| /* |
| * Copyright (c) 2008, 2009, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package sun.nio.fs; |
| |
| import java.nio.file.*; |
| import java.util.concurrent.*; |
| import java.io.IOException; |
| |
| /** |
| * Base implementation class for watch services. |
| */ |
| |
| abstract class AbstractWatchService extends WatchService { |
| |
| // signaled keys waiting to be dequeued |
| private final LinkedBlockingDeque<WatchKey> pendingKeys = |
| new LinkedBlockingDeque<WatchKey>(); |
| |
| // special key to indicate that watch service is closed |
| private final WatchKey CLOSE_KEY = |
| new AbstractWatchKey(null) { |
| @Override |
| public boolean isValid() { |
| return true; |
| } |
| |
| @Override |
| public void cancel() { |
| } |
| }; |
| |
| // used when closing watch service |
| private volatile boolean closed; |
| private Object closeLock = new Object(); |
| |
| protected AbstractWatchService() { |
| } |
| |
| /** |
| * Register the given object with this watch service |
| */ |
| abstract WatchKey register(Path path, |
| WatchEvent.Kind<?>[] events, |
| WatchEvent.Modifier... modifers) |
| throws IOException; |
| |
| // used by AbstractWatchKey to enqueue key |
| final void enqueueKey(WatchKey key) { |
| pendingKeys.offer(key); |
| } |
| |
| /** |
| * Throws ClosedWatchServiceException if watch service is closed |
| */ |
| private void checkOpen() { |
| if (closed) |
| throw new ClosedWatchServiceException(); |
| } |
| |
| /** |
| * Checks the key isn't the special CLOSE_KEY used to unblock threads when |
| * the watch service is closed. |
| */ |
| private void checkKey(WatchKey key) { |
| if (key == CLOSE_KEY) { |
| // re-queue in case there are other threads blocked in take/poll |
| enqueueKey(key); |
| } |
| checkOpen(); |
| } |
| |
| @Override |
| public final WatchKey poll() { |
| checkOpen(); |
| WatchKey key = pendingKeys.poll(); |
| checkKey(key); |
| return key; |
| } |
| |
| @Override |
| public final WatchKey poll(long timeout, TimeUnit unit) |
| throws InterruptedException |
| { |
| checkOpen(); |
| WatchKey key = pendingKeys.poll(timeout, unit); |
| checkKey(key); |
| return key; |
| } |
| |
| @Override |
| public final WatchKey take() |
| throws InterruptedException |
| { |
| checkOpen(); |
| WatchKey key = pendingKeys.take(); |
| checkKey(key); |
| return key; |
| } |
| |
| /** |
| * Tells whether or not this watch service is open. |
| */ |
| final boolean isOpen() { |
| return !closed; |
| } |
| |
| /** |
| * Retrieves the object upon which the close method synchronizes. |
| */ |
| final Object closeLock() { |
| return closeLock; |
| } |
| |
| /** |
| * Closes this watch service. This method is invoked by the close |
| * method to perform the actual work of closing the watch service. |
| */ |
| abstract void implClose() throws IOException; |
| |
| @Override |
| public final void close() |
| throws IOException |
| { |
| synchronized (closeLock) { |
| // nothing to do if already closed |
| if (closed) |
| return; |
| closed = true; |
| |
| implClose(); |
| |
| // clear pending keys and queue special key to ensure that any |
| // threads blocked in take/poll wakeup |
| pendingKeys.clear(); |
| pendingKeys.offer(CLOSE_KEY); |
| } |
| } |
| } |