def _count_righthand_zero_bits(number, bits):
    """Count the number of zero bits on the right hand side.

    Args:
        number: an integer.
        bits: maximum number of bits to count.

    Returns:
        The number of zero bits on the right hand side of the number.

    """
    if number == 0:
        return bits
    for i in range(bits):
        if (number >> i) & 1:
            return i
    # All bits of interest were zero, even if there are more in the number
    return bits