public Scheduler()
{
this.queueCount = 0;
this.holdCount = 0;
this.blocks = new TaskControlBlock[NUMBER_OF_IDS];
this.list = null;
this.currentTCB = null;
this.currentId = 0;//check this
}
/**
* Add the specified packet to the end of the worklist used by the task
* associated with the packet and make the task runnable if it is currently
* suspended.
* #param {Packet} packet the packet to add
*/
public TaskControlBlock queue(Packet packet)
{
TaskControlBlock t = this.blocks[packet.id];
if (t == null)
{
return(t);
}
this.queueCount++;
packet.link = null;
packet.id = this.currentId;
return(t.checkPriorityAdd(this.currentTCB, packet));
}
public TaskControlBlock(TaskControlBlock link, int id, int priority, Packet queue, Task task)
{
this.link = link;
this.id = id;
this.priority = priority;
this.queue = queue;
this.task = task;
if (queue == null)
{
this.state = States.SUSPENDED;
}
else
{
this.state = States.SUSPENDED_RUNNABLE;
}
}
/**
* Execute the tasks managed by this scheduler.
*/
public void schedule()
{
this.currentTCB = this.list;
while (this.currentTCB != null)
{
if (this.currentTCB.isHeldOrSuspended())
{
this.currentTCB = this.currentTCB.link;
}
else
{
this.currentId = this.currentTCB.id;
this.currentTCB = this.currentTCB.run();
}
}
}
/**
* Adds a packet to the worklist of this block's task, marks this as runnable if
* necessary, and returns the next runnable object to run (the one
* with the highest priority).
*/
public TaskControlBlock checkPriorityAdd(TaskControlBlock task, Packet packet)
{
if (this.queue == null)
{
this.queue = packet;
this.markAsRunnable();
if (this.priority > task.priority)
{
return(this);
}
}
else
{
this.queue = packet.addTo(this.queue);
}
return(task);
}
/**
* Release a task that is currently blocked and return the next block to run.
* #param {int} id the id of the task to suspend
*/
public TaskControlBlock release(int id)
{
TaskControlBlock tcb = this.blocks[id];
if (tcb == null)
{
return(tcb);
}
tcb.markAsNotHeld();
if (tcb.priority > this.currentTCB.priority)
{
return(tcb);
}
else
{
return(this.currentTCB);
}
}
/**
* Add the specified task to this scheduler.
* @param {int} id the identity of the task
* @param {int} priority the task's priority
* @param {Packet} queue the queue of work to be processed by the task
* @param {Task} task the task to add
*/
public void addTask(int id, int priority, Packet queue, Task task)
{
this.currentTCB = new TaskControlBlock(this.list, id, priority, queue, task);
this.list = this.currentTCB;
this.blocks[id] = this.currentTCB;
}
