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(**
* mvar.sml (copied from sample for myth)
*
* @copyright (C) 2021 SML# Development Team.
* @author UENO Katsuhiro
*)
structure MVar =
struct
type 'a mvar =
{mutex: Myth.mutex,
cond: Myth.cond,
content: 'a option ref}
fun new () =
let
val mutex = Myth.Mutex.create ()
val cond = Myth.Cond.create()
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 (Myth.Cond.wait (cond, mutex); waitUntil f mvar)
fun put (mvar as {mutex, cond, content}:'a mvar, value) =
(
Myth.Mutex.lock mutex;
waitUntil (not o isSome) mvar;
content := SOME value;
Myth.Cond.broadcast cond;
Myth.Mutex.unlock mutex;
()
)
fun take (mvar as {mutex, cond, content}:'a mvar) =
let
val _ = Myth.Mutex.lock mutex
val _ = waitUntil isSome mvar
val ret = valOf (!content)
in
content := NONE;
Myth.Cond.broadcast cond;
Myth.Mutex.unlock mutex;
ret
end
fun read (mvar as {mutex, cond, content}:'a mvar) =
let
val _ = Myth.Mutex.lock mutex
val _ = waitUntil isSome mvar
val ret = valOf (!content)
in
Myth.Mutex.unlock mutex;
ret
end
fun isSome (mvar as {mutex, cond, content}:'a mvar) =
let
val _ = Myth.Mutex.lock mutex
val ret = case !content of NONE => false | SOME _ => true
in
Myth.Cond.signal cond;
Myth.Mutex.unlock mutex;
ret
end
end
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