def size_as_number_of_bytes(size):
    """Returns the minimum number of bytes needed to fit given positive
    integer.

    """

    if size == 0:
        return 1
    else:
        number_of_bits = size.bit_length()
        rest = (number_of_bits % 8)

        if rest != 0:
            number_of_bits += (8 - rest)

        return number_of_bits // 8