Class SyncCounter[in Threading]

Implements a synchronization counter (semaphore).

class SyncCounter( [count] )

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Summary

class SyncCounter( [count] )

Implements a synchronization counter (semaphore).

This class implements a synchronization counter, commonly known as "semaphore", which provides the following behavior:

• If the counter is greater than zero, the item can be acquired, and the counter is atomically decremented.
• If the counter is zero, the acquiring thread must wait for the counter to become greater than zero.
• The release operation increments the counter and eventually wakes up waiting threads.
• The counter provides also a SyncCounter.post method which may increase the counter of more than one unit (allowing the structure to be acquired by more than one thread).

We have adopted the "counter" name rather than the more common "semaphore" to avoid confusion with the Semaphore class used for coroutines, and also because the post semantic is merged with the release method.

The counter is created with an initial count that defaults to zero; this means that the first thread trying to acquire this structure will block until a post or release is issued.

If a positive interger is given as count, then the same amount of threads will be able to acquire the semaphore before one thread being blocked.

Methods

post()

Releases the counter or increases the counter by more than one.

SyncCounter.post( [count] )

This method acts as release(), but it can be provided an optional parameter to give more than one thread the ability to acquire this structure.

It is not possible to use this method to reduce the internal count.