offering exclusive locking resources for multithread

ex_resource_lock.rb

class ExResourceLock

  def initialize(map)
    @rmap = map
    @mtx = Mutex.new
    @cv = ConditionVariable.new
    @mtx.synchronize do
      @free_resources = @rmap.keys
      @locked_resources = []
    end
  end

  def assign_and_lock
    resource_name = nil
    resource = nil
    
    @mtx.synchronize do
      while @free_resources.empty? do
        @cv.wait(@mtx)
      end
      
      resource_name = @free_resources.pop
      resource = @rmap[resource_name]
    end  
  
    return [resource_name, resource]
  end
  
  def unlock(resource_name)
    @mtx.synchronize do
      @free_resources << resource_name
      @locked_resources.delete(resource_name)
      @cv.signal
    end
    self
  end
  
end