mirror of
https://github.com/nlohmann/json.git
synced 2024-08-21 04:22:28 +02:00
615 lines
17 KiB
C++
615 lines
17 KiB
C++
#pragma once
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#include <ciso646> // not
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#include <iterator> // iterator, random_access_iterator_tag, bidirectional_iterator_tag, advance, next
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#include <type_traits> // conditional, is_const, remove_const
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#include <nlohmann/detail/exceptions.hpp>
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#include <nlohmann/detail/iterators/internal_iterator.hpp>
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#include <nlohmann/detail/iterators/primitive_iterator.hpp>
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#include <nlohmann/detail/macro_scope.hpp>
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#include <nlohmann/detail/meta.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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// forward declare, to be able to friend it later on
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template<typename IteratorType> class iteration_proxy;
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/*!
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@brief a template for a bidirectional iterator for the @ref basic_json class
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This class implements a both iterators (iterator and const_iterator) for the
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@ref basic_json class.
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@note An iterator is called *initialized* when a pointer to a JSON value has
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been set (e.g., by a constructor or a copy assignment). If the iterator is
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default-constructed, it is *uninitialized* and most methods are undefined.
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**The library uses assertions to detect calls on uninitialized iterators.**
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@requirement The class satisfies the following concept requirements:
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-
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[BidirectionalIterator](https://en.cppreference.com/w/cpp/concept/BidirectionalIterator):
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The iterator that can be moved can be moved in both directions (i.e.
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incremented and decremented).
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@since version 1.0.0, simplified in version 2.0.9, change to bidirectional
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iterators in version 3.0.0 (see https://github.com/nlohmann/json/issues/593)
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*/
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template<typename BasicJsonType>
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class iter_impl
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{
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/// allow basic_json to access private members
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friend iter_impl<typename std::conditional<std::is_const<BasicJsonType>::value, typename std::remove_const<BasicJsonType>::type, const BasicJsonType>::type>;
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friend BasicJsonType;
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friend iteration_proxy<iter_impl>;
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using object_t = typename BasicJsonType::object_t;
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using array_t = typename BasicJsonType::array_t;
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// make sure BasicJsonType is basic_json or const basic_json
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static_assert(is_basic_json<typename std::remove_const<BasicJsonType>::type>::value,
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"iter_impl only accepts (const) basic_json");
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public:
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/// The std::iterator class template (used as a base class to provide typedefs) is deprecated in C++17.
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/// The C++ Standard has never required user-defined iterators to derive from std::iterator.
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/// A user-defined iterator should provide publicly accessible typedefs named
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/// iterator_category, value_type, difference_type, pointer, and reference.
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/// Note that value_type is required to be non-const, even for constant iterators.
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using iterator_category = std::bidirectional_iterator_tag;
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/// the type of the values when the iterator is dereferenced
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using value_type = typename BasicJsonType::value_type;
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/// a type to represent differences between iterators
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using difference_type = typename BasicJsonType::difference_type;
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/// defines a pointer to the type iterated over (value_type)
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using pointer = typename std::conditional<std::is_const<BasicJsonType>::value,
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typename BasicJsonType::const_pointer,
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typename BasicJsonType::pointer>::type;
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/// defines a reference to the type iterated over (value_type)
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using reference =
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typename std::conditional<std::is_const<BasicJsonType>::value,
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typename BasicJsonType::const_reference,
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typename BasicJsonType::reference>::type;
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/// default constructor
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iter_impl() = default;
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/*!
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@brief constructor for a given JSON instance
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@param[in] object pointer to a JSON object for this iterator
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@pre object != nullptr
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@post The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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explicit iter_impl(pointer object) noexcept : m_object(object)
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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{
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m_it.object_iterator = typename object_t::iterator();
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break;
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}
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case value_t::array:
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{
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m_it.array_iterator = typename array_t::iterator();
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break;
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}
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default:
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{
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m_it.primitive_iterator = primitive_iterator_t();
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break;
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}
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}
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}
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/*!
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@note The conventional copy constructor and copy assignment are implicitly
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defined. Combined with the following converting constructor and
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assignment, they support: (1) copy from iterator to iterator, (2)
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copy from const iterator to const iterator, and (3) conversion from
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iterator to const iterator. However conversion from const iterator
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to iterator is not defined.
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*/
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/*!
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@brief converting constructor
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@param[in] other non-const iterator to copy from
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@note It is not checked whether @a other is initialized.
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*/
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iter_impl(const iter_impl<typename std::remove_const<BasicJsonType>::type>& other) noexcept
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: m_object(other.m_object), m_it(other.m_it) {}
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/*!
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@brief converting assignment
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@param[in,out] other non-const iterator to copy from
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@return const/non-const iterator
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@note It is not checked whether @a other is initialized.
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*/
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iter_impl& operator=(const iter_impl<typename std::remove_const<BasicJsonType>::type>& other) noexcept
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{
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m_object = other.m_object;
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m_it = other.m_it;
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return *this;
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}
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private:
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/*!
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@brief set the iterator to the first value
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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void set_begin() noexcept
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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{
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m_it.object_iterator = m_object->m_value.object->begin();
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break;
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}
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case value_t::array:
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{
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m_it.array_iterator = m_object->m_value.array->begin();
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break;
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}
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case value_t::null:
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{
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// set to end so begin()==end() is true: null is empty
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m_it.primitive_iterator.set_end();
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break;
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}
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default:
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{
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m_it.primitive_iterator.set_begin();
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break;
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}
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}
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}
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/*!
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@brief set the iterator past the last value
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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void set_end() noexcept
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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{
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m_it.object_iterator = m_object->m_value.object->end();
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break;
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}
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case value_t::array:
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{
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m_it.array_iterator = m_object->m_value.array->end();
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break;
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}
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default:
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{
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m_it.primitive_iterator.set_end();
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break;
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}
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}
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}
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public:
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/*!
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@brief return a reference to the value pointed to by the iterator
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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reference operator*() const
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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{
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assert(m_it.object_iterator != m_object->m_value.object->end());
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return m_it.object_iterator->second;
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}
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case value_t::array:
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{
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assert(m_it.array_iterator != m_object->m_value.array->end());
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return *m_it.array_iterator;
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}
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case value_t::null:
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JSON_THROW(invalid_iterator::create(214, "cannot get value"));
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default:
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{
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if (JSON_LIKELY(m_it.primitive_iterator.is_begin()))
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{
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return *m_object;
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}
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JSON_THROW(invalid_iterator::create(214, "cannot get value"));
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}
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}
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}
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/*!
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@brief dereference the iterator
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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pointer operator->() const
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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{
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assert(m_it.object_iterator != m_object->m_value.object->end());
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return &(m_it.object_iterator->second);
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}
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case value_t::array:
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{
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assert(m_it.array_iterator != m_object->m_value.array->end());
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return &*m_it.array_iterator;
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}
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default:
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{
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if (JSON_LIKELY(m_it.primitive_iterator.is_begin()))
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{
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return m_object;
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}
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JSON_THROW(invalid_iterator::create(214, "cannot get value"));
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}
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}
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}
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/*!
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@brief post-increment (it++)
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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iter_impl const operator++(int)
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{
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auto result = *this;
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++(*this);
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return result;
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}
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/*!
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@brief pre-increment (++it)
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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iter_impl& operator++()
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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{
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std::advance(m_it.object_iterator, 1);
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break;
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}
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case value_t::array:
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{
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std::advance(m_it.array_iterator, 1);
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break;
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}
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default:
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{
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++m_it.primitive_iterator;
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break;
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}
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}
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return *this;
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}
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/*!
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@brief post-decrement (it--)
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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iter_impl const operator--(int)
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{
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auto result = *this;
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--(*this);
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return result;
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}
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/*!
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@brief pre-decrement (--it)
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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iter_impl& operator--()
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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{
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std::advance(m_it.object_iterator, -1);
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break;
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}
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case value_t::array:
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{
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std::advance(m_it.array_iterator, -1);
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break;
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}
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default:
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{
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--m_it.primitive_iterator;
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break;
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}
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}
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return *this;
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}
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/*!
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@brief comparison: equal
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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bool operator==(const iter_impl& other) const
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{
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// if objects are not the same, the comparison is undefined
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if (JSON_UNLIKELY(m_object != other.m_object))
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{
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JSON_THROW(invalid_iterator::create(212, "cannot compare iterators of different containers"));
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}
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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return (m_it.object_iterator == other.m_it.object_iterator);
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case value_t::array:
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return (m_it.array_iterator == other.m_it.array_iterator);
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default:
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return (m_it.primitive_iterator == other.m_it.primitive_iterator);
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}
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}
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/*!
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@brief comparison: not equal
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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bool operator!=(const iter_impl& other) const
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{
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return not operator==(other);
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}
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/*!
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@brief comparison: smaller
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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bool operator<(const iter_impl& other) const
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{
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// if objects are not the same, the comparison is undefined
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if (JSON_UNLIKELY(m_object != other.m_object))
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{
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JSON_THROW(invalid_iterator::create(212, "cannot compare iterators of different containers"));
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}
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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JSON_THROW(invalid_iterator::create(213, "cannot compare order of object iterators"));
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case value_t::array:
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return (m_it.array_iterator < other.m_it.array_iterator);
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default:
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return (m_it.primitive_iterator < other.m_it.primitive_iterator);
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}
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}
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/*!
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@brief comparison: less than or equal
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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bool operator<=(const iter_impl& other) const
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{
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return not other.operator < (*this);
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}
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/*!
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@brief comparison: greater than
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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bool operator>(const iter_impl& other) const
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{
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return not operator<=(other);
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}
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/*!
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@brief comparison: greater than or equal
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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bool operator>=(const iter_impl& other) const
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{
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return not operator<(other);
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}
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/*!
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@brief add to iterator
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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iter_impl& operator+=(difference_type i)
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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JSON_THROW(invalid_iterator::create(209, "cannot use offsets with object iterators"));
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case value_t::array:
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{
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std::advance(m_it.array_iterator, i);
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break;
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}
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default:
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{
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m_it.primitive_iterator += i;
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break;
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}
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}
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return *this;
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}
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/*!
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@brief subtract from iterator
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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iter_impl& operator-=(difference_type i)
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{
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return operator+=(-i);
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}
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/*!
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@brief add to iterator
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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iter_impl operator+(difference_type i) const
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{
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auto result = *this;
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result += i;
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return result;
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}
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/*!
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@brief addition of distance and iterator
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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friend iter_impl operator+(difference_type i, const iter_impl& it)
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{
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auto result = it;
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result += i;
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return result;
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}
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/*!
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@brief subtract from iterator
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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iter_impl operator-(difference_type i) const
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{
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auto result = *this;
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result -= i;
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return result;
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}
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/*!
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@brief return difference
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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difference_type operator-(const iter_impl& other) const
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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JSON_THROW(invalid_iterator::create(209, "cannot use offsets with object iterators"));
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case value_t::array:
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return m_it.array_iterator - other.m_it.array_iterator;
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default:
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return m_it.primitive_iterator - other.m_it.primitive_iterator;
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}
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}
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/*!
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@brief access to successor
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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*/
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reference operator[](difference_type n) const
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{
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assert(m_object != nullptr);
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switch (m_object->m_type)
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{
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case value_t::object:
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JSON_THROW(invalid_iterator::create(208, "cannot use operator[] for object iterators"));
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case value_t::array:
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return *std::next(m_it.array_iterator, n);
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case value_t::null:
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JSON_THROW(invalid_iterator::create(214, "cannot get value"));
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default:
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{
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if (JSON_LIKELY(m_it.primitive_iterator.get_value() == -n))
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{
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return *m_object;
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}
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JSON_THROW(invalid_iterator::create(214, "cannot get value"));
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}
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}
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}
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/*!
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@brief return the key of an object iterator
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@pre The iterator is initialized; i.e. `m_object != nullptr`.
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|
*/
|
|
const typename object_t::key_type& key() const
|
|
{
|
|
assert(m_object != nullptr);
|
|
|
|
if (JSON_LIKELY(m_object->is_object()))
|
|
{
|
|
return m_it.object_iterator->first;
|
|
}
|
|
|
|
JSON_THROW(invalid_iterator::create(207, "cannot use key() for non-object iterators"));
|
|
}
|
|
|
|
/*!
|
|
@brief return the value of an iterator
|
|
@pre The iterator is initialized; i.e. `m_object != nullptr`.
|
|
*/
|
|
reference value() const
|
|
{
|
|
return operator*();
|
|
}
|
|
|
|
private:
|
|
/// associated JSON instance
|
|
pointer m_object = nullptr;
|
|
/// the actual iterator of the associated instance
|
|
internal_iterator<typename std::remove_const<BasicJsonType>::type> m_it;
|
|
};
|
|
}
|
|
}
|