src/org/ibex/Scheduler.java

   1 // Copyright 2004 Adam Megacz, see the COPYING file for licensing [GPL]
   2 package org.ibex;
   3
   4 import java.io.IOException;
   5
   6 import org.ibex.js.*;
   7 import org.ibex.util.*;
   8
   9 /** Implements cooperative multitasking */
  10 public class Scheduler {
  11
  12     // Public API Exposed to org.ibex /////////////////////////////////////////////////
  13
  14     private static Scheduler singleton;
  15     public static interface Task { public abstract void perform() throws IOException, JSExn; }
  16     public static void add(Task t) { Log.debug(Scheduler.class, "scheduling " + t); Scheduler.runnable.append(t); }
  17     public static void init() { if (singleton == null) (singleton = Platform.getScheduler()).run(); }
  18
  19     private static Task current = null;
  20
  21     private static volatile boolean rendering = false;
  22     private static volatile boolean again = false;
  23
  24     /** synchronizd so that we can safely call it from an event-delivery thread, in-context */
  25     public static void renderAll() {
  26         if (rendering) { again = true; return; }
  27         synchronized(Scheduler.class) {
  28             try {
  29                 rendering = true;
  30                 do {
  31                     // FEATURE: this could be cleaner
  32                     again = false;
  33                     for(int i=0; i<Surface.allSurfaces.size(); i++) {
  34                         Surface s = ((Surface)Surface.allSurfaces.elementAt(i));
  35                         do { s.render(); } while(s.abort);
  36                     }
  37                 } while(again);
  38             } finally {
  39                 rendering = false;
  40             }
  41         }
  42     }
  43
  44
  45
  46     // API which must be supported by subclasses /////////////////////////////////////
  47
  48     /**
  49      *  SCHEDULER INVARIANT: all scheduler implementations MUST invoke
  50      *  Surface.renderAll() after performing a Task if no tasks remain
  51      *  in the queue.  A scheduler may choose to invoke
  52      *  Surface.renderAll() more often than that if it so chooses.
  53      */
  54     public void run() { defaultRun(); }
  55     protected Scheduler() { }
  56
  57
  58     // Default Implementation //////////////////////////////////////////////////////
  59
  60     protected static Queue runnable = new Queue(50);
  61     public void defaultRun() {
  62         while(true) {
  63             current = (Task)runnable.remove(true);
  64             try {
  65                 // FIXME hideous
  66                 synchronized(this) {
  67                     for(int i=0; i<Surface.allSurfaces.size(); i++) {
  68                         Surface s = (Surface)Surface.allSurfaces.elementAt(i);
  69                         if (current instanceof JS) {
  70                             s._mousex = Integer.MAX_VALUE;
  71                             s._mousey = Integer.MAX_VALUE;
  72                         } else {
  73                             s._mousex = s.mousex;
  74                             s._mousey = s.mousey;
  75                         }
  76                     }
  77                     Log.debug(Scheduler.class, "performing " + current);
  78                     current.perform();
  79                 }
  80                 renderAll();
  81             } catch (JSExn e) {
  82                 Log.info(Scheduler.class, "a JavaScript thread spawned with ibex.thread() threw an exception:");
  83                 Log.info(Scheduler.class,e);
  84             } catch (Exception e) {
  85                 Log.info(Scheduler.class, "a Task threw an exception which was caught by the scheduler:");
  86                 Log.info(Scheduler.class, e);
  87             } catch (Throwable t) {
  88                 t.printStackTrace();
  89             }
  90             // if an Error is thrown it will cause the engine to quit
  91         }
  92     }
  93 }