Simple ruby implementation of Cirqle Queue and FIFO

cirqle_queue_and_fifo.rb

class CircleQueue
  include Enumerable
  
  class Head
    attr_accessor :first, :last
    
    def initialize
      self.first = self
      self.last = self
    end
  end
  
  class Element
    attr_accessor :prev, :next
    attr_accessor :params
    def initialize(params = {})
      @params = params
    end
  end
  
  attr_accessor :head, :size
  def initialize(*elements)
    self.head = Head.new
    @size = 0
  end
  
  def first
    head.first
  end
  
  def last
    head.last
  end
  
  def remove(element)
    if element.next == head
      head.last = element.prev
    else
      element.next.prev = element.prev
    end
    if element.prev == head
      head.first = element.next
    else
      element.prev.next = element.next
    end
    @size -= 1
  end
  
  def push(element)
    element.next = head
    element.prev = head.last
    if head.first == head
      head.first = element
    else
      head.last.next = element
    end
    head.last = element
    @size += 1
  end
  
  def unshift(element)
    element.next = head.first
    element.prev = head
    if head.last == head
      head.last = element
    else
      head.first.prev = element
    end
    head.first = element
    @size += 1
  end
  
  def shift
    if size > 0
      element = first
      remove element
      element
    else
      nil
    end
  end
  
  def pop
    if size > 0
      element = last
      remove element
      element
    else
      nil
    end
  end
  
  def each(&block)
    current = head.first
    while(current != head)
      block.call(current)
      current = current.next
    end
  end
end

class FIFO < CircleQueue
  
  attr_accessor :max_size
  def initialize(max_size)
    super
    @max_size = max_size
  end
  
  def push(element)
    super(element)
    if size > max_size
      remove head.first
    end
  end
  
  def unshift(element)
    super(element)
    if size > max_size
      remove head.last
    end
  end
    
end

require 'pp'

qu = CircleQueue.new
qu.push CircleQueue::Element.new(:name => "test1")
qu.push CircleQueue::Element.new(:name => "test2")
qu.unshift CircleQueue::Element.new(:name => 'test3')

qu.each do |el|
  pp el.params
end

qu = FIFO.new 5
qu.push CircleQueue::Element.new(:name => "test1")
qu.push CircleQueue::Element.new(:name => "test2")
qu.push CircleQueue::Element.new(:name => "test3")
qu.push CircleQueue::Element.new(:name => "test4")
qu.push CircleQueue::Element.new(:name => "test5")
qu.push CircleQueue::Element.new(:name => "test6")

qu.each do |el|
  pp el.params
end