A purely functional semaphore.
A purely functional semaphore.
A semaphore has a non-negative number of permits available. Acquiring a permit decrements the current number of permits and releasing a permit increases the current number of permits. An acquire that occurs when there are no permits available results in semantic blocking until a permit becomes available.
Blocking acquires are cancelable if the semaphore is created with Semaphore.apply
(and hence, with a Concurrent[F] instance). Blocking acquires are non-cancelable
if the semaphore is created with Semaphore.async (and hence, with an Async[F] instance).
- Companion
- object
Value members
Abstract methods
Acquires n permits.
Acquires n permits.
The returned effect semantically blocks until all requested permits are
available. Note that acquires are statisfied in strict FIFO order, so given
s: Semaphore[F] with 2 permits available, an acquireN(3) will
always be satisfied before a later call to acquireN(1).
- Value Params
- n
number of permits to acquire - must be >= 0
Returns the number of permits currently available. Always non-negative.
Returns the number of permits currently available. Always non-negative.
May be out of date the instant after it is retrieved.
Use [[tryAcquire]] or [[tryAcquireN]] if you wish to attempt an
acquire, returning immediately if the current count is not high enough
to satisfy the request.
Obtains a snapshot of the current count. May be negative.
Obtains a snapshot of the current count. May be negative.
Like available when permits are available but returns the number of permits callers are waiting for when there are no permits available.
Releases n permits, potentially unblocking up to n outstanding acquires.
Releases n permits, potentially unblocking up to n outstanding acquires.
- Value Params
- n
number of permits to release - must be >= 0
Acquires n permits now and returns true, or returns false immediately. Error if n < 0.
Acquires n permits now and returns true, or returns false immediately. Error if n < 0.
- Value Params
- n
number of permits to acquire - must be >= 0
Concrete methods
Acquires a single permit. Alias for [[acquireN]](1).
Acquires a single permit. Alias for [[acquireN]](1).
Modify the context F using natural isomorphism f with g.
Modify the context F using natural isomorphism f with g.