duke@435: /*
duke@435:  * Copyright 1997-2007 Sun Microsystems, Inc.  All Rights Reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
duke@435:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435:  * CA 95054 USA or visit www.sun.com if you need additional information or
duke@435:  * have any questions.
duke@435:  *
duke@435:  */
duke@435: 
duke@435: // A PeriodicTask has the sole purpose of executing its task
duke@435: // function with regular intervals.
duke@435: // Usage:
duke@435: //   PeriodicTask pf(10);
duke@435: //   pf.enroll();
duke@435: //   ...
duke@435: //   pf.disenroll();
duke@435: 
duke@435: class PeriodicTask: public CHeapObj {
duke@435:  public:
duke@435:   // Useful constants.
duke@435:   // The interval constants are used to ensure the declared interval
duke@435:   // is appropriate;  it must be between min_interval and max_interval,
duke@435:   // and have a granularity of interval_gran (all in millis).
duke@435:   enum { max_tasks     = 10,       // Max number of periodic tasks in system
duke@435:          interval_gran = 10,
duke@435:          min_interval  = 10,
duke@435:          max_interval  = 10000 };
duke@435: 
duke@435:   static int num_tasks()   { return _num_tasks; }
duke@435: 
duke@435:  private:
duke@435:   size_t _counter;
duke@435:   const size_t _interval;
duke@435: 
duke@435:   static int _num_tasks;
duke@435:   static PeriodicTask* _tasks[PeriodicTask::max_tasks];
duke@435:   static void real_time_tick(size_t delay_time);
duke@435: 
duke@435: #ifndef PRODUCT
duke@435:   static elapsedTimer _timer;                      // measures time between ticks
duke@435:   static int _ticks;                               // total number of ticks
duke@435:   static int _intervalHistogram[max_interval];     // to check spacing of timer interrupts
duke@435:  public:
duke@435:   static void print_intervals();
duke@435: #endif
duke@435:   // Only the WatcherThread can cause us to execute PeriodicTasks
duke@435:   friend class WatcherThread;
duke@435:  public:
duke@435:   PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time
duke@435:   ~PeriodicTask();
duke@435: 
duke@435:   // Tells whether is enrolled
duke@435:   bool is_enrolled() const;
duke@435: 
duke@435:   // Make the task active
duke@435:   // NOTE: this may only be called before the WatcherThread has been started
duke@435:   void enroll();
duke@435: 
duke@435:   // Make the task deactive
duke@435:   // NOTE: this may only be called either while the WatcherThread is
duke@435:   // inactive or by a task from within its task() method. One-shot or
duke@435:   // several-shot tasks may be implemented this way.
duke@435:   void disenroll();
duke@435: 
duke@435:   void execute_if_pending(size_t delay_time) {
duke@435:     _counter += delay_time;
duke@435:     if (_counter >= _interval) {
duke@435:       _counter = 0;
duke@435:       task();
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   // Returns how long (time in milliseconds) before the next time we should
duke@435:   // execute this task.
duke@435:   size_t time_to_next_interval() const {
duke@435:     assert(_interval > _counter,  "task counter greater than interval?");
duke@435:     return _interval - _counter;
duke@435:   }
duke@435: 
duke@435:   // Calculate when the next periodic task will fire.
duke@435:   // Called by the WatcherThread's run method.
duke@435:   // This assumes that periodic tasks aren't entering the system
duke@435:   // dynamically, except for during startup.
duke@435:   static size_t time_to_wait() {
duke@435:     if (_num_tasks == 0) {
duke@435:       // Don't wait any more; shut down the thread since we don't
duke@435:       // currently support dynamic enrollment.
duke@435:       return 0;
duke@435:     }
duke@435: 
duke@435:     size_t delay = _tasks[0]->time_to_next_interval();
duke@435:     for (int index = 1; index < _num_tasks; index++) {
duke@435:       delay = MIN2(delay, _tasks[index]->time_to_next_interval());
duke@435:     }
duke@435:     return delay;
duke@435:   }
duke@435: 
duke@435:   // The task to perform at each period
duke@435:   virtual void task() = 0;
duke@435: };