src: replace CONTAINER_OF with type-safe function

Replace the CONTAINER_OF macro with a template function that is as
type-safe as a reinterpret_cast<> of an arbitrary pointer can be made.

Signed-off-by: Fedor Indutny <fedor@indutny.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/util-inl.h b/src/util-inl.h
index 76015ccb3b..3709208f16 100644
--- a/src/util-inl.h
+++ b/src/util-inl.h
@@ -28,6 +28,26 @@
 
 namespace node {
 
+template <typename Inner, typename Outer>
+ContainerOfHelper<Inner, Outer>::ContainerOfHelper(Inner Outer::*field,
+                                                   Inner* pointer)
+    : pointer_(reinterpret_cast<Outer*>(
+          reinterpret_cast<uintptr_t>(pointer) -
+          reinterpret_cast<uintptr_t>(&(static_cast<Outer*>(0)->*field)))) {
+}
+
+template <typename Inner, typename Outer>
+template <typename TypeName>
+ContainerOfHelper<Inner, Outer>::operator TypeName*() const {
+  return static_cast<TypeName*>(pointer_);
+}
+
+template <typename Inner, typename Outer>
+inline ContainerOfHelper<Inner, Outer> ContainerOf(Inner Outer::*field,
+                                                   Inner* pointer) {
+  return ContainerOfHelper<Inner, Outer>(field, pointer);
+}
+
 template <class TypeName>
 inline v8::Local<TypeName> PersistentToLocal(
     v8::Isolate* isolate,