ThreadsafeMemoized

ThreadsafeMemoized.rb

class ThreadsafeMemoized
  def initialize
    @memoized = {}
    @mutex = Support::ReentrantMutex.new
  end

  def fetch_or_store(key)
    @memoized.fetch(key) do # only first access pays for synchronization
      @mutex.synchronize do
        @memoized.fetch(key) { @memoized[key] = yield }
      end
    end
  end
end