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Implement SFINAE friendly iterator_traits and use that instead.

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This commit is contained in:
David Avedissian 2018-11-07 18:39:25 +00:00
parent e3c28afb61
commit f665a92330
5 changed files with 120 additions and 20 deletions
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6
include/nlohmann/detail/input/input_adapters.hpp
View file

@ -331,7 +331,7 @@ class input_adapter
/// input adapter for iterator range with contiguous storage
template<class IteratorType,
typename std::enable_if<
std::is_same<typename std::iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
std::is_same<typename iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
int>::type = 0>
input_adapter(IteratorType first, IteratorType last)
{
@ -350,7 +350,7 @@ class input_adapter
// assertion to check that each element is 1 byte long
static_assert(
sizeof(typename std::iterator_traits<IteratorType>::value_type) == 1,
sizeof(typename iterator_traits<IteratorType>::value_type) == 1,
"each element in the iterator range must have the size of 1 byte");
const auto len = static_cast<size_t>(std::distance(first, last));
@ -374,7 +374,7 @@ class input_adapter
/// input adapter for contiguous container
template<class ContiguousContainer, typename
std::enable_if<not std::is_pointer<ContiguousContainer>::value and
std::is_base_of<std::random_access_iterator_tag, typename std::iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value,
std::is_base_of<std::random_access_iterator_tag, typename iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value,
int>::type = 0>
input_adapter(const ContiguousContainer& c)
: input_adapter(std::begin(c), std::end(c)) {}

47
include/nlohmann/detail/iterators/iterator_traits.hpp Normal file
View file

@ -0,0 +1,47 @@
#pragma once
#include <iterator> // random_access_iterator_tag
#include <nlohmann/detail/meta/void_t.hpp>
namespace nlohmann
{
namespace detail
{
template <class It, class = void>
struct _iterator_types {};
template <class It>
struct _iterator_types<
It,
void_t<typename It::difference_type, typename It::value_type, typename It::pointer,
typename It::reference, typename It::iterator_category>> {
using difference_type = typename It::difference_type;
using value_type = typename It::value_type;
using pointer = typename It::pointer;
using reference = typename It::reference;
using iterator_category = typename It::iterator_category;
};
template <class Iter>
struct iterator_traits : _iterator_types<Iter> {};
template <class T>
struct iterator_traits<T*> {
typedef std::random_access_iterator_tag iterator_category;
typedef T value_type;
typedef ptrdiff_t difference_type;
typedef T* pointer;
typedef T& reference;
};
template <class T>
struct iterator_traits<const T*> {
typedef std::random_access_iterator_tag iterator_category;
typedef T value_type;
typedef ptrdiff_t difference_type;
typedef const T* pointer;
typedef const T& reference;
};
}
}

9
include/nlohmann/detail/meta/type_traits.hpp
View file

@ -6,6 +6,7 @@
#include <utility> // declval
#include <nlohmann/json_fwd.hpp>
#include <nlohmann/detail/iterators/iterator_traits.hpp>
#include <nlohmann/detail/meta/cpp_future.hpp>
#include <nlohmann/detail/meta/detected.hpp>
#include <nlohmann/detail/macro_scope.hpp>
@ -131,10 +132,10 @@ template <typename T, typename = void>
struct is_iterator_traits : std::false_type {};
template <typename T>
struct is_iterator_traits<std::iterator_traits<T>>
struct is_iterator_traits<iterator_traits<T>>
{
private:
using traits = std::iterator_traits<T>;
using traits = iterator_traits<T>;
public:
static constexpr auto value =
@ -251,7 +252,7 @@ struct is_compatible_array_type_impl <
// Therefore it is detected as a CompatibleArrayType.
// The real fix would be to have an Iterable concept.
not is_iterator_traits<
std::iterator_traits<CompatibleArrayType>>::value >>
iterator_traits<CompatibleArrayType>>::value >>
{
static constexpr bool value =
std::is_constructible<BasicJsonType,
@ -288,7 +289,7 @@ struct is_constructible_array_type_impl <
// Therefore it is detected as a ConstructibleArrayType.
// The real fix would be to have an Iterable concept.
not is_iterator_traits <
std::iterator_traits<ConstructibleArrayType >>::value and
iterator_traits<ConstructibleArrayType >>::value and
(std::is_same<typename ConstructibleArrayType::value_type, typename BasicJsonType::array_t::value_type>::value or
has_from_json<BasicJsonType,

2
include/nlohmann/json.hpp
View file

@ -41,7 +41,7 @@ SOFTWARE.
#include <functional> // hash, less
#include <initializer_list> // initializer_list
#include <iosfwd> // istream, ostream
#include <iterator> // iterator_traits, random_access_iterator_tag
#include <iterator> // random_access_iterator_tag
#include <numeric> // accumulate
#include <string> // string, stoi, to_string
#include <utility> // declval, forward, move, pair, swap