From 89041a16862ec702db63c312e8f0f7e88ed82c4e Mon Sep 17 00:00:00 2001
From: Wouter van Oortmerssen <aardappel@gmail.com>
Date: Mon, 27 Mar 2017 17:46:34 -0700
Subject: [PATCH] Add a VectorCast function that safely casts from
 Vector<Offset<T>> to Vector<Offset<U>> if U is a base class of T.

This is useful for when you want to generically
iterate over a vector of objects that derive from
flatbuffers::Table.

Change-Id: I59161e3b9f40501f72e02b46509be9dc8ab86c6b
---
 include/flatbuffers/flatbuffers.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/flatbuffers/flatbuffers.h b/include/flatbuffers/flatbuffers.h
index 7b79891c4..140e176aa 100644
--- a/include/flatbuffers/flatbuffers.h
+++ b/include/flatbuffers/flatbuffers.h
@@ -483,6 +483,20 @@ private:
   VectorOfAny(const VectorOfAny&);
 };
 
+#ifndef FLATBUFFERS_CPP98_STL
+template<typename T, typename U>
+Vector<Offset<T>> *VectorCast(Vector<Offset<U>> *ptr) {
+  static_assert(std::is_base_of<T, U>::value, "Unrelated types");
+  return reinterpret_cast<Vector<Offset<T>> *>(ptr);
+}
+
+template<typename T, typename U>
+const Vector<Offset<T>> *VectorCast(const Vector<Offset<U>> *ptr) {
+  static_assert(std::is_base_of<T, U>::value, "Unrelated types");
+  return reinterpret_cast<const Vector<Offset<T>> *>(ptr);
+}
+#endif
+
 // Convenient helper function to get the length of any vector, regardless
 // of wether it is null or not (the field is not set).
 template<typename T> static inline size_t VectorLength(const Vector<T> *v) {