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