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| 1 | +/* | |
| 2 | + * Copyright (c) 2008, 2011, 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.concurrent.*; | |
| 30 | +import java.io.IOException; | |
| 31 | + | |
| 32 | +/** | |
| 33 | + * Base implementation class for watch services. | |
| 34 | + */ | |
| 35 | + | |
| 36 | +abstract class AbstractWatchService implements WatchService { | |
| 37 | + | |
| 38 | + // signaled keys waiting to be dequeued | |
| 39 | + private final LinkedBlockingDeque<WatchKey> pendingKeys = | |
| 40 | + new LinkedBlockingDeque<WatchKey>(); | |
| 41 | + | |
| 42 | + // special key to indicate that watch service is closed | |
| 43 | + private final WatchKey CLOSE_KEY = | |
| 44 | + new AbstractWatchKey(null, null) { | |
| 45 | + @Override | |
| 46 | + public boolean isValid() { | |
| 47 | + return true; | |
| 48 | + } | |
| 49 | + | |
| 50 | + @Override | |
| 51 | + public void cancel() { | |
| 52 | + } | |
| 53 | + }; | |
| 54 | + | |
| 55 | + // used when closing watch service | |
| 56 | + private volatile boolean closed; | |
| 57 | + private final Object closeLock = new Object(); | |
| 58 | + | |
| 59 | + protected AbstractWatchService() { | |
| 60 | + } | |
| 61 | + | |
| 62 | + /** | |
| 63 | + * Register the given object with this watch service | |
| 64 | + */ | |
| 65 | + abstract WatchKey register(Path path, | |
| 66 | + WatchEvent.Kind<?>[] events, | |
| 67 | + WatchEvent.Modifier... modifers) | |
| 68 | + throws IOException; | |
| 69 | + | |
| 70 | + // used by AbstractWatchKey to enqueue key | |
| 71 | + final void enqueueKey(WatchKey key) { | |
| 72 | + pendingKeys.offer(key); | |
| 73 | + } | |
| 74 | + | |
| 75 | + /** | |
| 76 | + * Throws ClosedWatchServiceException if watch service is closed | |
| 77 | + */ | |
| 78 | + private void checkOpen() { | |
| 79 | + if (closed) | |
| 80 | + throw new ClosedWatchServiceException(); | |
| 81 | + } | |
| 82 | + | |
| 83 | + /** | |
| 84 | + * Checks the key isn't the special CLOSE_KEY used to unblock threads when | |
| 85 | + * the watch service is closed. | |
| 86 | + */ | |
| 87 | + private void checkKey(WatchKey key) { | |
| 88 | + if (key == CLOSE_KEY) { | |
| 89 | + // re-queue in case there are other threads blocked in take/poll | |
| 90 | + enqueueKey(key); | |
| 91 | + } | |
| 92 | + checkOpen(); | |
| 93 | + } | |
| 94 | + | |
| 95 | + @Override | |
| 96 | + public final WatchKey poll() { | |
| 97 | + checkOpen(); | |
| 98 | + WatchKey key = pendingKeys.poll(); | |
| 99 | + checkKey(key); | |
| 100 | + return key; | |
| 101 | + } | |
| 102 | + | |
| 103 | + @Override | |
| 104 | + public final WatchKey poll(long timeout, TimeUnit unit) | |
| 105 | + throws InterruptedException | |
| 106 | + { | |
| 107 | + checkOpen(); | |
| 108 | + WatchKey key = pendingKeys.poll(timeout, unit); | |
| 109 | + checkKey(key); | |
| 110 | + return key; | |
| 111 | + } | |
| 112 | + | |
| 113 | + @Override | |
| 114 | + public final WatchKey take() | |
| 115 | + throws InterruptedException | |
| 116 | + { | |
| 117 | + checkOpen(); | |
| 118 | + WatchKey key = pendingKeys.take(); | |
| 119 | + checkKey(key); | |
| 120 | + return key; | |
| 121 | + } | |
| 122 | + | |
| 123 | + /** | |
| 124 | + * Tells whether or not this watch service is open. | |
| 125 | + */ | |
| 126 | + final boolean isOpen() { | |
| 127 | + return !closed; | |
| 128 | + } | |
| 129 | + | |
| 130 | + /** | |
| 131 | + * Retrieves the object upon which the close method synchronizes. | |
| 132 | + */ | |
| 133 | + final Object closeLock() { | |
| 134 | + return closeLock; | |
| 135 | + } | |
| 136 | + | |
| 137 | + /** | |
| 138 | + * Closes this watch service. This method is invoked by the close | |
| 139 | + * method to perform the actual work of closing the watch service. | |
| 140 | + */ | |
| 141 | + abstract void implClose() throws IOException; | |
| 142 | + | |
| 143 | + @Override | |
| 144 | + public final void close() | |
| 145 | + throws IOException | |
| 146 | + { | |
| 147 | + synchronized (closeLock) { | |
| 148 | + // nothing to do if already closed | |
| 149 | + if (closed) | |
| 150 | + return; | |
| 151 | + closed = true; | |
| 152 | + | |
| 153 | + implClose(); | |
| 154 | + | |
| 155 | + // clear pending keys and queue special key to ensure that any | |
| 156 | + // threads blocked in take/poll wakeup | |
| 157 | + pendingKeys.clear(); | |
| 158 | + pendingKeys.offer(CLOSE_KEY); | |
| 159 | + } | |
| 160 | + } | |
| 161 | +} | |