Add root handle extern (#12510)

Author: Aidan63

std/cpp/marshal/RootHandle.hx

@@ -0,0 +1,36 @@
+package cpp.marshal;
+
+/**
+ * An object which has been rooted will not be collected by the GC even if it has no other references.
+ * Rooted objects can also be used to safely pass managed objects into unmanaged code.
+ */
+@:semantics(value)
+@:cpp.ValueType({ namespace : [ "cpp", "marshal" ] })
+extern class RootHandle {
+	/**
+	 * Root the provided object and return a handle representing it.
+	 */
+	public static function create(obj:Dynamic):RootHandle;
+
+	/**
+	 * Reinterpret the provided `void*` as a rooted object.
+	 * If `ptr` is not a rooted object the behaviour is undefined.
+	 */
+	public static function fromVoidPointer(ptr:cpp.Pointer<cpp.Void>):RootHandle;
+
+	/**
+	 * Unroot the object represented by this handle.
+	 * If there are no other references to the object it will be eligible for collection by the GC.
+	 */
+	function close():Void;
+
+	/**
+	 * Return the object represented by this handle.
+	 */
+	function getObject():Dynamic;
+
+	/**
+	 * Returns the rooted object reinterpreted as a `void*`.
+	 */
+	function toVoidPointer():cpp.Pointer<cpp.Void>;
+}