Condition variable used together with external PIMutex. More...

#include <piconditionvar.h>

Public Member Functions
	PIConditionVariable ()
	Constructs condition variable.

virtual	~PIConditionVariable ()
	Destroys condition variable.

void	notifyOne ()
	Wakes one waiting thread, if any.

void	notifyAll ()
	Wakes all threads currently waiting on this variable.

virtual void	wait (PIMutex &lk)
	Waits until notification, temporarily releasing lk while blocked.

virtual void	wait (PIMutex &lk, const std::function< bool()> &condition)
	Waits until condition becomes true, rechecking it after each wakeup while lk is locked. More...

virtual bool	waitFor (PIMutex &lk, PISystemTime timeout)
	Waits for at most timeout and returns `true` if awakened before it expires.

virtual bool	waitFor (PIMutex &lk, PISystemTime timeout, const std::function< bool()> &condition)
	Waits until condition becomes true or timeout expires. More...

Detailed Description

Condition variable used together with external PIMutex.

Member Function Documentation

◆ wait()

void PIConditionVariable::wait	(	PIMutex &	lk,
		const std::function< bool()> &	condition
	)

virtual

Waits until condition becomes true, rechecking it after each wakeup while lk is locked.

The execution of the current thread (which shall have locked with lk method PIMutex::lock()) is blocked until notified.

At the moment of blocking the thread, the function automatically calls lk.unlock() (PIMutex::unlock()), allowing other locked threads to continue.

Once notified (explicitly, by some other thread), the function unblocks and calls lk.lock() (PIMutex::lock()), leaving lk in the same state as when the function was called. Then the function returns (notice that this last mutex locking may block again the thread before returning).

Generally, the function is notified to wake up by a call in another thread either to member notifyOne() or to member notifyAll(). But certain implementations may produce spurious wake-up calls without any of these functions being called. Therefore, users of this function shall ensure their condition for resumption is met.

If condition is specified, the function only blocks if condition returns false, and notifications can only unblock the thread when it becomes true (which is specially useful to check against spurious wake-up calls).

Parameters

lk	lock object used by method wait for data protection
condition	A callable object or function that takes no arguments and returns a value that can be evaluated as a bool. This is called repeatedly until it evaluates to true.

◆ waitFor()

bool PIConditionVariable::waitFor	(	PIMutex &	lk,
		PISystemTime	timeout,
		const std::function< bool()> &	condition
	)

virtual

Waits until condition becomes true or timeout expires.

The execution of the current thread (which shall have locked with lk method PIMutex::lock()) is blocked during timeout, or until notified (if the latter happens first).

At the moment of blocking the thread, the function automatically calls lk.lock() (PIMutex::lock()), allowing other locked threads to continue.

Once notified or once timeout has passed, the function unblocks and calls lk.unlock() (PIMutex::unlock()), leaving lk in the same state as when the function was called. Then the function returns (notice that this last mutex locking may block again the thread before returning).