你好,很高兴为你解答
have done 是很简单的“现在完成时”的体现.
having done 是动词-ing形式的完成式,表示该动作发生在谓语动词之前.
having done sth 一般出现在句首,表达出“在...的前提下”那层意思,后面必定跟着一条完整从句.
例如:
I have done(finished) my homework. 我已经完成我的作业了.
Having done(finished) all the homework, I'm going to watch a little TV now.
功课都已完成,我要来看会儿电视.
希望对你有帮助