General RefToBase to Ptr conversion

DataFormats/Common/interface/RefToBaseToPtr.h

@@ -0,0 +1,36 @@
+#ifndef DataFormats_Common_RefToPtr_h
+#define DataFormats_Common_RefToPtr_h
+
+/*----------------------------------------------------------------------
+  
+Ref: A function template for conversion from RefToBase to Ptr
+
+----------------------------------------------------------------------*/
+/*
+    ----------------------------------------------------------------------*/
+
+#include "DataFormats/Common/interface/RefToBase.h"
+#include "DataFormats/Common/interface/Ptr.h"
+
+namespace edm {
+  template <typename T>
+  Ptr<T> refToBaseToPtr(RefToBase<T> const& ref) {
+    if (ref.isNull()) {
+      return Ptr<T>();
+    }
+    if (ref.isTransient()) {
+      return Ptr<T>(ref.get(), ref.key());
+    } else {
+      //Another thread could change this value so get only once
+      EDProductGetter const* getter = ref.productGetter();
+      if (getter) {
+        return Ptr<T>(ref.id(), ref.key(), getter);
+      }
+    }
+    // If this is called in an iorule outside the framework, we cannot call
+    // ref.get() but since the Ptr will be able to get it later anyway, we can
+    // fill with a nullptr for now
+    return Ptr<T>(ref.id(), static_cast<const T*>(nullptr), ref.key());
+  }
+}  // namespace edm
+#endif