public Process(string name, Process parent, int priority)
{
Name = name;
Parent = parent;
Priority = priority;
HeldResources = new Dictionary<string, int>();
}
private void DestroyProcess(Process process)
{
// Cancel pending resource requests.
if (process.WaitingNode != null)
{
var resource = resources[process.WaitingResourceName];
Node<AccessRequest>.Remove(ref resource.WaitingList, process.WaitingNode);
process.WaitingNode = null;
process.WaitingResourceName = null;
}
// Release all resources.
foreach (var kvPair in process.HeldResources)
resources[kvPair.Key].Available += kvPair.Value;
process.HeldResources.Clear();
// Remove from ready queue.
if (process.ReadyNode != null)
{
Node<Process>.Remove(ref readyQueue[process.Priority], process.ReadyNode);
process.ReadyNode = null;
}
// Remove from master process list.
processes.Remove(process.Name);
}
private void OnInit(InitCommand command)
{
// Clear state.
processes.Clear();
readyQueue[0] = readyQueue[1] = readyQueue[2] = null;
resources.Clear();
resources["R1"] = new Resource("R1", 1);
resources["R2"] = new Resource("R2", 2);
resources["R3"] = new Resource("R3", 3);
resources["R4"] = new Resource("R4", 4);
resources["IO"] = new Resource("IO", 1);
// Start the Init process.
var init = new Process("Init", null, 0) {Status = ProcessStatus.Ready};
foreach (var resource in resources.Values)
init.HeldResources[resource.Name] = 0;
processes.Add(init.Name, init);
var readyQueueNode = new Node<Process>(init);
init.ReadyNode = readyQueueNode;
Node<Process>.AddToBack(ref readyQueue[0], readyQueueNode);
}
private void OnCreate(CreateCommand command)
{
// Check for duplicate name.
if (processes.ContainsKey(command.ProcessName))
{
output.WriteLine(Purpose.Error, "A process named \"{0}\" already exists.", command.ProcessName);
return;
}
// Create new process as child of currently running process,
// or of no process if there's no running process in the system.
var parent = GetReadyProcess();
var child = new Process(command.ProcessName, parent, command.Priority);
foreach (var resource in resources.Values)
child.HeldResources[resource.Name] = 0;
processes.Add(child.Name, child);
// Add to end of parent's linked list of children.
if (parent != null)
{
var childListNode = new Node<Process>(child);
Node<Process>.AddToBack(ref parent.ChildList, childListNode);
}
// Add to end of ready queue for proper priority.
var readyQueueNode = new Node<Process>(child);
child.ReadyNode = readyQueueNode;
Node<Process>.AddToBack(ref readyQueue[child.Priority], readyQueueNode);
child.Status = GetReadyProcess() == child
? ProcessStatus.Running
: ProcessStatus.Ready;
if (parent != null && child.Status == ProcessStatus.Running)
parent.Status = ProcessStatus.Ready;
}
private bool IsChildOf(Process parent, Process possibleChild)
{
if (parent.ChildList == null)
return false;
var current = parent.ChildList;
do
{
if (current.Data == possibleChild)
return true;
if (IsChildOf(current.Data, possibleChild))
return true;
}
while ((current = current.Next) != parent.ChildList);
return false;
}
private void DestroyProcessTree(Process root)
{
// Destroy all children...
Node<Process>.VisitAll(root.ChildList, DestroyProcessTree);
// ... before destroying root.
DestroyProcess(root);
}
public AccessRequest(Process process, int amount)
{
Process = process;
Amount = amount;
}