282 lines
6.4 KiB
C++
282 lines
6.4 KiB
C++
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//
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// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
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// Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com)
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// Copyright (c) 2021 Dmitry Arkhipov (grisumbras@gmail.com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/json
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//
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#ifndef BOOST_JSON_DETAIL_VALUE_TO_HPP
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#define BOOST_JSON_DETAIL_VALUE_TO_HPP
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#include <boost/json/value.hpp>
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#include <boost/json/detail/value_traits.hpp>
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#include <boost/mp11/integer_sequence.hpp>
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#include <type_traits>
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BOOST_JSON_NS_BEGIN
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template<class>
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struct value_to_tag { };
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template<class, class = void>
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struct has_value_to;
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template<class T, class U,
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typename std::enable_if<
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! std::is_reference<T>::value &&
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std::is_same<U, value>::value>::type>
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T value_to(U const&);
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namespace detail {
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template<class T, typename std::enable_if<
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(std::tuple_size<remove_cvref<T>>::value > 0)>::type* = nullptr>
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void
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try_reserve(
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T&,
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std::size_t size,
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priority_tag<2>)
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{
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constexpr std::size_t N = std::tuple_size<remove_cvref<T>>::value;
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if ( N != size )
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{
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detail::throw_invalid_argument(
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"target array size does not match source array size",
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BOOST_JSON_SOURCE_POS);
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}
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}
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template<typename T, void_t<decltype(
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std::declval<T&>().reserve(0))>* = nullptr>
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void
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try_reserve(
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T& cont,
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std::size_t size,
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priority_tag<1>)
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{
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cont.reserve(size);
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}
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template<typename T>
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void
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try_reserve(
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T&,
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std::size_t,
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priority_tag<0>)
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{
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}
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template<class T, typename std::enable_if<
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(std::tuple_size<remove_cvref<T>>::value > 0)>::type* = nullptr>
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typename remove_cvref<T>::iterator
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inserter(
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T& target,
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priority_tag<1>)
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{
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return target.begin();
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}
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template<class T>
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std::insert_iterator<T>
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inserter(
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T& target,
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priority_tag<0>)
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{
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return std::inserter(target, end(target));
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}
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//----------------------------------------------------------
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// Use native conversion
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// identity conversion
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inline
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value
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tag_invoke(
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value_to_tag<value>,
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value const& jv)
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{
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return jv;
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}
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// object
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inline
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object
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tag_invoke(
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value_to_tag<object>,
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value const& jv)
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{
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return jv.as_object();
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}
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// array
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inline
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array
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tag_invoke(
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value_to_tag<array>,
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value const& jv)
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{
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return jv.as_array();
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}
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// string
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inline
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string
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tag_invoke(
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value_to_tag<string>,
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value const& jv)
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{
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return jv.as_string();
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}
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// bool
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inline
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bool
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tag_invoke(
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value_to_tag<bool>,
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value const& jv)
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{
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return jv.as_bool();
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}
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// integral and floating point
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template<class T, typename std::enable_if<
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std::is_arithmetic<T>::value>::type* = nullptr>
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T
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tag_invoke(
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value_to_tag<T>,
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value const& jv)
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{
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return jv.to_number<T>();
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}
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//----------------------------------------------------------
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// Use generic conversion
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// string-like types
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// NOTE: original check for size used is_convertible but
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// MSVC-140 selects wrong specialisation if used
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template<class T, typename std::enable_if<
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std::is_constructible<T, const char*, std::size_t>::value &&
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std::is_convertible<decltype(std::declval<T&>().data()), const char*>::value &&
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std::is_integral<decltype(std::declval<T&>().size())>::value
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>::type* = nullptr>
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T
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value_to_generic(
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const value& jv,
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priority_tag<3>)
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{
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auto& str = jv.as_string();
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return T(str.data(), str.size());
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}
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// map-like containers; should go before other containers in order to be able
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// to tell them apart
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template<class T, typename std::enable_if<
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has_value_to<typename map_traits<T>::pair_value_type>::value &&
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std::is_constructible<typename map_traits<T>::pair_key_type,
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string_view>::value>::type* = nullptr>
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T
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value_to_generic(
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const value& jv,
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priority_tag<2>)
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{
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using value_type = typename
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container_traits<T>::value_type;
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const object& obj = jv.as_object();
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T result;
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try_reserve(result, obj.size(), priority_tag<2>());
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for (const auto& val : obj)
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result.insert(value_type{typename map_traits<T>::
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pair_key_type(val.key()), value_to<typename
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map_traits<T>::pair_value_type>(val.value())});
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return result;
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}
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// all other containers; should go before tuple-like in order to handle
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// std::array with this overload
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template<class T, typename std::enable_if<
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has_value_to<typename container_traits<T>::
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value_type>::value>::type* = nullptr>
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T
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value_to_generic(
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const value& jv,
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priority_tag<1>)
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{
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const array& arr = jv.as_array();
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T result;
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detail::try_reserve(result, arr.size(), priority_tag<2>());
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std::transform(arr.begin(), arr.end(),
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detail::inserter(result, priority_tag<1>()), [](value const& val) {
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return value_to<typename container_traits<T>::value_type>(val);
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});
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return result;
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}
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template <class T, std::size_t... Is>
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T
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make_tuple_like(const array& arr, boost::mp11::index_sequence<Is...>)
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{
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return T(value_to<typename std::tuple_element<Is, T>::type>(arr[Is])...);
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}
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// tuple-like types
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template<class T, typename std::enable_if<
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(std::tuple_size<remove_cvref<T>>::value > 0)>::type* = nullptr>
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T
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value_to_generic(
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const value& jv,
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priority_tag<0>)
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{
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auto& arr = jv.as_array();
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constexpr std::size_t N = std::tuple_size<remove_cvref<T>>::value;
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if ( N != arr.size() )
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{
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detail::throw_invalid_argument(
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"array size does not match tuple size",
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BOOST_JSON_SOURCE_POS);
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}
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return make_tuple_like<T>(arr, boost::mp11::make_index_sequence<N>());
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}
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// Matches containers
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template<class T, void_t<typename std::enable_if<
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!std::is_constructible<T, const value&>::value &&
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!std::is_arithmetic<T>::value>::type, decltype(
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value_to_generic<T>(std::declval<const value&>(),
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priority_tag<2>()))>* = nullptr>
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T
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tag_invoke(
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value_to_tag<T>,
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value const& jv)
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{
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return value_to_generic<T>(
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jv, priority_tag<3>());
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}
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//----------------------------------------------------------
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// Calls to value_to are forwarded to this function
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// so we can use ADL and hide the built-in tag_invoke
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// overloads in the detail namespace
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template<class T, void_t<
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decltype(tag_invoke(std::declval<value_to_tag<T>&>(),
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std::declval<const value&>()))>* = nullptr>
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T
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value_to_impl(
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value_to_tag<T> tag,
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value const& jv)
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{
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return tag_invoke(tag, jv);
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}
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} // detail
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BOOST_JSON_NS_END
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#endif
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