◆ wait() [1/3]

template<typename object_t >

static bool xtd::threading::monitor::wait	(	const object_t &	obj,
		int32	milliseconds_timeout
	)

inlinestatic

Releases the lock on an object and blocks the current thread until it reacquires the lock. If the specified time-out interval elapses, the thread enters the ready queue.

Parameters

obj	The object on which to wait.
milliseconds_timeout	The number of milliseconds to wait before the thread enters the ready queue.

Returns: true if the lock was reacquired before the specified time elapsed; false if the lock was reacquired after the specified time elapsed. The method does not return until the lock is reacquired.

Exceptions

xtd::threading::synchronization_lock_exception xtd::threading::monitor::wait is not invoked from within a synchronized block of code.

Remarks: This method does not return until it reacquires an exclusive lock on the obj parameter.; The thread that currently owns the lock on the specified object invokes this method in order to release the object so that another thread can access it. The caller is blocked while waiting to reacquire the lock. This method is called when the caller needs to wait for a state change that will occur as a result of another thread's operations.; The time-out ensures that the current thread does not block indefinitely if another thread releases the lock without first calling the xtd::threading::monitor::pulse or xtd::threading::monitor::pulse_all method. It also moves the thread to the ready queue, bypassing other threads ahead of it in the wait queue, so that it can reacquire the lock sooner. The thread can test the return value of the xtd::threading::monitor::wait method to determine whether it reacquired the lock prior to the time-out. The thread can evaluate the conditions that caused it to enter the wait, and if necessary call the xtd::threading::monitor::wait method again.; When a thread calls xtd::threading::monitor::wait, it releases the lock and enters the waiting queue. At this point, the next thread in the ready queue (if there is one) is allowed to take control of the lock. The thread that invoked Wait remains in the waiting queue until either a thread that holds the lock invokes xtd::threading::monitor::pulse_all, or it is the next in the queue and a thread that holds the lock invokes xtd::threading::monitor::pulse. However, if milliseconds_timeout elapses before another thread invokes this object's xtd::threading::monitor::pulse or xtd::threading::monitor::pulse_all method, the original thread is moved to the ready queue in order to regain the lock.

Note: If xtd::threading::timeout::infinite is specified for the milliseconds_timeout parameter, this method blocks indefinitely unless the holder of the lock calls xtd::threading::monitor::pulse or xtd::threading::monitor::pulse_all. If milliseconds_timeout equals 0, the thread that calls Wait releases the lock and then immediately enters the ready queue in order to regain the lock.

Remarks: The caller executes xtd::threading::monitor::wait once, regardless of the number of times xtd::threading::monitor::enter has been invoked for the specified object. Conceptually, the Wait method stores the number of times the caller invoked xtd::threading::monitor::enter on the object and invokes xtd::threading::monitor::exit as many times as necessary to fully release the locked object. The caller then blocks while waiting to reacquire the object. When the caller reacquires the lock, the system calls xtd::threading::monitor::enter as many times as necessary to restore the saved xtd::threading::monitor::enter count for the caller. Calling xtd::threading::monitor::wait releases the lock for the specified object only; if the caller is the owner of locks on other objects, these locks are not released.

Note: A synchronized object holds several references, including a reference to the thread that currently holds the lock, a reference to the ready queue, which contains the threads that are ready to obtain the lock, and a reference to the waiting queue, which contains the threads that are waiting for notification of a change in the object's state.

Remarks: The xtd::threading::monitor::pulse, xtd::threading::monitor::pulse_all, and Wait methods must be invoked from within a synchronized block of code.; The remarks for the xtd::threading::monitor::pulse method explain what happens if xtd::threading::monitor::pulse is called when no threads are waiting.