DobbyTimer Class Reference

Utility object that can be used to register a callback function to execute in the future. More...

#include <DobbyTimer.h>

Collaboration diagram for DobbyTimer:

Classes
struct	tagTimerEntry
class	TimerEntryCompare

Public Member Functions
void	stop ()
	Stops the poll loop thread and cancels all timers.
int	add (const std::chrono::milliseconds &timeout, bool oneShot, const std::function< bool()> &func)
	Adds a new timer to the timer queue. More...
bool	remove (int timerId)
	Removes the given timer from the timer queue. More...

Private Types
typedef struct DobbyTimer::tagTimerEntry	TimerEntry

Private Member Functions
void	timerThread ()
	The thread function that runs the timer poll loop. More...
void	updateTimerFd () const
	Writes the item on the head of the expiry queue into the timerfd for the next wake-up time.
struct timespec	calcAbsTime (const struct timespec &now, const std::chrono::milliseconds &timeout) const
	Calculates the a new time value based on the time now and the supplied millisecond offset. More...

Private Attributes
std::multiset< TimerEntry, TimerEntryCompare >	mTimersQueue
std::recursive_mutex	mLock
std::thread	mThread
int	mTimerFd
int	mEventFd
AICommon::IDGenerator< 6 >	mIdGenerator

Detailed Description

Utility object that can be used to register a callback function to execute in the future.

Multiple callbacks can be registered via this object, internally it runs a thread with a single timerfd that wakes up at the correct time and then calls any handlers registered.

All callbacks are processed in the same thread, so obviously one timer handler can block all the others, clients should bear this in mind.

Warning

Currently if you try and call DobbyTimer::remove from inside the handler callback function it will return with an error. If you want to stop a repeating timer then return false from the handler.

This object currently only supports a maximum of 63 timers.

Member Function Documentation

add()

int DobbyTimer::add	(	const std::chrono::milliseconds &	timeout,
		bool	oneShot,
		const std::function< bool()> &	handler
	)

Adds a new timer to the timer queue.

Parameters

[in]	timeout	The time after which to call the supplied handler.
[in]	oneShot	If true the timer is automatically removed after it times out the first time.
[in]	handler	The handler function to call when the timer times out.

Returns

on success returns a (greater than zero) timer id integer which identifies the timer, on failure -1 is returned.

calcAbsTime()

struct timespec DobbyTimer::calcAbsTime ( const struct timespec &  base, const std::chrono::milliseconds &  offset  ) const

private

Calculates the a new time value based on the time now and the supplied millisecond offset.

Parameters

[in]	base	The base time to calculate the new offset from
[in]	offset	The milliseconds offset

Returns

a timespec that is the base value plus the offset.

remove()

bool DobbyTimer::remove

(

int

timerId

)

Removes the given timer from the timer queue.

Once this method returns (successfully) you are guaranteed that the timer handler will not be called, i.e. this is synchronisation point.

This method will fail if called from the context of a timer handler, if you want to cancel a repeating timer then just return false in the handler.

Parameters

[in]

timerId

The id of the timer to remove as returned by the add() method

Returns

true if the timer was found and was removed from the queue, otherwise false

timerThread()

void DobbyTimer::timerThread ( )

private

The thread function that runs the timer poll loop.

This simply polls on an timerfd and eventfd. The timerfd is obviously for waking up and calling any installed timers at the right time. The eventfd is used to kill the poll loop at shutdown time.

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

• utils/source/DobbyTimer.h
• utils/source/DobbyTimer.cpp