Returns a timestamp in microseconds (1/1'000'000th of a second) as an integer (64bit). A typical use case is the exact measurement of time intervals, e.g. for profiling and logging purposes.
The time stamp is calculated in microseconds beginning at the Unix epoch. It's not guarantied that a time stamp is unique. On a sufficiently fast machine it is possible to retrieve two identical time stamps. In some cases, the utility function getSequenceNumber() may be the better solution.