add static_pointer_cast for SGSharedPtr

diff --git a/simgear/structure/SGSharedPtr.hxx b/simgear/structure/SGSharedPtr.hxx
index 3de62e6c7cb78819b411e5af6d1feffb31799402..479c197294247e96dbf90c46639863cabbadeb04 100644 (file)
--- a/simgear/structure/SGSharedPtr.hxx
+++ b/simgear/structure/SGSharedPtr.hxx
@@ -123,4 +123,13 @@ T* get_pointer(SGSharedPtr<T> const & p)
 {
   return p.ptr();
 }
+
+/**
+ * static_cast for SGSharedPtr
+ */
+template<class T, class U>
+SGSharedPtr<T> static_pointer_cast(SGSharedPtr<U> const & r)
+{
+  return SGSharedPtr<T>( static_cast<T*>(r.get()) );
+}
 #endif