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/*******************************************************************************
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* RRScheduler.java
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*
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* Implementation of a Round-Robin Scheduler for CS431 Project #1.
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*
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* Copyright (c) 2006, Ira W. Snyder (devel@irasnyder.com)
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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******************************************************************************/
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/**
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* A Round-Robin Scheduler.
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*
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* @class CS431 Fall 2006
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* @author Ira W. Snyder (devel@irasnyder.com)
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*/
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public class RRScheduler extends Scheduler
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{
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/** the interval at which to switch processes */
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protected final int interval;
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/** the amount of time that the current process has been running */
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protected int cur_proc_runtime = 0;
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/**
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* Constructor for the Round Robin Scheduler class.
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*/
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public RRScheduler (int interval)
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{
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super ();
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this.interval = interval;
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}
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/**
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* Emulates a single time unit in a Round Robin Scheduler.
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*
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* @return false if there is nothing left to do, true otherwise
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*/
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protected boolean step ()
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{
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/* Stop if we have nothing left to do */
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if (schedulerFinished ())
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return false;
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/* Pull in any new processes */
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queueWaitingProcesses ();
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/* Get a new process if we need to */
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if (cur_proc == null)
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{
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startProcess (run_queue.firstElement ());
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cur_proc_runtime = 0;
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}
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/* Run the process */
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if (cur_proc_runtime < interval)
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{
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if (cur_proc.time_left > 0)
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{
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scheduleCurrent ();
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cur_proc_runtime++;
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}
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else
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completeCurrent ();
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}
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else
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{
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if (cur_proc.time_left > 0)
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expireCurrent ();
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else
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completeCurrent ();
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}
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return true;
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}
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}
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/* vim: set ts=4 sts=4 sw=4 expandtab: */
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