Add poc files

h_program-lang/overlay_code.mli

@@ -0,0 +1,36 @@
+
+type overlay = {
+  (* the filenames are in a readable path format *)
+  orig_to_overlay: (Common.filename, Common.filename) Hashtbl.t;
+  overlay_to_orig: (Common.filename, Common.filename) Hashtbl.t;
+  data: (Common.filename (* overlay *) * Common.filename) list;
+
+  (* in realpath format *)
+  root_orig: Common.dirname;
+  root_overlay: Common.dirname;
+}
+val overlay_equivalences:
+  dir_orig:Common.dirname -> dir_overlay:Common.dirname ->
+  overlay
+
+val adapt_layer:
+  Layer_code.layer -> overlay -> Layer_code.layer
+
+val adapt_database:
+  Database_code.database -> overlay -> Database_code.database
+
+val load_overlay: Common.filename -> overlay
+val save_overlay: overlay -> Common.filename -> unit
+
+
+val check_overlay:
+  dir_orig:Common.dirname -> dir_overlay:Common.dirname -> unit
+
+val gen_overlay:
+  dir_orig:Common.dirname -> dir_overlay:Common.dirname -> 
+  output:Common.filename -> unit
+
+val adapt_layers:
+  overlay:overlay ->
+  dir_layers_orig:Common.dirname -> dir_layers_overlay:Common.dirname ->
+  unit