ThreadsafeQueue

class ThreadsafeQueue
  require 'thread'
  require 'timeout'

  def initialize
    @queue = []
    @mutex = Mutex.new
    @cv =  ConditionVariable.new
  end 

  def push(item)
    @mutex.synchronize do
      @queue.push(item)
    end 

    @cv.signal
  end 

  alias_method :<<, :push

  def pop 
    @mutex.synchronize do
      while true
        if @queue.empty?
          begin
            Timeout::timeout(5) do
              @cv.wait(@mutex)
            end 
          rescue Timeout::Error
            retry                                                                                                                                                                                                                                                                                                       
          end 
        else
          return @queue.shift
        end 
      end 
    end 
  end 
end