Package jmt.engine.NetStrategies.QueuePutStrategies

Source Code of jmt.engine.NetStrategies.QueuePutStrategies.HeadStrategyPriority

/**   
  * Copyright (C) 2006, Laboratorio di Valutazione delle Prestazioni - Politecnico di Milano

  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.

  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.

  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */

package jmt.engine.NetStrategies.QueuePutStrategies;

import java.util.List;
import java.util.ListIterator;

import jmt.engine.NetStrategies.QueuePutStrategy;
import jmt.engine.QueueNet.Job;
import jmt.engine.QueueNet.JobInfo;
import jmt.engine.QueueNet.JobInfoList;
import jmt.engine.QueueNet.NetNode;
import jmt.engine.QueueNet.NodeSection;

/**
* This class implements a specific queue put strategy: all arriving jobs
* are ordered according JobClass priorities. Between jobs of the same
* priority level, the last come is put at the beginning.
* @author Stefano Omini
*/
public class HeadStrategyPriority implements QueuePutStrategy {

  /** This method should be overridden to implement a specific job strategy.
   * @param job Job to be added to the queue.
   * @param queue Queue.
   * @param sourceSection Job source section.
   * @param sourceNode Job source node.
   * @param callingSection The section which calls this strategy.
   */
  public void put(Job job, JobInfoList queue, byte sourceSection, NetNode sourceNode, NodeSection callingSection) {

    //priority of this job
    int priority = job.getJobClass().getPriority();

    //list of jobs in queue
    List<JobInfo> list = queue.getJobList();

    if (list.size() == 0) {
      //empty list: add first in general and class lists
      queue.addFirst(new JobInfo(job), false);
      return;
    }

    //else creates an iterator and find the correct position
    //according to the job priority

    ListIterator<JobInfo> iterator = list.listIterator();
    JobInfo current = null;
    int currentJobPriority = 0;
    int index = -1;

    //iterator starts from the first (i.e. the job with highest priority)
    while (iterator.hasNext()) {
      index++;
      current = iterator.next();
      currentJobPriority = current.getJob().getJobClass().getPriority();

      if (priority >= currentJobPriority) {
        //the job to be added must be inserted before the current job
        //(because has greater priority or has equal priority but it is the last come)

        //index is the position of the current element, which will be shifted together
        //with the following ones

        queue.add(index, new JobInfo(job), false);
        return;
      }
      //else if priority is lower than current, continue iteration
    }

    //exiting from the "while" means that the job to be inserted is the job with
    //lowest priority
    //add last
    queue.addLast(new JobInfo(job), false);
    return;
  }

  /* (non-Javadoc)
   * @see jmt.common.AutoCheck#check()
   */
  public boolean check() {
    return true;
  }
}
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