Provide a way to get Fids

lib/client.ml

@@ -41,6 +41,9 @@ module type S = sig
     val clunk: t -> Types.Fid.t -> Response.Clunk.t Error.t Lwt.t
     val remove: t -> Types.Fid.t -> Response.Remove.t Error.t Lwt.t
   end
+
+  val walk_from_root: t -> Types.Fid.t -> string list -> Response.Walk.t Error.t Lwt.t
+  val with_fid: t -> (Types.Fid.t -> 'a Lwt.t) -> 'a Lwt.t
 end
 
 module Make(Log: S.LOG)(FLOW: V1_LWT.FLOW) = struct
@@ -254,6 +257,8 @@ module Make(Log: S.LOG)(FLOW: V1_LWT.FLOW) = struct
       | { Response.payload = p } -> return_error p
   end
 
+  let walk_from_root t = LowLevel.walk t t.root
+
   let rec allocate_fid t =
     let open Lwt in
     if t.free_fids = Types.Fid.Set.empty

lib/client.mli

@@ -79,6 +79,14 @@ module type S = sig
         server. The server will "clunk" the fid whether the call succeeds or
         fails. *)
   end
+
+  val walk_from_root: t -> Types.Fid.t -> string list -> Response.Walk.t Error.t Lwt.t
+  (** [walk_from_root t] is [LowLevel.walk t root], where [root] is the internal Fid
+      representing the root directory (which is not exposed by the API). *)
+
+  val with_fid: t -> (Types.Fid.t -> 'a Lwt.t) -> 'a Lwt.t
+  (** [with_fid t fn] is the result of running [fn x] with a fresh Fid [x], which
+      is returned to the free pool when the thread finishes. *)
 end
 
 (** Given a transport (a Mirage FLOW), construct a 9P client on top. *)

unix/client9p_unix.ml

@@ -106,4 +106,7 @@ module Inet(Log: S.LOG) = struct
 
     let remove { client } = LowLevel.remove client
   end
+
+  let walk_from_root { client } = Client.walk_from_root client
+  let with_fid { client } = Client.with_fid client
 end