+// ucs4_to_utf8
+
+std::vector<char> ucs4_to_utf8(char_type c);
+
+std::vector<char> ucs4_to_utf8(std::vector<char_type> const & ucs4str);
+
+std::vector<char> ucs4_to_utf8(char_type const * ucs4str, size_t ls);
+
+/// convert \p s from encoding \p encoding to ucs4.
+/// \p encoding must be a valid iconv 8bit encoding
+std::vector<char_type>
+eightbit_to_ucs4(char const * s, size_t ls, std::string const & encoding);
+
+/// convert \p s from ucs4 to encoding \p encoding.
+/// \p encoding must be a valid iconv 8bit encoding