+/// convert \p s from the encoding of the file system to ucs4.
+docstring const from_filesystem8bit(std::string const & s);
+
+/// convert \p s from ucs4 to the encoding of the file system.
+std::string const to_filesystem8bit(docstring const & s);
+
+/// normalize \p s to precomposed form c
+docstring const normalize_c(docstring const & s);
+