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/*******************************************************************************
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* SJFScheduler.java
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*
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* This file holds the implementation of the SJFScheduler class, which is a
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* Shortest Job First Scheduler, non-preemptive.
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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 Shortest Job First 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 SJFScheduler extends Scheduler
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{
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/**
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* Find the Process with the shortest timeslice in the run queue.
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*
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* @return the Process with the shortest timeslice
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*/
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private Process findShortest ()
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{
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Process shortest = new Process ("fake", Integer.MAX_VALUE);
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for (Process p : run_queue)
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if (p.timeslice < shortest.timeslice)
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shortest = p;
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return shortest;
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}
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/**
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* Emulate a single time unit in a Shortest Job First scheduler.
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*
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* @return false if the scheduler is finished, true otherwise
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*/
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protected boolean step ()
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{
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/* Leave if we are truly done */
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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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/* If there is no process, then get one! */
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if (cur_proc == null)
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startProcess (findShortest ());
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/* If the current process is set to run, do so, return false */
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if (cur_proc.time_left > 0)
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scheduleCurrent ();
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else
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completeCurrent ();
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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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