| /* |
| * Copyright (C) 2018 Apple Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' |
| * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, |
| * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS |
| * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF |
| * THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #pragma once |
| |
| #include <type_traits> |
| #include <utility> |
| |
| namespace rtc { |
| |
| template<typename T> class NeverDestroyed { |
| public: |
| template<typename... Args> NeverDestroyed(Args&&... args) |
| { |
| new (storagePointer()) T(std::forward<Args>(args)...); |
| } |
| |
| NeverDestroyed(NeverDestroyed&& other) |
| { |
| new (storagePointer()) T(std::move(*other.storagePointer())); |
| } |
| |
| operator T&() { return *storagePointer(); } |
| T& get() { return *storagePointer(); } |
| |
| operator const T&() const { return *storagePointer(); } |
| const T& get() const { return *storagePointer(); } |
| |
| private: |
| NeverDestroyed(const NeverDestroyed&) = delete; |
| NeverDestroyed& operator=(const NeverDestroyed&) = delete; |
| |
| using PointerType = typename std::remove_const<T>::type*; |
| |
| PointerType storagePointer() const { return const_cast<PointerType>(reinterpret_cast<const T*>(&m_storage)); } |
| |
| // FIXME: Investigate whether we should allocate a hunk of virtual memory |
| // and hand out chunks of it to NeverDestroyed instead, to reduce fragmentation. |
| typename std::aligned_storage<sizeof(T), std::alignment_of<T>::value>::type m_storage; |
| }; |
| |
| template<typename T> inline NeverDestroyed<T> makeNeverDestroyed(T&& argument) |
| { |
| return NeverDestroyed<T>(std::move(argument)); |
| } |
| |
| } // namespace rtc |