Description

A synchronization semaphore that can be used to synchronize multipleThreads. Initialized to zero on creation. For a binary version, seeMutex.

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 aSemaphore's reference count reaches zero and it is therefore destroyed, no threads must be waiting on it.

• When aThread's reference count reaches zero and it is therefore destroyed, it must not be waiting on any semaphore.

Tutorials

• Using multiple threads

• Thread-safe APIs

Methods

Method Descriptions

voidpost(count:int = 1)🔗

Lowers theSemaphore, allowing one thread in, or more ifcount is specified.

booltry_wait()🔗

Likewait(), but won't block, so if the value is zero, fails immediately and returnsfalse. If non-zero, it returnstrue to report success.

voidwait()🔗

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