division by bitshifting

my_div.rb

class Fixnum

  def my_div divisor
    return nil if divisor == 0
    return 0   if self == 0
    quotient, mask = 0, 1
    dividend = self
    while divisor < dividend
      divisor <<= 1
      mask    <<= 1
    end
    while mask != 0
      if dividend >= divisor
        dividend -= divisor
        quotient += mask
      end
      divisor >>= 1
      mask    >>= 1
    end
    [ quotient, dividend ]  # quotient, remainder
  end

This is a little program to do division by bit-shifting.