QP natvie, platform-independent, thread-safe event queue interface. More...

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Data Structures
struct	QEQueue
	Native QF Event Queue. More...

Macros
#define	QEQueue_getNFree(me_) ((me_)->nFree)
	"raw" thread-safe QF event queue operation for obtaining the number of free entries still available in the queue. More...

#define	QEQueue_getNMin(me_) ((me_)->nMin)
	"raw" thread-safe QF event queue operation for obtaining the minimum number of free entries ever in the queue (a.k.a. More...

#define	QEQueue_isEmpty(me_) ((me_)->frontEvt == (QEvt *)0)
	"raw" thread-safe QF event queue operation to find out if the queue is empty. More...

Typedefs
typedef uint8_t	QEQueueCtr
	The data type to store the ring-buffer counters based on the macro QF_EQUEUE_CTR_SIZE. More...

Functions
void	QEQueue_init (QEQueue const me, QEvt const *const qSto, uint_fast16_t const qLen)
	Initialize the native QF event queue. More...

bool	QEQueue_post (QEQueue const me, QEvt const const e, uint_fast16_t const margin)
	Post an event to the "raw" thread-safe event queue (FIFO). More...

void	QEQueue_postLIFO (QEQueue const me, QEvt const const e)
	Post an event to the "raw" thread-safe event queue (LIFO). More...

QEvt const *	QEQueue_get (QEQueue *const me)
	Obtain an event from the "raw" thread-safe queue. More...

Detailed Description

QP natvie, platform-independent, thread-safe event queue interface.

Definition in file qequeue.h.

Data Structure Documentation

◆ QEQueue

struct QEQueue

Native QF Event Queue.

Description: This class 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 QEQueue in the specific QF port header file.

The QEQueue structure 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 QEQueue structure is used with two sets of functions. One set is for the active object event queue, which might need to block the active object task when the event queue is empty and might need to unblock it when events are posted to the queue. The interface for the native active object event queue consists of the following functions: QActive_post(), QActive_postLIFO(), and QActive_get_(). Additionally the function QEQueue_init() is used to initialize the queue.

The other set of functions, uses QEQueue 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: QEQueue_post(), QEQueue_postLIFO(), and QEQueue_get(). Additionally the function 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.

See also: QEQueue for the description of the data members

Definition at line 130 of file qequeue.h.

Collaboration diagram for QEQueue:

Data Fields
QEvt const *volatile	frontEvt	pointer to event at the front of the queue. Description All incoming and outgoing events pass through the frontEvt location. When the queue is empty (which is most of the time), the extra frontEvt location allows to bypass the ring buffer altogether, greatly optimizing the performance of the queue. Only bursts of events engage the ring buffer. Note The additional role of this attribute is to indicate the empty status of the queue. The queue is empty when frontEvt is NULL.
QEvt const **	ring	pointer to the start of the ring buffer.
QEQueueCtr	end	offset of the end of the ring buffer from the start of the buffer.
QEQueueCtr volatile	head	offset to where next event will be inserted into the buffer.
QEQueueCtr volatile	tail	offset of where next event will be extracted from the buffer.
QEQueueCtr volatile	nFree	number of free events in the ring buffer.
QEQueueCtr	nMin	minimum number of free events ever in the ring buffer. Description this attribute remembers the low-watermark of the ring buffer, which provides a valuable information for sizing event queues. See also QF_getQueueMargin().

Macro Definition Documentation

◆ QEQueue_getNFree

#define QEQueue_getNFree ( me_ ) ((me_)->nFree)

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

Description: 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.

Parameters

[in] me_ pointer (see Object Orientation)

Returns: the current number of free slots in the queue.

Definition at line 201 of file qequeue.h.

◆ QEQueue_getNMin

#define QEQueue_getNMin ( me_ ) ((me_)->nMin)

"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.

Parameters

[in] me_ pointer (see Object Orientation)

Returns: the minimum number of free entries ever in the queue since init.

Definition at line 215 of file qequeue.h.

◆ QEQueue_isEmpty

#define QEQueue_isEmpty ( me_ ) ((me_)->frontEvt == (QEvt *)0)

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

Description: 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.

Parameters

[in] me_ pointer (see Object Orientation)

Returns: 'true' if the queue is current empty and 'false' otherwise.

Definition at line 231 of file qequeue.h.

Typedef Documentation

◆ QEQueueCtr

typedef uint8_t QEQueueCtr

The data type to store the ring-buffer counters based on the macro QF_EQUEUE_CTR_SIZE.

Description: This header file must be included in all QF ports that use native QF event queue for active objects. Also, this file needs to be included in the QP/C library when the application uses QActive_defer()/ QActive_recall(). Finally, this file is also needed when the "raw" thread-safe queues are used for communication between active objects and non-framework entities, such as ISRs, device drivers, or legacy code.

Description: The dynamic range of this data type determines the maximum length of the ring buffer managed by the native QF event queue.

Definition at line 76 of file qequeue.h.

Function Documentation

◆ QEQueue_init()

void QEQueue_init	(	QEQueue *const	me,
		QEvt const **const	qSto,
		uint_fast16_t const	qLen
	)

Initialize the native QF event queue.

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

Parameters

[in,out]	me	pointer (see Object Orientation)
[in]	qSto	an array of pointers to QEvt to sereve as the ring buffer for the event queue
[in]	qLen	the length of the `qSto` buffer (in 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 and QK kernels, as well as other QP ports to OSes/RTOSes that do provide a suitable message queue.

Definition at line 72 of file qf_qeq.c.

◆ QEQueue_post()

bool QEQueue_post	(	QEQueue *const	me,
		QEvt const *const	e,
		uint_fast16_t const	margin
	)

Post an event to the "raw" thread-safe event queue (FIFO).

Note: this function is used for the "raw" thread-safe queues and NOT for the queues of active objects.

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

Parameters

[in,out]	me	pointer (see Object Orientation)
[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 QF_NO_MARGIN means that this function will assert if posting

Note: The QF_NO_MARGIN value of the margin parameter 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: QEQueue_postLIFO(), QEQueue_get()

Note: assert if event cannot be posted and dropping events is not acceptable

Definition at line 115 of file qf_qeq.c.

◆ QEQueue_postLIFO()

void QEQueue_postLIFO	(	QEQueue *const	me,
		QEvt const *const	e
	)

Post an event to the "raw" thread-safe event queue (LIFO).

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

Parameters

[in,out]	me	pointer (see Object Orientation)
[in]	e	pointer to the event to be posted to the queue

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: QEQueue_post(), QEQueue_get(), QActive_defer()

Precondition: the queue must be able to accept the event (cannot overflow)

Definition at line 215 of file qf_qeq.c.

◆ QEQueue_get()

QEvt const* QEQueue_get ( QEQueue *const me )

Obtain an event from the "raw" thread-safe queue.

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,out] me pointer (see Object Orientation)

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: QEQueue_post(), QEQueue_postLIFO(), QActive_recall()

Definition at line 280 of file qf_qeq.c.

Data Structures

Macros

Typedefs

Functions

Detailed Description

Data Structure Documentation

◆ QEQueue

Macro Definition Documentation

◆ QEQueue_getNFree

◆ QEQueue_getNMin

◆ QEQueue_isEmpty

Typedef Documentation

◆ QEQueueCtr

Function Documentation

◆ QEQueue_init()

◆ QEQueue_post()

◆ QEQueue_postLIFO()

◆ QEQueue_get()