Module Eio.Condition

Waiting for a condition to become true.

Waiters call await in a loop as long as some condition is false. Fibers that modify inputs to the condition must call broadcast soon afterwards so that waiters can re-check the condition.

Example:

let x = ref 0
let cond = Eio.Condition.create ()
let mutex = Eio.Mutex.create ()

let set_x value =
  Eio.Mutex.use_rw ~protect:false mutex (fun () -> x := value);
  Eio.Condition.broadcast cond

let await_x p =
  Eio.Mutex.use_ro mutex (fun () ->
     while not (p !x) do                  (* [x] cannot change, as mutex is locked. *)
       Eio.Condition.await ~mutex cond    (* Mutex is unlocked while suspended. *)
     done
  )

It is used like this:

Fiber.both
  (fun () ->
     traceln "x = %d" !x;
     await_x ((=) 42);
     traceln "x = %d" !x
  )
  (fun () ->
     set_x 5;
     Fiber.yield ();
     set_x 7;
     set_x 42;
  )