Semaphores

Semaphores are a synchronisation mechanism used to control concurrent access to a shared resource. A counting semaphore is a special semaphore which has a counter that is bigger than zero. The counter is initialised in the constructor. Acquiring the semaphore decreases the counter and releasing the semaphore increases the counter. If a thread tries to acquire the semaphore when the counter is zero, the thread will block until another thread increments the counter by releasing the semaphore.

Methods of a semaphore sem

Method	Description
counting_semaphore::max()	Return the maximum value of the counter.
sem.release(upd = 1)	Atomically increases counter by upd.
sem.acquire()	Performs sem.try_acquire and blocks until counter is greater than zero.
sem.try_acquire()	Atomically decrements the counter.
sem.try_acquire_for(reTime...