+
+/* UTF-8. */
+ucs4_t ss_first_mb (struct substring);
+int ss_first_mblen (struct substring);
+ucs4_t ss_get_mb (struct substring *);
+ucs4_t ss_at_mb (struct substring, size_t ofs);
+int ss_at_mblen (struct substring, size_t ofs);
+size_t ss_utf8_count_columns (struct substring);
+struct substring ss_utf8_columns (struct substring, size_t start, size_t n);