1 files changed, 10 insertions, 0 deletions
diff --git a/src/sail_lib.ml b/src/sail_lib.ml
index 6e2deff7..3e304796 100644
--- a/src/sail_lib.ml
+++ b/src/sail_lib.ml
@@ -644,6 +644,16 @@ let spaces_matches_prefix s =
   | 0 -> ZNone ()
   | n -> ZSome ((), Big_int.of_int n)
 
+let hex_bits_5_matches_prefix s =
+  match maybe_int_of_prefix s with
+  | ZNone () -> ZNone ()
+  | ZSome (n, len) ->
+     let n = Big_int.to_int n in
+     if 0 <= n && n < 32 then
+       ZSome ((bits_of_int 16 n, len))
+     else
+       ZNone ()
+
 let hex_bits_6_matches_prefix s =
   match maybe_int_of_prefix s with
   | ZNone () -> ZNone ()