General Quantity Semaphores

QSemN is a quantity semaphore in which the resource is acquired and released in units of one. It provides guaranteed FIFO ordering for satisfying blocked waitQSemN calls.

The pattern

  bracket_ (waitQSemN n) (signalQSemN n) (...)

is safe; it never loses any of the resource.

Build a new QSemN with a supplied initial quantity. The initial quantity must be at least 0.

Wait for the specified quantity to become available.

Signal that a given quantity is now available from the QSemN.