Source Code Cross Referenced for EventManager.java in  » Web-Server » Jigsaw » org » w3c » tools » timers » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Web Server » Jigsaw » org.w3c.tools.timers 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        // EventManager.java
002:        // $Id: EventManager.java,v 1.4 1998/12/08 10:42:11 bmahe Exp $
003:        // (c) COPYRIGHT MIT and INRIA, 1996.
004:        // Please first read the full copyright statement in file COPYRIGHT.html
005:
006:        /**
007:         * A timer handling package.
008:         * This package was written by J Payne.
009:         */package org.w3c.tools.timers;
010:
011:        import java.util.Vector;
012:
013:        class Event {
014:            /** Absolute time, in ms, to deliver this event. */
015:            long time;
016:
017:            /** Piece of data to pass to the event handler. */
018:            Object data;
019:
020:            /** handler for this event */
021:            EventHandler handler;
022:
023:            Event(long time, EventHandler handler, Object data) {
024:                this .time = time;
025:                this .handler = handler;
026:                this .data = data;
027:            }
028:        }
029:
030:        /** This implements an event manager for timer events.  Timer events
031:          are a way to have events occur some time in the future.  They are an
032:          alternative to using separate threads which issue sleep requests
033:          themselves. */
034:
035:        public class EventManager extends Thread implements  EventHandler {
036:            static final boolean debug = false;
037:
038:            /** Vector of events, sorted by time. */
039:            Vector queue = new Vector();
040:
041:            public EventManager() {
042:                setName("Event Manager");
043:            }
044:
045:            /** registerTimer inserts a new timer event into the queue.  The
046:              queue is always sorted by time, in increasing order.  That is,
047:              things farther into the future are further down in the queue.
048:
049:              ms is milliseconds in the future, handler is the object that
050:              will handle the event, and data is a "rock" that is passed to
051:              the handler to do with what it will.
052:
053:              This returns an opaque object which can be used to recall the
054:              timer before it is delivered. */
055:
056:            public Object registerTimer(long ms, EventHandler handler,
057:                    Object data) {
058:                long time = ms + System.currentTimeMillis();
059:                Event event = new Event(time, handler, data);
060:
061:                return registerTimer(event);
062:            }
063:
064:            boolean done = false;
065:
066:            public synchronized void stopEventManager() {
067:                done = true;
068:                notify();
069:            }
070:
071:            /** This is like the above registerTimer, except it takes an event
072:              object with the deliver time filled in.  If deliver time is
073:              before the current time, the event is "immediately" delivered.
074:              Do a binary search to figure out where the event goes. */
075:
076:            public synchronized Object registerTimer(Event newEvent) {
077:                int lo = 0;
078:                int hi = queue.size();
079:                long newTime = newEvent.time;
080:                Event e;
081:                long midTime;
082:
083:                if (done) {
084:                    return null;
085:                }
086:
087:                if (hi == 0) {
088:                    queue.addElement(newEvent);
089:                } else {
090:                    while (hi - lo > 0) {
091:                        int mid = (hi + lo) >> 1;
092:                        e = (Event) queue.elementAt(mid);
093:                        midTime = e.time;
094:
095:                        if (midTime < newTime) {
096:                            lo = mid + 1;
097:                        } else if (midTime > newTime) {
098:                            hi = mid;
099:                        } else {
100:                            lo = mid;
101:                            break;
102:                        }
103:                    }
104:                    if (lo < hi && ((Event) queue.elementAt(lo)).time > newTime) {
105:                        lo += 1;
106:                    }
107:                    queue.insertElementAt(newEvent, lo);
108:                }
109:                if (debug) {
110:                    checkQueue();
111:                }
112:                notify();
113:
114:                return newEvent;
115:            }
116:
117:            /** This recalls a previously registered timer event. */
118:            public synchronized Object recallTimer(Object timer) {
119:                int lo = 0;
120:                int hi = queue.size();
121:                int limit = hi;
122:                long destTime = ((Event) timer).time;
123:                Event e;
124:                long midTime;
125:
126:                if (hi == 0) {
127:                    return null; /* already delivered or recalled */
128:                }
129:                while (hi - lo > 0) {
130:                    int mid = (hi + lo) >> 1;
131:                    e = (Event) queue.elementAt(mid);
132:                    midTime = e.time;
133:
134:                    if (midTime < destTime) {
135:                        lo = mid + 1;
136:                    } else if (midTime > destTime) {
137:                        hi = mid;
138:                    } else {
139:                        lo = mid;
140:                        for (int i = mid - 1; i >= 0; i--) {
141:                            e = (Event) queue.elementAt(i);
142:                            if (e.time == midTime) {
143:                                lo = i;
144:                            } else {
145:                                break;
146:                            }
147:                        }
148:                        break;
149:                    }
150:                }
151:                while (lo < limit) {
152:                    e = (Event) queue.elementAt(lo);
153:                    if (e.time == destTime) {
154:                        if (e == timer) {
155:                            queue.removeElementAt(lo);
156:                            break;
157:                        } else {
158:                            lo += 1;
159:                        }
160:                    } else {
161:                        return null;
162:                    }
163:                }
164:                if (debug) {
165:                    checkQueue();
166:                }
167:                if (lo == 0)
168:                    notify();
169:                return timer;
170:            }
171:
172:            /** This is a separate method so that it can be
173:               synchronized while the actual execution of the event
174:               does not lock the EventManager.  In other words, while
175:               one event is being processed by its handler, others can
176:               register or recall other events. */
177:
178:            synchronized Event getNextEvent() {
179:                while (true) {
180:                    while (queue.size() == 0) {
181:                        if (debug) {
182:                            System.out.println("Queue waiting for event.");
183:                        }
184:                        if (done) {
185:                            return null;
186:                        }
187:                        try {
188:                            wait();
189:                        } catch (InterruptedException e) {
190:                        }
191:                    }
192:                    Event e = (Event) queue.elementAt(0);
193:                    long now = System.currentTimeMillis();
194:                    long dt;
195:
196:                    dt = e.time - now;
197:
198:                    if (dt <= 0) {
199:                        queue.removeElementAt(0);
200:                        return e;
201:                    }
202:                    /* If we get here, we have no events scheduled for a while, so
203:                       we sleep until the next event needs delivering.  When we
204:                       wake up, it could be because the queue has been changed.
205:                       So we have to check again. */
206:                    if (debug) {
207:                        System.out.println("Queue sleeping for " + dt + "ms");
208:                    }
209:                    try {
210:                        wait(dt);
211:                    } catch (InterruptedException ex) {
212:                    }
213:                }
214:            }
215:
216:            public void run() {
217:                Thread.currentThread().setPriority(Thread.MAX_PRIORITY - 1);
218:                while (true) {
219:                    Event e = getNextEvent();
220:
221:                    if (done) {
222:                        break;
223:                    }
224:
225:                    try {
226:                        e.handler.handleTimerEvent(e.data, e.time);
227:                    } catch (Exception ex) {
228:                        System.out.println("Exception " + ex
229:                                + " in EventManager");
230:                        ex.printStackTrace();
231:                    } catch (Error er) {
232:                        System.out.println("Error " + er + " in EventManager");
233:                        er.printStackTrace();
234:                    }
235:                }
236:            }
237:
238:            /* This is here for testing purposes only. */
239:            public void handleTimerEvent(Object rock, long time) {
240:                long dt = (System.currentTimeMillis() - time);
241:
242:                System.out.println("Handling event with dt=" + dt);
243:            }
244:
245:            public static void main(String args[]) {
246:                EventManager mgr = new EventManager();
247:                int i;
248:
249:                for (i = 0; i < 30; i++) {
250:                    mgr.registerTimer(1000 + (int) (1000 * Math.random()), mgr,
251:                            null);
252:                }
253:                mgr.checkQueue();
254:            }
255:
256:            synchronized void checkQueue() {
257:                Vector q = queue;
258:
259:                if (q.size() == 0)
260:                    return;
261:                Event e = (Event) q.elementAt(0);
262:                int i, size = q.size();
263:                for (i = 1; i < size; i++) {
264:                    Event next = (Event) q.elementAt(i);
265:
266:                    if (next.time < e.time) {
267:                        System.out.println("Events out of order!\n");
268:                        System.out.println(q);
269:                    }
270:                    e = next;
271:                }
272:            }
273:        }
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