Class Semaphore

A synchronization mechanism used to control access to a shared resource by Threads.

Remarks

A synchronization semaphore that can be used to synchronize multiple Threads. Initialized to zero on creation. For a binary version, see Mutex.

Warning: Semaphores must be used carefully to avoid deadlocks.

Warning: To guarantee that the operating system is able to perform proper cleanup (no crashes, no deadlocks), these conditions must be met:

When a Semaphore's reference count reaches zero and it is therefore destroyed, no threads must be waiting on it.
When a Thread's reference count reaches zero and it is therefore destroyed, it must not be waiting on any semaphore.

Lowers the Semaphore, allowing one thread in, or more if count is specified.

void post(int count)

Like wait, but won't block, so if the value is zero, fails immediately and returns false. If non-zero, it returns true to report success.

bool try_wait

Waits for the Semaphore, if its value is zero, blocks until non-zero.

void wait