summaryrefslogtreecommitdiffstats
path: root/dom/bindings/UnionMember.h
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--dom/bindings/UnionMember.h45
1 files changed, 45 insertions, 0 deletions
diff --git a/dom/bindings/UnionMember.h b/dom/bindings/UnionMember.h
new file mode 100644
index 0000000000..2fba7910fa
--- /dev/null
+++ b/dom/bindings/UnionMember.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/. */
+
+/* A class for holding the members of a union. */
+
+#ifndef mozilla_dom_UnionMember_h
+#define mozilla_dom_UnionMember_h
+
+#include "mozilla/Alignment.h"
+#include "mozilla/Attributes.h"
+#include <utility>
+
+namespace mozilla::dom {
+
+// The union type has an enum to keep track of which of its UnionMembers has
+// been constructed.
+template <class T>
+class UnionMember {
+ AlignedStorage2<T> mStorage;
+
+ // Copy construction can't be supported because C++ requires that any enclosed
+ // T be initialized in a way C++ knows about -- that is, by |new| or similar.
+ UnionMember(const UnionMember&) = delete;
+
+ public:
+ UnionMember() = default;
+ ~UnionMember() = default;
+
+ template <typename... Args>
+ T& SetValue(Args&&... args) {
+ new (mStorage.addr()) T(std::forward<Args>(args)...);
+ return *mStorage.addr();
+ }
+
+ T& Value() { return *mStorage.addr(); }
+ const T& Value() const { return *mStorage.addr(); }
+ void Destroy() { mStorage.addr()->~T(); }
+} MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS;
+
+} // namespace mozilla::dom
+
+#endif // mozilla_dom_UnionMember_h