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///////////////////////////////////////////////////////////////////////////////
// Reference implementation of std::generator proposal P2168.
//
// See https://wg21.link/P2168 for details.
//
///////////////////////////////////////////////////////////////////////////////
// Copyright Lewis Baker, Corentin Jabot
//
// Use, modification and distribution is subject to the Boost Software License,
// Version 1.0.
// (See accompanying file LICENSE or http://www.boost.org/LICENSE_1_0.txt)
///////////////////////////////////////////////////////////////////////////////
module;
#include <concepts>
#include <memory>
export module nihil.generator:manual_lifetime;
namespace nihil {
template <typename T>
struct manual_lifetime {
manual_lifetime() noexcept {}
~manual_lifetime() {}
template <typename ...Args>
auto construct(this manual_lifetime &self, Args && ...args)
noexcept(std::is_nothrow_constructible_v<T, Args...>)
-> T &
{
return *::new (static_cast<void*>(std::addressof(self.m_value)))
T(static_cast<Args &&>(args)...);
}
void destruct(this manual_lifetime &self)
noexcept(std::is_nothrow_destructible_v<T>)
{
self.m_value.~T();
}
auto get(this manual_lifetime &self) noexcept -> T &
{
return self.m_value;
}
auto get(this manual_lifetime &&self) noexcept -> T &&
{
return static_cast<T&&>(self.m_value);
}
auto get(this manual_lifetime const &self) noexcept -> T const &
{
return self.m_value;
}
auto get(this manual_lifetime const &&self) noexcept -> T const &&
{
return static_cast<T const &&>(self.m_value);
}
private:
union {
std::remove_const_t<T> m_value;
};
};
template <typename T>
class manual_lifetime<T &> {
manual_lifetime() noexcept = default;
~manual_lifetime() = default;
auto construct(this manual_lifetime &self, T &value) noexcept -> T &
{
self.m_value = std::addressof(value);
return self.m_value;
}
auto destruct(this manual_lifetime &) noexcept -> void
{
}
auto get(this manual_lifetime const &self) noexcept -> T &
{
return *self.m_value;
}
private:
T *m_value = nullptr;
};
template <typename T>
class manual_lifetime<T &&> {
manual_lifetime() noexcept = default;
~manual_lifetime() = default;
auto construct(this manual_lifetime &self, T &&value) noexcept -> T &&
{
self.m_value = std::addressof(value);
return static_cast<T &&>(value);
}
void destruct(this manual_lifetime &) noexcept
{
}
auto get(this manual_lifetime const &self) noexcept -> T &&
{
return static_cast<T &&>(*self.m_value);
}
private:
T* m_value = nullptr;
};
}
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