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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