+/* Return the length (number of units) of the first character in S, putting
+ its 'ucs4_t' representation in *PUC. Upon failure, *PUC is set to 0xfffd,
+ and -1 is returned for an invalid sequence of units, -2 is returned for an
+ incomplete sequence of units.
+ The number of available units, N, must be > 0. */
+/* Similar to u*_mbtouc(), except that the return value gives more details
+ about the failure, similar to mbrtowc(). */
+
+#ifdef GNULIB_UNISTR_U8_MBTOUCR
+extern int
+ u8_mbtoucr (ucs4_t *puc, const uint8_t *s, size_t n);
+#endif
+
+#ifdef GNULIB_UNISTR_U16_MBTOUCR
+extern int
+ u16_mbtoucr (ucs4_t *puc, const uint16_t *s, size_t n);
+#endif
+
+#ifdef GNULIB_UNISTR_U32_MBTOUCR
+extern int
+ u32_mbtoucr (ucs4_t *puc, const uint32_t *s, size_t n);
+#endif
+