120 lines
3.8 KiB
C++
120 lines
3.8 KiB
C++
// Copyright (C) 2023 The Qt Company Ltd.
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// Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, [email protected], author Marc Mutz <[email protected]>
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// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
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#ifndef Q20MEMORY_H
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#define Q20MEMORY_H
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#include <QtCore/qtconfigmacros.h>
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#include <memory>
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#include <QtCore/q20type_traits.h>
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#include <utility>
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//
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// W A R N I N G
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// -------------
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//
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// This file is not part of the Qt API. Types and functions defined in this
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// file can reliably be replaced by their std counterparts, once available.
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// You may use these definitions in your own code, but be aware that we
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// will remove them once Qt depends on the C++ version that supports
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// them in namespace std. There will be NO deprecation warning, the
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// definitions will JUST go away.
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//
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// If you can't agree to these terms, don't use these definitions!
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//
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// We mean it.
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//
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QT_BEGIN_NAMESPACE
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// like std::construct_at (but not whitelisted for constexpr)
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namespace q20 {
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#ifdef __cpp_lib_constexpr_dynamic_alloc
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using std::construct_at;
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#else
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template <typename T,
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typename... Args,
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typename Enable = std::void_t<decltype(::new (std::declval<void *>()) T(std::declval<Args>()...))> >
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T *construct_at(T *ptr, Args && ... args)
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{
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return ::new (const_cast<void *>(static_cast<const volatile void *>(ptr)))
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T(std::forward<Args>(args)...);
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}
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#endif // __cpp_lib_constexpr_dynamic_alloc
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} // namespace q20
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// like std::make_unique_for_overwrite (excl. C++23-added constexpr)
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namespace q20 {
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#ifdef __cpp_lib_smart_ptr_for_overwrite
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using std::make_unique_for_overwrite;
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#else
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// https://eel.is/c++draft/unique.ptr.create#6
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template <typename T>
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std::enable_if_t<!std::is_array_v<T>, std::unique_ptr<T>>
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make_unique_for_overwrite()
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// https://eel.is/c++draft/unique.ptr.create#7
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{ return std::unique_ptr<T>(new T); }
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// https://eel.is/c++draft/unique.ptr.create#8
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template <typename T>
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std::enable_if_t<q20::is_unbounded_array_v<T>, std::unique_ptr<T>>
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make_unique_for_overwrite(std::size_t n)
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// https://eel.is/c++draft/unique.ptr.create#9
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{ return std::unique_ptr<T>(new std::remove_extent_t<T>[n]); }
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// https://eel.is/c++draft/unique.ptr.create#10
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template <typename T, typename...Args>
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std::enable_if_t<q20::is_bounded_array_v<T>>
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make_unique_for_overwrite(Args&&...) = delete;
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#endif // __cpp_lib_smart_ptr_for_overwrite
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} // namespace q20
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namespace q20 {
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// like std::to_address
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#ifdef __cpp_lib_to_address
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using std::to_address;
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#else
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// http://eel.is/c++draft/pointer.conversion
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template <typename T>
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constexpr T *to_address(T *p) noexcept {
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// http://eel.is/c++draft/pointer.conversion#1:
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// Mandates: T is not a function type.
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static_assert(!std::is_function_v<T>, "to_address must not be used on function types");
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return p;
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}
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template <typename Ptr, typename std::enable_if_t<!std::is_pointer_v<Ptr>, bool> = true>
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constexpr auto to_address(const Ptr &ptr) noexcept; // fwd declared
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namespace detail {
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// http://eel.is/c++draft/pointer.conversion#3
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template <typename Ptr, typename = void>
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struct to_address_helper {
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static auto get(const Ptr &ptr) noexcept
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{ return q20::to_address(ptr.operator->()); }
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};
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template <typename Ptr>
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struct to_address_helper<Ptr, std::void_t<
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decltype(std::pointer_traits<Ptr>::to_address(std::declval<const Ptr&>()))
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>>
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{
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static auto get(const Ptr &ptr) noexcept
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{ return std::pointer_traits<Ptr>::to_address(ptr); }
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};
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} // namespace detail
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template <typename Ptr, typename std::enable_if_t<!std::is_pointer_v<Ptr>, bool>>
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constexpr auto to_address(const Ptr &ptr) noexcept
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{ return detail::to_address_helper<Ptr>::get(ptr); }
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#endif // __cpp_lib_to_address
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} // namespace q20
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QT_END_NAMESPACE
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#endif /* Q20MEMORY_H */
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