Add util::cyclic_iterator

libs/util/include/psemek/util/cyclic_iterator.hpp

@@ -0,0 +1,97 @@
+#pragma once
+
+#include <psemek/util/range.hpp>
+
+#include <iterator>
+
+namespace psemek::util
+{
+
+	template <typename Iterator>
+	struct cyclic_iterator
+	{
+		using traits = std::iterator_traits<Iterator>;
+		using value_type = typename traits::value_type;
+		using reference = typename traits::reference;
+		using pointer = typename traits::pointer;
+		using difference_type = typename traits::difference_type;
+		using iterator_category = std::bidirectional_iterator_tag;
+
+		Iterator begin, end;
+		Iterator iter;
+
+		cyclic_iterator() = default;
+		cyclic_iterator(cyclic_iterator const &) = default;
+
+		cyclic_iterator(Iterator begin, Iterator end, Iterator iter)
+			: begin(begin)
+			, end(end)
+			, iter(iter)
+		{}
+
+		cyclic_iterator(Iterator begin, Iterator end)
+			: begin(begin)
+			, end(end)
+			, iter(begin)
+		{}
+
+		cyclic_iterator & operator = (cyclic_iterator const &) = default;
+
+		decltype(auto) operator *()
+		{
+			return *iter;
+		}
+
+		cyclic_iterator & operator++()
+		{
+			if (++iter == end)
+				iter = begin;
+			return *this;
+		}
+
+		cyclic_iterator operator++(int)
+		{
+			auto copy = *this;
+			this->operator++();
+			return copy;
+		}
+
+		cyclic_iterator & operator--()
+		{
+			if (iter == begin)
+				iter = end;
+			--iter;
+			return *this;
+		}
+
+		cyclic_iterator operator--(int)
+		{
+			auto copy = *this;
+			this->operator--();
+			return copy;
+		}
+
+		friend bool operator == (cyclic_iterator const & it1, cyclic_iterator const & it2)
+		{
+			return it1.iter == it2.iter;
+		}
+
+		friend bool operator != (cyclic_iterator const & it1, cyclic_iterator const & it2)
+		{
+			return it1.iter != it2.iter;
+		}
+	};
+
+	template <typename Iterator>
+	cyclic_iterator(Iterator, Iterator, Iterator) -> cyclic_iterator<Iterator>;
+
+	template <typename Iterator>
+	cyclic_iterator(Iterator, Iterator) -> cyclic_iterator<Iterator>;
+
+	template <typename Container>
+	auto make_cyclic_iterator(Container & container)
+	{
+		return cyclic_iterator{util::begin(container), util::end(container)};
+	}
+
+}