Add Destroyable::cleaner to help w/ shared_ptr<> wrapping

src/misc/pv/destroyable.h

@@ -22,18 +22,37 @@ namespace epics { namespace pvData {
          * @author mse
          */
         class epicsShareClass Destroyable {
-            public:
+        public:
             POINTER_DEFINITIONS(Destroyable);
             /**
              * Destroy this instance.
              */
             virtual void destroy() = 0;
             
-            protected:
+        protected:
             /**
              * Do not allow delete on this instance and derived classes, destroy() must be used instead.
              */ 
             virtual ~Destroyable() {};
+        public:
+
+            /** for use with shared_ptr<> when wrapping
+             *
+             @code
+               shared_ptr<foo> inner(new foo),
+                               outer(inner.get, Destroyable::cleaner(inner));
+             @endcode
+             */
+            class cleaner {
+                Destroyable::shared_pointer ptr;
+            public:
+                cleaner(const Destroyable::shared_pointer& ptr) :ptr(ptr) {}
+                void operator()(Destroyable*) {
+                    Destroyable::shared_pointer P;
+                    P.swap(ptr);
+                    P->destroy();
+                }
+            };
         };
 
 }}