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libexopt/include/boxed.h

87 lines
2.9 KiB

#pragma once
#include <memory>
#include <utility>
#include "pointer.h"
#include "util.hh"
#include "exopt.h"
namespace exopt::types { namespace boxed {
template<typename T>
struct [[gnu::visibility("internal")]] boxable_value_type { using type = std::conditional_t
<std::is_reference_v<T>
,std::reference_wrapper<std::remove_cvref_t<T> >
,T>; };
template<typename T>
constexpr std::unique_ptr<T> uniq_clone(std::unique_ptr<T> const& c) noexcept(std::is_nothrow_copy_constructible_v<T>) requires(std::is_copy_constructible_v<T>)
{ if(__builtin_expect(bool(c), true)) return std::make_unique<T>(*c); return nullptr; }
template<typename T>
constexpr std::unique_ptr<T> uniq_clone_unsafe(std::unique_ptr<T> const& c)
#ifndef DEBUG
noexcept(std::is_nothrow_copy_constructible_v<T>)
#endif
requires(std::is_copy_constructible_v<T>)
{ if(__builtin_expect(!bool(c), false))
#ifdef DEBUG
throw ptr::NullException{};
#else
__builtin_unreachable();
#endif
return std::make_unique<T>(*c); }
template<typename T>
struct Box {
typedef boxable_value_type<T>::type type;
constexpr Box() noexcept(std::is_nothrow_default_constructible_v<T>) requires(std::is_default_constructible_v<T>)
: m_ptr{std::make_unique<T>()} {}
template<typename... Args> requires(std::is_constructible_v<T, Args...>)
constexpr Box(Args&&... ctor) noexcept(std::is_nothrow_constructible_v<T, Args...>)
: m_ptr{std::make_unique<T>(std::forward<Args>(ctor)...)} {}
constexpr Box(T&& value) noexcept(std::is_nothrow_constructible_v<T>)
: m_ptr{std::make_unique<T>(std::move(value))} {}
constexpr Box(Box&&) noexcept = default;
constexpr Box& operator=(Box&&) noexcept = default;
constexpr Box(const Box& copy) noexcept(std::is_nothrow_copy_constructible_v<T>) requires(std::is_copy_constructible_v<T>)
: m_ptr{uniq_clone_unsafe(copy.m_ptr)} {}
constexpr Box& operator=(Box const& copy) noexcept(std::is_nothrow_copy_assignable_v<T>) requires(std::is_copy_assignable_v<T>)
{
if(__builtin_expect(this != std::addressof(copy), true)) {
m_ptr = uniq_clone_unsafe(copy.m_ptr);
} return *this;
}
//TODO: Accessors, `(explicit?) operator std::unique_ptr<T> const&[&]`?, etc.
constexpr ~Box() = default;
private:
std::unique_ptr<T> m_ptr; // Unique<T> m_ptr;
};
}
using boxed::Box;
}
namespace exopt::types { namespace optional [[gnu::visibility("internal")]] {
template<typename T>
struct null_optimise<boxed::Box<T> > { constexpr static inline bool value = true;
//XXX: Eh.. Idk if Option<T>'s lifetime design can make this work...
using held_type = boxed::Box<T>;
using type = boxed::Box<T>&;
constexpr static decltype(auto) convert_to_held(std::add_rvalue_reference_t<type> t) noexcept { return std::move(t); }
constexpr static decltype(auto) convert_from_held(std::add_rvalue_reference_t<held_type> t) noexcept { return std::forward<type>(t); }
constexpr static inline T* sentinel = nullptr;
};
}