- * Returns the number of characters in `dst', NOT including the trailing
- * null-byte. If an error occurred (empty array or `dst' too small) a value
- * smaller than zero will be returned.
+ * Returns the number of characters in the resulting string, excluding a
+ * tailing null byte. If this value is greater than or equal to "dst_len", the
+ * result in "dst" is truncated (but still null terminated). On error a
+ * negative value is returned.