Native QF Event Queue class. More...

#include <qequeue.hpp>

Collaboration diagram for QEQueue:

Public Member Functions
	QEQueue (void) noexcept
	public default constructor More...

void	init (QEvt const *qSto[], std::uint_fast16_t const qLen) noexcept
	Initializes the native QF event queue. More...

bool	post (QEvt const *const e, std::uint_fast16_t const margin, std::uint_fast8_t const qs_id) noexcept
	"raw" thread-safe QF event queue implementation for the event posting (FIFO). You can call this function from any task context or ISR context. This function uses internally a critical section. More...

void	postLIFO (QEvt const *const e, std::uint_fast8_t const qs_id) noexcept
	"raw" thread-safe QF event queue implementation for the First-In-First-Out (FIFO) event posting. You can call this function from any task context or ISR context. Please note that this function uses internally a critical section. More...

QEvt const *	get (std::uint_fast8_t const qs_id) noexcept
	"raw" thread-safe QF event queue implementation for the Last-In-First-Out (LIFO) event posting. More...

QEQueueCtr	getNFree (void) const noexcept
	"raw" thread-safe QF event queue operation for obtaining the number of free entries still available in the queue. More...

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. "low-watermark"). More...

bool	isEmpty (void) const noexcept
	"raw" thread-safe QF event queue operation to find out if the queue is empty More...

Private Member Functions
	QEQueue (QEQueue const &)=delete
	disallow copying of QEQueue More...

QEQueue &	operator= (QEQueue const &)=delete
	disallow assignment of QEQueue More...

Private Attributes
QEvt const *volatile	m_frontEvt
	pointer to event at the front of the queue More...

QEvt const **	m_ring
	pointer to the start of the ring buffer More...

QEQueueCtr	m_end
	offset of the end of the ring buffer from the start of the buffer More...

QEQueueCtr volatile	m_head
	offset to where next event will be inserted into the buffer More...

QEQueueCtr volatile	m_tail
	offset of where next event will be extracted from the buffer More...

QEQueueCtr volatile	m_nFree
	number of free events in the ring buffer More...

QEQueueCtr	m_nMin
	minimum number of free events ever in the ring buffer. More...

Friends
class	QF

class	QActive

class	QXThread

class	QTicker

class	QS

Detailed Description

Native QF Event Queue class.

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 123 of file qequeue.hpp.

Constructor & Destructor Documentation

◆ QEQueue() [1/2]

QEQueue ( void )

noexcept

public default constructor

Description: Default constructor

Definition at line 58 of file qf_qeq.cpp.

◆ QEQueue() [2/2]

QEQueue ( QEQueue const & )

privatedelete

disallow copying of QEQueue

Member Function Documentation

◆ init()

void init	(	QEvt const *	qSto[],
		std::uint_fast16_t const	qLen
	)

noexcept

Initializes the native QF event queue.

Description: The parameters are as follows: qSto[] is the ring buffer storage, qLen is the length of the ring buffer in the units of event- pointers.

Note: The actual capacity of the queue is qLen + 1, because of the extra location fornEvt_.

Description: Initialize the event queue by giving it the storage for the ring buffer.

Parameters

[in]	qSto	an array of pointers to QP::QEvt to sereve 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.; 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 84 of file qf_qeq.cpp.

◆ post()

bool post	(	QEvt const *const	e,
		std::uint_fast16_t const	margin,
		std::uint_fast8_t const	qs_id
	)

noexcept

"raw" thread-safe QF event queue implementation for the event posting (FIFO). You can call this function from any task context or ISR context. This function uses internally a critical section.

Description: The argument margin specifies the minimum number of free entries in the queue that must be available for posting to succeed. The function returns true (success) if the posting succeeded (with the provided margin) and false (failure) when the posting fails.

Note: The function raises an assertion if the margin is zero and the queue becomes full and cannot accept the event.

See also: QP::QEQueue::postLIFO(), QP::QEQueue::get()

Description: Post an event to the "raw" thread-safe event queue using the First-In-First-Out (FIFO) order.

Parameters

[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 122 of file qf_qeq.cpp.

◆ postLIFO()

void postLIFO	(	QEvt const *const	e,
		std::uint_fast8_t const	qs_id
	)

noexcept

"raw" thread-safe QF event queue implementation for the First-In-First-Out (FIFO) event posting. You can call this function from any task context or ISR context. Please note that this function uses internally a critical section.

Note: The function raises an assertion if the native QF queue becomes full and cannot accept the event.

See also: QP::QEQueue::postLIFO(), QP::QEQueue::get()

Description: Post an event to the "raw" thread-safe event queue using the Last-In-First-Out (LIFO) order.

Parameters

[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.; 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 221 of file qf_qeq.cpp.

◆ get()

QEvt const * get ( std::uint_fast8_t const qs_id )

noexcept

"raw" thread-safe QF event queue implementation for the Last-In-First-Out (LIFO) event posting.

Note: The LIFO policy should be used only with great caution because it alters order of events in the queue.; The function raises an assertion if the native QF queue becomes full and cannot accept the event. You can call this function from any task context or ISR context. Please note that this function uses internally a critical section.

See also: QP::QEQueue::post(), QP::QEQueue::postLIFO(), QP::QEQueue::get()

Description: Retrieves an event from the front of the "raw" thread-safe queue and returns a pointer to this event to the caller.

Parameters

[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 287 of file qf_qeq.cpp.

◆ getNFree()

QEQueueCtr getNFree ( void ) const

inlinenoexcept

"raw" thread-safe QF event queue operation for obtaining the number of free entries still available in the queue.

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 225 of file qequeue.hpp.

◆ getNMin()

QEQueueCtr getNMin ( void ) const

inlinenoexcept

"raw" thread-safe QF event queue operation for obtaining the minimum number of free entries ever in the queue (a.k.a. "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 240 of file qequeue.hpp.

◆ isEmpty()

bool isEmpty ( void ) const

inlinenoexcept

"raw" thread-safe QF event queue operation to find out if the queue is empty

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 254 of file qequeue.hpp.

◆ operator=()

QEQueue& operator= ( QEQueue const & )

privatedelete

disallow assignment of QEQueue

Friends And Related Function Documentation

◆ QF

friend class QF

friend

Definition at line 265 of file qequeue.hpp.

◆ QActive

friend class QActive

friend

Definition at line 266 of file qequeue.hpp.

◆ QXThread

friend class QXThread

friend

Definition at line 267 of file qequeue.hpp.

◆ QTicker

friend class QTicker

friend

Definition at line 268 of file qequeue.hpp.

◆ QS

friend class QS

friend

Definition at line 269 of file qequeue.hpp.

Field Documentation

◆ m_frontEvt

QEvt const* volatile m_frontEvt

private

pointer to event at the front of the queue

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 136 of file qequeue.hpp.

◆ m_ring

QEvt const** m_ring

private

pointer to the start of the ring buffer

Definition at line 139 of file qequeue.hpp.

◆ m_end

QEQueueCtr m_end

private

offset of the end of the ring buffer from the start of the buffer

Definition at line 142 of file qequeue.hpp.

◆ m_head

QEQueueCtr volatile m_head

private

offset to where next event will be inserted into the buffer

Definition at line 145 of file qequeue.hpp.

◆ m_tail

QEQueueCtr volatile m_tail

private

offset of where next event will be extracted from the buffer

Definition at line 148 of file qequeue.hpp.

◆ m_nFree

QEQueueCtr volatile m_nFree

private

number of free events in the ring buffer

Definition at line 151 of file qequeue.hpp.

◆ m_nMin

QEQueueCtr m_nMin

private

minimum number of free events ever in the ring buffer.

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 157 of file qequeue.hpp.

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

Public Member Functions

Private Member Functions

Private Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

◆ QEQueue() [1/2]

◆ QEQueue() [2/2]

Member Function Documentation

◆ init()

◆ post()

◆ postLIFO()

◆ get()

◆ getNFree()

◆ getNMin()

◆ isEmpty()

◆ operator=()

Friends And Related Function Documentation

◆ QF

◆ QActive

◆ QXThread

◆ QTicker

◆ QS

Field Documentation

◆ m_frontEvt

◆ m_ring

◆ m_end

◆ m_head

◆ m_tail

◆ m_nFree

◆ m_nMin