+/* Returns the start of the next grapheme cluster following S, or NULL if the
+ end of the string has been reached. */
+extern const uint8_t *
+ u8_grapheme_next (const uint8_t *s, const uint8_t *end);
+extern const uint16_t *
+ u16_grapheme_next (const uint16_t *s, const uint16_t *end);
+extern const uint32_t *
+ u32_grapheme_next (const uint32_t *s, const uint32_t *end);
+
+/* Returns the start of the previous grapheme cluster before S, or NULL if the
+ start of the string has been reached. */
+extern const uint8_t *
+ u8_grapheme_prev (const uint8_t *s, const uint8_t *start);
+extern const uint16_t *
+ u16_grapheme_prev (const uint16_t *s, const uint16_t *start);
+extern const uint32_t *
+ u32_grapheme_prev (const uint32_t *s, const uint32_t *start);
+
+/* Determine the grapheme cluster boundaries in S, and store the result at
+ p[0..n-1]. p[i] = 1 means that a new grapheme cluster begins at s[i]. p[i]
+ = 0 means that s[i-1] and s[i] are part of the same grapheme cluster. p[0]
+ will always be 1.
+ */
+extern void
+ u8_grapheme_breaks (const uint8_t *s, size_t n, char *p);
+extern void
+ u16_grapheme_breaks (const uint16_t *s, size_t n, char *p);
+extern void
+ u32_grapheme_breaks (const uint32_t *s, size_t n, char *p);
+extern void
+ ulc_grapheme_breaks (const char *s, size_t n, char *p);
+