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uyhauyha
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implement as and pack for std::variant 
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‎include/msgpack/adaptor/cpp17/variant.hpp‎

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//
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// MessagePack for C++ static resolution routine
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//
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// Copyright (C) 2023 Uy Ha
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef MSGPACK_TYPE_CPP17_VARIANT_HPP
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#define MSGPACK_TYPE_CPP17_VARIANT_HPP
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#include "msgpack/v1/adaptor/cpp17/variant.hpp"
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#endif // MSGPACK_TYPE_CPP17_VARIANT_HPP

‎include/msgpack/type.hpp‎

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#include "adaptor/cpp17/carray_byte.hpp"
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#include "adaptor/cpp17/vector_byte.hpp"
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#if MSGPACK_HAS_INCLUDE(<variant>)
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#include "adaptor/cpp17/variant.hpp"
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#endif // MSGPACK_HAS_INCLUDE(<variant>)
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#if MSGPACK_HAS_INCLUDE(<span>)
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#include "adaptor/cpp20/span.hpp"
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#endif // MSGPACK_HAS_INCLUDE(<span>)

‎include/msgpack/v1/adaptor/cpp17/variant.hpp‎

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//
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// MessagePack for C++ static resolution routine
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//
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// Copyright (C) 2023 Uy Ha
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef MSGPACK_V1_TYPE_VARIANT_HPP
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#define MSGPACK_V1_TYPE_VARIANT_HPP
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#define MSGPACK_USE_STD_VARIANT_ADAPTOR
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#if defined(MSGPACK_USE_STD_VARIANT_ADAPTOR)
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#include "msgpack/cpp_version.hpp"
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#if MSGPACK_CPP_VERSION >= 201703
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#include "msgpack/adaptor/adaptor_base.hpp"
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#include "msgpack/object.hpp"
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#include "msgpack/versioning.hpp"
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#include <variant>
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namespace msgpack {
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MSGPACK_API_VERSION_NAMESPACE(v1) {
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namespace adaptor {
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namespace detail {
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template <typename Variant, typename T, typename... Ts, std::size_t current_index, std::size_t... indices>
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Variant construct_variant(std::size_t index,
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msgpack::object &object,
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std::index_sequence<current_index, indices...>) {
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if constexpr(sizeof...(Ts) == 0) {
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return object.as<T>();
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} else {
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if (index == current_index) {
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return object.as<T>();
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}
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return construct_variant<Variant, Ts...>(index, object, std::index_sequence<indices...>());
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}
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}
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} // namespace detail
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template <typename... Ts>
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struct as<std::variant<Ts...>, std::enable_if_t<(msgpack::has_as<Ts>::value && ...)>> {
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std::variant<Ts...> operator()(msgpack::object const &o) const {
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if (o.type != msgpack::type::ARRAY) {
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throw msgpack::type_error{};
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}
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if (o.via.array.size != 2) {
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throw msgpack::type_error{};
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}
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if (o.via.array.ptr[0].type != msgpack::type::POSITIVE_INTEGER) {
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throw msgpack::type_error{};
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}
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return detail::construct_variant<std::variant<Ts...>, Ts...>(
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o.via.array.ptr[0].as<std::size_t>(),
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o.via.array.ptr[1],
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std::make_index_sequence<sizeof...(Ts)>()
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);
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}
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};
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template<typename... Ts>
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struct convert<std::variant<Ts...>> {
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msgpack::object const &operator()(msgpack::object const &o, std::variant<Ts...> &v) const {
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if (o.type != msgpack::type::ARRAY) {
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throw msgpack::type_error{};
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}
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if (o.via.array.size != 2) {
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throw msgpack::type_error{};
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}
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if (o.via.array.ptr[0].type != msgpack::type::POSITIVE_INTEGER) {
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throw msgpack::type_error{};
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}
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v = detail::construct_variant<std::variant<Ts...>, Ts...>(
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o.via.array.ptr[0].as<std::size_t>(),
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o.via.array.ptr[1],
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std::make_index_sequence<sizeof...(Ts)>()
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);
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return o;
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}
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};
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template <typename... Ts>
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struct pack<std::variant<Ts...>>{
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template<typename Stream>
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msgpack::packer<Stream>& operator()(msgpack::packer<Stream> &o, std::variant<Ts...> const &v) const {
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o.pack_array(2);
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o.pack_uint64(v.index());
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std::visit([&o](auto const &real_value){o.pack(real_value);}, v);
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return o;
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}
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};
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// template <typename... Ts>
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// struct object<std::variant<Ts...>> {
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// void operator()(msgpack::object &o, std::variant<Ts...> const &v) const {
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// o.type = msgpack::type::ARRAY;
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// o.via.array.size = 2;
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// msgpack::adaptor::object<std::size_t>(o.via.array.ptr[0], v.index());
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// std::visit([&o](auto const &value) {
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// msgpack::adaptor::object(o.via.array.ptr[1], value);
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// }, v);
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// }
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// };
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//
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// template<typename... Ts>
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// struct object_with_zone<std::variant<Ts...>> {
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// void operator()(msgpack::object::with_zone &o, std::variant<Ts...> const &v) const {
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// o.type = msgpack::type::ARRAY;
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//
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// msgpack::object *p = static_cast<msgpack::object *>(o.zone.allocate_align(sizeof(msgpack::object) * 2, MSGPACK_ZONE_ALIGNOF(msgpack::object)));
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//
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// o.via.array.size = 2;
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// o.via.array.ptr = p;
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// msgpack::adaptor::object_with_zone<std::size_t>()(o.via.array.ptr[0], v.index(), o.zone);
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// std::visit([&o](auto const &real_value){
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// o.via.array.ptr[1] = msgpack::adaptor::object()(real_value, o.zone);
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// }, v);
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// }
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// };
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} // namespace adaptor
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}
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} // namespace msgpack
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#endif // MSGPACK_CPP_VERSION >= 201703
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#endif // defined(MSGPACK_USE_STD_VARIANT_ADAPTOR)
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#endif // MSGPACK_V1_TYPE_VARIANT_HPP

‎test/msgpack_cpp17.cpp‎

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}
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}
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BOOST_AUTO_TEST_CASE(variant_as) {
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std::stringstream ss;
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std::variant<bool, int, float, double> val1{1.0};
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msgpack::pack(ss, val1);
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std::string const& str = ss.str();
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msgpack::object_handle oh =
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msgpack::unpack(str.data(), str.size());
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std::variant<bool, int, float, double> val2 = oh.get().as<std::variant<bool, int, float, double> >();
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BOOST_CHECK(val1 == val2);
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}
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#endif // MSGPACK_CPP_VERSION >= 201703

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