2 files changed, 23 insertions, 0 deletions
diff --git a/lib/kernel/Storage.ml b/lib/kernel/Storage.ml
index e6a84ba..dd06783 100644
--- a/lib/kernel/Storage.ml
+++ b/lib/kernel/Storage.ml
@@ -11,6 +11,22 @@ module Make (S : Abstract.Storage.STORAGE) = struct
     let deref tx { addr; loader } = loader tx addr
   end
 
+  let as_hash = function
+    | S.Hash h -> h
+    | _ -> failwith "A label was provided where a hash was expected."
+
+  let to_hum_string = function
+    | S.Hash h -> "Hash " ^ (Concepts.Hash.to_hum_string h)
+    | S.Label l -> "Label " ^ l
+
+  module Error = struct
+    open Concepts.Condition
+
+    let missing_data addr =
+      condition "missing-data" "An expected value was not found on the underlying storage. Is your database corrupted?"
+        ("address" |=| Concepts.Value.String (to_hum_string addr))
+  end
+
   let finish tx = function
     | Ok value ->
        let open Utilities.Result in
@@ -31,4 +47,8 @@ module Make (S : Abstract.Storage.STORAGE) = struct
     let* () = S.put tx (S.Hash address) blob in
     Ok address
 
+  let get_req tx addr =
+    S.get tx addr
+    |> Utilities.Result.fmap (Option.to_result ~none:(Error.missing_data addr))
+
 end
diff --git a/lib/kernel/Storage.mli b/lib/kernel/Storage.mli
index 9a10984..b8c0e5b 100644
--- a/lib/kernel/Storage.mli
+++ b/lib/kernel/Storage.mli
@@ -8,7 +8,10 @@ module Make : functor (S : Abstract.Storage.STORAGE) -> sig
     val deref : S.transaction -> 'a t -> ('a, Concepts.Condition.condition) result
   end
 
+  val as_hash : S.address -> Concepts.Hash.hash
+
   val finish : S.transaction -> ('a, Concepts.Condition.condition) result -> ('a, Concepts.Condition.condition) result
   val with_transaction : S.connection -> (S.transaction -> ('a, Concepts.Condition.condition) result) -> ('a, Concepts.Condition.condition) result
   val store_blob : S.transaction -> Concepts.Blob.t -> (Concepts.Hash.hash, Concepts.Condition.condition) result
+  val get_req: S.transaction -> S.address -> (Concepts.Blob.t, Concepts.Condition.condition) result
 end