Add function to get the byte length of n characters in a utf8 string.

utils/utf8.c

@@ -117,6 +117,24 @@ size_t utf8_bounded_length(const char *s, size_t l)
 	return len;
 }
 
+/**
+ * Calculate the length (in bytes) of a bounded UTF-8 string
+ *
+ * \param s  The string
+ * \param l  Maximum length of input (in bytes)
+ * \param c  Maximum number of characters to measure
+ * \return Length of string, in bytes
+ */
+size_t utf8_bounded_byte_length(const char *s, size_t l, size_t c)
+{
+	size_t len = 0;
+
+	while (len < l && c-- > 0)
+		len = utf8_next(s, l, len);
+
+	return len;
+}
+
 /**
  * Calculate the length (in bytes) of a UTF-8 character
  *

utils/utf8.h

@@ -37,6 +37,7 @@ size_t utf8_from_ucs4(uint32_t c, char *s);
 
 size_t utf8_length(const char *s);
 size_t utf8_bounded_length(const char *s, size_t l);
+size_t utf8_bounded_byte_length(const char *s, size_t l, size_t c);
 
 size_t utf8_char_byte_length(const char *s);