//--------------------------------------------------------------------
// OffsetClock - A simple wrapper to simulate a settable clock
//               by maintaining an offset to the system clock.
//
// CSEP590SG Winter 2004 - University of Washington
// Andy Collins - acollins@cs.washington.edu
//--------------------------------------------------------------------
import java.util.*;
import java.io.*;

public class OffsetClock
{
   // Create a clock with no extra drift, 
   // and starting in sync with the system clock
   public OffsetClock ()
   {
      offset = 0;
      rho = 0.0;
      lastRhoChangeActualTime = System.currentTimeMillis ();
   }

   // Create a clock with no extra drift, 
   // but starting at the specified time
   public OffsetClock (long startTimeMS)
   {
      offset = startTimeMS - System.currentTimeMillis ();
      rho = 0.0;
      lastRhoChangeActualTime = System.currentTimeMillis ();
   }

   // Create a clock with extra drift, 
   // and starting at the specified time
   public OffsetClock (double rhoValue, long startTimeMS)
   {
      offset = startTimeMS - System.currentTimeMillis ();
      rho = rhoValue;
      lastRhoChangeActualTime = System.currentTimeMillis ();
   }

   public synchronized void SetRho (double rhoValue)
   {
      rho = rhoValue;
      lastRhoChangeActualTime = System.currentTimeMillis ();
   }

   public synchronized long CurrentTimeMillis ()
   {
      // Read the real clock.  Note that this is itself subject
      // to error, a fact we studiously ignore in the hope that
      // our applied error will dominate.

      long actualTime = System.currentTimeMillis ();
      long reportedTime = actualTime + offset + 
               (long) ((double) (actualTime - lastRhoChangeActualTime)*rho);

      return reportedTime;
   }

   public synchronized void SetCurrentTimeMillis (long newTime)
   {
      offset = newTime - System.currentTimeMillis ();
   }

   private double rho;
   private long lastRhoChangeActualTime;
   private long offset;
}