1 files changed, 85 insertions, 0 deletions
diff --git a/src/mapbox/variant_cast.hpp b/src/mapbox/variant_cast.hpp
new file mode 100644
index 0000000..fe1ab35
--- /dev/null
+++ b/src/mapbox/variant_cast.hpp
@@ -0,0 +1,85 @@
+#ifndef VARIANT_CAST_HPP
+#define VARIANT_CAST_HPP
+
+#include <type_traits>
+
+namespace mapbox {
+namespace util {
+
+namespace detail {
+
+template <class T>
+class static_caster
+{
+public:
+    template <class V>
+    T& operator()(V& v) const
+    {
+        return static_cast<T&>(v);
+    }
+};
+
+template <class T>
+class dynamic_caster
+{
+public:
+    using result_type = T&;
+    template <class V>
+    T& operator()(V& v, typename std::enable_if<!std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        throw std::bad_cast();
+    }
+    template <class V>
+    T& operator()(V& v, typename std::enable_if<std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        return dynamic_cast<T&>(v);
+    }
+};
+
+template <class T>
+class dynamic_caster<T*>
+{
+public:
+    using result_type = T*;
+    template <class V>
+    T* operator()(V& v, typename std::enable_if<!std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        return nullptr;
+    }
+    template <class V>
+    T* operator()(V& v, typename std::enable_if<std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        return dynamic_cast<T*>(&v);
+    }
+};
+}
+
+template <class T, class V>
+typename detail::dynamic_caster<T>::result_type
+dynamic_variant_cast(V& v)
+{
+    return mapbox::util::apply_visitor(detail::dynamic_caster<T>(), v);
+}
+
+template <class T, class V>
+typename detail::dynamic_caster<const T>::result_type
+dynamic_variant_cast(const V& v)
+{
+    return mapbox::util::apply_visitor(detail::dynamic_caster<const T>(), v);
+}
+
+template <class T, class V>
+T& static_variant_cast(V& v)
+{
+    return mapbox::util::apply_visitor(detail::static_caster<T>(), v);
+}
+
+template <class T, class V>
+const T& static_variant_cast(const V& v)
+{
+    return mapbox::util::apply_visitor(detail::static_caster<const T>(), v);
+}
+}
+}
+
+#endif // VARIANT_CAST_HPP