Support operator--() for util::utf8_iterator

libs/util/include/psemek/util/unicode.hpp

@@ -17,12 +17,16 @@ namespace psemek::util
 		using pointer = void;
 		using reference = void;
 		using difference_type = std::ptrdiff_t;
-		using iterator_category = std::input_iterator_tag;
+		using iterator_category = std::bidirectional_iterator_tag;
 
 		char const * ptr;
 
 		utf8_iterator & operator ++();
 		utf8_iterator operator ++(int);
+
+		utf8_iterator & operator --();
+		utf8_iterator operator --(int);
+
 		char32_t operator *() const;
 	};
 

libs/util/source/unicode.cpp

@@ -82,6 +82,21 @@ namespace psemek::util
 		return copy;
 	}
 
+	utf8_iterator & utf8_iterator::operator --()
+	{
+		--ptr;
+		while (is_middle_byte(*ptr))
+			--ptr;
+		return *this;
+	}
+
+	utf8_iterator utf8_iterator::operator --(int)
+	{
+		utf8_iterator copy(*this);
+		--(*this);
+		return copy;
+	}
+
 	char32_t utf8_iterator::operator *() const
 	{
 		if (is_1_byte(ptr[0]))