Add try_get functions for Rvars

src/sync/lock.ml

@@ -35,6 +35,14 @@ let get l =
   Mutex.unlock l.mutex;
   x
 
+let try_get l =
+  if Mutex.try_lock l.mutex then (
+    let x = l.content in
+    Mutex.unlock l.mutex;
+    Some x
+  ) else
+    None
+
 let set l x =
   Mutex.lock l.mutex;
   l.content <- x;

src/sync/lock.mli

@@ -25,6 +25,10 @@ val get : 'a t -> 'a
 (** Atomically get the value in the lock. The value that is returned isn't
     protected! *)
 
+val try_get : 'a t -> 'a option
+(** Atomically get the value in the lock, but only if we get the lock
+    immediately. *)
+
 val set : 'a t -> 'a -> unit
 (** Atomically set the value. *)
 

src/thread/rvar.ml

@@ -17,6 +17,12 @@ type 'a st = {
 type 'a t = { st: 'a st Lock.t } [@@unboxed]
 
 let[@inline] get (self : 'a t) : 'a = (Lock.get self.st).v
+
+let[@inline] try_get (self : 'a t) : 'a option =
+  match Lock.try_get self.st with
+  | Some v -> Some v.v
+  | None -> None
+
 let[@inline] pp ppx out self : unit = ppx out (get self)
 
 let[@inline] return x =

src/thread/rvar.mli

@@ -11,6 +11,9 @@ val return : 'a -> 'a t
 val get : 'a t -> 'a
 (** Get the current value. *)
 
+val try_get : 'a t -> 'a option
+(** Get the current value, but only if we get the lock immediately. *)
+
 val pp : 'a Fmt.printer -> 'a t Fmt.printer
 
 exception Frozen