added ffi-obj-ref

original commit: d5ae83a9339a8af4c3ab40175913ca8295be809b

collects/mzlib/foreign.ss

@@ -184,6 +184,17 @@
     (hash-table-put! ffi-objects-ref-table ffi-obj new)
     (ptr-set! ffi-obj type new)))
 
+(provide* ffi-obj-ref)
+(define ffi-obj-ref
+  (case-lambda
+   [(name lib) (ffi-obj-ref name lib #f)]
+   [(name lib failure)
+    (let ([name (get-ffi-obj-name 'ffi-obj-ref name)]
+          [lib  (get-ffi-lib lib)])
+      (with-handlers ([exn:fail:filesystem?
+                       (lambda (e) (if failure (failure) (raise e)))])
+        (ffi-obj name lib)))]))
+
 ;; get-ffi-obj is implemented as a syntax only to be able to propagate the
 ;; foreign name into the type syntax, which allows generated wrappers to have a
 ;; proper name.