dom/bindings/UnionMember.h
author Jared Wein <jwein@mozilla.com>
Mon, 24 Dec 2018 16:19:20 +0000
changeset 511855 28805dd1b97ab5b421d9e886fd5d96460d5d26ab
parent 508163 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1507595 - Convert about:support to Fluent. r=Gijs,flod Initial patch by Collin Wing (masterkrombi@gmail.com). Differential Revision: https://phabricator.services.mozilla.com/D14905

/* -*- 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"

namespace mozilla {
namespace 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;

  T& SetValue() {
    new (mStorage.addr()) T();
    return *mStorage.addr();
  }
  template <typename T1>
  T& SetValue(const T1& aValue) {
    new (mStorage.addr()) T(aValue);
    return *mStorage.addr();
  }
  template <typename T1, typename T2>
  T& SetValue(const T1& aValue1, const T2& aValue2) {
    new (mStorage.addr()) T(aValue1, aValue2);
    return *mStorage.addr();
  }
  T& Value() { return *mStorage.addr(); }
  const T& Value() const { return *mStorage.addr(); }
  void Destroy() { mStorage.addr()->~T(); }
};

}  // namespace dom
}  // namespace mozilla

#endif  // mozilla_dom_UnionMember_h