buf := make([]byte, len(input)*4)
	dst := (*C.char)(unsafe.Pointer(&buf[0]))
	src := C.CString(input)

	cn := C.int32_t(0)

	switch caser {
	case "fold":
		cn = C.ucasemap_utf8FoldCase(cm,
			dst, C.int32_t(len(buf)),
			src, C.int32_t(len(input)),
			&err)
	case "lower":
		cn = C.ucasemap_utf8ToLower(cm,
			dst, C.int32_t(len(buf)),
			src, C.int32_t(len(input)),
			&err)