diff options
Diffstat (limited to 'include/lib/modernjson/detail/iterators/iteration_proxy.hpp')
-rw-r--r-- | include/lib/modernjson/detail/iterators/iteration_proxy.hpp | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/include/lib/modernjson/detail/iterators/iteration_proxy.hpp b/include/lib/modernjson/detail/iterators/iteration_proxy.hpp new file mode 100644 index 0000000..31cc9f0 --- /dev/null +++ b/include/lib/modernjson/detail/iterators/iteration_proxy.hpp @@ -0,0 +1,125 @@ +#pragma once + +#include <cstddef> // size_t +#include <string> // string, to_string +#include <iterator> // input_iterator_tag + +#include <lib/modernjson/detail/value_t.hpp> + +namespace nlohmann +{ +namespace detail +{ +/// proxy class for the items() function +template<typename IteratorType> class iteration_proxy +{ + private: + /// helper class for iteration + class iteration_proxy_internal + { + public: + using difference_type = std::ptrdiff_t; + using value_type = iteration_proxy_internal; + using pointer = iteration_proxy_internal*; + using reference = iteration_proxy_internal&; + using iterator_category = std::input_iterator_tag; + + private: + /// the iterator + IteratorType anchor; + /// an index for arrays (used to create key names) + std::size_t array_index = 0; + /// last stringified array index + mutable std::size_t array_index_last = 0; + /// a string representation of the array index + mutable std::string array_index_str = "0"; + /// an empty string (to return a reference for primitive values) + const std::string empty_str = ""; + + public: + explicit iteration_proxy_internal(IteratorType it) noexcept : anchor(it) {} + + /// dereference operator (needed for range-based for) + iteration_proxy_internal& operator*() + { + return *this; + } + + /// increment operator (needed for range-based for) + iteration_proxy_internal& operator++() + { + ++anchor; + ++array_index; + + return *this; + } + + /// equality operator (needed for InputIterator) + bool operator==(const iteration_proxy_internal& o) const noexcept + { + return anchor == o.anchor; + } + + /// inequality operator (needed for range-based for) + bool operator!=(const iteration_proxy_internal& o) const noexcept + { + return anchor != o.anchor; + } + + /// return key of the iterator + const std::string& key() const + { + assert(anchor.m_object != nullptr); + + switch (anchor.m_object->type()) + { + // use integer array index as key + case value_t::array: + { + if (array_index != array_index_last) + { + array_index_str = std::to_string(array_index); + array_index_last = array_index; + } + return array_index_str; + } + + // use key from the object + case value_t::object: + return anchor.key(); + + // use an empty key for all primitive types + default: + return empty_str; + } + } + + /// return value of the iterator + typename IteratorType::reference value() const + { + return anchor.value(); + } + }; + + /// the container to iterate + typename IteratorType::reference container; + + public: + /// construct iteration proxy from a container + explicit iteration_proxy(typename IteratorType::reference cont) noexcept + : container(cont) {} + + /// return iterator begin (needed for range-based for) + iteration_proxy_internal begin() noexcept + { + return iteration_proxy_internal(container.begin()); + } + + /// return iterator end (needed for range-based for) + iteration_proxy_internal end() noexcept + { + return iteration_proxy_internal(container.end()); + } +}; +} // namespace detail +} // namespace nlohmann |