mirror of
https://github.com/nlohmann/json
synced 2024-11-26 22:00:07 +00:00
8711ec6034
Before this patch, `basic_json` types with different template arguments were treated as `CompatibleArrayType`. Which sometimes leads to recursive calls and stack overflows. This patch adds a constructor and a `get` overload to deal with different `basic_json` types.
259 lines
9.3 KiB
C++
259 lines
9.3 KiB
C++
#pragma once
|
|
|
|
#include <ciso646> // not
|
|
#include <cstddef> // size_t
|
|
#include <limits> // numeric_limits
|
|
#include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
|
|
#include <utility> // declval
|
|
|
|
#include <nlohmann/json_fwd.hpp>
|
|
#include <nlohmann/detail/macro_scope.hpp>
|
|
|
|
namespace nlohmann
|
|
{
|
|
/*!
|
|
@brief detail namespace with internal helper functions
|
|
|
|
This namespace collects functions that should not be exposed,
|
|
implementations of some @ref basic_json methods, and meta-programming helpers.
|
|
|
|
@since version 2.1.0
|
|
*/
|
|
namespace detail
|
|
{
|
|
/////////////
|
|
// helpers //
|
|
/////////////
|
|
|
|
template<typename> struct is_basic_json : std::false_type {};
|
|
|
|
NLOHMANN_BASIC_JSON_TPL_DECLARATION
|
|
struct is_basic_json<NLOHMANN_BASIC_JSON_TPL> : std::true_type {};
|
|
|
|
// 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> {};
|
|
|
|
////////////////////////
|
|
// has_/is_ functions //
|
|
////////////////////////
|
|
|
|
// source: https://stackoverflow.com/a/37193089/4116453
|
|
|
|
template <typename T, typename = void>
|
|
struct is_complete_type : std::false_type {};
|
|
|
|
template <typename T>
|
|
struct is_complete_type<T, decltype(void(sizeof(T)))> : std::true_type {};
|
|
|
|
NLOHMANN_JSON_HAS_HELPER(mapped_type);
|
|
NLOHMANN_JSON_HAS_HELPER(key_type);
|
|
NLOHMANN_JSON_HAS_HELPER(value_type);
|
|
NLOHMANN_JSON_HAS_HELPER(iterator);
|
|
|
|
template<bool B, class RealType, class CompatibleObjectType>
|
|
struct is_compatible_object_type_impl : std::false_type {};
|
|
|
|
template<class RealType, class CompatibleObjectType>
|
|
struct is_compatible_object_type_impl<true, RealType, CompatibleObjectType>
|
|
{
|
|
static constexpr auto value =
|
|
std::is_constructible<typename RealType::key_type, typename CompatibleObjectType::key_type>::value and
|
|
std::is_constructible<typename RealType::mapped_type, typename CompatibleObjectType::mapped_type>::value;
|
|
};
|
|
|
|
template<class BasicJsonType, class CompatibleObjectType>
|
|
struct is_compatible_object_type
|
|
{
|
|
static auto constexpr value = is_compatible_object_type_impl <
|
|
conjunction<negation<std::is_same<void, CompatibleObjectType>>,
|
|
has_mapped_type<CompatibleObjectType>,
|
|
has_key_type<CompatibleObjectType>>::value,
|
|
typename BasicJsonType::object_t, CompatibleObjectType >::value;
|
|
};
|
|
|
|
template<typename BasicJsonType, typename T>
|
|
struct is_basic_json_nested_type
|
|
{
|
|
static auto constexpr value = std::is_same<T, typename BasicJsonType::iterator>::value or
|
|
std::is_same<T, typename BasicJsonType::const_iterator>::value or
|
|
std::is_same<T, typename BasicJsonType::reverse_iterator>::value or
|
|
std::is_same<T, typename BasicJsonType::const_reverse_iterator>::value;
|
|
};
|
|
|
|
template<class BasicJsonType, class CompatibleArrayType>
|
|
struct is_compatible_array_type
|
|
{
|
|
static auto constexpr value =
|
|
conjunction<negation<std::is_same<void, CompatibleArrayType>>,
|
|
negation<is_compatible_object_type<
|
|
BasicJsonType, CompatibleArrayType>>,
|
|
negation<std::is_constructible<typename BasicJsonType::string_t,
|
|
CompatibleArrayType>>,
|
|
negation<is_basic_json_nested_type<BasicJsonType, CompatibleArrayType>>,
|
|
has_value_type<CompatibleArrayType>,
|
|
has_iterator<CompatibleArrayType>>::value;
|
|
};
|
|
|
|
template<bool, typename, typename>
|
|
struct is_compatible_integer_type_impl : std::false_type {};
|
|
|
|
template<typename RealIntegerType, typename CompatibleNumberIntegerType>
|
|
struct is_compatible_integer_type_impl<true, RealIntegerType, CompatibleNumberIntegerType>
|
|
{
|
|
// is there an assert somewhere on overflows?
|
|
using RealLimits = std::numeric_limits<RealIntegerType>;
|
|
using CompatibleLimits = std::numeric_limits<CompatibleNumberIntegerType>;
|
|
|
|
static constexpr auto value =
|
|
std::is_constructible<RealIntegerType, CompatibleNumberIntegerType>::value and
|
|
CompatibleLimits::is_integer and
|
|
RealLimits::is_signed == CompatibleLimits::is_signed;
|
|
};
|
|
|
|
template<typename RealIntegerType, typename CompatibleNumberIntegerType>
|
|
struct is_compatible_integer_type
|
|
{
|
|
static constexpr auto value =
|
|
is_compatible_integer_type_impl <
|
|
std::is_integral<CompatibleNumberIntegerType>::value and
|
|
not std::is_same<bool, CompatibleNumberIntegerType>::value,
|
|
RealIntegerType, CompatibleNumberIntegerType > ::value;
|
|
};
|
|
|
|
// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
|
|
template<typename BasicJsonType, typename T>
|
|
struct has_from_json
|
|
{
|
|
private:
|
|
// also check the return type of from_json
|
|
template<typename U, typename = enable_if_t<std::is_same<void, decltype(uncvref_t<U>::from_json(
|
|
std::declval<BasicJsonType>(), std::declval<T&>()))>::value>>
|
|
static int detect(U&&);
|
|
static void detect(...);
|
|
|
|
public:
|
|
static constexpr bool value = std::is_integral<decltype(
|
|
detect(std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
|
|
};
|
|
|
|
// This trait checks if JSONSerializer<T>::from_json(json const&) exists
|
|
// this overload is used for non-default-constructible user-defined-types
|
|
template<typename BasicJsonType, typename T>
|
|
struct has_non_default_from_json
|
|
{
|
|
private:
|
|
template <
|
|
typename U,
|
|
typename = enable_if_t<std::is_same<
|
|
T, decltype(uncvref_t<U>::from_json(std::declval<BasicJsonType>()))>::value >>
|
|
static int detect(U&&);
|
|
static void detect(...);
|
|
|
|
public:
|
|
static constexpr bool value = std::is_integral<decltype(detect(
|
|
std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
|
|
};
|
|
|
|
// This trait checks if BasicJsonType::json_serializer<T>::to_json exists
|
|
template<typename BasicJsonType, typename T>
|
|
struct has_to_json
|
|
{
|
|
private:
|
|
template<typename U, typename = decltype(uncvref_t<U>::to_json(
|
|
std::declval<BasicJsonType&>(), std::declval<T>()))>
|
|
static int detect(U&&);
|
|
static void detect(...);
|
|
|
|
public:
|
|
static constexpr bool value = std::is_integral<decltype(detect(
|
|
std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
|
|
};
|
|
|
|
template <typename BasicJsonType, typename CompatibleCompleteType>
|
|
struct is_compatible_complete_type
|
|
{
|
|
static constexpr bool value =
|
|
not std::is_base_of<std::istream, CompatibleCompleteType>::value and
|
|
not is_basic_json<CompatibleCompleteType>::value and
|
|
not is_basic_json_nested_type<BasicJsonType, CompatibleCompleteType>::value and
|
|
has_to_json<BasicJsonType, CompatibleCompleteType>::value;
|
|
};
|
|
|
|
template <typename BasicJsonType, typename CompatibleType>
|
|
struct is_compatible_type
|
|
: conjunction<is_complete_type<CompatibleType>,
|
|
is_compatible_complete_type<BasicJsonType, CompatibleType>>
|
|
{
|
|
};
|
|
|
|
// taken from ranges-v3
|
|
template<typename T>
|
|
struct static_const
|
|
{
|
|
static constexpr T value{};
|
|
};
|
|
|
|
template<typename T>
|
|
constexpr T static_const<T>::value;
|
|
}
|
|
}
|