class Reline::KillRing::RingBuffer

def <<(point)
  if @size.zero?
    @head = point
    @head.backward = @head
    @head.forward = @head
    @size = 1
  elsif @size >= @max
    tail = @head.forward
    new_tail = tail.forward
    @head.forward = point
    point.backward = @head
    new_tail.backward = point
    point.forward = new_tail
    @head = point
  else
    tail = @head.forward
    @head.forward = point
    point.backward = @head
    tail.backward = point
    point.forward = tail
    @head = point
    @size += 1
  end
end

def empty?
  @size.zero?
end

def initialize(max = 1024)
  @max = max
  @size = 0
  @head = nil # reading head of ring-shaped tape
end