The ReadNow interface is intended for split-phase low-latency reading of small values. The type of the value is given as a template argument. Because this interface is split-phase, these values may be backed by hardware. Providers of this interface should also provide a Resource interface, and this interface should only be used after the resource has been acquired. Otherwise, the low-latency requirement may be impossible to meet.
This interface has the same calling semantics as the Read interface described in TEP 114, except that it is async.
val_t - the type of the object that will be returned
result - SUCCESS if the read() was successful
val - the value that has been read