State: export predecessor_n

src/lib_shell/state.ml

@@ -541,6 +541,11 @@ module Block = struct
       read_exn net_state header.shell.predecessor >>= fun block ->
       Lwt.return (Some block)
 
+  let predecessor_n (net: Net.t) (b: Block_hash.t) (distance: int) : Block_hash.t option Lwt.t =
+    Shared.use net.block_store (fun store ->
+        predecessor_n store b distance)
+
+
   type error += Inconsistent_hash of Context_hash.t * Context_hash.t
 
   let () =

src/lib_shell/state.mli

@@ -138,6 +138,7 @@ module Block : sig
 
   val is_genesis: t -> bool
   val predecessor: t -> block option Lwt.t
+  val predecessor_n: Net.t -> Block_hash.t -> int -> Block_hash.t option Lwt.t
 
   val context: t -> Context.t Lwt.t
   val protocol_hash: t -> Protocol_hash.t Lwt.t