module Counting: sig .. end
type t;
The type of counting semaphores.
let make: int => t;
make n
returns a new counting semaphore, with initial value n
.
The initial value n
must be nonnegative.
Invalid_argument
if n < 0
let release: t => unit;
release s
increments the value of semaphore s
.
If other threads are waiting on s
, one of them is restarted.
If the current value of s
is equal to max_int
, the value of
the semaphore is unchanged and a Sys_error
exception is raised
to signal overflow.
Sys_error
if the value of the semaphore would overflow max_int
let acquire: t => unit;
acquire s
blocks the calling thread until the value of semaphore s
is not zero, then atomically decrements the value of s
and returns.
let try_acquire: t => bool;
try_acquire s
immediately returns false
if the value of semaphore s
is zero. Otherwise, the value of s
is atomically decremented
and try_acquire s
returns true
.
let get_value: t => int;
get_value s
returns the current value of semaphore s
.
The current value can be modified at any time by concurrent
Semaphore.Counting.release
and Semaphore.Counting.acquire
operations. Hence, the get_value
operation is racy, and its result should only be used for debugging
or informational messages.