ccond and TopicsProvider

[cloudzhou]

I hava some confusions, delete this issue if I make it wrong.
1 code: https://github.com/surgemq/surgemq/blob/master/service/buffer.go#L121-L123
is:
this.pcond.L.Lock()
this.ccond.Broadcast()
this.pcond.L.Unlock()
or just:
this.ccond.L.Lock()
this.ccond.Broadcast()
this.ccond.L.Unlock()
?
2 https://github.com/surgemq/surgemq/blob/master/topics/memtopics.go#L30-L48
why there are two same lines:
var _ TopicsProvider = (*memTopics)(nil)

Appreciate!

[zhenjl]

On buffer.go, I think what's there is correct. I need to look back and document the logic.

On memtopics.go, it's a dup line. Thanks for finding it. Though that line is really ignored during compilation. I will fix though.

[ankoh]

@cloudzhou Regarding your first question: The variable naming is a little bit demanding to be honest but pcond is the PRODUCER condition. So what the code correctly does is it gains exclusive PRODUCER access and then notifies the CONSUMERS about new data.