mirror of
https://github.com/nlohmann/json.git
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171 lines
5.1 KiB
C++
171 lines
5.1 KiB
C++
#pragma once
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#include <cstddef> // size_t
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#include <iterator> // input_iterator_tag
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#include <string> // string, to_string
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#include <tuple> // tuple_size, get, tuple_element
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#include <nlohmann/detail/meta/type_traits.hpp>
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#include <nlohmann/detail/value_t.hpp>
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namespace nlohmann
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{
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namespace detail
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{
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template <typename IteratorType> class iteration_proxy_value
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{
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public:
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using difference_type = std::ptrdiff_t;
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using value_type = iteration_proxy_value;
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using pointer = value_type * ;
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using reference = value_type & ;
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using iterator_category = std::input_iterator_tag;
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private:
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/// the iterator
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IteratorType anchor;
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/// an index for arrays (used to create key names)
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std::size_t array_index = 0;
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/// last stringified array index
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mutable std::size_t array_index_last = 0;
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/// a string representation of the array index
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mutable std::string array_index_str = "0";
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/// an empty string (to return a reference for primitive values)
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const std::string empty_str = "";
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public:
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explicit iteration_proxy_value(IteratorType it) noexcept : anchor(it) {}
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/// dereference operator (needed for range-based for)
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iteration_proxy_value& operator*()
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{
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return *this;
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}
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/// increment operator (needed for range-based for)
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iteration_proxy_value& operator++()
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{
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++anchor;
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++array_index;
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return *this;
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}
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/// equality operator (needed for InputIterator)
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bool operator==(const iteration_proxy_value& o) const
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{
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return anchor == o.anchor;
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}
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/// inequality operator (needed for range-based for)
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bool operator!=(const iteration_proxy_value& o) const
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{
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return anchor != o.anchor;
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}
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/// return key of the iterator
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const std::string& key() const
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{
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assert(anchor.m_object != nullptr);
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switch (anchor.m_object->type())
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{
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// use integer array index as key
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case value_t::array:
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{
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if (array_index != array_index_last)
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{
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array_index_str = std::to_string(array_index);
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array_index_last = array_index;
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}
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return array_index_str;
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}
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// use key from the object
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case value_t::object:
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return anchor.key();
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// use an empty key for all primitive types
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default:
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return empty_str;
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}
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}
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/// return value of the iterator
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typename IteratorType::reference value() const
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{
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return anchor.value();
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}
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};
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/// proxy class for the items() function
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template<typename IteratorType> class iteration_proxy
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{
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private:
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/// the container to iterate
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typename IteratorType::reference container;
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public:
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/// construct iteration proxy from a container
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explicit iteration_proxy(typename IteratorType::reference cont) noexcept
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: container(cont) {}
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/// return iterator begin (needed for range-based for)
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iteration_proxy_value<IteratorType> begin() noexcept
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{
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return iteration_proxy_value<IteratorType>(container.begin());
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}
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/// return iterator end (needed for range-based for)
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iteration_proxy_value<IteratorType> end() noexcept
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{
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return iteration_proxy_value<IteratorType>(container.end());
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}
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};
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// Structured Bindings Support
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// For further reference see https://blog.tartanllama.xyz/structured-bindings/
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// And see https://github.com/nlohmann/json/pull/1391
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template <std::size_t N, typename IteratorType, enable_if_t<N == 0, int> = 0>
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auto get(const nlohmann::detail::iteration_proxy_value<IteratorType>& i) -> decltype(i.key())
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{
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return i.key();
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}
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// Structured Bindings Support
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// For further reference see https://blog.tartanllama.xyz/structured-bindings/
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// And see https://github.com/nlohmann/json/pull/1391
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template <std::size_t N, typename IteratorType, enable_if_t<N == 1, int> = 0>
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auto get(const nlohmann::detail::iteration_proxy_value<IteratorType>& i) -> decltype(i.value())
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{
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return i.value();
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}
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} // namespace detail
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} // namespace nlohmann
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// The Addition to the STD Namespace is required to add
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// Structured Bindings Support to the iteration_proxy_value class
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// For further reference see https://blog.tartanllama.xyz/structured-bindings/
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// And see https://github.com/nlohmann/json/pull/1391
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namespace std
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{
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#if defined(__clang__)
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// Fix: https://github.com/nlohmann/json/issues/1401
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#pragma clang diagnostic push
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#pragma clang diagnostic ignored "-Wmismatched-tags"
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#endif
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template <typename IteratorType>
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class tuple_size<::nlohmann::detail::iteration_proxy_value<IteratorType>>
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: public std::integral_constant<std::size_t, 2> {};
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template <std::size_t N, typename IteratorType>
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class tuple_element<N, ::nlohmann::detail::iteration_proxy_value<IteratorType >>
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{
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public:
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using type = decltype(
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get<N>(std::declval <
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::nlohmann::detail::iteration_proxy_value<IteratorType >> ()));
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};
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#if defined(__clang__)
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#pragma clang diagnostic pop
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#endif
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} // namespace std
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