LockedBox is missing; there is no way to asynchronously memcpy DeviceBox D2H or H2D #69

Maybe this is by design, but there is currently no way to asynchronously memcpy DeviceBox

DeviceBox's AsyncCopyDestination implementation only allows for device-to-device copies, there is no way to do a device-to-host or host-to-device asynchronous memcpy for a DeviceBox.