feat(picos): add shutdown and max_fds

src/picos/nanoev_picos.ml

@@ -55,10 +55,24 @@ module Global_ = struct
            nanoev = ev;
            th = Thread.create (bg_thread_ ~active ~evloop:ev) ();
          }
+
+  let shutdown_bg_thread () =
+    let@ () = with_lock lock in
+    match Atomic.exchange st None with
+    | None -> ()
+    | Some st ->
+      Atomic.set st.active false;
+      Nanoev.wakeup_from_outside st.nanoev;
+      Thread.join st.th
 end
 
 let has_bg_thread = Global_.has_bg_thread
 let setup_bg_thread = Global_.setup_bg_thread
+let shutdown_bg_thread = Global_.shutdown_bg_thread
+
+let with_setup_bg_thread ev f =
+  setup_bg_thread ev;
+  Fun.protect ~finally:shutdown_bg_thread f
 
 let[@inline] get_loop_exn_ () : Nanoev.t =
   match Atomic.get Global_.st with
@@ -136,6 +150,11 @@ let write fd buf i len : int =
 
 let connect fd addr = retry_write_ fd (fun () -> Unix.connect fd addr)
 
+let[@inline] max_fds () =
+  match Atomic.get Global_.st with
+  | None -> 1024
+  | Some st -> Nanoev.max_fds st.nanoev
+
 let sleep t =
   if t > 0. then (
     let ev = get_loop_exn_ () in

src/picos/nanoev_picos.mli

@@ -1,11 +1,18 @@
 (** Basic interface with picos *)
 
+module Background_thread : sig
   val setup_bg_thread : Nanoev.t -> unit
   (** Install this event loop in a background thread *)
 
+  val shutdown_bg_thread : unit -> unit
+  (** Shutdown background thread, assuming {! has_bg_thread} returns [true] *)
+
+  val with_setup_bg_thread : Nanoev.t -> (unit -> 'a) -> 'a
+
   val has_bg_thread : unit -> bool
   (** [has_bg_thread ()] is [true] iff a background thread is running a nanoev
       loop *)
+end
 
 (** {2 Non blocking IO primitives} *)
 
@@ -33,4 +40,9 @@ val accept : Unix.file_descr -> Unix.file_descr * Unix.sockaddr
     @raise Nanoev.Closed if the FD is closed.
     @raise Unix.Unix_error for other errors *)
 
+val max_fds : unit -> int
+(** Maximum number of file descriptors one can await on. See {!Nanoev.max_fds}
+*)
+
 val sleep : float -> unit
+(** Suspend current fiber for [n] seconds *)