@Contract(pure = true)
  public static byte @NotNull [] parseHexString(@NotNull String str) {
    int len = str.length();
    if (len % 2 != 0) throw new IllegalArgumentException("Non-even-length: " + str);
    byte[] bytes = new byte[len / 2];
    for (int i = 0; i < len; i += 2) {
      bytes[i / 2] = (byte)((Character.digit(str.charAt(i), 16) << 4) + Character.digit(str.charAt(i + 1), 16));
    }
    return bytes;
  }
@Contract(pure = true)
  public static byte @NotNull [] parseHexString(@NotNull String str)