IOCP doesn't do it[1]. Well, if it does then it's not documented. You can post custom completion packets so at first glance it looks easy to make open/close be async...I think there is probably a good reason why NT won't do that for you.
That's pretty awesome though, that you have to worry about latency of open().
That's pretty awesome though, that you have to worry about latency of open().
[1] https://docs.microsoft.com/en-us/windows/desktop/fileio/i-o-...