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proxy.h
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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
#ifndef _MSFT_PROXY_
#define _MSFT_PROXY_
#include <cstddef>
#include <bit>
#include <concepts>
#include <initializer_list>
#include <memory>
#include <tuple>
#include <type_traits>
#include <utility>
#if __has_cpp_attribute(msvc::no_unique_address)
#define ___PRO_NO_UNIQUE_ADDRESS_ATTRIBUTE msvc::no_unique_address
#elif __has_cpp_attribute(no_unique_address)
#define ___PRO_NO_UNIQUE_ADDRESS_ATTRIBUTE no_unique_address
#else
#error "Proxy requires C++20 attribute no_unique_address"
#endif
#if defined(_MSC_VER) && !defined(__clang__)
#define ___PRO_ENFORCE_EBO __declspec(empty_bases)
#else
#define ___PRO_ENFORCE_EBO
#endif // defined(_MSC_VER) && !defined(__clang__)
namespace pro {
enum class constraint_level { none, nontrivial, nothrow, trivial };
struct proxiable_ptr_constraints {
std::size_t max_size;
std::size_t max_align;
constraint_level copyability;
constraint_level relocatability;
constraint_level destructibility;
};
template <class F> class proxy;
namespace details {
template <bool A>
struct conditional_traits { static constexpr bool applicable = A; };
using applicable_traits = conditional_traits<true>;
using inapplicable_traits = conditional_traits<false>;
enum class qualifier_type { lv, const_lv, rv, const_rv };
template <class T, qualifier_type Q> struct add_qualifier_traits;
template <class T>
struct add_qualifier_traits<T, qualifier_type::lv> : std::type_identity<T&> {};
template <class T>
struct add_qualifier_traits<T, qualifier_type::const_lv>
: std::type_identity<const T&> {};
template <class T>
struct add_qualifier_traits<T, qualifier_type::rv> : std::type_identity<T&&> {};
template <class T>
struct add_qualifier_traits<T, qualifier_type::const_rv>
: std::type_identity<const T&&> {};
template <class T, qualifier_type Q>
using add_qualifier_t = typename add_qualifier_traits<T, Q>::type;
template <class T, qualifier_type Q>
using add_qualifier_ptr_t = std::remove_reference_t<add_qualifier_t<T, Q>>*;
template <template <class, class> class R, class O, class... Is>
struct recursive_reduction : std::type_identity<O> {};
template <template <class, class> class R, class O, class... Is>
using recursive_reduction_t = typename recursive_reduction<R, O, Is...>::type;
template <template <class, class> class R, class O, class I, class... Is>
struct recursive_reduction<R, O, I, Is...>
{ using type = recursive_reduction_t<R, R<O, I>, Is...>; };
template <template <class> class T, class... Is> struct first_applicable {};
template <template <class> class T, class I, class... Is>
requires(T<I>::applicable)
struct first_applicable<T, I, Is...> : std::type_identity<I> {};
template <template <class> class T, class I, class... Is>
struct first_applicable<T, I, Is...> : first_applicable<T, Is...> {};
template <template <class> class T, class... Is>
using first_applicable_t = typename first_applicable<T, Is...>::type;
template <class Expr>
consteval bool is_consteval(Expr)
{ return requires { typename std::bool_constant<(Expr{}(), false)>; }; }
template <class T, std::size_t I>
concept has_tuple_element = requires { typename std::tuple_element_t<I, T>; };
template <class T>
consteval bool is_tuple_like_well_formed() {
if constexpr (requires { { std::tuple_size<T>::value } ->
std::same_as<const std::size_t&>; }) {
if constexpr (is_consteval([] { return std::tuple_size<T>::value; })) {
return []<std::size_t... I>(std::index_sequence<I...>) {
return (has_tuple_element<T, I> && ...);
}(std::make_index_sequence<std::tuple_size_v<T>>{});
}
}
return false;
}
template <template <class...> class T, class TL, class Is, class... Args>
struct instantiated_traits;
template <template <class...> class T, class TL, std::size_t... Is,
class... Args>
struct instantiated_traits<T, TL, std::index_sequence<Is...>, Args...>
{ using type = T<Args..., std::tuple_element_t<Is, TL>...>; };
template <template <class...> class T, class TL, class... Args>
using instantiated_t = typename instantiated_traits<
T, TL, std::make_index_sequence<std::tuple_size_v<TL>>, Args...>::type;
template <class T>
consteval bool has_copyability(constraint_level level) {
switch (level) {
case constraint_level::none: return true;
case constraint_level::nontrivial: return std::is_copy_constructible_v<T>;
case constraint_level::nothrow:
return std::is_nothrow_copy_constructible_v<T>;
case constraint_level::trivial:
return std::is_trivially_copy_constructible_v<T> &&
std::is_trivially_destructible_v<T>;
default: return false;
}
}
template <class T>
consteval bool has_relocatability(constraint_level level) {
switch (level) {
case constraint_level::none: return true;
case constraint_level::nontrivial:
return std::is_move_constructible_v<T> && std::is_destructible_v<T>;
case constraint_level::nothrow:
return std::is_nothrow_move_constructible_v<T> &&
std::is_nothrow_destructible_v<T>;
case constraint_level::trivial:
return std::is_trivially_move_constructible_v<T> &&
std::is_trivially_destructible_v<T>;
default: return false;
}
}
template <class T>
consteval bool has_destructibility(constraint_level level) {
switch (level) {
case constraint_level::none: return true;
case constraint_level::nontrivial: return std::is_destructible_v<T>;
case constraint_level::nothrow: return std::is_nothrow_destructible_v<T>;
case constraint_level::trivial: return std::is_trivially_destructible_v<T>;
default: return false;
}
}
template <class P, qualifier_type Q, bool NE>
struct ptr_traits : inapplicable_traits {};
template <class P, qualifier_type Q, bool NE>
requires(requires { *std::declval<add_qualifier_t<P, Q>>(); } &&
(!NE || noexcept(*std::declval<add_qualifier_t<P, Q>>())))
struct ptr_traits<P, Q, NE> : applicable_traits
{ using target_type = decltype(*std::declval<add_qualifier_t<P, Q>>()); };
template <class D, bool NE, class R, class... Args>
concept invocable_dispatch = (NE && std::is_nothrow_invocable_r_v<
R, D, Args...>) || (!NE && std::is_invocable_r_v<R, D, Args...>);
template <class D, class P, qualifier_type Q, bool NE, class R, class... Args>
concept invocable_dispatch_ptr_indirect = ptr_traits<P, Q, NE>::applicable &&
invocable_dispatch<
D, NE, R, typename ptr_traits<P, Q, NE>::target_type, Args...>;
template <class D, class P, qualifier_type Q, bool NE, class R, class... Args>
concept invocable_dispatch_ptr_direct = invocable_dispatch<
D, NE, R, add_qualifier_t<P, Q>, Args...>;
template <bool NE, class R, class... Args>
using func_ptr_t = std::conditional_t<
NE, R (*)(Args...) noexcept, R (*)(Args...)>;
template <class D, class R, class... Args>
R invoke_dispatch(Args&&... args) {
if constexpr (std::is_void_v<R>) {
D{}(std::forward<Args>(args)...);
} else {
return D{}(std::forward<Args>(args)...);
}
}
template <class D, class P, qualifier_type Q, class R, class... Args>
R indirect_conv_dispatcher(add_qualifier_t<std::byte, Q> self, Args... args)
noexcept(invocable_dispatch_ptr_indirect<D, P, Q, true, R, Args...>) {
return invoke_dispatch<D, R>(*std::forward<add_qualifier_t<P, Q>>(
*std::launder(reinterpret_cast<add_qualifier_ptr_t<P, Q>>(&self))),
std::forward<Args>(args)...);
}
template <class D, class P, qualifier_type Q, class R, class... Args>
R direct_conv_dispatcher(add_qualifier_t<std::byte, Q> self, Args... args)
noexcept(invocable_dispatch_ptr_direct<D, P, Q, true, R, Args...>) {
return invoke_dispatch<D, R>(std::forward<add_qualifier_t<P, Q>>(
*std::launder(reinterpret_cast<add_qualifier_ptr_t<P, Q>>(&self))),
std::forward<Args>(args)...);
}
template <class D, qualifier_type Q, class R, class... Args>
R default_conv_dispatcher(add_qualifier_t<std::byte, Q>, Args... args)
noexcept(invocable_dispatch<D, true, R, std::nullptr_t, Args...>)
{ return invoke_dispatch<D, R>(nullptr, std::forward<Args>(args)...); }
template <class P>
void copying_dispatcher(std::byte& self, const std::byte& rhs)
noexcept(has_copyability<P>(constraint_level::nothrow)) {
std::construct_at(reinterpret_cast<P*>(&self),
*std::launder(reinterpret_cast<const P*>(&rhs)));
}
template <std::size_t Len, std::size_t Align>
void copying_default_dispatcher(std::byte& self, const std::byte& rhs)
noexcept {
std::uninitialized_copy_n(
std::assume_aligned<Align>(&rhs), Len, std::assume_aligned<Align>(&self));
}
template <class P>
void relocation_dispatcher(std::byte& self, const std::byte& rhs)
noexcept(has_relocatability<P>(constraint_level::nothrow)) {
P* other = std::launder(reinterpret_cast<P*>(const_cast<std::byte*>(&rhs)));
std::construct_at(reinterpret_cast<P*>(&self), std::move(*other));
std::destroy_at(other);
}
template <class P>
void destruction_dispatcher(std::byte& self)
noexcept(has_destructibility<P>(constraint_level::nothrow))
{ std::destroy_at(std::launder(reinterpret_cast<P*>(&self))); }
inline void destruction_default_dispatcher(std::byte&) noexcept {}
template <class O> struct overload_traits : inapplicable_traits {};
template <qualifier_type Q, bool NE, class R, class... Args>
struct overload_traits_impl : applicable_traits {
template <bool IS_DIRECT, class D>
struct meta_provider {
template <class P>
static constexpr auto get()
-> func_ptr_t<NE, R, add_qualifier_t<std::byte, Q>, Args...> {
if constexpr (!IS_DIRECT &&
invocable_dispatch_ptr_indirect<D, P, Q, NE, R, Args...>) {
return &indirect_conv_dispatcher<D, P, Q, R, Args...>;
} else if constexpr (IS_DIRECT &&
invocable_dispatch_ptr_direct<D, P, Q, NE, R, Args...>) {
return &direct_conv_dispatcher<D, P, Q, R, Args...>;
} else if constexpr (invocable_dispatch<
D, NE, R, std::nullptr_t, Args...>) {
return &default_conv_dispatcher<D, Q, R, Args...>;
} else {
return nullptr;
}
}
};
struct resolver {
overload_traits_impl operator()(add_qualifier_t<std::byte, Q>, Args...);
};
template <bool IS_DIRECT, class D, class P>
static constexpr bool applicable_ptr =
meta_provider<IS_DIRECT, D>::template get<P>() != nullptr;
};
template <class R, class... Args>
struct overload_traits<R(Args...)>
: overload_traits_impl<qualifier_type::lv, false, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) noexcept>
: overload_traits_impl<qualifier_type::lv, true, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) &>
: overload_traits_impl<qualifier_type::lv, false, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) & noexcept>
: overload_traits_impl<qualifier_type::lv, true, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) &&>
: overload_traits_impl<qualifier_type::rv, false, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) && noexcept>
: overload_traits_impl<qualifier_type::rv, true, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) const>
: overload_traits_impl<qualifier_type::const_lv, false, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) const noexcept>
: overload_traits_impl<qualifier_type::const_lv, true, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) const&>
: overload_traits_impl<qualifier_type::const_lv, false, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) const& noexcept>
: overload_traits_impl<qualifier_type::const_lv, true, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) const&&>
: overload_traits_impl<qualifier_type::const_rv, false, R, Args...> {};
template <class R, class... Args>
struct overload_traits<R(Args...) const&& noexcept>
: overload_traits_impl<qualifier_type::const_rv, true, R, Args...> {};
template <class T> struct nullable_traits : inapplicable_traits {};
template <class T>
requires(
requires(const T& cv, T& v) {
{ T{} } noexcept;
{ cv.has_value() } noexcept -> std::same_as<bool>;
{ v.reset() } noexcept;
})
struct nullable_traits<T> : applicable_traits {};
template <class MP>
struct dispatcher_meta {
constexpr dispatcher_meta() noexcept : dispatcher(nullptr) {}
template <class P>
constexpr explicit dispatcher_meta(std::in_place_type_t<P>) noexcept
: dispatcher(MP::template get<P>()) {}
bool has_value() const noexcept { return dispatcher != nullptr; }
void reset() noexcept { dispatcher = nullptr; }
decltype(MP::template get<void>()) dispatcher;
};
template <class... Ms>
struct composite_meta_impl : Ms... {
static constexpr bool is_nullable =
requires { typename first_applicable_t<nullable_traits, Ms...>; };
constexpr composite_meta_impl() noexcept requires(is_nullable) = default;
template <class P>
constexpr explicit composite_meta_impl(std::in_place_type_t<P>) noexcept
: Ms(std::in_place_type<P>)... {}
bool has_value() const noexcept requires(is_nullable)
{ return first_applicable_t<nullable_traits, Ms...>::has_value(); }
void reset() noexcept requires(is_nullable)
{ first_applicable_t<nullable_traits, Ms...>::reset(); }
};
template <class O, class I> struct meta_reduction : std::type_identity<O> {};
template <class... Ms, class I> requires(!std::is_void_v<I>)
struct meta_reduction<composite_meta_impl<Ms...>, I>
: std::type_identity<composite_meta_impl<Ms..., I>> {};
template <class... Ms1, class... Ms2>
struct meta_reduction<composite_meta_impl<Ms1...>, composite_meta_impl<Ms2...>>
: std::type_identity<composite_meta_impl<Ms1..., Ms2...>> {};
template <class O, class I>
using meta_reduction_t = typename meta_reduction<O, I>::type;
template <class... Ms>
using composite_meta =
recursive_reduction_t<meta_reduction_t, composite_meta_impl<>, Ms...>;
template <class C>
consteval bool is_conv_is_direct_well_formed() {
if constexpr (requires { { C::is_direct } -> std::same_as<const bool&>; }) {
if constexpr (is_consteval([] { return C::is_direct; })) {
return true;
}
}
return false;
}
template <class C, class... Os>
struct conv_traits_impl : inapplicable_traits {};
template <class C, class... Os>
requires(sizeof...(Os) > 0u && (overload_traits<Os>::applicable && ...))
struct conv_traits_impl<C, Os...> : applicable_traits {
struct overload_resolver : overload_traits<Os>::resolver...
{ using overload_traits<Os>::resolver::operator()...; };
using meta = composite_meta_impl<dispatcher_meta<typename overload_traits<Os>
::template meta_provider<C::is_direct, typename C::dispatch_type>>...>;
template <qualifier_type Q, class... Args>
using matched_overload_traits = std::invoke_result_t<
overload_resolver, add_qualifier_t<std::byte, Q>, Args...>;
template <class P>
static constexpr bool applicable_ptr =
(overload_traits<Os>::template applicable_ptr<
C::is_direct, typename C::dispatch_type, P> && ...);
};
template <class C> struct conv_traits : inapplicable_traits {};
template <class C>
requires(
requires {
typename C::dispatch_type;
typename C::overload_types;
} &&
is_conv_is_direct_well_formed<C>() &&
std::is_trivial_v<typename C::dispatch_type> &&
is_tuple_like_well_formed<typename C::overload_types>())
struct conv_traits<C>
: instantiated_t<conv_traits_impl, typename C::overload_types, C> {};
template <bool NE>
struct copyability_meta_provider {
template <class P>
static constexpr func_ptr_t<NE, void, std::byte&, const std::byte&> get() {
if constexpr (has_copyability<P>(constraint_level::trivial)) {
return ©ing_default_dispatcher<sizeof(P), alignof(P)>;
} else {
return ©ing_dispatcher<P>;
}
}
};
template <bool NE>
struct relocatability_meta_provider {
template <class P>
static constexpr func_ptr_t<NE, void, std::byte&, const std::byte&> get() {
if constexpr (has_relocatability<P>(constraint_level::trivial)) {
return ©ing_default_dispatcher<sizeof(P), alignof(P)>;
} else {
return &relocation_dispatcher<P>;
}
}
};
template <bool NE>
struct destructibility_meta_provider {
template <class P>
static constexpr func_ptr_t<NE, void, std::byte&> get() {
if constexpr (has_destructibility<P>(constraint_level::trivial)) {
return &destruction_default_dispatcher;
} else {
return &destruction_dispatcher<P>;
}
}
};
template <template <bool> class MP, constraint_level C>
struct lifetime_meta_traits : std::type_identity<void> {};
template <template <bool> class MP>
struct lifetime_meta_traits<MP, constraint_level::nothrow>
: std::type_identity<dispatcher_meta<MP<true>>> {};
template <template <bool> class MP>
struct lifetime_meta_traits<MP, constraint_level::nontrivial>
: std::type_identity<dispatcher_meta<MP<false>>> {};
template <template <bool> class MP, constraint_level C>
using lifetime_meta_t = typename lifetime_meta_traits<MP, C>::type;
template <class... As>
class ___PRO_ENFORCE_EBO composite_accessor_impl : public As... {
template <class> friend class pro::proxy;
composite_accessor_impl() noexcept = default;
composite_accessor_impl(const composite_accessor_impl&) noexcept = default;
composite_accessor_impl& operator=(const composite_accessor_impl&) noexcept
= default;
};
template <template <class> class TA, class O, class I>
struct composite_accessor_reduction : std::type_identity<O> {};
template <template <class> class TA, class... As, class I>
requires(requires { typename TA<I>; } && std::is_trivial_v<TA<I>> &&
!std::is_final_v<TA<I>>)
struct composite_accessor_reduction<TA, composite_accessor_impl<As...>, I>
{ using type = composite_accessor_impl<As..., TA<I>>; };
template <bool IS_DIRECT, class F>
struct composite_accessor_helper {
template <class C> requires(C::is_direct == IS_DIRECT)
using single_accessor = typename C::template accessor<F>;
template <class O, class I>
using reduction_t =
typename composite_accessor_reduction<single_accessor, O, I>::type;
};
template <bool IS_DIRECT, class F, class... Cs>
using composite_accessor = recursive_reduction_t<
composite_accessor_helper<IS_DIRECT, F>::template reduction_t,
composite_accessor_impl<>, Cs...>;
template <class F>
consteval bool is_facade_constraints_well_formed() {
if constexpr (requires {
{ F::constraints } -> std::same_as<const proxiable_ptr_constraints&>; }) {
if constexpr (is_consteval([] { return F::constraints; })) {
return std::has_single_bit(F::constraints.max_align) &&
F::constraints.max_size % F::constraints.max_align == 0u;
}
}
return false;
}
template <class R, class P>
consteval bool is_reflection_type_well_formed() {
if constexpr (std::is_constructible_v<R, std::in_place_type_t<P>>) {
if constexpr (is_consteval([] { return R{std::in_place_type<P>}; })) {
return true;
}
}
return false;
}
template <class F, class... Cs>
struct facade_conv_traits_impl : inapplicable_traits {};
template <class F, class... Cs> requires(conv_traits<Cs>::applicable && ...)
struct facade_conv_traits_impl<F, Cs...> : applicable_traits {
using conv_meta = composite_meta<typename conv_traits<Cs>::meta...>;
using indirect_accessor = composite_accessor<false, F, Cs...>;
using direct_accessor = composite_accessor<true, F, Cs...>;
template <class P>
static constexpr bool conv_applicable_ptr =
(conv_traits<Cs>::template applicable_ptr<P> && ...);
};
template <class F, class... Rs>
struct facade_refl_traits_impl {
using refl_meta = composite_meta<Rs...>;
template <class P>
static constexpr bool refl_applicable_ptr =
(is_reflection_type_well_formed<Rs, P>() && ...);
};
template <class F> struct facade_traits : inapplicable_traits {};
template <class F>
requires(
requires {
typename F::convention_types;
typename F::reflection_types;
} &&
is_facade_constraints_well_formed<F>() &&
is_tuple_like_well_formed<typename F::convention_types>() &&
instantiated_t<facade_conv_traits_impl, typename F::convention_types, F>
::applicable &&
is_tuple_like_well_formed<typename F::reflection_types>())
struct facade_traits<F>
: instantiated_t<facade_conv_traits_impl, typename F::convention_types, F>,
instantiated_t<facade_refl_traits_impl, typename F::reflection_types, F> {
using copyability_meta = lifetime_meta_t<
copyability_meta_provider, F::constraints.copyability>;
using relocatability_meta = lifetime_meta_t<
relocatability_meta_provider,
F::constraints.copyability == constraint_level::trivial ?
constraint_level::trivial : F::constraints.relocatability>;
using destructibility_meta = lifetime_meta_t<
destructibility_meta_provider, F::constraints.destructibility>;
using meta = composite_meta<copyability_meta, relocatability_meta,
destructibility_meta, typename facade_traits::conv_meta,
typename facade_traits::refl_meta>;
static constexpr bool has_indirection = !std::is_same_v<
typename facade_traits::indirect_accessor, composite_accessor_impl<>>;
};
using ptr_prototype = void*[2];
template <class M>
struct meta_ptr {
constexpr meta_ptr() noexcept : ptr_(nullptr) {};
template <class P>
constexpr explicit meta_ptr(std::in_place_type_t<P>) noexcept
: ptr_(&storage<P>) {}
bool has_value() const noexcept { return ptr_ != nullptr; }
void reset() noexcept { ptr_ = nullptr; }
const M* operator->() const noexcept { return ptr_; }
private:
const M* ptr_;
template <class P> static constexpr M storage{std::in_place_type<P>};
};
template <class M>
requires(sizeof(M) <= sizeof(ptr_prototype) &&
alignof(M) <= alignof(ptr_prototype) && nullable_traits<M>::applicable)
struct meta_ptr<M> : M {
using M::M;
const M* operator->() const noexcept { return this; }
};
template <class F>
struct proxy_helper {
static inline const auto& get_meta(const proxy<F>& p) noexcept
{ return *p.meta_.operator->(); }
template <class C, qualifier_type Q, class... Args>
static decltype(auto) invoke(add_qualifier_t<proxy<F>, Q> p, Args&&... args) {
using MetaProvider = typename conv_traits<C>
::template matched_overload_traits<Q, Args...>
::template meta_provider<C::is_direct, typename C::dispatch_type>;
return p.meta_->template dispatcher_meta<MetaProvider>::dispatcher(
std::forward<add_qualifier_t<std::byte, Q>>(*p.ptr_),
std::forward<Args>(args)...);
}
template <class A, qualifier_type Q>
static add_qualifier_t<proxy<F>, Q> access(add_qualifier_t<A, Q> a) {
if constexpr (std::is_base_of_v<A, proxy<F>>) {
return static_cast<add_qualifier_t<proxy<F>, Q>>(
std::forward<add_qualifier_t<A, Q>>(a));
} else {
return reinterpret_cast<add_qualifier_t<proxy<F>, Q>>(
*(reinterpret_cast<add_qualifier_ptr_t<std::byte, Q>>(
static_cast<add_qualifier_ptr_t<
typename facade_traits<F>::indirect_accessor, Q>>(
std::addressof(a))) - offsetof(proxy<F>, ia_)));
}
}
};
} // namespace details
template <class F>
concept facade = details::facade_traits<F>::applicable;
template <class P, class F>
concept proxiable = facade<F> && sizeof(P) <= F::constraints.max_size &&
alignof(P) <= F::constraints.max_align &&
details::has_copyability<P>(F::constraints.copyability) &&
details::has_relocatability<P>(F::constraints.relocatability) &&
details::has_destructibility<P>(F::constraints.destructibility) &&
details::facade_traits<F>::template conv_applicable_ptr<P> &&
details::facade_traits<F>::template refl_applicable_ptr<P>;
template <class F>
class proxy : public details::facade_traits<F>::direct_accessor {
static_assert(facade<F>);
friend struct details::proxy_helper<F>;
using _Traits = details::facade_traits<F>;
public:
proxy() noexcept = default;
proxy(std::nullptr_t) noexcept {}
proxy(const proxy&) noexcept requires(F::constraints.copyability ==
constraint_level::trivial) = default;
proxy(const proxy& rhs)
noexcept(F::constraints.copyability == constraint_level::nothrow)
requires(F::constraints.copyability == constraint_level::nontrivial ||
F::constraints.copyability == constraint_level::nothrow) {
if (rhs.meta_.has_value()) {
rhs.meta_->_Traits::copyability_meta::dispatcher(*ptr_, *rhs.ptr_);
meta_ = rhs.meta_;
}
}
proxy(proxy&& rhs)
noexcept(F::constraints.relocatability == constraint_level::nothrow)
requires(F::constraints.relocatability >= constraint_level::nontrivial &&
F::constraints.copyability != constraint_level::trivial) {
if (rhs.meta_.has_value()) {
if constexpr (F::constraints.relocatability ==
constraint_level::trivial) {
std::ranges::uninitialized_copy(rhs.ptr_, ptr_);
} else {
rhs.meta_->_Traits::relocatability_meta::dispatcher(*ptr_, *rhs.ptr_);
}
meta_ = rhs.meta_;
rhs.meta_.reset();
}
}
template <class P>
proxy(P&& ptr) noexcept(std::is_nothrow_constructible_v<std::decay_t<P>, P>)
requires(proxiable<std::decay_t<P>, F> &&
std::is_constructible_v<std::decay_t<P>, P>)
{ initialize<std::decay_t<P>>(std::forward<P>(ptr)); }
template <proxiable<F> P, class... Args>
explicit proxy(std::in_place_type_t<P>, Args&&... args)
noexcept(std::is_nothrow_constructible_v<P, Args...>)
requires(std::is_constructible_v<P, Args...>)
{ initialize<P>(std::forward<Args>(args)...); }
template <proxiable<F> P, class U, class... Args>
explicit proxy(std::in_place_type_t<P>, std::initializer_list<U> il,
Args&&... args)
noexcept(std::is_nothrow_constructible_v<
P, std::initializer_list<U>&, Args...>)
requires(std::is_constructible_v<P, std::initializer_list<U>&, Args...>)
{ initialize<P>(il, std::forward<Args>(args)...); }
proxy& operator=(std::nullptr_t)
noexcept(F::constraints.destructibility >= constraint_level::nothrow)
requires(F::constraints.destructibility >= constraint_level::nontrivial)
{ reset(); return *this; }
proxy& operator=(const proxy&) noexcept requires(F::constraints.copyability ==
constraint_level::trivial) = default;
proxy& operator=(const proxy& rhs)
noexcept(F::constraints.copyability >= constraint_level::nothrow &&
F::constraints.destructibility >= constraint_level::nothrow)
requires((F::constraints.copyability == constraint_level::nontrivial ||
F::constraints.copyability == constraint_level::nothrow) &&
F::constraints.destructibility >= constraint_level::nontrivial) {
if (this != &rhs) {
if constexpr (F::constraints.copyability == constraint_level::nothrow) {
std::destroy_at(this);
std::construct_at(this, rhs);
} else {
*this = proxy{rhs};
}
}
return *this;
}
proxy& operator=(proxy&& rhs)
noexcept(F::constraints.relocatability >= constraint_level::nothrow &&
F::constraints.destructibility >= constraint_level::nothrow)
requires(F::constraints.relocatability >= constraint_level::nontrivial &&
F::constraints.destructibility >= constraint_level::nontrivial &&
F::constraints.copyability != constraint_level::trivial) {
if (this != &rhs) {
reset();
std::construct_at(this, std::move(rhs));
}
return *this;
}
template <class P>
proxy& operator=(P&& ptr)
noexcept(std::is_nothrow_constructible_v<std::decay_t<P>, P> &&
F::constraints.destructibility >= constraint_level::nothrow)
requires(proxiable<std::decay_t<P>, F> &&
std::is_constructible_v<std::decay_t<P>, P> &&
F::constraints.destructibility >= constraint_level::nontrivial) {
if constexpr (std::is_nothrow_constructible_v<std::decay_t<P>, P>) {
std::destroy_at(this);
initialize<std::decay_t<P>>(std::forward<P>(ptr));
} else {
*this = proxy{std::forward<P>(ptr)};
}
return *this;
}
~proxy() requires(F::constraints.destructibility == constraint_level::trivial)
= default;
~proxy() noexcept(F::constraints.destructibility == constraint_level::nothrow)
requires(F::constraints.destructibility == constraint_level::nontrivial ||
F::constraints.destructibility == constraint_level::nothrow) {
if (meta_.has_value()) {
meta_->_Traits::destructibility_meta::dispatcher(*ptr_);
}
}
bool has_value() const noexcept { return meta_.has_value(); }
explicit operator bool() const noexcept { return meta_.has_value(); }
void reset()
noexcept(F::constraints.destructibility >= constraint_level::nothrow)
requires(F::constraints.destructibility >= constraint_level::nontrivial)
{ std::destroy_at(this); meta_.reset(); }
void swap(proxy& rhs)
noexcept(F::constraints.relocatability >= constraint_level::nothrow ||
F::constraints.copyability == constraint_level::trivial)
requires(F::constraints.relocatability >= constraint_level::nontrivial ||
F::constraints.copyability == constraint_level::trivial) {
if constexpr (F::constraints.relocatability == constraint_level::trivial ||
F::constraints.copyability == constraint_level::trivial) {
std::swap(meta_, rhs.meta_);
std::swap(ptr_, rhs.ptr);
} else {
if (meta_.has_value()) {
if (rhs.meta_.has_value()) {
proxy temp = std::move(*this);
std::construct_at(this, std::move(rhs));
std::construct_at(&rhs, std::move(temp));
} else {
std::construct_at(&rhs, std::move(*this));
}
} else if (rhs.meta_.has_value()) {
std::construct_at(this, std::move(rhs));
}
}
}
template <proxiable<F> P, class... Args>
P& emplace(Args&&... args)
noexcept(std::is_nothrow_constructible_v<P, Args...> &&
F::constraints.destructibility >= constraint_level::nothrow)
requires(std::is_constructible_v<P, Args...> &&
F::constraints.destructibility >= constraint_level::nontrivial)
{ reset(); return initialize<P>(std::forward<Args>(args)...); }
template <proxiable<F> P, class U, class... Args>
P& emplace(std::initializer_list<U> il, Args&&... args)
noexcept(std::is_nothrow_constructible_v<
P, std::initializer_list<U>&, Args...> &&
F::constraints.destructibility >= constraint_level::nothrow)
requires(std::is_constructible_v<P, std::initializer_list<U>&, Args...> &&
F::constraints.destructibility >= constraint_level::nontrivial)
{ reset(); return initialize<P>(il, std::forward<Args>(args)...); }
auto operator->() noexcept requires(_Traits::has_indirection)
{ return std::addressof(ia_); }
auto operator->() const noexcept requires(_Traits::has_indirection)
{ return std::addressof(ia_); }
auto& operator*() & noexcept requires(_Traits::has_indirection)
{ return ia_; }
auto& operator*() const& noexcept requires(_Traits::has_indirection)
{ return ia_; }
auto&& operator*() && noexcept requires(_Traits::has_indirection)
{ return std::forward<typename _Traits::indirect_accessor>(ia_); }
auto&& operator*() const&& noexcept requires(_Traits::has_indirection)
{ return std::forward<const typename _Traits::indirect_accessor>(ia_); }
friend void swap(proxy& lhs, proxy& rhs) noexcept(noexcept(lhs.swap(rhs)))
{ lhs.swap(rhs); }
friend bool operator==(const proxy& lhs, std::nullptr_t) noexcept
{ return !lhs.has_value(); }
private:
template <class P, class... Args>
P& initialize(Args&&... args) {
std::construct_at(reinterpret_cast<P*>(ptr_), std::forward<Args>(args)...);
meta_ = details::meta_ptr<typename _Traits::meta>{std::in_place_type<P>};
return *std::launder(reinterpret_cast<P*>(ptr_));
}
[[___PRO_NO_UNIQUE_ADDRESS_ATTRIBUTE]]
typename _Traits::indirect_accessor ia_;
details::meta_ptr<typename _Traits::meta> meta_;
alignas(F::constraints.max_align) std::byte ptr_[F::constraints.max_size];
};
template <class C, class F, class... Args>
decltype(auto) proxy_invoke(proxy<F>& p, Args&&... args) {
return details::proxy_helper<F>::template invoke<
C, details::qualifier_type::lv>(p, std::forward<Args>(args)...);
}
template <class C, class F, class... Args>
decltype(auto) proxy_invoke(const proxy<F>& p, Args&&... args) {
return details::proxy_helper<F>::template invoke<
C, details::qualifier_type::const_lv>(p, std::forward<Args>(args)...);
}
template <class C, class F, class... Args>
decltype(auto) proxy_invoke(proxy<F>&& p, Args&&... args) {
return details::proxy_helper<F>::template invoke<
C, details::qualifier_type::rv>(
std::forward<proxy<F>>(p), std::forward<Args>(args)...);
}
template <class C, class F, class... Args>
decltype(auto) proxy_invoke(const proxy<F>&& p, Args&&... args) {
return details::proxy_helper<F>::template invoke<
C, details::qualifier_type::const_rv>(
std::forward<const proxy<F>>(p), std::forward<Args>(args)...);
}
template <class F, class A>
proxy<F>& access_proxy(A& a) noexcept {
return details::proxy_helper<F>::template access<
A, details::qualifier_type::lv>(a);
}
template <class F, class A>
const proxy<F>& access_proxy(const A& a) noexcept {
return details::proxy_helper<F>::template access<
A, details::qualifier_type::const_lv>(a);
}
template <class F, class A>
proxy<F>&& access_proxy(A&& a) noexcept {
return details::proxy_helper<F>::template access<
A, details::qualifier_type::rv>(std::forward<A>(a));
}
template <class F, class A>
const proxy<F>&& access_proxy(const A&& a) noexcept {
return details::proxy_helper<F>::template access<
A, details::qualifier_type::const_rv>(std::forward<const A>(a));
}
template <class R, class F>
const R& proxy_reflect(const proxy<F>& p) noexcept
{ return details::proxy_helper<F>::get_meta(p); }
namespace details {
template <class T>
class inplace_ptr {
public:
template <class... Args>
inplace_ptr(Args&&... args)
noexcept(std::is_nothrow_constructible_v<T, Args...>)
requires(std::is_constructible_v<T, Args...>)
: value_(std::forward<Args>(args)...) {}
inplace_ptr(const inplace_ptr&)
noexcept(std::is_nothrow_copy_constructible_v<T>) = default;
inplace_ptr(inplace_ptr&&)
noexcept(std::is_nothrow_move_constructible_v<T>) = default;
T* operator->() noexcept { return &value_; }
const T* operator->() const noexcept { return &value_; }
T& operator*() & noexcept { return value_; }
const T& operator*() const& noexcept { return value_; }
T&& operator*() && noexcept { return std::forward<T>(value_); }
const T&& operator*() const&& noexcept
{ return std::forward<const T>(value_); }
private:
T value_;
};
#if __STDC_HOSTED__
template <class T, class Alloc>
static auto rebind_allocator(const Alloc& alloc) {
return typename std::allocator_traits<Alloc>::template rebind_alloc<T>(alloc);
}
template <class T, class Alloc, class... Args>
static T* allocate(const Alloc& alloc, Args&&... args) {
auto al = rebind_allocator<T>(alloc);
auto deleter = [&](T* ptr) { al.deallocate(ptr, 1); };
std::unique_ptr<T, decltype(deleter)> result{al.allocate(1), deleter};
std::construct_at(result.get(), std::forward<Args>(args)...);
return result.release();
}
template <class Alloc, class T>
static void deallocate(const Alloc& alloc, T* ptr) {
auto al = rebind_allocator<T>(alloc);
std::destroy_at(ptr);
al.deallocate(ptr, 1);
}
template <class T, class Alloc>
class allocated_ptr {
public:
template <class... Args>
allocated_ptr(const Alloc& alloc, Args&&... args)
requires(std::is_constructible_v<T, Args...>)
: alloc_(alloc), ptr_(allocate<T>(alloc, std::forward<Args>(args)...)) {}
allocated_ptr(const allocated_ptr& rhs)
requires(std::is_copy_constructible_v<T>)
: alloc_(rhs.alloc_), ptr_(rhs.ptr_ == nullptr ? nullptr :
allocate<T>(alloc_, std::as_const(*rhs.ptr_))) {}
allocated_ptr(allocated_ptr&& rhs)
noexcept(std::is_nothrow_move_constructible_v<Alloc>)
: alloc_(std::move(rhs.alloc_)), ptr_(std::exchange(rhs.ptr_, nullptr)) {}
~allocated_ptr() { if (ptr_ != nullptr) { deallocate(alloc_, ptr_); } }
T* operator->() noexcept { return ptr_; }
const T* operator->() const noexcept { return ptr_; }
T& operator*() & noexcept { return *ptr_; }
const T& operator*() const& noexcept { return *ptr_; }
T&& operator*() && noexcept { return std::forward<T>(*ptr_); }
const T&& operator*() const&& noexcept
{ return std::forward<const T>(*ptr_); }
private:
[[___PRO_NO_UNIQUE_ADDRESS_ATTRIBUTE]]
Alloc alloc_;
T* ptr_;
};
template <class T, class Alloc>
class compact_ptr {
public:
template <class... Args>
compact_ptr(const Alloc& alloc, Args&&... args)
requires(std::is_constructible_v<T, Args...>)
: ptr_(allocate<storage>(alloc, alloc, std::forward<Args>(args)...)) {}
compact_ptr(const compact_ptr& rhs) requires(std::is_copy_constructible_v<T>)
: ptr_(rhs.ptr_ == nullptr ? nullptr : allocate<storage>(rhs.ptr_->alloc,
rhs.ptr_->alloc, std::as_const(rhs.ptr_->value))) {}
compact_ptr(compact_ptr&& rhs) noexcept
: ptr_(std::exchange(rhs.ptr_, nullptr)) {}
~compact_ptr() { if (ptr_ != nullptr) { deallocate(ptr_->alloc, ptr_); } }
T* operator->() noexcept { return &ptr_->value; }
const T* operator->() const noexcept { return &ptr_->value; }
T& operator*() & noexcept { return ptr_->value; }
const T& operator*() const& noexcept { return ptr_->value; }
T&& operator*() && noexcept { return std::forward<T>(ptr_->value); }
const T&& operator*() const&& noexcept
{ return std::forward<const T>(ptr_->value); }
private:
struct storage {
template <class... Args>
explicit storage(const Alloc& alloc, Args&&... args)
: value(std::forward<Args>(args)...), alloc(alloc) {}
T value;
Alloc alloc;
};
storage* ptr_;
};
template <class F, class T, class Alloc, class... Args>
proxy<F> allocate_proxy_impl(const Alloc& alloc, Args&&... args) {
if constexpr (proxiable<allocated_ptr<T, Alloc>, F>) {
return proxy<F>{std::in_place_type<allocated_ptr<T, Alloc>>,
alloc, std::forward<Args>(args)...};
} else {
return proxy<F>{std::in_place_type<compact_ptr<T, Alloc>>,
alloc, std::forward<Args>(args)...};
}
}
template <class F, class T, class... Args>
proxy<F> make_proxy_impl(Args&&... args) {
if constexpr (proxiable<inplace_ptr<T>, F>) {
return proxy<F>{std::in_place_type<inplace_ptr<T>>,
std::forward<Args>(args)...};
} else {
return allocate_proxy_impl<F, T>(
std::allocator<T>{}, std::forward<Args>(args)...);
}
}
#endif // __STDC_HOSTED__
} // namespace details
template <class T, class F>
concept inplace_proxiable_target = proxiable<details::inplace_ptr<T>, F>;
template <facade F, inplace_proxiable_target<F> T, class... Args>
proxy<F> make_proxy_inplace(Args&&... args)
noexcept(std::is_nothrow_constructible_v<T, Args...>) {
return proxy<F>{std::in_place_type<details::inplace_ptr<T>>,
std::forward<Args>(args)...};
}
template <facade F, inplace_proxiable_target<F> T, class U, class... Args>
proxy<F> make_proxy_inplace(std::initializer_list<U> il, Args&&... args)
noexcept(std::is_nothrow_constructible_v<
T, std::initializer_list<U>&, Args...>) {
return proxy<F>{std::in_place_type<details::inplace_ptr<T>>,
il, std::forward<Args>(args)...};
}
template <facade F, class T>
proxy<F> make_proxy_inplace(T&& value)
noexcept(std::is_nothrow_constructible_v<std::decay_t<T>, T>)
requires(inplace_proxiable_target<std::decay_t<T>, F>) {
return proxy<F>{std::in_place_type<details::inplace_ptr<std::decay_t<T>>>,
std::forward<T>(value)};
}
#if __STDC_HOSTED__
template <facade F, class T, class Alloc, class... Args>
proxy<F> allocate_proxy(const Alloc& alloc, Args&&... args) {
return details::allocate_proxy_impl<F, T>(alloc, std::forward<Args>(args)...);
}
template <facade F, class T, class Alloc, class U,
class... Args>
proxy<F> allocate_proxy(const Alloc& alloc, std::initializer_list<U> il,
Args&&... args) {
return details::allocate_proxy_impl<F, T>(
alloc, il, std::forward<Args>(args)...);
}
template <facade F, class Alloc, class T>