Native QF Event Queue class.
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#include <qequeue.hpp>
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| | QEQueue (void) noexcept |
| | public default constructor More...
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| void | init (QEvt const *qSto[], std::uint_fast16_t const qLen) noexcept |
| | Initializes the native QF event queue. More...
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| bool | post (QEvt const *const e, std::uint_fast16_t const margin, std::uint_fast8_t const qs_id) noexcept |
| | Posts (FIFO) an event to the "raw" thread-safe QF event queue. More...
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| void | postLIFO (QEvt const *const e, std::uint_fast8_t const qs_id) noexcept |
| | Posts (LIFO) an event to the "raw" thread-safe QF event queue. More...
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| QEvt const * | get (std::uint_fast8_t const qs_id) noexcept |
| | Gets an event from the "raw" thread-safe QF event queue. More...
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| QEQueueCtr | getNFree (void) const noexcept |
| | Gets the number of free slots currently in "raw" thread-safe QF event queue. More...
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| QEQueueCtr | getNMin (void) const noexcept |
| | "raw" thread-safe QF event queue operation for obtaining the minimum number of free entries ever in the queue (a.k.a. More...
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| bool | isEmpty (void) const noexcept |
| | "raw" thread-safe QF event queue operation to find out if the queue is empty More...
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- Description
- This structure describes the native QF event queue, which can be used as the event queue for active objects, or as a simple "raw" event queue for thread-safe event passing among non-framework entities, such as ISRs, device drivers, or other third-party components.
The native QF event queue is configured by defining the macro QF_EQUEUE_TYPE as QP::QEQueue in the specific QF port header file.
The QP::QEQueue class contains only data members for managing an event queue, but does not contain the storage for the queue buffer, which must be provided externally during the queue initialization.
The event queue can store only event pointers, not the whole events. The internal implementation uses the standard ring-buffer plus one external location that optimizes the queue operation for the most frequent case of empty queue.
The QP::QEQueue class is used with two sets of functions. One set is for the active object event queue, which needs to block the active object task when the event queue is empty and unblock it when events are posted to the queue. The interface for the native active object event queue consists of the following functions: QP::QMActive::post(), QP::QMActive::postLIFO(), and QP::QMActive::get_(). Additionally the function QP::QEQueue::init() is used to initialize the queue.
The other set of functions, uses this class as a simple "raw" event queue to pass events between entities other than active objects, such as ISRs. The "raw" event queue is not capable of blocking on the get() operation, but is still thread-safe because it uses QF critical section to protect its integrity. The interface for the "raw" thread-safe queue consists of the following functions: QP::QEQueue::post(), QP::QEQueue::postLIFO(), and QP::QEQueue::get(). Additionally the function QP::QEQueue::init() is used to initialize the queue.
- Note
- Most event queue operations (both the active object queues and the "raw" queues) internally use the QF critical section. You should be careful not to invoke those operations from other critical sections when nesting of critical sections is not supported.
Definition at line 113 of file qequeue.hpp.
◆ QEQueue() [1/2]
◆ QEQueue() [2/2]
◆ init()
| void init |
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QEvt const * |
qSto[], |
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std::uint_fast16_t const |
qLen |
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) |
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noexcept |
- Description
- Initialize the event queue by giving it the storage for the ring buffer.
- Parameters
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| [in] | qSto | an array of pointers to QP::QEvt to serve as the ring buffer for the event queue |
| [in] | qLen | the length of the qSto[] buffer (in QP::QEvt pointers) |
- Note
- The actual capacity of the queue is qLen + 1, because of the extra location forntEvt.
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This function is also used to initialize the event queues of active objects in the built-int QV, QK and QXK kernels, as well as other QP ports to OSes/RTOSes that do provide a suitable message queue.
Definition at line 63 of file qf_qeq.cpp.
◆ post()
| bool post |
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QEvt const *const |
e, |
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std::uint_fast16_t const |
margin, |
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std::uint_fast8_t const |
qs_id |
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) |
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noexcept |
- Description
- Post an event to the "raw" thread-safe event queue using the First-In-First-Out (FIFO) order.
- Parameters
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| [in] | e | pointer to the event to be posted to the queue |
| [in] | margin | number of required free slots in the queue after posting the event. The special value QP::QF_NO_MARGIN means that this function will assert if posting |
| [in] | qs_id | QS-id of this state machine (for QS local filter) |
- Note
- The QP::QF_NO_MARGIN value of the
margin argument is special and denotes situation when the post() operation is assumed to succeed (event delivery guarantee). An assertion fires, when the event cannot be delivered in this case.
- Returns
- 'true' (success) when the posting succeeded with the provided margin and 'false' (failure) when the posting fails.
- Note
- This function can be called from any task context or ISR context.
- See also
- QP::QEQueue::postLIFO(), QP::QEQueue::get()
- Precondition
- event must be valid
- Note
- assert if event cannot be posted and dropping events is not acceptable
Definition at line 78 of file qf_qeq.cpp.
◆ postLIFO()
| void postLIFO |
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QEvt const *const |
e, |
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std::uint_fast8_t const |
qs_id |
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) |
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noexcept |
- Description
- Post an event to the "raw" thread-safe event queue using the Last-In-First-Out (LIFO) order.
- Parameters
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| [in] | e | pointer to the event to be posted to the queue |
| [in] | qs_id | QS-id of this state machine (for QS local filter) |
- Attention
- The LIFO policy should be used only with great caution, because it alters the order of events in the queue.
- Note
- This function can be called from any task context or ISR context.
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This function is used for the "raw" thread-safe queues and not for the queues of active objects.
- See also
- QP::QEQueue::post(), QP::QEQueue::get(), QP::QActive::defer()
- Precondition
- the queue must be able to accept the event (cannot overflow)
Definition at line 155 of file qf_qeq.cpp.
◆ get()
| QEvt const * get |
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std::uint_fast8_t const |
qs_id | ) |
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noexcept |
- Description
- Retrieves an event from the front of the "raw" thread-safe queue and returns a pointer to this event to the caller.
- Parameters
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| [in] | qs_id | QS-id of this state machine (for QS local filter) |
- Returns
- pointer to event at the front of the queue, if the queue is not empty and NULL if the queue is empty.
- Note
- this function is used for the "raw" thread-safe queues and not for the queues of active objects.
- See also
- QP::QEQueue::post(), QP::QEQueue::postLIFO(), QP::QActive::recall()
Definition at line 202 of file qf_qeq.cpp.
◆ getNFree()
- Note
- This operation needs to be used with caution because the number of free entries can change unexpectedly. The main intent for using this operation is in conjunction with event deferral. In this case the queue is accessed only from a single thread (by a single AO), so the number of free entries cannot change unexpectedly.
- See also
- QP::QMActive::defer(), QP::QMActive::recall()
Definition at line 263 of file qequeue.hpp.
◆ getNMin()
"low-watermark").
- Description
- This operation needs to be used with caution because the "low-watermark" can change unexpectedly. The main intent for using this operation is to get an idea of queue usage to size the queue adequately.
- Returns
- the minimum number of free entries ever in the queue since init.
Definition at line 278 of file qequeue.hpp.
◆ isEmpty()
| bool isEmpty |
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void |
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const |
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inlinenoexcept |
- Note
- This operation needs to be used with caution because the queue status can change unexpectedly. The main intent for using this operation is in conjunction with event deferral. In this case the queue is accessed only from a single thread (by a single AO), so no other entity can post events to the queue.
- See also
- QP::QMActive::defer(), QP::QMActive::recall()
Definition at line 292 of file qequeue.hpp.
◆ operator=()
◆ QF
◆ QActive
◆ QXThread
◆ QTicker
◆ QS
◆ m_frontEvt
| QEvt const* volatile m_frontEvt |
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private |
- Description
- All incoming and outgoing events pass through the m_frontEvt location. When the queue is empty (which is most of the time), the extra m_frontEvt location allows to bypass the ring buffer altogether, greatly optimizing the performance of the queue. Only bursts of events engage the ring buffer.
The additional role of this attribute is to indicate the empty status of the queue. The queue is empty if the m_frontEvt location is NULL.
Definition at line 126 of file qequeue.hpp.
◆ m_ring
◆ m_end
◆ m_head
◆ m_tail
◆ m_nFree
◆ m_nMin
- Note
- this attribute remembers the low-watermark of the ring buffer, which provides a valuable information for sizing event queues.
- See also
- QP::QF::getQueueMin().
Definition at line 147 of file qequeue.hpp.
The documentation for this class was generated from the following files:
