mirror of https://github.com/axmolengine/axmol.git
63 lines
1.9 KiB
C++
63 lines
1.9 KiB
C++
// C++20 demo: Heterogeneous lookup for unordered containers (transparent hashing)
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// https://en.cppreference.com/w/cpp/container/unordered_map/find
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#pragma once
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#include <string>
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#include <string_view>
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#include <map>
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#include <set>
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#include <unordered_map>
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#include <unordered_set>
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#include "tsl/robin_map.h"
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#include "tsl/robin_set.h"
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using namespace std::string_literals;
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using namespace std::string_view_literals;
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namespace hlookup
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{
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struct string_hash
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{
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using hash_type = std::hash<std::string_view>;
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using is_transparent = void;
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size_t operator()(const char* str) const { return hash_type{}(str); }
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size_t operator()(std::string_view str) const { return hash_type{}(str); }
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size_t operator()(std::string const& str) const { return hash_type{}(str); }
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};
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struct equal_to
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{
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template <class _Ty1, class _Ty2>
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constexpr auto operator()(_Ty1&& _Left, _Ty2&& _Right) const
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noexcept(noexcept(static_cast<_Ty1&&>(_Left) == static_cast<_Ty2&&>(_Right))) // strengthened
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-> decltype(static_cast<_Ty1&&>(_Left) == static_cast<_Ty2&&>(_Right))
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{
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return static_cast<_Ty1&&>(_Left) == static_cast<_Ty2&&>(_Right);
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}
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using is_transparent = int;
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};
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template <typename _Valty>
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using stl_string_map = std::map<std::string, _Valty, std::less<>>;
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using stl_string_set = std::set<std::string, std::less<>>;
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template <typename _Valty>
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using string_map = tsl::robin_map<std::string, _Valty, string_hash, equal_to>;
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using string_set = tsl::robin_set<std::string, string_hash, equal_to>;
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template <typename _Cont, typename _Valty>
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inline auto set_item(_Cont& cont, std::string_view key, _Valty&& _Val)
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{
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typename _Cont::iterator it = cont.find(key);
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if (it != cont.end())
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it.value() = std::move(_Val);
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else
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it = cont.emplace(std::string{key}, std::forward<_Valty>(_Val)).first;
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return it;
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}
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constexpr auto empty_sv = ""sv;
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} // namespace hlookup
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