common: Add Bitwise functor for bitwise enums.

common/bitwise.ml

@@ -0,0 +1,40 @@
+open Ctypes
+
+module type Size = sig
+  type t
+  val zero : t
+  val logor : t -> t -> t
+  val logand : t -> t -> t
+end
+
+module type Elems = sig
+  type t
+  module Size : Size
+  val size : Size.t typ
+  val desc : (t * Size.t) list
+end
+
+module type Enum = sig
+  type elem
+  type t
+  val t : t
+end
+
+module Make (E : Elems) : Enum = struct
+  type elem = E.t
+  type t = E.t list typ
+  let t : t =
+    let read i =
+      List.filter_map (fun (x, cst) ->
+          if (E.Size.logand i cst) <> E.Size.zero then
+            Some x
+          else None
+        ) E.desc
+    in
+    let write items =
+      List.fold_left (fun i item ->
+          E.Size.logor (List.assoc item E.desc) i
+        ) E.Size.zero items
+    in
+    view ~read ~write E.size
+end