
. . .
QP::QState Philo::eating(Philo * const me, QP::QEvt const * const e) {
QP::QState status;
switch (e->sig) {
case Q_ENTRY_SIG: {
me->m_timeEvt.postIn(me, eat_time());
status = Q_HANDLED();
break;
}
case Q_EXIT_SIG: {
TableEvt *pe = Q_NEW(TableEvt, DONE_SIG);
pe->philoNum = PHILO_ID(me);
QP::QF::PUBLISH(pe, me);
(void)me->m_timeEvt.disarm();
status = Q_HANDLED();
break;
}
case TIMEOUT_SIG: {
status = Q_TRAN(&Philo::thinking);
break;
}
case EAT_SIG: // intentionally fall through
case DONE_SIG: {
// EAT or DONE must be for other Philos than this one
Q_ASSERT(Q_EVT_CAST(TableEvt)->philoNum != PHILO_ID(me));
status = Q_HANDLED();
break;
}
default: {
status = Q_SUPER(&QHsm::top);
break;
}
}
return status;
}
} // namespace DPP
Precondition
the host AO must be valid, time evnet must be disarmed, number of clock ticks cannot be zero, and the signal must be valid.

Definition at line 315 of file qf_time.cpp.

◆ ctr()

QTimeEvtCtr QP::QTimeEvt::ctr ( void  ) const

Get the current value of the down-counter of a time event.

Description
Useful for checking how many clock ticks (at the tick rate associated with the time event) remain until the time event expires.
Returns
The current value of the down-counter for an armed time event or 0 for an unarmed time event.

/note The function is thread-safe.

Definition at line 518 of file qf_time.cpp.

◆ disarm()

bool QP::QTimeEvt::disarm ( void  )

Disarm a time event.

Description
Disarm the time event so it can be safely reused.
Returns
'true' if the time event was truly disarmed, that is, it was running. The return of 'false' means that the time event was not truly disarmed because it was not running. The 'false' return is only possible for one-shot time events that have been automatically disarmed upon expiration. In this case the 'false' return means that the time event has already been posted or published and should be expected in the active object's state machine.
Note
there is no harm in disarming an already disarmed time event /

Definition at line 380 of file qf_time.cpp.

◆ rearm()

bool QP::QTimeEvt::rearm ( QTimeEvtCtr const  nTicks)

Rearm a time event.

Description
Rearms a time event with a new number of clock ticks. This function can be used to adjust the current period of a periodic time event or to prevent a one-shot time event from expiring (e.g., a watchdog time event). Rearming a periodic timer leaves the interval unchanged and is a convenient method to adjust the phasing of a periodic time event.
Parameters
[in]nTicksnumber of clock ticks (at the associated rate) to rearm the time event with.
Returns
'true' if the time event was running as it was re-armed. The 'false' return means that the time event was not truly rearmed because it was not running. The 'false' return is only possible for one-shot time events that have been automatically disarmed upon expiration. In this case the 'false' return means that the time event has already been posted or published and should be expected in the active object's state machine.
Precondition
AO must be valid, tick rate must be in range, nTicks must not be zero, and the signal of this time event must be valid

Definition at line 439 of file qf_time.cpp.


The documentation for this class was generated from the following files: