| // Copyright 2021 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef BASE_CXX20_TO_ADDRESS_H_ |
| #define BASE_CXX20_TO_ADDRESS_H_ |
| |
| #include <memory> |
| #include <type_traits> |
| |
| namespace base { |
| |
| namespace { |
| |
| template <typename Ptr, typename = void> |
| struct has_std_to_address : std::false_type {}; |
| |
| template <typename Ptr> |
| struct has_std_to_address< |
| Ptr, |
| std::void_t<decltype(std::pointer_traits<Ptr>::to_address( |
| std::declval<Ptr>()))>> : std::true_type {}; |
| |
| } // namespace |
| |
| // Implementation of C++20's std::to_address. |
| // Note: This does consider specializations of pointer_traits<>::to_address, |
| // even though it's a C++20 member function, because CheckedContiguousIterator |
| // specializes pointer_traits<> with a to_address() member. |
| // |
| // Reference: https://wg21.link/pointer.conversion#lib:to_address |
| template <typename T> |
| constexpr T* to_address(T* p) noexcept { |
| static_assert(!std::is_function<T>::value, |
| "Error: T must not be a function type."); |
| return p; |
| } |
| |
| template <typename Ptr> |
| constexpr auto to_address(const Ptr& p) noexcept { |
| if constexpr (has_std_to_address<Ptr>::value) { |
| return std::pointer_traits<Ptr>::to_address(p); |
| } else { |
| return base::to_address(p.operator->()); |
| } |
| } |
| |
| } // namespace base |
| |
| #endif // BASE_CXX20_TO_ADDRESS_H_ |