622def check_hex(hex, bytes_size = None):
623 assert hex is not None, "Error: Missing hex string"
624 size = len(hex)
625 assert size > 0, "Error: hex string is empty"
626 assert size % 2 == 0, "Error: invalid size of hex string"
627 if bytes_size is not None:
628 n = int(size / 2)
629 assert n == bytes_size, "Error: invalid number of bytes %d, expected %d" % (n, bytes_size)
630