dom/bindings/UnionMember.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /* A class for holding the members of a union. */
   8
   9 #ifndef mozilla_dom_UnionMember_h
  10 #define mozilla_dom_UnionMember_h
  11
  12 #include "mozilla/Alignment.h"
  13
  14 namespace mozilla {
  15 namespace dom {
  16
  17 // The union type has an enum to keep track of which of its UnionMembers has
  18 // been constructed.
  19 template <class T>
  20 class UnionMember {
  21   AlignedStorage2<T> mStorage;
  22
  23   // Copy construction can't be supported because C++ requires that any enclosed
  24   // T be initialized in a way C++ knows about -- that is, by |new| or similar.
  25   UnionMember(const UnionMember&) = delete;
  26
  27  public:
  28   UnionMember() = default;
  29   ~UnionMember() = default;
  30
  31   T& SetValue() {
  32     new (mStorage.addr()) T();
  33     return *mStorage.addr();
  34   }
  35   template <typename T1>
  36   T& SetValue(const T1& aValue) {
  37     new (mStorage.addr()) T(aValue);
  38     return *mStorage.addr();
  39   }
  40   template <typename T1, typename T2>
  41   T& SetValue(const T1& aValue1, const T2& aValue2) {
  42     new (mStorage.addr()) T(aValue1, aValue2);
  43     return *mStorage.addr();
  44   }
  45   T& Value() { return *mStorage.addr(); }
  46   const T& Value() const { return *mStorage.addr(); }
  47   void Destroy() { mStorage.addr()->~T(); }
  48 };
  49
  50 }  // namespace dom
  51 }  // namespace mozilla
  52
  53 #endif  // mozilla_dom_UnionMember_h