1 files changed, 45 insertions, 0 deletions
diff --git a/layout/style/RustCell.h b/layout/style/RustCell.h
new file mode 100644
index 0000000000..24f2ebc74d
--- /dev/null
+++ b/layout/style/RustCell.h
@@ -0,0 +1,45 @@
+/* -*- 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/. */
+
+/* an object with the same layout as a Rust std::cell::Cell<T> */
+
+#ifndef mozilla_RustCell_h
+#define mozilla_RustCell_h
+
+namespace mozilla {
+
+/**
+ * Object with the same layout as std::cell::Cell<T>.
+ *
+ * ServoBindings.toml defines a mapping so that generated bindings use a
+ * real std::cell::Cell<T>.
+ *
+ * Note that while the layout matches, this doesn't have the same ABI as a
+ * std::cell::Cell<T>, so values of this type can't be passed over FFI
+ * functions.
+ */
+template <typename T>
+class RustCell {
+ public:
+  RustCell() : mValue() {}
+  explicit RustCell(T aValue) : mValue(aValue) {}
+
+  T Get() const { return mValue; }
+  void Set(T aValue) { mValue = aValue; }
+
+  // That this API doesn't mirror the API of rust's Cell because all values in
+  // C++ effectively act like they're wrapped in Cell<...> already, so this type
+  // only exists for FFI purposes.
+  T* AsPtr() { return &mValue; }
+  const T* AsPtr() const { return &mValue; }
+
+ private:
+  T mValue;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_RustCell_h