Actually issues the request, starting the operation.
Cancels the request. This will cause isComplete to return true once the cancellation has been processed, but AsyncOperationResponse.wasSuccessful will return false (unless it completed before the cancellation was processed, in which case it is still allowed to finish successfully).
Returns true if the operation has been completed. It may be completed successfully, cancelled, or have errored out - to check this, call waitForCompletion and check the members on the response object.
Waits until the request has completed - successfully or otherwise - and returns the response object. It will run an ad-hoc event loop that may call other callbacks while waiting.
You can write to a file asynchronously by creating one of these.