#include <EventQueue.h>

Inheritance diagram for EventQueue:

Public Member Functions
	EventQueue (unsigned size=(32 (EQUEUE_EVENT_SIZE-2 sizeof(void )+sizeof(mbed::Callback< void()>))), unsigned char buffer=NULL)
	Create an EventQueue. More...

	~EventQueue ()
	Destroy an EventQueue. More...

void	dispatch (int ms=-1)
	Dispatch events. More...

void	dispatch_forever ()
	Dispatch events without a timeout. More...

void	break_dispatch ()
	Break out of a running event loop. More...

unsigned	tick ()
	Millisecond counter. More...

bool	cancel (int id)
	Cancel an in-flight event. More...

template<typename F , typename A >
bool	cancel (UserAllocatedEvent< F, A > *event)
	Cancel an in-flight user allocated event. More...

int	time_left (int id)
	Query how much time is left for delayed event. More...

template<typename F , typename A >
int	time_left (UserAllocatedEvent< F, A > *event)
	Query how much time is left for delayed UserAllocatedEvent. More...

void	background (mbed::Callback< void(int)> update)
	Background an event queue onto a single-shot timer-interrupt. More...

int	chain (EventQueue *target)
	Chain an event queue onto another event queue. More...

template<typename F , typename... Args>
int	call (F f, Args...args)
	Calls an event on the queue. More...

template<typename T , typename R , typename... Args>
int	call (T obj, R(T::method)(Args...args), Args...args)
	Calls an event on the queue. More...

template<typename F , typename... ArgTs>
int	call_in (duration ms, F f, ArgTs...args)
	Calls an event on the queue after a specified delay. More...

template<typename T , typename R , typename... ArgTs>
int	call_in (duration ms, T obj, R(T::method)(ArgTs...args), ArgTs...args)
	Calls an event on the queue after a specified delay. More...

template<typename F , typename... ArgTs>
int	call_every (duration ms, F f, ArgTs...args)
	Calls an event on the queue periodically. More...

template<typename T , typename R , typename... ArgTs>
int	call_every (duration ms, T obj, R(T::method)(ArgTs...args), ArgTs...args)
	Calls an event on the queue periodically. More...

template<typename R , typename... BoundArgTs, typename... ContextArgTs, typename... ArgTs>
Event< void(ArgTs...)>	event (R(*func)(BoundArgTs..., ArgTs...), ContextArgTs...context_args)
	Creates an event bound to the event queue. More...

template<typename T , typename R , typename... BoundArgTs, typename... ContextArgTs, typename... ArgTs>
Event< void(ArgTs...)>	event (T obj, R(T::method)(BoundArgTs..., ArgTs...), ContextArgTs...context_args)
	Creates an event bound to the event queue. More...

template<typename R , typename... BoundArgTs, typename... ContextArgTs, typename... ArgTs>
Event< void(ArgTs...)>	event (mbed::Callback< R(BoundArgTs..., ArgTs...)> cb, ContextArgTs...context_args)
	Creates an event bound to the event queue. More...

template<typename F , typename... ArgTs>
UserAllocatedEvent< F, void(ArgTs...)>	make_user_allocated_event (F f, ArgTs...args)
	Creates an user allocated event bound to the event queue. More...

template<typename T , typename R , typename... ArgTs>
UserAllocatedEvent< mbed::Callback< void(ArgTs...)>, void(ArgTs...)>	make_user_allocated_event (T obj, R(T::method)(ArgTs...args), ArgTs...args)
	Creates an user allocated event bound to the event queue. More...

Detailed Description

EventQueue.

Flexible event queue for dispatching events

Definition at line 62 of file EventQueue.h.

Constructor & Destructor Documentation

EventQueue	(	unsigned	size = `(32 (EQUEUE_EVENT_SIZE-2 sizeof(void *)+sizeof(mbed::Callback< void()>)))`,
		unsigned char *	buffer = `NULL`
	)

Create an EventQueue.

Create an event queue. The event queue either allocates a buffer of the specified size with malloc or uses the user provided buffer or uses 1B dummy buffer if 0 size passed.

0 size queue is a special purpose queue to dispatch static events only (see UserAllocatedEvent). Such a queue gives the guarantee that no dynamic memory allocation will take place while queue creation and events posting & dispatching.

Parameters

size	Size of buffer to use for events in bytes (default to EVENTS_QUEUE_SIZE) If 0 provided then 1B dummy buffer is used
buffer	Pointer to buffer to use for events (default to NULL)

~EventQueue ( )

Destroy an EventQueue.

Member Function Documentation

void background ( mbed::Callback< void(int)> update )

Background an event queue onto a single-shot timer-interrupt.

When updated, the event queue will call the provided update function with a timeout indicating when the queue should be dispatched. A negative timeout will be passed to the update function when the timer-interrupt is no longer needed.

Passing a null function disables the existing update function.

The background function allows an event queue to take advantage of hardware timers or other event loops, allowing an event queue to be ran in the background without consuming the foreground thread.

Parameters

update Function called to indicate when the queue should be dispatched

void break_dispatch ( )

Break out of a running event loop.

Forces the specified event queue's dispatch loop to terminate. Pending events may finish executing, but no new events will be executed.

int call	(	F	f,
		Args...	args
	)

Calls an event on the queue.

The specified callback will be executed in the context of the event queue's dispatch loop.

The call function is IRQ safe and can act as a mechanism for moving events out of IRQ contexts.

Parameters

f	Function to execute in the context of the dispatch loop
args	Arguments to pass to the callback

Returns: A unique id that represents the posted event and can be passed to cancel, or an id of 0 if there is not enough memory to allocate the event. Returned id will remain valid until event has finished executing.

#include "mbed.h"
int main() {
    // creates a queue with the default size
    EventQueue queue;
    // events are simple callbacks
    queue.call(printf, "called immediately\n");
    // the dispatch method executes events
    queue.dispatch();
}

int call	(	T *	obj,
		R(T::*)(Args...args)	method,
		Args...	args
	)

Calls an event on the queue.

The specified callback is executed in the context of the event queue's dispatch loop.

The call function is IRQ safe and can act as a mechanism for moving events out of IRQ contexts.

Parameters

obj	Object to call with the member function
method	Member function to execute in the context of the dispatch loop
args	Arguments to pass to the callback

Returns: A unique ID that represents the posted event and can be passed to cancel, or an ID of 0 if there is not enough memory to allocate the event. Returned ID remains valid until event has finished executing.

#include "mbed.h"
class EventHandler {
    int _id;
public:
    EventHandler(int id) : _id(id) { }
    void handler(int c) {
        printf("ID: %d Param: %d\r\n", _id, c);
    }
};
int main() {
    // creates a queue with the default size
    EventQueue queue;
    // Create EventHandler object with state
    EventHandler handler_cb(1);
    // events are simple callbacks, call object method
    // with provided parameter
    queue.call(&handler_cb, &EventHandler::handler, 2);
    // the dispath method executes events
    queue.dispatch();
}

int call_every	(	duration	ms,
		F	f,
		ArgTs...	args
	)

Calls an event on the queue periodically.

Note: The first call_every event occurs after the specified delay. To create a periodic event that fires immediately,

See also: Event.

The specified callback is executed in the context of the event queue's dispatch loop.

The call_every function is IRQ safe and can act as a mechanism for moving events out of IRQ contexts.

Parameters

ms	Period of the event in milliseconds
f	Function to execute in the context of the dispatch loop
args	Arguments to pass to the callback

Returns: A unique ID that represents the posted event and can be passed to cancel, or an ID of 0 if there is not enough memory to allocate the event.

#include "mbed.h"
using namespace std::chrono_literals;
class EventHandler {
    int _id;
public:
    EventHandler(int id) : _id(id) { }
    void handler(int c) {
        printf("ID: %d Param: %d\r\n", _id, c);
    }
};
int main() {
    // creates a queue with the default size
    EventQueue queue;
    // events are simple callbacks, call every 2 seconds
    queue.call_every(2s, printf, "Calling every 2 seconds\n");
    // the dispatch method executes events
    queue.dispatch();
}

int call_every	(	duration	ms,
		T *	obj,
		R(T::*)(ArgTs...args)	method,
		ArgTs...	args
	)

Calls an event on the queue periodically.

Note: The first call_every event occurs after the specified delay. To create a periodic event that fires immediately,

See also: Event.

The specified callback is executed in the context of the event queue's dispatch loop.

The call_every function is IRQ safe and can act as a mechanism for moving events out of IRQ contexts.

Parameters

ms	Period of the event in milliseconds
obj	Object to call with the member function
method	Member function to execute in the context of the dispatch loop
args	Arguments to pass to the callback

#include "mbed.h"
using namespace std::chrono_literals;
class EventHandler {
    int _id;
public:
    EventHandler(int id) : _id(id) { }
    void handler(int c) {
        printf("ID: %d Param: %d\r\n", _id, c);
    }
};
int main() {
    // creates a queue with the default size
    EventQueue queue;
    // Create EventHandler object with state
    EventHandler handler_cb(5);
    // events are simple callbacks, call object method every 2 seconds
    // with provided parameter
    queue.call_every(2s, &handler_cb, &EventHandler::handler, 6);
    // the dispatch method executes events
    queue.dispatch();
}

int call_in	(	duration	ms,
		F	f,
		ArgTs...	args
	)

Calls an event on the queue after a specified delay.

The specified callback is executed in the context of the event queue's dispatch loop.

The call_in function is IRQ safe and can act as a mechanism for moving events out of IRQ contexts.

Parameters

ms	Time to delay in milliseconds
f	Function to execute in the context of the dispatch loop
args	Arguments to pass to the callback

Returns: A unique ID that represents the posted event and can be passed to cancel, or an ID of 0 if there is not enough memory to allocate the event.

#include "mbed.h"
using namespace std::chrono_literals;
int main() {
    // creates a queue with the default size
    EventQueue queue;
    // events are simple callbacks
    queue.call_in(2s, printf, "called in 2 seconds\n");
    // the dispatch methods executes events
    queue.dispatch();
}

int call_in	(	duration	ms,
		T *	obj,
		R(T::*)(ArgTs...args)	method,
		ArgTs...	args
	)

Calls an event on the queue after a specified delay.

The specified callback is executed in the context of the event queue's dispatch loop.

The call_in function is IRQ safe and can act as a mechanism for moving events out of IRQ contexts.

Parameters

ms	Time to delay in milliseconds
obj	Object to call with the member function
method	Member function to execute in the context of the dispatch loop
args	Arguments to pass to the callback

Returns: A unique ID that represents the posted event and can be passed to cancel, or an ID of 0 if there is not enough memory to allocate the event.

#include "mbed.h"
using namespace std::chrono_literals;
class EventHandler {
    int _id;
public:
    EventHandler(int id) : _id(id) { }
    void handler(int c) {
        printf("ID: %d Param: %d\r\n", _id, c);
    }
};
int main() {
    // creates a queue with the default size
    EventQueue queue;
    // Create EventHandler object with state
    EventHandler handler_cb(3);
    // events are simple callbacks, call object method in 2 seconds
    // with provided parameter
    queue.call_in(2s, &handler_cb, &EventHandler::handler, 4);
    // the dispatch method executes events
    queue.dispatch();
}

bool cancel ( int id )

Cancel an in-flight event.

Attempts to cancel an event referenced by the unique id returned from one of the call functions. It is safe to call cancel after an event has already been dispatched.

id must be valid i.e. event must have not finished executing.

The cancel function is IRQ safe.

If called while the event queue's dispatch loop is active in another thread, the cancel function does not guarantee that the event will not execute after it returns, as the event may have already begun executing. A call made from the same thread as the dispatch loop will always succeed with a valid id.

Parameters

id	Unique id of the event

Returns: true if event was successfully cancelled false if event was not cancelled (invalid id or executing already begun)

bool cancel ( UserAllocatedEvent< F, A > * event )

Cancel an in-flight user allocated event.

Attempts to cancel an UserAllocatedEvent referenced by its address It is safe to call cancel after an event has already been dispatched.

Event must be valid i.e. event must have not finished executing and must have been bound to this queue.

The cancel function is IRQ safe.

If called while the event queue's dispatch loop is active in another thread, the cancel function does not guarantee that the event will not execute after it returns, as the event may have already begun executing. A call made from the same thread as the dispatch loop will always succeed with a valid id.

Parameters

event Address of the event

Returns: true if event was successfully cancelled false if event was not cancelled (invalid queue or executing already begun)

Definition at line 175 of file EventQueue.h.

int chain ( EventQueue * target )

Chain an event queue onto another event queue.

After chaining a queue to a target, calling dispatch on the target queue will also dispatch events from this queue. The queues use their own buffers and events must be handled independently.

A null queue as the target will unchain the existing queue.

The chain function allows multiple event queues to be composed, sharing the context of a dispatch loop while still being managed independently

Parameters

target Queue that will dispatch this queue's events as a part of its dispatch loop

Returns: Zero on success and negative error code value if chaining fails

void dispatch ( int ms = -1 )

Dispatch events.

Executes events until the specified milliseconds have passed. If ms is negative, the dispatch function will dispatch events indefinitely or until break_dispatch is called on this queue.

When called with a finite timeout, the dispatch function is guaranteed to terminate. When called with a timeout of 0, the dispatch function does not wait and is IRQ safe.

Parameters

ms	Time to wait for events in milliseconds, a negative value will dispatch events indefinitely (default to -1)

void dispatch_forever ( )

Dispatch events without a timeout.

This is equivalent to EventQueue::dispatch with no arguments, but avoids overload ambiguities when passed as a callback.

See also: EventQueue::dispatch

Definition at line 112 of file EventQueue.h.

Event<void(ArgTs...)> event	(	R(*)(BoundArgTs..., ArgTs...)	func,
		ContextArgTs...	context_args
	)

Creates an event bound to the event queue.

Constructs an event bound to the specified event queue. The specified callback acts as the target for the event and is executed in the context of the event queue's dispatch loop once posted.

Parameters

func	Function to execute when the event is dispatched
context_args	Arguments to pass to the callback

Returns: Event that dispatches on the specific queue

#include "mbed.h"
void handler(int c) {
    printf("Param: %d\r\n", c);
}
int main()
{
    EventQueue queue;
    // Create event with parameter
    Event<void()>    e  = queue.event(handler, 1);
    e();
    // Create event and post parameter later
    Event<void(int)> e2 = queue.event(handler);
    // Post the event with paramter 8
    e.post(8);
    // The dispatch method executes events
    queue.dispatch();
    e2.post(2);
    queue.dispatch();
}

Event<void(ArgTs...)> event	(	T *	obj,
		R(T::*)(BoundArgTs..., ArgTs...)	method,
		ContextArgTs...	context_args
	)

Creates an event bound to the event queue.

Constructs an event bound to the specified event queue. The specified callback acts as the target for the event and is executed in the context of the event queue's dispatch loop once posted.

Parameters

obj	Object to call with the member function
method	Member function to execute in the context of the dispatch loop
context_args	Arguments to pass to the callback

Returns: Event that dispatches on the specific queue

#include "mbed.h"
class EventHandler {
    int _id;
public:
    EventHandler(int id) : _id(id) { }
    void handler(int c) {
        printf("ID: %d Param: %d\r\n", _id, c);
    }
};
int main()
{
    EventQueue queue;
    EventHandler handler_cb(10);
    // Create event on the eventqueue with a method callback
    Event<void(int)> e = queue.event(&handler_cb, &EventHandler::handler);
    // Post the event with paramter 8
    e.post(11);
    // The dispatch method executes events
    queue.dispatch();
}

Event<void(ArgTs...)> event	(	mbed::Callback< R(BoundArgTs..., ArgTs...)>	cb,
		ContextArgTs...	context_args
	)

Creates an event bound to the event queue.

Constructs an event bound to the specified event queue. The specified callback acts as the target for the event and is executed in the context of the event queue's dispatch loop once posted.

Parameters

cb	Callback object
context_args	Arguments to pass to the callback

Returns: Event that dispatches on the specific queue

#include "mbed.h"
void handler(int c) {
    printf("Param: %d\r\n", c);
}
int main()
{
    EventQueue queue;
    // Create callback object acting as a function
    // pointer to handler
    Callback<void(int)> cb(handler);
    // Pass the callback object to the eventqueue
    Event<void(int)> e = queue.event(cb);
    // Post the event with parameter 8
    e.post(9);
    // The dispatch method executes events
    q.dispatch();
}

unsigned tick ( )

Millisecond counter.

Returns the underlying tick of the event queue represented as the number of milliseconds that have passed since an arbitrary point in time. Intentionally overflows to 0 after 2^32-1.

Returns: The underlying tick of the event queue in milliseconds

int time_left ( int id )

Query how much time is left for delayed event.

If the event is delayed, this function can be used to query how much time is left until the event is due to be dispatched.

id must be valid i.e. event must have not finished executing.

This function is IRQ safe.

Parameters

id	Unique id of the event

Returns: Remaining time in milliseconds or 0 if event is already due to be dispatched or is currently executing. Undefined if id is invalid.

int time_left ( UserAllocatedEvent< F, A > * event )

Query how much time is left for delayed UserAllocatedEvent.

If the event is delayed, this function can be used to query how much time is left until the event is due to be dispatched.

Event must be valid i.e. event must have not finished executing and must have been bound to this queue.

This function is IRQ safe.

Parameters

event Address of the event

Returns: Remaining time in milliseconds or 0 if event is already due to be dispatched or is currently executing. Undefined if id is invalid.

Definition at line 221 of file EventQueue.h.

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Important Information for this Arm website