Async requests

src/base/snark0.ml

@@ -1428,6 +1428,27 @@ module Run = struct
       in
       Staged.stage finish_computation
 
+    let request_manual (req : unit -> 'a Request.t) () : 'a =
+      Request.Handler.run (Run_state.handler !state) (req ())
+      |> Option.value_exn ~message:"Unhandled request"
+
+    module Async_generic (Promise : Base.Monad.S) = struct
+      let run_prover ~(else_ : unit -> 'a) (f : unit -> 'a Promise.t) :
+          'a Promise.t =
+        if Run_state.has_witness !state then (
+          let old = Run_state.as_prover !state in
+          Run_state.set_as_prover !state true ;
+          let%map.Promise result = f () in
+          Run_state.set_as_prover !state old ;
+          result )
+        else Promise.return (else_ ())
+
+      let as_prover (f : unit -> unit Promise.t) : unit Promise.t =
+        run_prover ~else_:(fun () -> ()) f
+
+      let unit_request req = as_prover (request_manual req)
+    end
+
     let run_unchecked x =
       finalize_is_running (fun () ->
           Perform.run_unchecked ~run:as_stateful (fun () -> mark_active ~f:x) )

src/base/snark_intf.ml

@@ -1405,6 +1405,12 @@ module type Run_basic = sig
   (* Callback, low-level version of [as_prover] and [exists]. *)
   val as_prover_manual : int -> (field array option -> Field.t array) Staged.t
 
+  module Async_generic (Promise : Base.Monad.S) : sig
+    val as_prover : (unit -> unit Promise.t) -> unit Promise.t
+
+    val unit_request : (unit -> unit Promise.t Request.t) -> unit Promise.t
+  end
+
   (** Generate the public input vector for a given statement. *)
   val generate_public_input :
     ('input_var, 'input_value) Typ.t -> 'input_value -> Field.Constant.Vector.t