2cc07ffcf1
2004-11-17 Michael Koch <konqueror@gmx.de> * java/util/Timer.java (DEFAULT_SIZE): Made static. From-SVN: r90798
609 lines
17 KiB
Java
609 lines
17 KiB
Java
/* Timer.java -- Timer that runs TimerTasks at a later time.
|
|
Copyright (C) 2000, 2001 Free Software Foundation, Inc.
|
|
|
|
This file is part of GNU Classpath.
|
|
|
|
GNU Classpath 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, or (at your option)
|
|
any later version.
|
|
|
|
GNU Classpath 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 GNU Classpath; see the file COPYING. If not, write to the
|
|
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
|
02111-1307 USA.
|
|
|
|
Linking this library statically or dynamically with other modules is
|
|
making a combined work based on this library. Thus, the terms and
|
|
conditions of the GNU General Public License cover the whole
|
|
combination.
|
|
|
|
As a special exception, the copyright holders of this library give you
|
|
permission to link this library with independent modules to produce an
|
|
executable, regardless of the license terms of these independent
|
|
modules, and to copy and distribute the resulting executable under
|
|
terms of your choice, provided that you also meet, for each linked
|
|
independent module, the terms and conditions of the license of that
|
|
module. An independent module is a module which is not derived from
|
|
or based on this library. If you modify this library, you may extend
|
|
this exception to your version of the library, but you are not
|
|
obligated to do so. If you do not wish to do so, delete this
|
|
exception statement from your version. */
|
|
|
|
package java.util;
|
|
|
|
/**
|
|
* Timer that can run TimerTasks at a later time.
|
|
* TimerTasks can be scheduled for one time execution at some time in the
|
|
* future. They can be scheduled to be rescheduled at a time period after the
|
|
* task was last executed. Or they can be scheduled to be executed repeatedly
|
|
* at a fixed rate.
|
|
* <p>
|
|
* The normal scheduling will result in a more or less even delay in time
|
|
* between successive executions, but the executions could drift in time if
|
|
* the task (or other tasks) takes a long time to execute. Fixed delay
|
|
* scheduling guarantees more or less that the task will be executed at a
|
|
* specific time, but if there is ever a delay in execution then the period
|
|
* between successive executions will be shorter. The first method of
|
|
* repeated scheduling is preferred for repeated tasks in response to user
|
|
* interaction, the second method of repeated scheduling is preferred for tasks
|
|
* that act like alarms.
|
|
* <p>
|
|
* The Timer keeps a binary heap as a task priority queue which means that
|
|
* scheduling and serving of a task in a queue of n tasks costs O(log n).
|
|
*
|
|
* @see TimerTask
|
|
* @since 1.3
|
|
* @author Mark Wielaard (mark@klomp.org)
|
|
*/
|
|
public class Timer
|
|
{
|
|
/**
|
|
* Priority Task Queue.
|
|
* TimerTasks are kept in a binary heap.
|
|
* The scheduler calls sleep() on the queue when it has nothing to do or
|
|
* has to wait. A sleeping scheduler can be notified by calling interrupt()
|
|
* which is automatically called by the enqueue(), cancel() and
|
|
* timerFinalized() methods.
|
|
*/
|
|
private static final class TaskQueue
|
|
{
|
|
/** Default size of this queue */
|
|
private static final int DEFAULT_SIZE = 32;
|
|
|
|
/** Whether to return null when there is nothing in the queue */
|
|
private boolean nullOnEmpty;
|
|
|
|
/**
|
|
* The heap containing all the scheduled TimerTasks
|
|
* sorted by the TimerTask.scheduled field.
|
|
* Null when the stop() method has been called.
|
|
*/
|
|
private TimerTask heap[];
|
|
|
|
/**
|
|
* The actual number of elements in the heap
|
|
* Can be less then heap.length.
|
|
* Note that heap[0] is used as a sentinel.
|
|
*/
|
|
private int elements;
|
|
|
|
/**
|
|
* Creates a TaskQueue of default size without any elements in it.
|
|
*/
|
|
public TaskQueue()
|
|
{
|
|
heap = new TimerTask[DEFAULT_SIZE];
|
|
elements = 0;
|
|
nullOnEmpty = false;
|
|
}
|
|
|
|
/**
|
|
* Adds a TimerTask at the end of the heap.
|
|
* Grows the heap if necessary by doubling the heap in size.
|
|
*/
|
|
private void add(TimerTask task)
|
|
{
|
|
elements++;
|
|
if (elements == heap.length)
|
|
{
|
|
TimerTask new_heap[] = new TimerTask[heap.length * 2];
|
|
System.arraycopy(heap, 0, new_heap, 0, heap.length);
|
|
heap = new_heap;
|
|
}
|
|
heap[elements] = task;
|
|
}
|
|
|
|
/**
|
|
* Removes the last element from the heap.
|
|
* Shrinks the heap in half if
|
|
* elements+DEFAULT_SIZE/2 <= heap.length/4.
|
|
*/
|
|
private void remove()
|
|
{
|
|
// clear the entry first
|
|
heap[elements] = null;
|
|
elements--;
|
|
if (elements + DEFAULT_SIZE / 2 <= (heap.length / 4))
|
|
{
|
|
TimerTask new_heap[] = new TimerTask[heap.length / 2];
|
|
System.arraycopy(heap, 0, new_heap, 0, elements + 1);
|
|
heap = new_heap;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Adds a task to the queue and puts it at the correct place
|
|
* in the heap.
|
|
*/
|
|
public synchronized void enqueue(TimerTask task)
|
|
{
|
|
// Check if it is legal to add another element
|
|
if (heap == null)
|
|
{
|
|
throw new IllegalStateException
|
|
("cannot enqueue when stop() has been called on queue");
|
|
}
|
|
|
|
heap[0] = task; // sentinel
|
|
add(task); // put the new task at the end
|
|
// Now push the task up in the heap until it has reached its place
|
|
int child = elements;
|
|
int parent = child / 2;
|
|
while (heap[parent].scheduled > task.scheduled)
|
|
{
|
|
heap[child] = heap[parent];
|
|
child = parent;
|
|
parent = child / 2;
|
|
}
|
|
// This is the correct place for the new task
|
|
heap[child] = task;
|
|
heap[0] = null; // clear sentinel
|
|
// Maybe sched() is waiting for a new element
|
|
this.notify();
|
|
}
|
|
|
|
/**
|
|
* Returns the top element of the queue.
|
|
* Can return null when no task is in the queue.
|
|
*/
|
|
private TimerTask top()
|
|
{
|
|
if (elements == 0)
|
|
{
|
|
return null;
|
|
}
|
|
else
|
|
{
|
|
return heap[1];
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns the top task in the Queue.
|
|
* Removes the element from the heap and reorders the heap first.
|
|
* Can return null when there is nothing in the queue.
|
|
*/
|
|
public synchronized TimerTask serve()
|
|
{
|
|
// The task to return
|
|
TimerTask task = null;
|
|
|
|
while (task == null)
|
|
{
|
|
// Get the next task
|
|
task = top();
|
|
|
|
// return null when asked to stop
|
|
// or if asked to return null when the queue is empty
|
|
if ((heap == null) || (task == null && nullOnEmpty))
|
|
{
|
|
return null;
|
|
}
|
|
|
|
// Do we have a task?
|
|
if (task != null)
|
|
{
|
|
// The time to wait until the task should be served
|
|
long time = task.scheduled - System.currentTimeMillis();
|
|
if (time > 0)
|
|
{
|
|
// This task should not yet be served
|
|
// So wait until this task is ready
|
|
// or something else happens to the queue
|
|
task = null; // set to null to make sure we call top()
|
|
try
|
|
{
|
|
this.wait(time);
|
|
}
|
|
catch (InterruptedException _)
|
|
{
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// wait until a task is added
|
|
// or something else happens to the queue
|
|
try
|
|
{
|
|
this.wait();
|
|
}
|
|
catch (InterruptedException _)
|
|
{
|
|
}
|
|
}
|
|
}
|
|
|
|
// reconstruct the heap
|
|
TimerTask lastTask = heap[elements];
|
|
remove();
|
|
|
|
// drop lastTask at the beginning and move it down the heap
|
|
int parent = 1;
|
|
int child = 2;
|
|
heap[1] = lastTask;
|
|
while (child <= elements)
|
|
{
|
|
if (child < elements)
|
|
{
|
|
if (heap[child].scheduled > heap[child + 1].scheduled)
|
|
{
|
|
child++;
|
|
}
|
|
}
|
|
|
|
if (lastTask.scheduled <= heap[child].scheduled)
|
|
break; // found the correct place (the parent) - done
|
|
|
|
heap[parent] = heap[child];
|
|
parent = child;
|
|
child = parent * 2;
|
|
}
|
|
|
|
// this is the correct new place for the lastTask
|
|
heap[parent] = lastTask;
|
|
|
|
// return the task
|
|
return task;
|
|
}
|
|
|
|
/**
|
|
* When nullOnEmpty is true the serve() method will return null when
|
|
* there are no tasks in the queue, otherwise it will wait until
|
|
* a new element is added to the queue. It is used to indicate to
|
|
* the scheduler that no new tasks will ever be added to the queue.
|
|
*/
|
|
public synchronized void setNullOnEmpty(boolean nullOnEmpty)
|
|
{
|
|
this.nullOnEmpty = nullOnEmpty;
|
|
this.notify();
|
|
}
|
|
|
|
/**
|
|
* When this method is called the current and all future calls to
|
|
* serve() will return null. It is used to indicate to the Scheduler
|
|
* that it should stop executing since no more tasks will come.
|
|
*/
|
|
public synchronized void stop()
|
|
{
|
|
this.heap = null;
|
|
this.elements = 0;
|
|
this.notify();
|
|
}
|
|
|
|
} // TaskQueue
|
|
|
|
/**
|
|
* The scheduler that executes all the tasks on a particular TaskQueue,
|
|
* reschedules any repeating tasks and that waits when no task has to be
|
|
* executed immediatly. Stops running when canceled or when the parent
|
|
* Timer has been finalized and no more tasks have to be executed.
|
|
*/
|
|
private static final class Scheduler implements Runnable
|
|
{
|
|
// The priority queue containing all the TimerTasks.
|
|
private TaskQueue queue;
|
|
|
|
/**
|
|
* Creates a new Scheduler that will schedule the tasks on the
|
|
* given TaskQueue.
|
|
*/
|
|
public Scheduler(TaskQueue queue)
|
|
{
|
|
this.queue = queue;
|
|
}
|
|
|
|
public void run()
|
|
{
|
|
TimerTask task;
|
|
while ((task = queue.serve()) != null)
|
|
{
|
|
// If this task has not been canceled
|
|
if (task.scheduled >= 0)
|
|
{
|
|
|
|
// Mark execution time
|
|
task.lastExecutionTime = task.scheduled;
|
|
|
|
// Repeatable task?
|
|
if (task.period < 0)
|
|
{
|
|
// Last time this task is executed
|
|
task.scheduled = -1;
|
|
}
|
|
|
|
// Run the task
|
|
try
|
|
{
|
|
task.run();
|
|
}
|
|
catch (Throwable t)
|
|
{
|
|
/* ignore all errors */
|
|
}
|
|
}
|
|
|
|
// Calculate next time and possibly re-enqueue.
|
|
if (task.scheduled >= 0)
|
|
{
|
|
if (task.fixed)
|
|
{
|
|
task.scheduled += task.period;
|
|
}
|
|
else
|
|
{
|
|
task.scheduled = task.period + System.currentTimeMillis();
|
|
}
|
|
|
|
try
|
|
{
|
|
queue.enqueue(task);
|
|
}
|
|
catch (IllegalStateException ise)
|
|
{
|
|
// Ignore. Apparently the Timer queue has been stopped.
|
|
}
|
|
}
|
|
}
|
|
}
|
|
} // Scheduler
|
|
|
|
// Number of Timers created.
|
|
// Used for creating nice Thread names.
|
|
private static int nr;
|
|
|
|
// The queue that all the tasks are put in.
|
|
// Given to the scheduler
|
|
private TaskQueue queue;
|
|
|
|
// The Scheduler that does all the real work
|
|
private Scheduler scheduler;
|
|
|
|
// Used to run the scheduler.
|
|
// Also used to checked if the Thread is still running by calling
|
|
// thread.isAlive(). Sometimes a Thread is suddenly killed by the system
|
|
// (if it belonged to an Applet).
|
|
private Thread thread;
|
|
|
|
// When cancelled we don't accept any more TimerTasks.
|
|
private boolean canceled;
|
|
|
|
/**
|
|
* Creates a new Timer with a non daemon Thread as Scheduler, with normal
|
|
* priority and a default name.
|
|
*/
|
|
public Timer()
|
|
{
|
|
this(false);
|
|
}
|
|
|
|
/**
|
|
* Creates a new Timer with a daemon Thread as scheduler if daemon is true,
|
|
* with normal priority and a default name.
|
|
*/
|
|
public Timer(boolean daemon)
|
|
{
|
|
this(daemon, Thread.NORM_PRIORITY);
|
|
}
|
|
|
|
/**
|
|
* Creates a new Timer with a daemon Thread as scheduler if daemon is true,
|
|
* with the priority given and a default name.
|
|
*/
|
|
private Timer(boolean daemon, int priority)
|
|
{
|
|
this(daemon, priority, "Timer-" + (++nr));
|
|
}
|
|
|
|
/**
|
|
* Creates a new Timer with a daemon Thread as scheduler if daemon is true,
|
|
* with the priority and name given.E
|
|
*/
|
|
private Timer(boolean daemon, int priority, String name)
|
|
{
|
|
canceled = false;
|
|
queue = new TaskQueue();
|
|
scheduler = new Scheduler(queue);
|
|
thread = new Thread(scheduler, name);
|
|
thread.setDaemon(daemon);
|
|
thread.setPriority(priority);
|
|
thread.start();
|
|
}
|
|
|
|
/**
|
|
* Cancels the execution of the scheduler. If a task is executing it will
|
|
* normally finish execution, but no other tasks will be executed and no
|
|
* more tasks can be scheduled.
|
|
*/
|
|
public void cancel()
|
|
{
|
|
canceled = true;
|
|
queue.stop();
|
|
}
|
|
|
|
/**
|
|
* Schedules the task at Time time, repeating every period
|
|
* milliseconds if period is positive and at a fixed rate if fixed is true.
|
|
*
|
|
* @exception IllegalArgumentException if time is negative
|
|
* @exception IllegalStateException if the task was already scheduled or
|
|
* canceled or this Timer is canceled or the scheduler thread has died
|
|
*/
|
|
private void schedule(TimerTask task, long time, long period, boolean fixed)
|
|
{
|
|
if (time < 0)
|
|
throw new IllegalArgumentException("negative time");
|
|
|
|
if (task.scheduled == 0 && task.lastExecutionTime == -1)
|
|
{
|
|
task.scheduled = time;
|
|
task.period = period;
|
|
task.fixed = fixed;
|
|
}
|
|
else
|
|
{
|
|
throw new IllegalStateException
|
|
("task was already scheduled or canceled");
|
|
}
|
|
|
|
if (!this.canceled && this.thread != null)
|
|
{
|
|
queue.enqueue(task);
|
|
}
|
|
else
|
|
{
|
|
throw new IllegalStateException
|
|
("timer was canceled or scheduler thread has died");
|
|
}
|
|
}
|
|
|
|
private static void positiveDelay(long delay)
|
|
{
|
|
if (delay < 0)
|
|
{
|
|
throw new IllegalArgumentException("delay is negative");
|
|
}
|
|
}
|
|
|
|
private static void positivePeriod(long period)
|
|
{
|
|
if (period < 0)
|
|
{
|
|
throw new IllegalArgumentException("period is negative");
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Schedules the task at the specified data for one time execution.
|
|
*
|
|
* @exception IllegalArgumentException if date.getTime() is negative
|
|
* @exception IllegalStateException if the task was already scheduled or
|
|
* canceled or this Timer is canceled or the scheduler thread has died
|
|
*/
|
|
public void schedule(TimerTask task, Date date)
|
|
{
|
|
long time = date.getTime();
|
|
schedule(task, time, -1, false);
|
|
}
|
|
|
|
/**
|
|
* Schedules the task at the specified date and reschedules the task every
|
|
* period milliseconds after the last execution of the task finishes until
|
|
* this timer or the task is canceled.
|
|
*
|
|
* @exception IllegalArgumentException if period or date.getTime() is
|
|
* negative
|
|
* @exception IllegalStateException if the task was already scheduled or
|
|
* canceled or this Timer is canceled or the scheduler thread has died
|
|
*/
|
|
public void schedule(TimerTask task, Date date, long period)
|
|
{
|
|
positivePeriod(period);
|
|
long time = date.getTime();
|
|
schedule(task, time, period, false);
|
|
}
|
|
|
|
/**
|
|
* Schedules the task after the specified delay milliseconds for one time
|
|
* execution.
|
|
*
|
|
* @exception IllegalArgumentException if delay or
|
|
* System.currentTimeMillis + delay is negative
|
|
* @exception IllegalStateException if the task was already scheduled or
|
|
* canceled or this Timer is canceled or the scheduler thread has died
|
|
*/
|
|
public void schedule(TimerTask task, long delay)
|
|
{
|
|
positiveDelay(delay);
|
|
long time = System.currentTimeMillis() + delay;
|
|
schedule(task, time, -1, false);
|
|
}
|
|
|
|
/**
|
|
* Schedules the task after the delay milliseconds and reschedules the
|
|
* task every period milliseconds after the last execution of the task
|
|
* finishes until this timer or the task is canceled.
|
|
*
|
|
* @exception IllegalArgumentException if delay or period is negative
|
|
* @exception IllegalStateException if the task was already scheduled or
|
|
* canceled or this Timer is canceled or the scheduler thread has died
|
|
*/
|
|
public void schedule(TimerTask task, long delay, long period)
|
|
{
|
|
positiveDelay(delay);
|
|
positivePeriod(period);
|
|
long time = System.currentTimeMillis() + delay;
|
|
schedule(task, time, period, false);
|
|
}
|
|
|
|
/**
|
|
* Schedules the task at the specified date and reschedules the task at a
|
|
* fixed rate every period milliseconds until this timer or the task is
|
|
* canceled.
|
|
*
|
|
* @exception IllegalArgumentException if period or date.getTime() is
|
|
* negative
|
|
* @exception IllegalStateException if the task was already scheduled or
|
|
* canceled or this Timer is canceled or the scheduler thread has died
|
|
*/
|
|
public void scheduleAtFixedRate(TimerTask task, Date date, long period)
|
|
{
|
|
positivePeriod(period);
|
|
long time = date.getTime();
|
|
schedule(task, time, period, true);
|
|
}
|
|
|
|
/**
|
|
* Schedules the task after the delay milliseconds and reschedules the task
|
|
* at a fixed rate every period milliseconds until this timer or the task
|
|
* is canceled.
|
|
*
|
|
* @exception IllegalArgumentException if delay or
|
|
* System.currentTimeMillis + delay is negative
|
|
* @exception IllegalStateException if the task was already scheduled or
|
|
* canceled or this Timer is canceled or the scheduler thread has died
|
|
*/
|
|
public void scheduleAtFixedRate(TimerTask task, long delay, long period)
|
|
{
|
|
positiveDelay(delay);
|
|
positivePeriod(period);
|
|
long time = System.currentTimeMillis() + delay;
|
|
schedule(task, time, period, true);
|
|
}
|
|
|
|
/**
|
|
* Tells the scheduler that the Timer task died
|
|
* so there will be no more new tasks scheduled.
|
|
*/
|
|
protected void finalize() throws Throwable
|
|
{
|
|
queue.setNullOnEmpty(true);
|
|
}
|
|
}
|