module Semaphore: Semaphore
type 'a t
Type of semaphores
val init : 'a option -> 'a t
init v initializes a semaphore with an optional value
v. If it is
Some x, then
Semaphore.wait will return immediately with
x,
otherwise it will block until
Semaphore.signal is called.
val signal : 'a t -> 'a -> unit
signal sem v allows one thread blocked in
Semaphore.wait on
semaphore
sem to continue. The semaphore will then block again
further threads.
val wait : 'a t -> 'a
wait sem blocks the calling thread on semaphore sem if it was not
initialized with Some x or not signalled before. The semaphore
is reset to None, i.e. calling wait again will block unless the
semaphore was signalled inbetween.
val get : 'a t -> 'a option
get sem
Returns None if semaphore is not set, Some value
otherwise. The semaphore is reset to None, and a subsequent wait
will block again.
val look : 'a t -> 'a option
look sem
Returns None if semaphore is not set, Some value
otherwise. The state of the semaphore remains unchanged.