Time Event class.
More...
#include <qf.hpp>
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, from the clock tick ISR or from the special QP::QTicker active object.
-
Even though QP::QTimeEvt is a subclass of QP::QEvt, QP::QTimeEvt instances can NOT be allocated dynamically from event pools. In other words, it is illegal to allocate QP::QTimeEvt instances with the Q_NEW() or Q_NEW_X() macros.
Definition at line 404 of file qf.hpp.
◆ QTimeEvt() [1/3]
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] | act | pointer to the active object associated with this time event. The time event will post itself to this AO. |
| [in] | sgnl | signal to associate with this time event. |
| [in] | tickRate | system tick rate to associate with this time event. |
- Precondition
- The signal must be valid and the tick rate in range
Definition at line 231 of file qf_time.cpp.
◆ QTimeEvt() [2/3]
private default constructor only for friends
- Note
- private default ctor for internal use only
Definition at line 268 of file qf_time.cpp.
◆ QTimeEvt() [3/3]
private copy constructor to disallow copying of QTimeEvts
◆ armX()
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] | nTicks | number of clock ticks (at the associated rate) to rearm the time event with. |
| [in] | interval | interval (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 {
. . .
Q_STATE_DEF(Philo, eating) {
switch (e->sig) {
case Q_ENTRY_SIG: {
m_timeEvt.armX(eat_time());
status = Q_RET_HANDLED;
break;
}
case Q_EXIT_SIG: {
TableEvt *pe =
Q_NEW(TableEvt, DONE_SIG);
pe->philoNum = PHILO_ID(this);
m_timeEvt.disarm();
status = Q_RET_HANDLED);
break;
}
case TIMEOUT_SIG: {
status = tran(&thinking);
break;
}
case EAT_SIG:
case DONE_SIG: {
status = Q_RET_HANDLED;
break;
}
default: {
status = super(&top);
break;
}
}
return status;
}
}
std::uint_fast8_t QState
Type returned from state-handler functions.
#define Q_ASSERT(test_)
General purpose assertion.
#define Q_EVT_CAST(class_)
Perform downcast of an event onto a subclass of QEvt class_.
#define Q_NEW(evtT_, sig_)
Allocate a dynamic event.
#define PUBLISH(e_, sender_)
Invoke the event publishing facility QP::QF::publish_(). This macro.
- 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 324 of file qf_time.cpp.
◆ disarm()
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 400 of file qf_time.cpp.
◆ rearm()
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] | nTicks | number 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 460 of file qf_time.cpp.
◆ wasDisarmed()
| bool wasDisarmed |
( |
void |
| ) |
|
|
noexcept |
Check the "was disarmed" status of a time event.
- Description
- Useful for checking whether a one-shot time event was disarmed in the QTimeEvt_disarm() operation.
- Returns
- 'true' if the time event was truly disarmed in the last QTimeEvt::disarm() operation. The 'false' return means that the time event was not truly disarmed, because it was not running at that time. 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 event queue.
- Note
- This function has a side effect of setting the "was disarmed" status, which means that the second and subsequent times this function is called the function will return 'true'.
Definition at line 541 of file qf_time.cpp.
◆ currCtr()
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
- For an armed time event, the function returns the current value of the down-counter of the given time event. If the time event is not armed, the function returns 0.
- Note
- The function is thread-safe.
Definition at line 560 of file qf_time.cpp.
◆ operator=()
private assignment operator to disallow assigning of QTimeEvts
◆ toActive()
encapsulate the cast the m_act attribute to QActive*
Definition at line 464 of file qf.hpp.
◆ toTimeEvt()
encapsulate the cast the m_act attribute to QTimeEvt*
Definition at line 469 of file qf.hpp.
◆ QF
◆ QS
◆ m_next
link to the next time event in the list
Definition at line 408 of file qf.hpp.
◆ m_act
the active object that receives the time events
- Description
- The m_act pointer is reused inside the QP implementation to hold the head of the list of newly armed time events.
Definition at line 414 of file qf.hpp.
◆ m_ctr
the internal down-counter of the time event.
- Description
- The down-counter is decremented by 1 in every TICK_X() invocation. The time event fires (gets posted or published) when the down-counter reaches zero.
Definition at line 421 of file qf.hpp.
◆ m_interval
the interval for the periodic time event (zero for the one-shot time event).
- Description
- The value of the interval is re-loaded to the internal down-counter when the time event expires, so that the time event keeps timing out periodically.
Definition at line 429 of file qf.hpp.
The documentation for this class was generated from the following files:
QP/C++
6.9.3
Data Fields inherited from QEvt