--- /dev/null
+/*
+ * @(#)Timer.java 1.9 03/01/23
+ *
+ * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
+ * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
+ */
+
+package instrumented.java.util;
+import java.util.Date;
+/**
+ * A facility for threads to schedule tasks for future execution in a
+ * background thread. Tasks may be scheduled for one-time execution, or for
+ * repeated execution at regular intervals.
+ *
+ * <p>Corresponding to each <tt>Timer</tt> object is a single background
+ * thread that is used to execute all of the timer's tasks, sequentially.
+ * Timer tasks should complete quickly. If a timer task takes excessive time
+ * to complete, it "hogs" the timer's task execution thread. This can, in
+ * turn, delay the execution of subsequent tasks, which may "bunch up" and
+ * execute in rapid succession when (and if) the offending task finally
+ * completes.
+ *
+ * <p>After the last live reference to a <tt>Timer</tt> object goes away
+ * <i>and</i> all outstanding tasks have completed execution, the timer's task
+ * execution thread terminates gracefully (and becomes subject to garbage
+ * collection). However, this can take arbitrarily long to occur. By
+ * default, the task execution thread does not run as a <i>daemon thread</i>,
+ * so it is capable of keeping an application from terminating. If a caller
+ * wants to terminate a timer's task execution thread rapidly, the caller
+ * should invoke the the timer's <tt>cancel</tt> method.
+ *
+ * <p>If the timer's task execution thread terminates unexpectedly, for
+ * example, because its <tt>stop</tt> method is invoked, any further
+ * attempt to schedule a task on the timer will result in an
+ * <tt>IllegalStateException</tt>, as if the timer's <tt>cancel</tt>
+ * method had been invoked.
+ *
+ * <p>This class is thread-safe: multiple threads can share a single
+ * <tt>Timer</tt> object without the need for external synchronization.
+ *
+ * <p>This class does <i>not</i> offer real-time guarantees: it schedules
+ * tasks using the <tt>Object.wait(long)</tt> method.
+ *
+ * <p>Implementation note: This class scales to large numbers of concurrently
+ * scheduled tasks (thousands should present no problem). Internally,
+ * it uses a binary heap to represent its task queue, so the cost to schedule
+ * a task is O(log n), where n is the number of concurrently scheduled tasks.
+ *
+ * @author Josh Bloch
+ * @version 1.9, 01/23/03
+ * @see TimerTask
+ * @see Object#wait(long)
+ * @since 1.3
+ */
+
+public class Timer {
+ /**
+ * The timer task queue. This data structure is shared with the timer
+ * thread. The timer produces tasks, via its various schedule calls,
+ * and the timer thread consumes, executing timer tasks as appropriate,
+ * and removing them from the queue when they're obsolete.
+ */
+ private TaskQueue queue = new TaskQueue();
+
+ /**
+ * The timer thread.
+ */
+ private TimerThread thread = new TimerThread(queue);
+
+ /**
+ * This object causes the timer's task execution thread to exit
+ * gracefully when there are no live references to the Timer object and no
+ * tasks in the timer queue. It is used in preference to a finalizer on
+ * Timer as such a finalizer would be susceptible to a subclass's
+ * finalizer forgetting to call it.
+ */
+ private Object threadReaper = new Object() {
+ protected void finalize() throws Throwable {
+ synchronized(queue) {
+ thread.newTasksMayBeScheduled = false;
+ queue.notify(); // In case queue is empty.
+ }
+ }
+ };
+
+ /**
+ * Creates a new timer. The associated thread does <i>not</i> run as
+ * a daemon.
+ *
+ * @see Thread
+ * @see #cancel()
+ */
+ public Timer() {
+ thread.start();
+ }
+
+ /**
+ * Creates a new timer whose associated thread may be specified to
+ * run as a daemon. A deamon thread is called for if the timer will
+ * be used to schedule repeating "maintenance activities", which must
+ * be performed as long as the application is running, but should not
+ * prolong the lifetime of the application.
+ *
+ * @param isDaemon true if the associated thread should run as a daemon.
+ *
+ * @see Thread
+ * @see #cancel()
+ */
+ public Timer(boolean isDaemon) {
+ thread.setDaemon(isDaemon);
+ thread.start();
+ }
+
+ /**
+ * Schedules the specified task for execution after the specified delay.
+ *
+ * @param task task to be scheduled.
+ * @param delay delay in milliseconds before task is to be executed.
+ * @throws IllegalArgumentException if <tt>delay</tt> is negative, or
+ * <tt>delay + System.currentTimeMillis()</tt> is negative.
+ * @throws IllegalStateException if task was already scheduled or
+ * cancelled, or timer was cancelled.
+ */
+ public void schedule(TimerTask task, long delay) {
+ if (delay < 0)
+ throw new IllegalArgumentException("Negative delay.");
+ sched(task, System.currentTimeMillis()+delay, 0);
+ }
+
+ /**
+ * Schedules the specified task for execution at the specified time. If
+ * the time is in the past, the task is scheduled for immediate execution.
+ *
+ * @param task task to be scheduled.
+ * @param time time at which task is to be executed.
+ * @throws IllegalArgumentException if <tt>time.getTime()</tt> is negative.
+ * @throws IllegalStateException if task was already scheduled or
+ * cancelled, timer was cancelled, or timer thread terminated.
+ */
+ public void schedule(TimerTask task, Date time) {
+ sched(task, time.getTime(), 0);
+ }
+
+ /**
+ * Schedules the specified task for repeated <i>fixed-delay execution</i>,
+ * beginning after the specified delay. Subsequent executions take place
+ * at approximately regular intervals separated by the specified period.
+ *
+ * <p>In fixed-delay execution, each execution is scheduled relative to
+ * the actual execution time of the previous execution. If an execution
+ * is delayed for any reason (such as garbage collection or other
+ * background activity), subsequent executions will be delayed as well.
+ * In the long run, the frequency of execution will generally be slightly
+ * lower than the reciprocal of the specified period (assuming the system
+ * clock underlying <tt>Object.wait(long)</tt> is accurate).
+ *
+ * <p>Fixed-delay execution is appropriate for recurring activities
+ * that require "smoothness." In other words, it is appropriate for
+ * activities where it is more important to keep the frequency accurate
+ * in the short run than in the long run. This includes most animation
+ * tasks, such as blinking a cursor at regular intervals. It also includes
+ * tasks wherein regular activity is performed in response to human
+ * input, such as automatically repeating a character as long as a key
+ * is held down.
+ *
+ * @param task task to be scheduled.
+ * @param delay delay in milliseconds before task is to be executed.
+ * @param period time in milliseconds between successive task executions.
+ * @throws IllegalArgumentException if <tt>delay</tt> is negative, or
+ * <tt>delay + System.currentTimeMillis()</tt> is negative.
+ * @throws IllegalStateException if task was already scheduled or
+ * cancelled, timer was cancelled, or timer thread terminated.
+ */
+ public void schedule(TimerTask task, long delay, long period) {
+ if (delay < 0)
+ throw new IllegalArgumentException("Negative delay.");
+ if (period <= 0)
+ throw new IllegalArgumentException("Non-positive period.");
+ sched(task, System.currentTimeMillis()+delay, -period);
+ }
+
+ /**
+ * Schedules the specified task for repeated <i>fixed-delay execution</i>,
+ * beginning at the specified time. Subsequent executions take place at
+ * approximately regular intervals, separated by the specified period.
+ *
+ * <p>In fixed-delay execution, each execution is scheduled relative to
+ * the actual execution time of the previous execution. If an execution
+ * is delayed for any reason (such as garbage collection or other
+ * background activity), subsequent executions will be delayed as well.
+ * In the long run, the frequency of execution will generally be slightly
+ * lower than the reciprocal of the specified period (assuming the system
+ * clock underlying <tt>Object.wait(long)</tt> is accurate).
+ *
+ * <p>Fixed-delay execution is appropriate for recurring activities
+ * that require "smoothness." In other words, it is appropriate for
+ * activities where it is more important to keep the frequency accurate
+ * in the short run than in the long run. This includes most animation
+ * tasks, such as blinking a cursor at regular intervals. It also includes
+ * tasks wherein regular activity is performed in response to human
+ * input, such as automatically repeating a character as long as a key
+ * is held down.
+ *
+ * @param task task to be scheduled.
+ * @param firstTime First time at which task is to be executed.
+ * @param period time in milliseconds between successive task executions.
+ * @throws IllegalArgumentException if <tt>time.getTime()</tt> is negative.
+ * @throws IllegalStateException if task was already scheduled or
+ * cancelled, timer was cancelled, or timer thread terminated.
+ */
+ public void schedule(TimerTask task, Date firstTime, long period) {
+ if (period <= 0)
+ throw new IllegalArgumentException("Non-positive period.");
+ sched(task, firstTime.getTime(), -period);
+ }
+
+ /**
+ * Schedules the specified task for repeated <i>fixed-rate execution</i>,
+ * beginning after the specified delay. Subsequent executions take place
+ * at approximately regular intervals, separated by the specified period.
+ *
+ * <p>In fixed-rate execution, each execution is scheduled relative to the
+ * scheduled execution time of the initial execution. If an execution is
+ * delayed for any reason (such as garbage collection or other background
+ * activity), two or more executions will occur in rapid succession to
+ * "catch up." In the long run, the frequency of execution will be
+ * exactly the reciprocal of the specified period (assuming the system
+ * clock underlying <tt>Object.wait(long)</tt> is accurate).
+ *
+ * <p>Fixed-rate execution is appropriate for recurring activities that
+ * are sensitive to <i>absolute</i> time, such as ringing a chime every
+ * hour on the hour, or running scheduled maintenance every day at a
+ * particular time. It is also appropriate for for recurring activities
+ * where the total time to perform a fixed number of executions is
+ * important, such as a countdown timer that ticks once every second for
+ * ten seconds. Finally, fixed-rate execution is appropriate for
+ * scheduling multiple repeating timer tasks that must remain synchronized
+ * with respect to one another.
+ *
+ * @param task task to be scheduled.
+ * @param delay delay in milliseconds before task is to be executed.
+ * @param period time in milliseconds between successive task executions.
+ * @throws IllegalArgumentException if <tt>delay</tt> is negative, or
+ * <tt>delay + System.currentTimeMillis()</tt> is negative.
+ * @throws IllegalStateException if task was already scheduled or
+ * cancelled, timer was cancelled, or timer thread terminated.
+ */
+ public void scheduleAtFixedRate(TimerTask task, long delay, long period) {
+ if (delay < 0)
+ throw new IllegalArgumentException("Negative delay.");
+ if (period <= 0)
+ throw new IllegalArgumentException("Non-positive period.");
+ sched(task, System.currentTimeMillis()+delay, period);
+ }
+
+ /**
+ * Schedules the specified task for repeated <i>fixed-rate execution</i>,
+ * beginning at the specified time. Subsequent executions take place at
+ * approximately regular intervals, separated by the specified period.
+ *
+ * <p>In fixed-rate execution, each execution is scheduled relative to the
+ * scheduled execution time of the initial execution. If an execution is
+ * delayed for any reason (such as garbage collection or other background
+ * activity), two or more executions will occur in rapid succession to
+ * "catch up." In the long run, the frequency of execution will be
+ * exactly the reciprocal of the specified period (assuming the system
+ * clock underlying <tt>Object.wait(long)</tt> is accurate).
+ *
+ * <p>Fixed-rate execution is appropriate for recurring activities that
+ * are sensitive to <i>absolute</i> time, such as ringing a chime every
+ * hour on the hour, or running scheduled maintenance every day at a
+ * particular time. It is also appropriate for for recurring activities
+ * where the total time to perform a fixed number of executions is
+ * important, such as a countdown timer that ticks once every second for
+ * ten seconds. Finally, fixed-rate execution is appropriate for
+ * scheduling multiple repeating timer tasks that must remain synchronized
+ * with respect to one another.
+ *
+ * @param task task to be scheduled.
+ * @param firstTime First time at which task is to be executed.
+ * @param period time in milliseconds between successive task executions.
+ * @throws IllegalArgumentException if <tt>time.getTime()</tt> is negative.
+ * @throws IllegalStateException if task was already scheduled or
+ * cancelled, timer was cancelled, or timer thread terminated.
+ */
+ public void scheduleAtFixedRate(TimerTask task, Date firstTime,
+ long period) {
+ if (period <= 0)
+ throw new IllegalArgumentException("Non-positive period.");
+ sched(task, firstTime.getTime(), period);
+ }
+
+ /**
+ * Schedule the specifed timer task for execution at the specified
+ * time with the specified period, in milliseconds. If period is
+ * positive, the task is scheduled for repeated execution; if period is
+ * zero, the task is scheduled for one-time execution. Time is specified
+ * in Date.getTime() format. This method checks timer state, task state,
+ * and initial execution time, but not period.
+ *
+ * @throws IllegalArgumentException if <tt>time()</tt> is negative.
+ * @throws IllegalStateException if task was already scheduled or
+ * cancelled, timer was cancelled, or timer thread terminated.
+ */
+ private void sched(TimerTask task, long time, long period) {
+ if (time < 0)
+ throw new IllegalArgumentException("Illegal execution time.");
+
+ synchronized(queue) {
+ if (!thread.newTasksMayBeScheduled)
+ throw new IllegalStateException("Timer already cancelled.");
+
+ synchronized(task.lock) {
+ if (task.state != TimerTask.VIRGIN)
+ throw new IllegalStateException(
+ "Task already scheduled or cancelled");
+ task.nextExecutionTime = time;
+ task.period = period;
+ task.state = TimerTask.SCHEDULED;
+ }
+
+ queue.add(task);
+ if (queue.getMin() == task)
+ queue.notify();
+ }
+ }
+
+ /**
+ * Terminates this timer, discarding any currently scheduled tasks.
+ * Does not interfere with a currently executing task (if it exists).
+ * Once a timer has been terminated, its execution thread terminates
+ * gracefully, and no more tasks may be scheduled on it.
+ *
+ * <p>Note that calling this method from within the run method of a
+ * timer task that was invoked by this timer absolutely guarantees that
+ * the ongoing task execution is the last task execution that will ever
+ * be performed by this timer.
+ *
+ * <p>This method may be called repeatedly; the second and subsequent
+ * calls have no effect.
+ */
+ public void cancel() {
+ synchronized(queue) {
+ thread.newTasksMayBeScheduled = false;
+ queue.clear();
+ queue.notify(); // In case queue was already empty.
+ }
+ }
+}
+
+/**
+ * This "helper class" implements the timer's task execution thread, which
+ * waits for tasks on the timer queue, executions them when they fire,
+ * reschedules repeating tasks, and removes cancelled tasks and spent
+ * non-repeating tasks from the queue.
+ */
+class TimerThread extends Thread {
+ /**
+ * This flag is set to false by the reaper to inform us that there
+ * are no more live references to our Timer object. Once this flag
+ * is true and there are no more tasks in our queue, there is no
+ * work left for us to do, so we terminate gracefully. Note that
+ * this field is protected by queue's monitor!
+ */
+ boolean newTasksMayBeScheduled = true;
+
+ /**
+ * Our Timer's queue. We store this reference in preference to
+ * a reference to the Timer so the reference graph remains acyclic.
+ * Otherwise, the Timer would never be garbage-collected and this
+ * thread would never go away.
+ */
+ private TaskQueue queue;
+
+ TimerThread(TaskQueue queue) {
+ this.queue = queue;
+ }
+
+ public void run() {
+ try {
+ mainLoop();
+ } finally {
+ // Somone killed this Thread, behave as if Timer cancelled
+ synchronized(queue) {
+ newTasksMayBeScheduled = false;
+ queue.clear(); // Eliminate obsolete references
+ }
+ }
+ }
+
+ /**
+ * The main timer loop. (See class comment.)
+ */
+ private void mainLoop() {
+ while (true) {
+ try {
+ TimerTask task;
+ boolean taskFired;
+ synchronized(queue) {
+ // Wait for queue to become non-empty
+ while (queue.isEmpty() && newTasksMayBeScheduled)
+ queue.wait();
+ if (queue.isEmpty())
+ break; // Queue is empty and will forever remain; die
+
+ // Queue nonempty; look at first evt and do the right thing
+ long currentTime, executionTime;
+ task = queue.getMin();
+ synchronized(task.lock) {
+ if (task.state == TimerTask.CANCELLED) {
+ queue.removeMin();
+ continue; // No action required, poll queue again
+ }
+ currentTime = System.currentTimeMillis();
+ executionTime = task.nextExecutionTime;
+ if (taskFired = (executionTime<=currentTime)) {
+ if (task.period == 0) { // Non-repeating, remove
+ queue.removeMin();
+ task.state = TimerTask.EXECUTED;
+ } else { // Repeating task, reschedule
+ queue.rescheduleMin(
+ task.period<0 ? currentTime - task.period
+ : executionTime + task.period);
+ }
+ }
+ }
+ if (!taskFired) // Task hasn't yet fired; wait
+ queue.wait(executionTime - currentTime);
+ }
+ if (taskFired) // Task fired; run it, holding no locks
+ task.run();
+ } catch(InterruptedException e) {
+ }
+ }
+ }
+}
+
+/**
+ * This class represents a timer task queue: a priority queue of TimerTasks,
+ * ordered on nextExecutionTime. Each Timer object has one of these, which it
+ * shares with its TimerThread. Internally this class uses a heap, which
+ * offers log(n) performance for the add, removeMin and rescheduleMin
+ * operations, and constant time performance for the the getMin operation.
+ */
+class TaskQueue {
+ /**
+ * Priority queue represented as a balanced binary heap: the two children
+ * of queue[n] are queue[2*n] and queue[2*n+1]. The priority queue is
+ * ordered on the nextExecutionTime field: The TimerTask with the lowest
+ * nextExecutionTime is in queue[1] (assuming the queue is nonempty). For
+ * each node n in the heap, and each descendant of n, d,
+ * n.nextExecutionTime <= d.nextExecutionTime.
+ */
+ private TimerTask[] queue = new TimerTask[128];
+
+ /**
+ * The number of tasks in the priority queue. (The tasks are stored in
+ * queue[1] up to queue[size]).
+ */
+ private int size = 0;
+
+ /**
+ * Adds a new task to the priority queue.
+ */
+ void add(TimerTask task) {
+ // Grow backing store if necessary
+ if (++size == queue.length) {
+ TimerTask[] newQueue = new TimerTask[2*queue.length];
+ System.arraycopy(queue, 0, newQueue, 0, size);
+ queue = newQueue;
+ }
+
+ queue[size] = task;
+ fixUp(size);
+ }
+
+ /**
+ * Return the "head task" of the priority queue. (The head task is an
+ * task with the lowest nextExecutionTime.)
+ */
+ TimerTask getMin() {
+ return queue[1];
+ }
+
+ /**
+ * Remove the head task from the priority queue.
+ */
+ void removeMin() {
+ queue[1] = queue[size];
+ queue[size--] = null; // Drop extra reference to prevent memory leak
+ fixDown(1);
+ }
+
+ /**
+ * Sets the nextExecutionTime associated with the head task to the
+ * specified value, and adjusts priority queue accordingly.
+ */
+ void rescheduleMin(long newTime) {
+ queue[1].nextExecutionTime = newTime;
+ fixDown(1);
+ }
+
+ /**
+ * Returns true if the priority queue contains no elements.
+ */
+ boolean isEmpty() {
+ return size==0;
+ }
+
+ /**
+ * Removes all elements from the priority queue.
+ */
+ void clear() {
+ // Null out task references to prevent memory leak
+ for (int i=1; i<=size; i++)
+ queue[i] = null;
+
+ size = 0;
+ }
+
+ /**
+ * Establishes the heap invariant (described above) assuming the heap
+ * satisfies the invariant except possibly for the leaf-node indexed by k
+ * (which may have a nextExecutionTime less than its parent's).
+ *
+ * This method functions by "promoting" queue[k] up the hierarchy
+ * (by swapping it with its parent) repeatedly until queue[k]'s
+ * nextExecutionTime is greater than or equal to that of its parent.
+ */
+ private void fixUp(int k) {
+ while (k > 1) {
+ int j = k >> 1;
+ if (queue[j].nextExecutionTime <= queue[k].nextExecutionTime)
+ break;
+ TimerTask tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
+ k = j;
+ }
+ }
+
+ /**
+ * Establishes the heap invariant (described above) in the subtree
+ * rooted at k, which is assumed to satisfy the heap invariant except
+ * possibly for node k itself (which may have a nextExecutionTime greater
+ * than its children's).
+ *
+ * This method functions by "demoting" queue[k] down the hierarchy
+ * (by swapping it with its smaller child) repeatedly until queue[k]'s
+ * nextExecutionTime is less than or equal to those of its children.
+ */
+ private void fixDown(int k) {
+ int j;
+ while ((j = k << 1) <= size) {
+ if (j < size &&
+ queue[j].nextExecutionTime > queue[j+1].nextExecutionTime)
+ j++; // j indexes smallest kid
+ if (queue[k].nextExecutionTime <= queue[j].nextExecutionTime)
+ break;
+ TimerTask tmp = queue[j]; queue[j] = queue[k]; queue[k] = tmp;
+ k = j;
+ }
+ }
+}
projects / Benchmarks_CSolver.git / blobdiff