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Merge pull request #624 from theodelrieu/feature/pair_tuple_conversions

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add pair/tuple conversions
This commit is contained in:
Niels Lohmann
2017-06-19 17:31:10 +02:00
committed by GitHub
parent 112a6f4e53 08d781058c
commit 4e6f548c0b
2 changed files with 136 additions and 2 deletions
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80
src/json.hpp
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@ -465,6 +465,39 @@ using enable_if_t = typename std::enable_if<B, T>::type;
template<typename T>
using uncvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
// implementation of C++14 index_sequence and affiliates
// source: https://stackoverflow.com/a/32223343
template <std::size_t... Ints>
struct index_sequence
{
using type = index_sequence;
using value_type = std::size_t;
static constexpr std::size_t size() noexcept
{
return sizeof...(Ints);
}
};
template <class Sequence1, class Sequence2>
struct merge_and_renumber;
template <std::size_t... I1, std::size_t... I2>
struct merge_and_renumber<index_sequence<I1...>, index_sequence<I2...>>
: index_sequence < I1..., (sizeof...(I1) + I2)... >
{ };
template <std::size_t N>
struct make_index_sequence
: merge_and_renumber < typename make_index_sequence < N / 2 >::type,
typename make_index_sequence < N - N / 2 >::type >
{ };
template<> struct make_index_sequence<0> : index_sequence<> { };
template<> struct make_index_sequence<1> : index_sequence<0> { };
template<typename... Ts>
using index_sequence_for = make_index_sequence<sizeof...(Ts)>;
/*
Implementation of two C++17 constructs: conjunction, negation. This is needed
to avoid evaluating all the traits in a condition
@ -866,6 +899,24 @@ void to_json(BasicJsonType& j, T (&arr)[N])
external_constructor<value_t::array>::construct(j, arr);
}
template <typename BasicJsonType, typename... Args>
void to_json(BasicJsonType& j, const std::pair<Args...>& p)
{
j = {p.first, p.second};
}
template <typename BasicJsonType, typename Tuple, std::size_t... Idx>
void to_json_tuple_impl(BasicJsonType& j, const Tuple& t, index_sequence<Idx...>)
{
j = {std::get<Idx>(t)...};
}
template <typename BasicJsonType, typename... Args>
void to_json(BasicJsonType& j, const std::tuple<Args...>& t)
{
to_json_tuple_impl(j, t, index_sequence_for<Args...> {});
}
///////////////
// from_json //
///////////////
@ -1012,6 +1063,15 @@ auto from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, prio
});
}
template <typename BasicJsonType, typename T, std::size_t N>
void from_json_array_impl(const BasicJsonType& j, std::array<T, N>& arr, priority_tag<2>)
{
for (std::size_t i = 0; i < N; ++i)
{
arr[i] = j.at(i).template get<T>();
}
}
template<typename BasicJsonType, typename CompatibleArrayType,
enable_if_t<is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value and
std::is_convertible<BasicJsonType, typename CompatibleArrayType::value_type>::value and
@ -1023,7 +1083,7 @@ void from_json(const BasicJsonType& j, CompatibleArrayType& arr)
JSON_THROW(type_error::create(302, "type must be array, but is " + j.type_name()));
}
from_json_array_impl(j, arr, priority_tag<1> {});
from_json_array_impl(j, arr, priority_tag<2> {});
}
template<typename BasicJsonType, typename CompatibleObjectType,
@ -1094,6 +1154,24 @@ void from_json(const BasicJsonType& j, ArithmeticType& val)
}
}
template <typename BasicJsonType, typename... Args>
void from_json(const BasicJsonType& j, std::pair<Args...>& p)
{
p = {j.at(0), j.at(1)};
}
template <typename BasicJsonType, typename Tuple, std::size_t... Idx>
void from_json_tuple_impl(const BasicJsonType& j, Tuple& t, index_sequence<Idx...>)
{
t = std::make_tuple(j.at(Idx)...);
}
template <typename BasicJsonType, typename... Args>
void from_json(const BasicJsonType& j, std::tuple<Args...>& t)
{
from_json_tuple_impl(j, t, index_sequence_for<Args...> {});
}
struct to_json_fn
{
private: