Source Code : Thread Pool 2

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Thread Pool 2

    
/*
 *
 * Copyright (c) 1997-1999 Scott Oaks and Henry Wong. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and
 * without fee is hereby granted.
 *
 * This sample source code is provided for example only,
 * on an unsupported, as-is basis. 
 *
 * AUTHOR MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. AUTHOR SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 *
 * THIS SOFTWARE IS NOT DESIGNED OR INTENDED FOR USE OR RESALE AS ON-LINE
 * CONTROL EQUIPMENT IN HAZARDOUS ENVIRONMENTS REQUIRING FAIL-SAFE
 * PERFORMANCE, SUCH AS IN THE OPERATION OF NUCLEAR FACILITIES, AIRCRAFT
 * NAVIGATION OR COMMUNICATION SYSTEMS, AIR TRAFFIC CONTROL, DIRECT LIFE
 * SUPPORT MACHINES, OR WEAPONS SYSTEMS, IN WHICH THE FAILURE OF THE
 * SOFTWARE COULD LEAD DIRECTLY TO DEATH, PERSONAL INJURY, OR SEVERE
 * PHYSICAL OR ENVIRONMENTAL DAMAGE ("HIGH RISK ACTIVITIES").  AUTHOR
 * SPECIFICALLY DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR
 * HIGH RISK ACTIVITIES.
 */

import java.util.*;

public class ThreadPool {

  class ThreadPoolRequest {
    Runnable target;
    Object lock;

    ThreadPoolRequest(Runnable t, Object l) {
      target = t;
      lock = l;
    }
  }

  class ThreadPoolThread extends Thread {
    ThreadPool parent;
    boolean shouldRun = true;

    ThreadPoolThread(ThreadPool parent, int i) {
      super("ThreadPoolThread " + i);
      this.parent = parent;
    }

    public void run() {
      ThreadPoolRequest obj = null;
      while (shouldRun) {
        try {
          parent.cvFlag.getBusyFlag();
          while (obj == null && shouldRun) {
            try {
              obj = (ThreadPoolRequest)
                  parent.objects.elementAt(0);
              parent.objects.removeElementAt(0);
            } catch (ArrayIndexOutOfBoundsException aiobe) {
              obj = null;
            } catch (ClassCastException cce) {
              System.err.println("Unexpected data");
              obj = null;
            }
            if (obj == null) {
              try {
                parent.cvAvailable.cvWait();
              } catch (InterruptedException ie) {
                return;
              }
            }
          }
        } finally {
          parent.cvFlag.freeBusyFlag();
        }
        if (!shouldRun)
          return;
        obj.target.run();
        try {
          parent.cvFlag.getBusyFlag();
          nObjects--;
          if (nObjects == 0)
            parent.cvEmpty.cvSignal();
        } finally {
          parent.cvFlag.freeBusyFlag();
        }
        if (obj.lock != null) {
          synchronized(obj.lock) {
            obj.lock.notify();
          }
        }
        obj = null;
      }
    }
  }

  Vector objects;
  int  nObjects = 0;
  CondVar cvAvailable, cvEmpty;
  BusyFlag cvFlag;
  ThreadPoolThread poolThreads[];
  boolean terminated = false;

  public ThreadPool(int n) {
    cvFlag = new BusyFlag();
    cvAvailable = new CondVar(cvFlag);
    cvEmpty = new CondVar(cvFlag);
    objects = new Vector();
    poolThreads = new ThreadPoolThread[n];
    for (int i = 0; i < n; i++) {
      poolThreads[i] = new ThreadPoolThread(this, i);
      poolThreads[i].start();
    }
  }

  private void add(Runnable target, Object lock) {
    try {
      cvFlag.getBusyFlag();
      if (terminated)
        throw new IllegalStateException("Thread pool has shutdown");
      objects.addElement(new ThreadPoolRequest(target, lock));
      nObjects++;
      cvAvailable.cvSignal();
    } finally {
      cvFlag.freeBusyFlag();
    }
  }

  public void addRequest(Runnable target) {
    add(target, null);
  }

  public void addRequestAndWait(Runnable target)
              throws InterruptedException {
    Object lock = new Object();
    synchronized(lock) {
      add(target, lock);
      lock.wait();
    }
  }

  public void waitForAll(boolean terminate) throws InterruptedException {
    try {
      cvFlag.getBusyFlag();
      while (nObjects != 0)
        cvEmpty.cvWait();
      if (terminate) {
        for (int i = 0; i < poolThreads.length; i++)
          poolThreads[i].shouldRun = false;
        cvAvailable.cvBroadcast();
        terminated = true;
      }
    } finally {
      cvFlag.freeBusyFlag();
    }
  }

  public void waitForAll() throws InterruptedException {
    waitForAll(false);
  }
}



           
         
    
    
    
  

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