src: move DeleteFnPtr into util.h

This is more generally useful than just in a crypto context.

PR-URL: #20885
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

src/node_crypto.h

@@ -75,15 +75,6 @@ struct MarkPopErrorOnReturn {
   ~MarkPopErrorOnReturn() { ERR_pop_to_mark(); }
 };
 
-template <typename T, void (*function)(T*)>
-struct FunctionDeleter {
-  void operator()(T* pointer) const { function(pointer); }
-  typedef std::unique_ptr<T, FunctionDeleter> Pointer;
-};
-
-template <typename T, void (*function)(T*)>
-using DeleteFnPtr = typename FunctionDeleter<T, function>::Pointer;
-
 // Define smart pointers for the most commonly used OpenSSL types:
 using X509Pointer = DeleteFnPtr<X509, X509_free>;
 using BIOPointer = DeleteFnPtr<BIO, BIO_free_all>;

src/util.h

@@ -456,6 +456,15 @@ struct is_callable<T, typename std::enable_if<
     std::is_same<decltype(void(&T::operator())), void>::value
     >::type> : std::true_type { };
 
+template <typename T, void (*function)(T*)>
+struct FunctionDeleter {
+  void operator()(T* pointer) const { function(pointer); }
+  typedef std::unique_ptr<T, FunctionDeleter> Pointer;
+};
+
+template <typename T, void (*function)(T*)>
+using DeleteFnPtr = typename FunctionDeleter<T, function>::Pointer;
+
 }  // namespace node
 
 #endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS