1 files changed, 37 insertions, 0 deletions
diff --git a/cparser/Cutil.ml b/cparser/Cutil.ml
index f5d5c425..66ea19e4 100644
--- a/cparser/Cutil.ml
+++ b/cparser/Cutil.ml
@@ -533,6 +533,43 @@ let sizeof_struct env members =
       end
   in sizeof_rec 0 members
 
+(* Compute the offset of a struct member *)
+let offsetof env ty fields =
+  let align_field ofs ty =
+    let a =  match alignof env ty with
+      | Some a -> a
+      | None -> assert false in
+    align ofs a in
+  let rec offsetof_rec ofs field rest = function
+    | [] -> ofs
+    | m :: rem as ml ->
+      if m.fld_name = field.fld_name then begin
+        match rest with
+        | [] -> align_field ofs field.fld_typ
+        | _ -> lookup_field ofs field.fld_typ rest
+      end else if m.fld_bitfield = None then begin
+        match alignof env m.fld_typ, sizeof env m.fld_typ with
+        | Some a, Some s -> offsetof_rec (align ofs a + s) field rest rem
+        | _, _ -> assert false (* should never happen *)
+      end else begin
+        let (s, a, ml') = pack_bitfields ml in
+        let ofs = align ofs a + s in
+        offsetof_rec ofs field rest ml'
+      end
+  and lookup_field ofs ty = function
+    | [] -> align_field ofs ty
+    | fld::rest ->
+      begin match unroll env ty with
+        | TStruct (id,_) ->
+          let str = Env.find_struct env id in
+          offsetof_rec ofs fld rest str.ci_members
+        | TUnion (id,_) ->
+          lookup_field ofs fld.fld_typ rest
+        | _ -> assert false
+      end
+  in
+  lookup_field 0  ty (List.rev fields)
+
 (* Simplified version to compute offsets on structs without bitfields *)
 let struct_layout env members =
   let rec struct_layout_rec mem ofs = function