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(**
* mvar.sml
*
* @copyright (C) 2021 SML# Development Team.
* @author UENO Katsuhiro
*)
structure MVar :> sig
type 'a mvar
val new : unit -> 'a mvar
val put : 'a mvar * 'a -> unit
val take : 'a mvar -> 'a
end =
struct
type 'a mvar =
{mutex: Pthread.pthread_mutex_t,
cond: Pthread.pthread_cond_t,
content: 'a option ref}
fun new () =
let
val mutex = Pthread.new_pthread_mutex_t ()
val _ = Pthread.pthread_mutex_init (mutex, Pointer.NULL ())
val cond = Pthread.new_pthread_cond_t ()
val _ = Pthread.pthread_cond_init (cond, Pointer.NULL ())
in
{mutex = mutex, cond = cond, content = ref NONE} : 'a mvar
end
fun waitUntil f (mvar as {mutex, cond, content}:'a mvar) =
if f (!content) then ()
else (Pthread.pthread_cond_wait (cond, mutex); waitUntil f mvar)
fun put (mvar as {mutex, cond, content}:'a mvar, value) =
(
Pthread.pthread_mutex_lock mutex;
waitUntil (not o isSome) mvar;
content := SOME value;
Pthread.pthread_cond_signal cond;
Pthread.pthread_mutex_unlock mutex;
()
)
fun take (mvar as {mutex, cond, content}:'a mvar) =
let
val _ = Pthread.pthread_mutex_lock mutex
val _ = waitUntil isSome mvar
val ret = valOf (!content)
in
content := NONE;
Pthread.pthread_cond_signal cond;
Pthread.pthread_mutex_unlock mutex;
ret
end
end
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