mysql/impl/pfr.hpp

0001 //
0002 // Copyright (c) 2019-2024 Ruben Perez Hidalgo (rubenperez038 at gmail dot com)
0003 //
0004 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0005 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 //
0007
0008 #ifndef BOOST_MYSQL_IMPL_PFR_HPP
0009 #define BOOST_MYSQL_IMPL_PFR_HPP
0010
0011 #pragma once
0012
0013 #include <boost/config.hpp>
0014
0015 // Silence PFR warnings caused by https://github.com/boostorg/pfr/issues/166
0016 // Only affecting gcc-11+, and caused during the inclusion of the library
0017 #if BOOST_GCC >= 110000
0018 #pragma GCC diagnostic push
0019 #pragma GCC diagnostic ignored "-Wpragmas"
0020 #endif
0021
0022 // Silence MSVC 14.1 warnings caused by https://github.com/boostorg/pfr/issues/167
0023 #if defined(BOOST_MSVC) && BOOST_MSVC < 1920
0024 #pragma warning(push)
0025 #pragma warning(disable : 4100)
0026 #endif
0027
0028 #include <boost/mysql/pfr.hpp>
0029 #include <boost/mysql/string_view.hpp>
0030
0031 #include <boost/mysql/detail/typing/row_traits.hpp>
0032
0033 #include <boost/pfr/core.hpp>
0034 #include <boost/pfr/core_name.hpp>
0035 #include <boost/pfr/traits.hpp>
0036
0037 #include <type_traits>
0038 #include <utility>
0039
0040 #if BOOST_PFR_CORE_NAME_ENABLED
0041 #include <array>
0042 #include <cstddef>
0043 #include <string_view>
0044 #endif
0045
0046 #if BOOST_GCC >= 110000
0047 #pragma GCC diagnostic pop
0048 #endif
0049
0050 namespace boost {
0051 namespace mysql {
0052 namespace detail {
0053
0054 // Not all types reflected by PFR are acceptable for us - this function performs this checking
0055 template <class T>
0056 constexpr bool is_pfr_reflectable() noexcept
0057 {
0058     return std::is_class<T>::value && !std::is_const<T>::value
0059     // is_implicitly_reflectable_v returns always false when implicit reflection
0060     // (which requires structured bindings and C++17) is not available
0061 #if BOOST_PFR_ENABLE_IMPLICIT_REFLECTION
0062            && pfr::is_implicitly_reflectable_v<T, struct mysql_tag>
0063 #endif
0064         ;
0065 }
0066
0067 template <class T>
0068 using pfr_fields_t = decltype(pfr::structure_to_tuple(std::declval<const T&>()));
0069
0070 #if BOOST_PFR_CORE_NAME_ENABLED
0071
0072 // PFR field names use std::string_view
0073 template <std::size_t N>
0074 constexpr std::array<string_view, N> to_name_table_storage(std::array<std::string_view, N> input) noexcept
0075 {
0076     std::array<string_view, N> res;
0077     for (std::size_t i = 0; i < N; ++i)
0078         res[i] = input[i];
0079     return res;
0080 }
0081
0082 // Workaround for https://github.com/boostorg/pfr/issues/165
0083 constexpr std::array<string_view, 0u> to_name_table_storage(std::array<std::nullptr_t, 0u>) noexcept
0084 {
0085     return {};
0086 }
0087
0088 template <class T>
0089 constexpr inline auto pfr_names_storage = to_name_table_storage(pfr::names_as_array<T>());
0090
0091 template <class T>
0092 class row_traits<pfr_by_name<T>, false>
0093 {
0094     static_assert(
0095         is_pfr_reflectable<T>(),
0096         "T needs to be a non-const object type that supports PFR reflection"
0097     );
0098
0099 public:
0100     using underlying_row_type = T;
0101     using field_types = pfr_fields_t<T>;
0102
0103     static constexpr name_table_t name_table() noexcept { return pfr_names_storage<T>; }
0104
0105     template <class F>
0106     static void for_each_member(T& to, F&& function)
0107     {
0108         pfr::for_each_field(to, std::forward<F>(function));
0109     }
0110 };
0111
0112 #endif
0113
0114 template <class T>
0115 class row_traits<pfr_by_position<T>, false>
0116 {
0117     static_assert(
0118         is_pfr_reflectable<T>(),
0119         "T needs to be a non-const object type that supports PFR reflection"
0120     );
0121
0122 public:
0123     using underlying_row_type = T;
0124     using field_types = pfr_fields_t<T>;
0125
0126     static constexpr name_table_t name_table() noexcept { return {}; }
0127
0128     template <class F>
0129     static void for_each_member(T& to, F&& function)
0130     {
0131         pfr::for_each_field(to, std::forward<F>(function));
0132     }
0133 };
0134
0135 }  // namespace detail
0136 }  // namespace mysql
0137 }  // namespace boost
0138
0139 #if defined(BOOST_MSVC) && BOOST_MSVC < 1920
0140 #pragma warning(pop)
0141 #endif
0142
0143 #endif