On Windows, the normal ReadFile function can return synchronously or async (if you pass the appropriate arguments to it) depending on presence in the cache. Sin

On Windows, the normal ReadFile function can return synchronously or async (if you pass the appropriate arguments to it) depending on presence in the cache. Since it is all one atomic operation, there's no race condition; you just call it and see in the return value if it succeeded immediately or queued the operation. (If you haven't read about Windows' overlapped i/o, do so, it is actually quite nice to use.) io_uring brings something similar to Linux.