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iteration_proxy.hpp
1#pragma once
2
3#include <cstddef> // size_t
4#include <iterator> // input_iterator_tag
5#include <string> // string, to_string
6#include <tuple> // tuple_size, get, tuple_element
7#include <utility> // move
8
9#include <nlohmann/detail/meta/type_traits.hpp>
10#include <nlohmann/detail/value_t.hpp>
11
12namespace nlohmann
13{
14namespace detail
15{
16template<typename string_type>
17void int_to_string( string_type& target, std::size_t value )
18{
19 // For ADL
20 using std::to_string;
21 target = to_string(value);
22}
23template<typename IteratorType> class iteration_proxy_value
24{
25 public:
26 using difference_type = std::ptrdiff_t;
28 using pointer = value_type * ;
29 using reference = value_type & ;
30 using iterator_category = std::input_iterator_tag;
31 using string_type = typename std::remove_cv< typename std::remove_reference<decltype( std::declval<IteratorType>().key() ) >::type >::type;
32
33 private:
35 IteratorType anchor;
37 std::size_t array_index = 0;
39 mutable std::size_t array_index_last = 0;
41 mutable string_type array_index_str = "0";
43 const string_type empty_str{};
44
45 public:
46 explicit iteration_proxy_value(IteratorType it) noexcept
47 : anchor(std::move(it))
48 {}
49
52 {
53 return *this;
54 }
55
58 {
59 ++anchor;
60 ++array_index;
61
62 return *this;
63 }
64
66 bool operator==(const iteration_proxy_value& o) const
67 {
68 return anchor == o.anchor;
69 }
70
72 bool operator!=(const iteration_proxy_value& o) const
73 {
74 return anchor != o.anchor;
75 }
76
78 const string_type& key() const
79 {
80 JSON_ASSERT(anchor.m_object != nullptr);
81
82 switch (anchor.m_object->type())
83 {
84 // use integer array index as key
85 case value_t::array:
86 {
87 if (array_index != array_index_last)
88 {
89 int_to_string( array_index_str, array_index );
90 array_index_last = array_index;
91 }
92 return array_index_str;
93 }
94
95 // use key from the object
96 case value_t::object:
97 return anchor.key();
98
99 // use an empty key for all primitive types
100 case value_t::null:
101 case value_t::string:
102 case value_t::boolean:
106 case value_t::binary:
108 default:
109 return empty_str;
110 }
111 }
112
114 typename IteratorType::reference value() const
115 {
116 return anchor.value();
117 }
118};
119
121template<typename IteratorType> class iteration_proxy
122{
123 private:
125 typename IteratorType::reference container;
126
127 public:
129 explicit iteration_proxy(typename IteratorType::reference cont) noexcept
130 : container(cont) {}
131
134 {
135 return iteration_proxy_value<IteratorType>(container.begin());
136 }
137
140 {
141 return iteration_proxy_value<IteratorType>(container.end());
142 }
143};
144// Structured Bindings Support
145// For further reference see https://blog.tartanllama.xyz/structured-bindings/
146// And see https://github.com/nlohmann/json/pull/1391
147template<std::size_t N, typename IteratorType, enable_if_t<N == 0, int> = 0>
148auto get(const nlohmann::detail::iteration_proxy_value<IteratorType>& i) -> decltype(i.key())
149{
150 return i.key();
151}
152// Structured Bindings Support
153// For further reference see https://blog.tartanllama.xyz/structured-bindings/
154// And see https://github.com/nlohmann/json/pull/1391
155template<std::size_t N, typename IteratorType, enable_if_t<N == 1, int> = 0>
156auto get(const nlohmann::detail::iteration_proxy_value<IteratorType>& i) -> decltype(i.value())
157{
158 return i.value();
159}
160} // namespace detail
161} // namespace nlohmann
162
163// The Addition to the STD Namespace is required to add
164// Structured Bindings Support to the iteration_proxy_value class
165// For further reference see https://blog.tartanllama.xyz/structured-bindings/
166// And see https://github.com/nlohmann/json/pull/1391
167namespace std
168{
169#if defined(__clang__)
170 // Fix: https://github.com/nlohmann/json/issues/1401
171 #pragma clang diagnostic push
172 #pragma clang diagnostic ignored "-Wmismatched-tags"
173#endif
174template<typename IteratorType>
175class tuple_size<::nlohmann::detail::iteration_proxy_value<IteratorType>>
176 : public std::integral_constant<std::size_t, 2> {};
177
178template<std::size_t N, typename IteratorType>
179class tuple_element<N, ::nlohmann::detail::iteration_proxy_value<IteratorType >>
180{
181 public:
182 using type = decltype(
183 get<N>(std::declval <
185};
186#if defined(__clang__)
187 #pragma clang diagnostic pop
188#endif
189} // namespace std
Definition iteration_proxy.hpp:24
bool operator!=(const iteration_proxy_value &o) const
inequality operator (needed for range-based for)
Definition iteration_proxy.hpp:72
IteratorType::reference value() const
return value of the iterator
Definition iteration_proxy.hpp:114
iteration_proxy_value & operator++()
increment operator (needed for range-based for)
Definition iteration_proxy.hpp:57
iteration_proxy_value & operator*()
dereference operator (needed for range-based for)
Definition iteration_proxy.hpp:51
const string_type & key() const
return key of the iterator
Definition iteration_proxy.hpp:78
bool operator==(const iteration_proxy_value &o) const
equality operator (needed for InputIterator)
Definition iteration_proxy.hpp:66
proxy class for the items() function
Definition iteration_proxy.hpp:122
iteration_proxy_value< IteratorType > begin() noexcept
return iterator begin (needed for range-based for)
Definition iteration_proxy.hpp:133
iteration_proxy_value< IteratorType > end() noexcept
return iterator end (needed for range-based for)
Definition iteration_proxy.hpp:139
iteration_proxy(typename IteratorType::reference cont) noexcept
construct iteration proxy from a container
Definition iteration_proxy.hpp:129
@ number_integer
number value (signed integer)
@ discarded
discarded by the parser callback function
@ binary
binary array (ordered collection of bytes)
@ object
object (unordered set of name/value pairs)
@ number_float
number value (floating-point)
@ number_unsigned
number value (unsigned integer)
@ array
array (ordered collection of values)
@ value
the parser finished reading a JSON value
namespace for Niels Lohmann
Definition adl_serializer.hpp:12
NLOHMANN_BASIC_JSON_TPL_DECLARATION std::string to_string(const NLOHMANN_BASIC_JSON_TPL &j)
user-defined to_string function for JSON values
Definition json.hpp:8969