Module Semaphore

module Semaphore: sig .. end

Semaphores.

type t = java'util'concurrent'Semaphore java_instance

The type of semaphores, each maintaining a set of available permits.

val make : ?fair:bool -> java_int -> t

make ~fair:f p returns a new semaphore with p permits, f indicating whether a fair ordering policy is requested (defaulting to false); see Semaphore(...).

p can be negative, meaning that permits should be released before any acquisition.

val acquire : t -> java_int -> unit

acquire s p acquires p permits from semaphore s, blocking until they are available; see acquire(...).
Raises

Java_exception if p is negative
Java_exception if the thread is interrupted

val acquire_uninterruptibly : t -> java_int -> unit

acquire_uninterruptibly s p is similar to acquire s p, except that waiting thread cannot be interrupted; see acquireUninterruptibly(...).
Raises Java_exception if p is negative

val available_permits : t -> java_int

Returns the number of available permits for the semaphore; see availablePermits(...).

val drain_permits : t -> java_int

Acquires and returns all available permits from the semaphore, returning immediately; see drainPermits(...).

val get_queue_length : t -> java_int

Returns an estimate of the number of threads waiting on the semaphore to acquire permits; see getQueueLength(...).

val has_queued_threads : t -> bool

Tests whether there are threads waiting on the semaphore to acquire permits; see hasQueuedThreads(...).

val is_fair : t -> bool

Tests whether the semaphore uses a fair policy; see isFair(...).

val release : t -> java_int -> unit

release s p releases p permits from semaphore s; see release(...).
Raises Java_exception if p is negative

val try_acquire : t -> java_int -> bool

try_acquire s p is similar to acquire s p, except the function always returns immediately returning true if acquisition was successful; see tryAcquire(...).
Raises Java_exception if p is negative

val try_acquire_time : t -> java_int -> java_long -> TimeUnit.t -> bool

try_acquire_time s p t u is similar to try_acquire s p, except that the current thread will at most wait for t (time value whose unit is u); see tryAcquire(...).
Raises

Java_exception if p is negative
Java_exception if the thread is interrupted

Null value

val null : t

The null value.

val is_null : t -> bool

is_null obj returns true iff obj is equal to null.

val is_not_null : t -> bool

is_not_null obj returns false iff obj is equal to null.

Miscellaneous

val wrap : t -> t option

wrap obj wraps the reference obj into an option type:

Some x if obj is not null;
None if obj is null.

val unwrap : t option -> t

unwrap obj unwraps the option obj into a bare reference:

Some x is mapped to x;
None is mapped to null.