mirror of
https://github.com/nlohmann/json.git
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317 lines
11 KiB
C++
317 lines
11 KiB
C++
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#ifndef NLOHMANN_JSON_DETAIL_CONVERSIONS_FROM_JSON_HPP
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#define NLOHMANN_JSON_DETAIL_CONVERSIONS_FROM_JSON_HPP
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#include <array>
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#include <tuple>
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#include <utility>
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#include <valarray>
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#include "detail/exceptions.hpp"
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#include "detail/macro_scope.hpp"
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#include "detail/meta.hpp"
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#include "detail/value_t.hpp"
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namespace nlohmann
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{
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namespace detail
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{
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///////////////
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// from_json //
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///////////////
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// overloads for basic_json template parameters
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template<typename BasicJsonType, typename ArithmeticType,
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enable_if_t<std::is_arithmetic<ArithmeticType>::value and
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not std::is_same<ArithmeticType, typename BasicJsonType::boolean_t>::value,
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int> = 0>
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void get_arithmetic_value(const BasicJsonType& j, ArithmeticType& val)
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{
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switch (static_cast<value_t>(j))
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{
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case value_t::number_unsigned:
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{
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val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_unsigned_t*>());
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break;
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}
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case value_t::number_integer:
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{
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val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_integer_t*>());
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break;
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}
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case value_t::number_float:
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{
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val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_float_t*>());
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break;
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}
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default:
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JSON_THROW(type_error::create(302, "type must be number, but is " + std::string(j.type_name())));
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}
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}
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template<typename BasicJsonType>
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void from_json(const BasicJsonType& j, typename BasicJsonType::boolean_t& b)
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{
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if (JSON_UNLIKELY(not j.is_boolean()))
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{
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JSON_THROW(type_error::create(302, "type must be boolean, but is " + std::string(j.type_name())));
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}
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b = *j.template get_ptr<const typename BasicJsonType::boolean_t*>();
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}
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template<typename BasicJsonType>
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void from_json(const BasicJsonType& j, typename BasicJsonType::string_t& s)
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{
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if (JSON_UNLIKELY(not j.is_string()))
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{
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JSON_THROW(type_error::create(302, "type must be string, but is " + std::string(j.type_name())));
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}
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s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
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}
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template<typename BasicJsonType>
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void from_json(const BasicJsonType& j, typename BasicJsonType::number_float_t& val)
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{
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get_arithmetic_value(j, val);
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}
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template<typename BasicJsonType>
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void from_json(const BasicJsonType& j, typename BasicJsonType::number_unsigned_t& val)
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{
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get_arithmetic_value(j, val);
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}
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template<typename BasicJsonType>
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void from_json(const BasicJsonType& j, typename BasicJsonType::number_integer_t& val)
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{
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get_arithmetic_value(j, val);
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}
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template<typename BasicJsonType, typename EnumType,
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enable_if_t<std::is_enum<EnumType>::value, int> = 0>
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void from_json(const BasicJsonType& j, EnumType& e)
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{
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typename std::underlying_type<EnumType>::type val;
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get_arithmetic_value(j, val);
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e = static_cast<EnumType>(val);
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}
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template<typename BasicJsonType>
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void from_json(const BasicJsonType& j, typename BasicJsonType::array_t& arr)
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{
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if (JSON_UNLIKELY(not j.is_array()))
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{
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JSON_THROW(type_error::create(302, "type must be array, but is " + std::string(j.type_name())));
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}
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arr = *j.template get_ptr<const typename BasicJsonType::array_t*>();
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}
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// forward_list doesn't have an insert method
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template<typename BasicJsonType, typename T, typename Allocator,
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enable_if_t<std::is_convertible<BasicJsonType, T>::value, int> = 0>
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void from_json(const BasicJsonType& j, std::forward_list<T, Allocator>& l)
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{
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if (JSON_UNLIKELY(not j.is_array()))
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{
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JSON_THROW(type_error::create(302, "type must be array, but is " + std::string(j.type_name())));
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}
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std::transform(j.rbegin(), j.rend(),
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std::front_inserter(l), [](const BasicJsonType & i)
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{
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return i.template get<T>();
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});
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}
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// valarray doesn't have an insert method
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template<typename BasicJsonType, typename T,
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enable_if_t<std::is_convertible<BasicJsonType, T>::value, int> = 0>
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void from_json(const BasicJsonType& j, std::valarray<T>& l)
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{
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if (JSON_UNLIKELY(not j.is_array()))
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{
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JSON_THROW(type_error::create(302, "type must be array, but is " + std::string(j.type_name())));
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}
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l.resize(j.size());
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std::copy(j.m_value.array->begin(), j.m_value.array->end(), std::begin(l));
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}
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template<typename BasicJsonType, typename CompatibleArrayType>
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void from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, priority_tag<0> /*unused*/)
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{
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using std::end;
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std::transform(j.begin(), j.end(),
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std::inserter(arr, end(arr)), [](const BasicJsonType & i)
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{
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// get<BasicJsonType>() returns *this, this won't call a from_json
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// method when value_type is BasicJsonType
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return i.template get<typename CompatibleArrayType::value_type>();
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});
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}
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template<typename BasicJsonType, typename CompatibleArrayType>
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auto from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, priority_tag<1> /*unused*/)
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-> decltype(
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arr.reserve(std::declval<typename CompatibleArrayType::size_type>()),
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void())
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{
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using std::end;
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arr.reserve(j.size());
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std::transform(j.begin(), j.end(),
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std::inserter(arr, end(arr)), [](const BasicJsonType & i)
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{
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// get<BasicJsonType>() returns *this, this won't call a from_json
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// method when value_type is BasicJsonType
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return i.template get<typename CompatibleArrayType::value_type>();
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});
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}
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template<typename BasicJsonType, typename T, std::size_t N>
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void from_json_array_impl(const BasicJsonType& j, std::array<T, N>& arr, priority_tag<2> /*unused*/)
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{
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for (std::size_t i = 0; i < N; ++i)
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{
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arr[i] = j.at(i).template get<T>();
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}
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}
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template<typename BasicJsonType, typename CompatibleArrayType,
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enable_if_t<is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value and
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std::is_convertible<BasicJsonType, typename CompatibleArrayType::value_type>::value and
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not std::is_same<typename BasicJsonType::array_t, CompatibleArrayType>::value, int> = 0>
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void from_json(const BasicJsonType& j, CompatibleArrayType& arr)
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{
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if (JSON_UNLIKELY(not j.is_array()))
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{
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JSON_THROW(type_error::create(302, "type must be array, but is " + std::string(j.type_name())));
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}
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from_json_array_impl(j, arr, priority_tag<2> {});
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}
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template<typename BasicJsonType, typename CompatibleObjectType,
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enable_if_t<is_compatible_object_type<BasicJsonType, CompatibleObjectType>::value, int> = 0>
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void from_json(const BasicJsonType& j, CompatibleObjectType& obj)
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{
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if (JSON_UNLIKELY(not j.is_object()))
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{
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JSON_THROW(type_error::create(302, "type must be object, but is " + std::string(j.type_name())));
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}
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auto inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
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using value_type = typename CompatibleObjectType::value_type;
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std::transform(
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inner_object->begin(), inner_object->end(),
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std::inserter(obj, obj.begin()),
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[](typename BasicJsonType::object_t::value_type const & p)
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{
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return value_type(p.first, p.second.template get<typename CompatibleObjectType::mapped_type>());
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});
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}
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// overload for arithmetic types, not chosen for basic_json template arguments
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// (BooleanType, etc..); note: Is it really necessary to provide explicit
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// overloads for boolean_t etc. in case of a custom BooleanType which is not
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// an arithmetic type?
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template<typename BasicJsonType, typename ArithmeticType,
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enable_if_t <
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std::is_arithmetic<ArithmeticType>::value and
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not std::is_same<ArithmeticType, typename BasicJsonType::number_unsigned_t>::value and
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not std::is_same<ArithmeticType, typename BasicJsonType::number_integer_t>::value and
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not std::is_same<ArithmeticType, typename BasicJsonType::number_float_t>::value and
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not std::is_same<ArithmeticType, typename BasicJsonType::boolean_t>::value,
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int> = 0>
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void from_json(const BasicJsonType& j, ArithmeticType& val)
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{
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switch (static_cast<value_t>(j))
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{
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case value_t::number_unsigned:
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{
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val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_unsigned_t*>());
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break;
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}
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case value_t::number_integer:
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{
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val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_integer_t*>());
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break;
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}
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case value_t::number_float:
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{
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val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_float_t*>());
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break;
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}
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case value_t::boolean:
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{
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val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::boolean_t*>());
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break;
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}
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default:
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JSON_THROW(type_error::create(302, "type must be number, but is " + std::string(j.type_name())));
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}
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}
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template<typename BasicJsonType, typename A1, typename A2>
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void from_json(const BasicJsonType& j, std::pair<A1, A2>& p)
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{
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p = {j.at(0).template get<A1>(), j.at(1).template get<A2>()};
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}
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template<typename BasicJsonType, typename Tuple, std::size_t... Idx>
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void from_json_tuple_impl(const BasicJsonType& j, Tuple& t, index_sequence<Idx...>)
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{
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t = std::make_tuple(j.at(Idx).template get<typename std::tuple_element<Idx, Tuple>::type>()...);
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}
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template<typename BasicJsonType, typename... Args>
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void from_json(const BasicJsonType& j, std::tuple<Args...>& t)
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{
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from_json_tuple_impl(j, t, index_sequence_for<Args...> {});
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}
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struct from_json_fn
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{
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private:
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template<typename BasicJsonType, typename T>
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auto call(const BasicJsonType& j, T& val, priority_tag<1> /*unused*/) const
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noexcept(noexcept(from_json(j, val)))
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-> decltype(from_json(j, val), void())
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{
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return from_json(j, val);
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}
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template<typename BasicJsonType, typename T>
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void call(const BasicJsonType& /*unused*/, T& /*unused*/, priority_tag<0> /*unused*/) const noexcept
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{
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static_assert(sizeof(BasicJsonType) == 0,
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"could not find from_json() method in T's namespace");
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#ifdef _MSC_VER
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// MSVC does not show a stacktrace for the above assert
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using decayed = uncvref_t<T>;
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static_assert(sizeof(typename decayed::force_msvc_stacktrace) == 0,
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"forcing MSVC stacktrace to show which T we're talking about.");
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#endif
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}
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public:
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template<typename BasicJsonType, typename T>
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void operator()(const BasicJsonType& j, T& val) const
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noexcept(noexcept(std::declval<from_json_fn>().call(j, val, priority_tag<1> {})))
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{
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return call(j, val, priority_tag<1> {});
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}
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};
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}
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/// namespace to hold default `from_json` function
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/// to see why this is required:
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/// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4381.html
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namespace
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{
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constexpr const auto& from_json = detail::static_const<detail::from_json_fn>::value;
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}
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}
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#endif
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