1 files changed, 67 insertions, 0 deletions
diff --git a/js/public/shadow/Object.h b/js/public/shadow/Object.h
new file mode 100644
index 0000000000..6f77de71ba
--- /dev/null
+++ b/js/public/shadow/Object.h
@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Shadow definition of |JSObject| innards.  (|js::NativeObject| is more
+ * accurate, but portions can sometimes be used in some non-native objects.)  Do
+ * not use this directly!
+ */
+
+#ifndef js_shadow_Object_h
+#define js_shadow_Object_h
+
+#include <stddef.h>  // size_t
+
+#include "js/shadow/Shape.h"  // JS::shadow::Shape
+#include "js/Value.h"         // JS::Value
+
+class JS_PUBLIC_API JSObject;
+
+namespace JS {
+
+class JS_PUBLIC_API Value;
+
+namespace shadow {
+
+/**
+ * This layout is shared by all native objects. For non-native objects, the
+ * shape may always be accessed safely, and other members may be as well,
+ * depending on the object's specific layout.
+ */
+struct Object {
+  shadow::Shape* shape;
+#ifndef JS_64BIT
+  uint32_t padding_;
+#endif
+  Value* slots;
+  void* _1;
+
+  static constexpr size_t MAX_FIXED_SLOTS = 16;
+
+  size_t numFixedSlots() const {
+    return (shape->immutableFlags & shadow::Shape::FIXED_SLOTS_MASK) >>
+           shadow::Shape::FIXED_SLOTS_SHIFT;
+  }
+
+  Value* fixedSlots() const {
+    auto address = reinterpret_cast<uintptr_t>(this);
+    return reinterpret_cast<JS::Value*>(address + sizeof(shadow::Object));
+  }
+
+  Value& slotRef(size_t slot) const {
+    size_t nfixed = numFixedSlots();
+    if (slot < nfixed) {
+      return fixedSlots()[slot];
+    }
+    return slots[slot - nfixed];
+  }
+};
+
+}  // namespace shadow
+
+}  // namespace JS
+
+#endif  // js_shadow_Object_h