71 lines
2.2 KiB
C++
71 lines
2.2 KiB
C++
#pragma once
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#include <functional> // less
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#include <memory> // allocator
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#include <utility> // pair
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#include <vector> // vector
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namespace nlohmann
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{
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/// ordered_map: a minimal map-like container that preserves insertion order
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/// for use within nlohmann::basic_json<ordered_map>
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template <class Key, class T, class IgnoredLess = std::less<Key>,
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class Allocator = std::allocator<std::pair<const Key, T>>>
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struct ordered_map : std::vector<std::pair<const Key, T>, Allocator>
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{
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using key_type = Key;
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using mapped_type = T;
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using Container = std::vector<std::pair<const Key, T>, Allocator>;
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using typename Container::iterator;
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using typename Container::size_type;
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using typename Container::value_type;
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// Explicit constructors instead of `using Container::Container`
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// otherwise older compilers choke on it (GCC <= 5.5, xcode <= 9.4)
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ordered_map(const Allocator& alloc = Allocator()) : Container{alloc} {}
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template <class It>
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ordered_map(It first, It last, const Allocator& alloc = Allocator())
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: Container{first, last, alloc} {}
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ordered_map(std::initializer_list<T> init, const Allocator& alloc = Allocator() )
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: Container{init, alloc} {}
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std::pair<iterator, bool> emplace(key_type&& key, T&& t)
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{
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for (auto it = this->begin(); it != this->end(); ++it)
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{
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if (it->first == key)
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{
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return {it, false};
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}
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}
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Container::emplace_back(key, t);
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return {--this->end(), true};
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}
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T& operator[](Key&& key)
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{
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return emplace(std::move(key), T{}).first->second;
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}
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size_type erase(const Key& key)
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{
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for (auto it = this->begin(); it != this->end(); ++it)
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{
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if (it->first == key)
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{
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// Since we cannot move const Keys, re-construct them in place
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for (auto next = it; ++next != this->end(); ++it)
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{
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it->~value_type(); // Destroy but keep allocation
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new (&*it) value_type{std::move(*next)};
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}
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Container::pop_back();
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return 1;
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}
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}
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return 0;
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}
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};
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} // namespace nlohmann
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