Add util::hstring - both owning & not owning string - for use to emulate heterogeneous containers

libs/util/include/psemek/util/hstring.hpp

@@ -0,0 +1,80 @@
+#pragma once
+
+#include <string>
+#include <string_view>
+#include <functional>
+
+namespace psemek::util
+{
+
+	struct hstring
+	{
+		hstring(std::string string)
+			: string_(std::move(string))
+			, view_(string_)
+		{}
+
+		hstring(std::string_view const & view)
+			: view_(view)
+		{}
+
+		hstring(hstring const & other)
+			: string_(other.string_)
+			, view_(other.owns() ? std::string_view(string_) : other.view_)
+		{}
+
+		hstring(hstring && other)
+		{
+			if (other.owns())
+			{
+				string_ = std::move(other.string_);
+				view_ = string_;
+			}
+			else
+			{
+				view_ = other.view_;
+			}
+
+			other.view_ = std::string_view();
+		}
+
+		std::string_view view() const
+		{
+			return view_;
+		}
+
+		bool owns() const
+		{
+			return view_.data() == string_.data();
+		}
+
+	private:
+		std::string string_;
+		std::string_view view_;
+	};
+
+	inline auto operator == (hstring const & str1, hstring const & str2)
+	{
+		return str1.view() == str2.view();
+	}
+
+	inline auto operator <=> (hstring const & str1, hstring const & str2)
+	{
+		return str1.view() <=> str2.view();
+	}
+
+}
+
+namespace std
+{
+
+	template <>
+	struct hash<::psemek::util::hstring>
+	{
+		std::size_t operator()(::psemek::util::hstring const & str) const
+		{
+			return std::hash<std::string_view>()(str.view());
+		}
+	};
+
+}