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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 | } | ||