check for the minimal encoding length
diff --git a/skeletons/UTF8String.h b/skeletons/UTF8String.h
index a1149e4..4580159 100644
--- a/skeletons/UTF8String.h
+++ b/skeletons/UTF8String.h
@@ -14,8 +14,15 @@
asn_struct_print_f UTF8String_print;
asn_constr_check_f UTF8String_constraint;
-/* Returns length of UTF-8 string in characters or -1 if error. */
-ssize_t UTF8String_length(const UTF8String_t *st, const char *opt_type_name,
- asn_app_consume_bytes_f *app_errlog, void *app_key);
+/*
+ * Returns length of the given UTF-8 string in characters,
+ * or a negative error code:
+ * -1: UTF-8 sequence truncated
+ * -2: Illegal UTF-8 sequence start
+ * -3: Continuation expectation failed
+ * -4: Not minimal length encoding
+ * -5: Invalid arguments
+ */
+ssize_t UTF8String_length(const UTF8String_t *st);
#endif /* _UTF8String_H_ */