mirror of
https://github.com/nlohmann/json.git
synced 2024-08-23 13:32:28 +02:00
84 lines
2.7 KiB
C++
84 lines
2.7 KiB
C++
#pragma once
|
|
|
|
#include <ciso646> // not
|
|
#include <cstddef> // size_t
|
|
#include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
|
|
|
|
namespace nlohmann
|
|
{
|
|
namespace detail
|
|
{
|
|
// alias templates to reduce boilerplate
|
|
template<bool B, typename T = void>
|
|
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
|
|
|
|
For example: not std::is_same<void, T>::value and has_value_type<T>::value
|
|
will not compile when T = void (on MSVC at least). Whereas
|
|
conjunction<negation<std::is_same<void, T>>, has_value_type<T>>::value will
|
|
stop evaluating if negation<...>::value == false
|
|
|
|
Please note that those constructs must be used with caution, since symbols can
|
|
become very long quickly (which can slow down compilation and cause MSVC
|
|
internal compiler errors). Only use it when you have to (see example ahead).
|
|
*/
|
|
template<class...> struct conjunction : std::true_type {};
|
|
template<class B1> struct conjunction<B1> : B1 {};
|
|
template<class B1, class... Bn>
|
|
struct conjunction<B1, Bn...> : std::conditional<bool(B1::value), conjunction<Bn...>, B1>::type {};
|
|
|
|
template<class B> struct negation : std::integral_constant<bool, not B::value> {};
|
|
|
|
// dispatch utility (taken from ranges-v3)
|
|
template<unsigned N> struct priority_tag : priority_tag < N - 1 > {};
|
|
template<> struct priority_tag<0> {};
|
|
|
|
// taken from ranges-v3
|
|
template<typename T>
|
|
struct static_const
|
|
{
|
|
static constexpr T value{};
|
|
};
|
|
|
|
template<typename T>
|
|
constexpr T static_const<T>::value;
|
|
}
|
|
}
|