1 /* 2 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package sun.nio.fs; 27 28 import java.nio.file.*; 29 import java.util.*; 30 31 /** 32 * Base implementation class for watch keys. 33 */ 34 35 abstract class AbstractWatchKey extends WatchKey { 36 37 /** 38 * Maximum size of event list (in the future this may be tunable) 39 */ 40 static final int MAX_EVENT_LIST_SIZE = 512; 41 42 /** 43 * Special event to signal overflow 44 */ 45 static final Event<Void> OVERFLOW_EVENT = 46 new Event<Void>(StandardWatchEventKind.OVERFLOW, null); 47 48 /** 49 * Possible key states 50 */ 51 private static enum State { READY, SIGNALLED }; 52 53 // reference to watcher 54 private final AbstractWatchService watcher; 55 56 // key state 57 private State state; 58 59 // pending events 60 private List<WatchEvent<?>> events; 61 62 // maps a context to the last event for the context (iff the last queued 63 // event for the context is an ENTRY_MODIFY event). 64 private Map<Object,WatchEvent<?>> lastModifyEvents; 65 66 protected AbstractWatchKey(AbstractWatchService watcher) { 67 this.watcher = watcher; 68 this.state = State.READY; 69 this.events = new ArrayList<WatchEvent<?>>(); 70 this.lastModifyEvents = new HashMap<Object,WatchEvent<?>>(); 71 } 72 73 final AbstractWatchService watcher() { 74 return watcher; 75 } 76 77 /** 78 * Enqueues this key to the watch service 79 */ 80 final void signal() { 81 synchronized (this) { 82 if (state == State.READY) { 83 state = State.SIGNALLED; 84 watcher.enqueueKey(this); 85 } 86 } 87 } 88 89 /** 90 * Adds the event to this key and signals it. 91 */ 92 @SuppressWarnings("unchecked") 93 final void signalEvent(WatchEvent.Kind<?> kind, Object context) { 94 boolean isModify = (kind == StandardWatchEventKind.ENTRY_MODIFY); 95 synchronized (this) { 96 int size = events.size(); 97 if (size > 0) { 98 // if the previous event is an OVERFLOW event or this is a 99 // repeated event then we simply increment the counter 100 WatchEvent<?> prev = events.get(size-1); 101 if ((prev.kind() == StandardWatchEventKind.OVERFLOW) || 102 ((kind == prev.kind() && 103 Objects.equals(context, prev.context())))) 104 { 105 ((Event<?>)prev).increment(); 106 return; 107 } 108 109 // if this is a modify event and the last entry for the context 110 // is a modify event then we simply increment the count 111 if (!lastModifyEvents.isEmpty()) { 112 if (isModify) { 113 WatchEvent<?> ev = lastModifyEvents.get(context); 114 if (ev != null) { 115 assert ev.kind() == StandardWatchEventKind.ENTRY_MODIFY; 116 ((Event<?>)ev).increment(); 117 return; 118 } 119 } else { 120 // not a modify event so remove from the map as the 121 // last event will no longer be a modify event. 122 lastModifyEvents.remove(context); 123 } 124 } 125 126 // if the list has reached the limit then drop pending events 127 // and queue an OVERFLOW event 128 if (size >= MAX_EVENT_LIST_SIZE) { 129 kind = StandardWatchEventKind.OVERFLOW; 130 isModify = false; 131 context = null; 132 } 133 } 134 135 // non-repeated event 136 Event<Object> ev = 137 new Event<Object>((WatchEvent.Kind<Object>)kind, context); 138 if (isModify) { 139 lastModifyEvents.put(context, ev); 140 } else if (kind == StandardWatchEventKind.OVERFLOW) { 141 // drop all pending events 142 events.clear(); 143 lastModifyEvents.clear(); 144 } 145 events.add(ev); 146 signal(); 147 } 148 } 149 150 @Override 151 public final List<WatchEvent<?>> pollEvents() { 152 synchronized (this) { 153 List<WatchEvent<?>> result = events; 154 events = new ArrayList<WatchEvent<?>>(); 155 lastModifyEvents.clear(); 156 return result; 157 } 158 } 159 160 @Override 161 public final boolean reset() { 162 synchronized (this) { 163 if (state == State.SIGNALLED && isValid()) { 164 if (events.isEmpty()) { 165 state = State.READY; 166 } else { 167 // pending events so re-queue key 168 watcher.enqueueKey(this); 169 } 170 } 171 return isValid(); 172 } 173 } 174 175 /** 176 * WatchEvent implementation 177 */ 178 private static class Event<T> extends WatchEvent<T> { 179 private final WatchEvent.Kind<T> kind; 180 private final T context; 181 182 // synchronize on watch key to access/increment count 183 private int count; 184 185 Event(WatchEvent.Kind<T> type, T context) { 186 this.kind = type; 187 this.context = context; 188 this.count = 1; 189 } 190 191 @Override 192 public WatchEvent.Kind<T> kind() { 193 return kind; 194 } 195 196 @Override 197 public T context() { 198 return context; 199 } 200 201 @Override 202 public int count() { 203 return count; 204 } 205 206 // for repeated events 207 void increment() { 208 count++; 209 } 210 } 211 }