private bool CheckForFartherRequests(scanDirection direction)
{
if (direction == scanDirection.FORWARD)
{
foreach (Request req in allRequests)
{
if (req.GetPosition() > drive.GetPosition())
{
return(true);
}
}
}
if (direction == scanDirection.BACKWARD)
{
foreach (Request req in allRequests)
{
if (req.GetPosition() < drive.GetPosition())
{
return(true);
}
}
}
return(false);
}
private void DoCSCAN(ref scanDirection direction)
{
if (drive.GetPosition() == drive.GetSize())
{
direction = scanDirection.BACKWARD;
}
if (drive.GetPosition() <= 0)
{
direction = scanDirection.FORWARD;
}
Scan(direction);
foreach (Request req in allRequests)
{
if (req.CheckRequestState() == Request.requestState.QUEUED)
{
if (CheckIfHeadOverRequest(req))
{
FinishRequest(req);
}
}
}
}
private void DoSCAN(ref scanDirection direction)
{
Scan(direction);
if (!CheckForFartherRequests(direction))
{
if (direction == scanDirection.FORWARD)
{
direction = scanDirection.BACKWARD;
}
else
{
direction = scanDirection.FORWARD;
}
}
foreach (Request req in allRequests)
{
if (req.CheckRequestState() == Request.requestState.QUEUED)
{
if (CheckIfHeadOverRequest(req))
{
FinishRequest(req);
//Console.WriteLine("Process " + allRequests.IndexOf(req) + "finished");
}
}
}
}
private void DoFDSCAN(ref scanDirection direction, ref Request movingTowards, List <RealTimeRequest> RealTimeRequests, int time)
{
List <RealTimeRequest> requestsPossible = FindRequestsThatCanBeServed(RealTimeRequests, time);
if (CheckFDSCANDirection(requestsPossible, time, direction) && movingTowards == null)
{
if (direction == scanDirection.FORWARD)
{
direction = scanDirection.BACKWARD;
}
else
{
direction = scanDirection.FORWARD;
}
movingTowards = requestsPossible.First(); // So that it does not check for new Requests when the head is moving towards the chosen request
}
Scan(direction);
foreach (Request req in allRequests)
{
if (req.CheckRequestState() == Request.requestState.QUEUED)
{
if (req.GetPosition() == drive.GetPosition())
{
if (req.Equals(movingTowards))
{
movingTowards = null;
}
FinishRequest(req);
}
}
}
}
private void Scan(scanDirection direction)
{
if (direction == scanDirection.BACKWARD)
{
drive.MoveHeadBack();
}
else
{
drive.MoveHeadForward();
}
}
public void Simulate()
{
int time = 0;
scanDirection direction = scanDirection.FORWARD;
Request movingTowards = null;
simulationMode previousMode = currentMode;
while (!CheckIfSimulationFinished())
{
UpdateQueue(time);
List <RealTimeRequest> realTimeRequests = FindRealtimeRequests(time);
if (realTimeRequests.Count > 0)
{
switch (RTRmode)
{
case RTRServiceModes.FDSCAN:
currentMode = simulationMode.FDSCAN;
break;
case RTRServiceModes.EDF:
currentMode = simulationMode.EDF;
break;
}
} // Change mode to EDF/FDSCAN if there are any RTR's in the queue.
else
{
currentMode = previousMode; //Go back to previous mode after serving all RTR
}
switch (currentMode)
{
case simulationMode.FCFS:
DoFCFS();
break;
case simulationMode.SSTF:
DoSSTF();
break;
case simulationMode.CSCAN:
DoCSCAN(ref direction);
break;
case simulationMode.SCAN:
DoSCAN(ref direction);
break;
case simulationMode.EDF:
DoEDF(time, realTimeRequests);
break;
case simulationMode.FDSCAN:
DoFDSCAN(ref direction, ref movingTowards, realTimeRequests, time);
break;
}
time++;
}
}
private bool CheckFDSCANDirection(List <RealTimeRequest> realTimeRequests, int currentTime, scanDirection currentDirection)
{
List <RealTimeRequest> realTimeRequestsThatCanBeServed = FindRequestsThatCanBeServed(realTimeRequests, currentTime);
try {
RealTimeRequest requestToBeServed = realTimeRequestsThatCanBeServed.First();
if (currentDirection == scanDirection.FORWARD)
{
if (requestToBeServed.GetPosition() > drive.GetPosition())
{
return(false);
}
else
{
return(true);
}
}
else if (currentDirection == scanDirection.BACKWARD)
{
if (requestToBeServed.GetPosition() > drive.GetPosition())
{
return(true);
}
return(false);
}
else
{
return(false);
}
}
catch (NullReferenceException exception)
{
return(false);
}
}
