331 lines
14 KiB
C++
331 lines
14 KiB
C++
|
// Copyright (c) 2016-2022 Antony Polukhin
|
||
|
|
//
|
||
|
|
// Distributed under the Boost Software License, Version 1.0. (See accompanying
|
||
|
|
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
|
||
|
|
|
||
|
|
#ifndef BOOST_PFR_DETAIL_FIELDS_COUNT_HPP
|
||
|
|
#define BOOST_PFR_DETAIL_FIELDS_COUNT_HPP
|
||
|
|
#pragma once
|
||
|
|
|
||
|
|
#include <boost/pfr/detail/config.hpp>
|
||
|
|
#include <boost/pfr/detail/make_integer_sequence.hpp>
|
||
|
|
#include <boost/pfr/detail/size_t_.hpp>
|
||
|
|
#include <boost/pfr/detail/unsafe_declval.hpp>
|
||
|
|
|
||
|
|
#include <climits> // CHAR_BIT
|
||
|
|
#include <type_traits>
|
||
|
|
#include <utility> // metaprogramming stuff
|
||
|
|
|
||
|
|
#ifdef __clang__
|
||
|
|
# pragma clang diagnostic push
|
||
|
|
# pragma clang diagnostic ignored "-Wmissing-braces"
|
||
|
|
# pragma clang diagnostic ignored "-Wundefined-inline"
|
||
|
|
# pragma clang diagnostic ignored "-Wundefined-internal"
|
||
|
|
# pragma clang diagnostic ignored "-Wmissing-field-initializers"
|
||
|
|
#endif
|
||
|
|
|
||
|
|
namespace boost { namespace pfr { namespace detail {
|
||
|
|
|
||
|
|
///////////////////// Structure that can be converted to reference to anything
|
||
|
|
struct ubiq_lref_constructor {
|
||
|
|
std::size_t ignore;
|
||
|
|
template <class Type> constexpr operator Type&() const && noexcept { // tweak for template_unconstrained.cpp like cases
|
||
|
|
return detail::unsafe_declval<Type&>();
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class Type> constexpr operator Type&() const & noexcept { // tweak for optional_chrono.cpp like cases
|
||
|
|
return detail::unsafe_declval<Type&>();
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
///////////////////// Structure that can be converted to rvalue reference to anything
|
||
|
|
struct ubiq_rref_constructor {
|
||
|
|
std::size_t ignore;
|
||
|
|
template <class Type> /*constexpr*/ operator Type() const && noexcept { // Allows initialization of rvalue reference fields and move-only types
|
||
|
|
return detail::unsafe_declval<Type>();
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
|
||
|
|
#ifndef __cpp_lib_is_aggregate
|
||
|
|
///////////////////// Hand-made is_aggregate_initializable_n<T> trait
|
||
|
|
|
||
|
|
// Structure that can be converted to reference to anything except reference to T
|
||
|
|
template <class T, bool IsCopyConstructible>
|
||
|
|
struct ubiq_constructor_except {
|
||
|
|
std::size_t ignore;
|
||
|
|
template <class Type> constexpr operator std::enable_if_t<!std::is_same<T, Type>::value, Type&> () const noexcept; // Undefined
|
||
|
|
};
|
||
|
|
|
||
|
|
template <class T>
|
||
|
|
struct ubiq_constructor_except<T, false> {
|
||
|
|
std::size_t ignore;
|
||
|
|
template <class Type> constexpr operator std::enable_if_t<!std::is_same<T, Type>::value, Type&&> () const noexcept; // Undefined
|
||
|
|
};
|
||
|
|
|
||
|
|
|
||
|
|
// `std::is_constructible<T, ubiq_constructor_except<T>>` consumes a lot of time, so we made a separate lazy trait for it.
|
||
|
|
template <std::size_t N, class T> struct is_single_field_and_aggregate_initializable: std::false_type {};
|
||
|
|
template <class T> struct is_single_field_and_aggregate_initializable<1, T>: std::integral_constant<
|
||
|
|
bool, !std::is_constructible<T, ubiq_constructor_except<T, std::is_copy_constructible<T>::value>>::value
|
||
|
|
> {};
|
||
|
|
|
||
|
|
// Hand-made is_aggregate<T> trait:
|
||
|
|
// Before C++20 aggregates could be constructed from `decltype(ubiq_?ref_constructor{I})...` but type traits report that
|
||
|
|
// there's no constructor from `decltype(ubiq_?ref_constructor{I})...`
|
||
|
|
// Special case for N == 1: `std::is_constructible<T, ubiq_?ref_constructor>` returns true if N == 1 and T is copy/move constructible.
|
||
|
|
template <class T, std::size_t N>
|
||
|
|
struct is_aggregate_initializable_n {
|
||
|
|
template <std::size_t ...I>
|
||
|
|
static constexpr bool is_not_constructible_n(std::index_sequence<I...>) noexcept {
|
||
|
|
return (!std::is_constructible<T, decltype(ubiq_lref_constructor{I})...>::value && !std::is_constructible<T, decltype(ubiq_rref_constructor{I})...>::value)
|
||
|
|
|| is_single_field_and_aggregate_initializable<N, T>::value
|
||
|
|
;
|
||
|
|
}
|
||
|
|
|
||
|
|
static constexpr bool value =
|
||
|
|
std::is_empty<T>::value
|
||
|
|
|| std::is_array<T>::value
|
||
|
|
|| std::is_fundamental<T>::value
|
||
|
|
|| is_not_constructible_n(detail::make_index_sequence<N>{})
|
||
|
|
;
|
||
|
|
};
|
||
|
|
|
||
|
|
#endif // #ifndef __cpp_lib_is_aggregate
|
||
|
|
|
||
|
|
///////////////////// Detect aggregates with inheritance
|
||
|
|
template <class Derived, class U>
|
||
|
|
constexpr bool static_assert_non_inherited() noexcept {
|
||
|
|
static_assert(
|
||
|
|
!std::is_base_of<U, Derived>::value,
|
||
|
|
"====================> Boost.PFR: Boost.PFR: Inherited types are not supported."
|
||
|
|
);
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class Derived>
|
||
|
|
struct ubiq_lref_base_asserting {
|
||
|
|
template <class Type> constexpr operator Type&() const && // tweak for template_unconstrained.cpp like cases
|
||
|
|
noexcept(detail::static_assert_non_inherited<Derived, Type>()) // force the computation of assert function
|
||
|
|
{
|
||
|
|
return detail::unsafe_declval<Type&>();
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class Type> constexpr operator Type&() const & // tweak for optional_chrono.cpp like cases
|
||
|
|
noexcept(detail::static_assert_non_inherited<Derived, Type>()) // force the computation of assert function
|
||
|
|
{
|
||
|
|
return detail::unsafe_declval<Type&>();
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
template <class Derived>
|
||
|
|
struct ubiq_rref_base_asserting {
|
||
|
|
template <class Type> /*constexpr*/ operator Type() const && // Allows initialization of rvalue reference fields and move-only types
|
||
|
|
noexcept(detail::static_assert_non_inherited<Derived, Type>()) // force the computation of assert function
|
||
|
|
{
|
||
|
|
return detail::unsafe_declval<Type>();
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
template <class T, std::size_t I0, std::size_t... I, class /*Enable*/ = typename std::enable_if<std::is_copy_constructible<T>::value>::type>
|
||
|
|
constexpr auto assert_first_not_base(std::index_sequence<I0, I...>) noexcept
|
||
|
|
-> typename std::add_pointer<decltype(T{ ubiq_lref_base_asserting<T>{}, ubiq_lref_constructor{I}... })>::type
|
||
|
|
{
|
||
|
|
return nullptr;
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class T, std::size_t I0, std::size_t... I, class /*Enable*/ = typename std::enable_if<!std::is_copy_constructible<T>::value>::type>
|
||
|
|
constexpr auto assert_first_not_base(std::index_sequence<I0, I...>) noexcept
|
||
|
|
-> typename std::add_pointer<decltype(T{ ubiq_rref_base_asserting<T>{}, ubiq_rref_constructor{I}... })>::type
|
||
|
|
{
|
||
|
|
return nullptr;
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class T>
|
||
|
|
constexpr void* assert_first_not_base(std::index_sequence<>) noexcept
|
||
|
|
{
|
||
|
|
return nullptr;
|
||
|
|
}
|
||
|
|
|
||
|
|
///////////////////// Helper for SFINAE on fields count
|
||
|
|
template <class T, std::size_t... I, class /*Enable*/ = typename std::enable_if<std::is_copy_constructible<T>::value>::type>
|
||
|
|
constexpr auto enable_if_constructible_helper(std::index_sequence<I...>) noexcept
|
||
|
|
-> typename std::add_pointer<decltype(T{ ubiq_lref_constructor{I}... })>::type;
|
||
|
|
|
||
|
|
template <class T, std::size_t... I, class /*Enable*/ = typename std::enable_if<!std::is_copy_constructible<T>::value>::type>
|
||
|
|
constexpr auto enable_if_constructible_helper(std::index_sequence<I...>) noexcept
|
||
|
|
-> typename std::add_pointer<decltype(T{ ubiq_rref_constructor{I}... })>::type;
|
||
|
|
|
||
|
|
template <class T, std::size_t N, class /*Enable*/ = decltype( enable_if_constructible_helper<T>(detail::make_index_sequence<N>()) ) >
|
||
|
|
using enable_if_constructible_helper_t = std::size_t;
|
||
|
|
|
||
|
|
///////////////////// Helpers for range size detection
|
||
|
|
template <std::size_t Begin, std::size_t Last>
|
||
|
|
using is_one_element_range = std::integral_constant<bool, Begin == Last>;
|
||
|
|
|
||
|
|
using multi_element_range = std::false_type;
|
||
|
|
using one_element_range = std::true_type;
|
||
|
|
|
||
|
|
///////////////////// Non greedy fields count search. Templates instantiation depth is log(sizeof(T)), templates instantiation count is log(sizeof(T)).
|
||
|
|
template <class T, std::size_t Begin, std::size_t Middle>
|
||
|
|
constexpr std::size_t detect_fields_count(detail::one_element_range, long) noexcept {
|
||
|
|
static_assert(
|
||
|
|
Begin == Middle,
|
||
|
|
"====================> Boost.PFR: Internal logic error."
|
||
|
|
);
|
||
|
|
return Begin;
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class T, std::size_t Begin, std::size_t Middle>
|
||
|
|
constexpr std::size_t detect_fields_count(detail::multi_element_range, int) noexcept;
|
||
|
|
|
||
|
|
template <class T, std::size_t Begin, std::size_t Middle>
|
||
|
|
constexpr auto detect_fields_count(detail::multi_element_range, long) noexcept
|
||
|
|
-> detail::enable_if_constructible_helper_t<T, Middle>
|
||
|
|
{
|
||
|
|
constexpr std::size_t next_v = Middle + (Middle - Begin + 1) / 2;
|
||
|
|
return detail::detect_fields_count<T, Middle, next_v>(detail::is_one_element_range<Middle, next_v>{}, 1L);
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class T, std::size_t Begin, std::size_t Middle>
|
||
|
|
constexpr std::size_t detect_fields_count(detail::multi_element_range, int) noexcept {
|
||
|
|
constexpr std::size_t next_v = Begin + (Middle - Begin) / 2;
|
||
|
|
return detail::detect_fields_count<T, Begin, next_v>(detail::is_one_element_range<Begin, next_v>{}, 1L);
|
||
|
|
}
|
||
|
|
|
||
|
|
///////////////////// Greedy search. Templates instantiation depth is log(sizeof(T)), templates instantiation count is log(sizeof(T))*T in worst case.
|
||
|
|
template <class T, std::size_t N>
|
||
|
|
constexpr auto detect_fields_count_greedy_remember(long) noexcept
|
||
|
|
-> detail::enable_if_constructible_helper_t<T, N>
|
||
|
|
{
|
||
|
|
return N;
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class T, std::size_t N>
|
||
|
|
constexpr std::size_t detect_fields_count_greedy_remember(int) noexcept {
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class T, std::size_t Begin, std::size_t Last>
|
||
|
|
constexpr std::size_t detect_fields_count_greedy(detail::one_element_range) noexcept {
|
||
|
|
static_assert(
|
||
|
|
Begin == Last,
|
||
|
|
"====================> Boost.PFR: Internal logic error."
|
||
|
|
);
|
||
|
|
return detail::detect_fields_count_greedy_remember<T, Begin>(1L);
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class T, std::size_t Begin, std::size_t Last>
|
||
|
|
constexpr std::size_t detect_fields_count_greedy(detail::multi_element_range) noexcept {
|
||
|
|
constexpr std::size_t middle = Begin + (Last - Begin) / 2;
|
||
|
|
constexpr std::size_t fields_count_big_range = detail::detect_fields_count_greedy<T, middle + 1, Last>(
|
||
|
|
detail::is_one_element_range<middle + 1, Last>{}
|
||
|
|
);
|
||
|
|
|
||
|
|
constexpr std::size_t small_range_begin = (fields_count_big_range ? 0 : Begin);
|
||
|
|
constexpr std::size_t small_range_last = (fields_count_big_range ? 0 : middle);
|
||
|
|
constexpr std::size_t fields_count_small_range = detail::detect_fields_count_greedy<T, small_range_begin, small_range_last>(
|
||
|
|
detail::is_one_element_range<small_range_begin, small_range_last>{}
|
||
|
|
);
|
||
|
|
return fields_count_big_range ? fields_count_big_range : fields_count_small_range;
|
||
|
|
}
|
||
|
|
|
||
|
|
///////////////////// Choosing between array size, greedy and non greedy search.
|
||
|
|
template <class T, std::size_t N>
|
||
|
|
constexpr auto detect_fields_count_dispatch(size_t_<N>, long, long) noexcept
|
||
|
|
-> typename std::enable_if<std::is_array<T>::value, std::size_t>::type
|
||
|
|
{
|
||
|
|
return sizeof(T) / sizeof(typename std::remove_all_extents<T>::type);
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class T, std::size_t N>
|
||
|
|
constexpr auto detect_fields_count_dispatch(size_t_<N>, long, int) noexcept
|
||
|
|
-> decltype(sizeof(T{}))
|
||
|
|
{
|
||
|
|
constexpr std::size_t middle = N / 2 + 1;
|
||
|
|
return detail::detect_fields_count<T, 0, middle>(detail::multi_element_range{}, 1L);
|
||
|
|
}
|
||
|
|
|
||
|
|
template <class T, std::size_t N>
|
||
|
|
constexpr std::size_t detect_fields_count_dispatch(size_t_<N>, int, int) noexcept {
|
||
|
|
// T is not default aggregate initialzable. It means that at least one of the members is not default constructible,
|
||
|
|
// so we have to check all the aggregate initializations for T up to N parameters and return the bigest succeeded
|
||
|
|
// (we can not use binary search for detecting fields count).
|
||
|
|
return detail::detect_fields_count_greedy<T, 0, N>(detail::multi_element_range{});
|
||
|
|
}
|
||
|
|
|
||
|
|
///////////////////// Returns fields count
|
||
|
|
template <class T>
|
||
|
|
constexpr std::size_t fields_count() noexcept {
|
||
|
|
using type = std::remove_cv_t<T>;
|
||
|
|
|
||
|
|
static_assert(
|
||
|
|
!std::is_reference<type>::value,
|
||
|
|
"====================> Boost.PFR: Attempt to get fields count on a reference. This is not allowed because that could hide an issue and different library users expect different behavior in that case."
|
||
|
|
);
|
||
|
|
|
||
|
|
#if !BOOST_PFR_HAS_GUARANTEED_COPY_ELISION
|
||
|
|
static_assert(
|
||
|
|
std::is_copy_constructible<std::remove_all_extents_t<type>>::value || (
|
||
|
|
std::is_move_constructible<std::remove_all_extents_t<type>>::value
|
||
|
|
&& std::is_move_assignable<std::remove_all_extents_t<type>>::value
|
||
|
|
),
|
||
|
|
"====================> Boost.PFR: Type and each field in the type must be copy constructible (or move constructible and move assignable)."
|
||
|
|
);
|
||
|
|
#endif // #if !BOOST_PFR_HAS_GUARANTEED_COPY_ELISION
|
||
|
|
|
||
|
|
static_assert(
|
||
|
|
!std::is_polymorphic<type>::value,
|
||
|
|
"====================> Boost.PFR: Type must have no virtual function, because otherwise it is not aggregate initializable."
|
||
|
|
);
|
||
|
|
|
||
|
|
#ifdef __cpp_lib_is_aggregate
|
||
|
|
static_assert(
|
||
|
|
std::is_aggregate<type>::value // Does not return `true` for built-in types.
|
||
|
|
|| std::is_scalar<type>::value,
|
||
|
|
"====================> Boost.PFR: Type must be aggregate initializable."
|
||
|
|
);
|
||
|
|
#endif
|
||
|
|
|
||
|
|
// Can't use the following. See the non_std_layout.cpp test.
|
||
|
|
//#if !BOOST_PFR_USE_CPP17
|
||
|
|
// static_assert(
|
||
|
|
// std::is_standard_layout<type>::value, // Does not return `true` for structs that have non standard layout members.
|
||
|
|
// "Type must be aggregate initializable."
|
||
|
|
// );
|
||
|
|
//#endif
|
||
|
|
|
||
|
|
#if defined(_MSC_VER) && (_MSC_VER <= 1920)
|
||
|
|
// Workaround for msvc compilers. Versions <= 1920 have a limit of max 1024 elements in template parameter pack
|
||
|
|
constexpr std::size_t max_fields_count = (sizeof(type) * CHAR_BIT >= 1024 ? 1024 : sizeof(type) * CHAR_BIT);
|
||
|
|
#else
|
||
|
|
constexpr std::size_t max_fields_count = (sizeof(type) * CHAR_BIT); // We multiply by CHAR_BIT because the type may have bitfields in T
|
||
|
|
#endif
|
||
|
|
|
||
|
|
constexpr std::size_t result = detail::detect_fields_count_dispatch<type>(size_t_<max_fields_count>{}, 1L, 1L);
|
||
|
|
|
||
|
|
detail::assert_first_not_base<type>(detail::make_index_sequence<result>{});
|
||
|
|
|
||
|
|
#ifndef __cpp_lib_is_aggregate
|
||
|
|
static_assert(
|
||
|
|
is_aggregate_initializable_n<type, result>::value,
|
||
|
|
"====================> Boost.PFR: Types with user specified constructors (non-aggregate initializable types) are not supported."
|
||
|
|
);
|
||
|
|
#endif
|
||
|
|
|
||
|
|
static_assert(
|
||
|
|
result != 0 || std::is_empty<type>::value || std::is_fundamental<type>::value || std::is_reference<type>::value,
|
||
|
|
"====================> Boost.PFR: If there's no other failed static asserts then something went wrong. Please report this issue to the github along with the structure you're reflecting."
|
||
|
|
);
|
||
|
|
|
||
|
|
return result;
|
||
|
|
}
|
||
|
|
|
||
|
|
}}} // namespace boost::pfr::detail
|
||
|
|
|
||
|
|
#ifdef __clang__
|
||
|
|
# pragma clang diagnostic pop
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#endif // BOOST_PFR_DETAIL_FIELDS_COUNT_HPP
|