Add util::unique_sequential_storage for storing an array of unique elements

libs/util/include/psemek/util/unique_sequential_storage.hpp

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <unordered_map>
+#include <vector>
+#include <cstdint>
+
+namespace psemek::util
+{
+
+	template <typename T, typename Hash = std::hash<T>>
+	struct unique_sequential_storage
+	{
+		using index = std::uint32_t;
+
+		template <typename H>
+		index insert(H && value)
+		{
+			if (auto it = value_to_index_.find(value); it != value_to_index_.end())
+				return it->second;
+
+			index result = index_to_value_.size();
+			index_to_value_.push_back(value);
+			value_to_index_[std::forward<H>(value)] = result;
+			return result;
+		}
+
+		T const & get(index i) const
+		{
+			return index_to_value_[i];
+		}
+
+	private:
+		std::unordered_map<T, index, Hash> value_to_index_;
+		std::vector<T> index_to_value_;
+	};
+
+}