javafx.scene.web.DirectoryLock Maven / Gradle / Ivy
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* 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.
*
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package javafx.scene.web;
import com.sun.javafx.logging.PlatformLogger;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import static java.lang.String.format;
import java.nio.channels.FileLock;
import java.nio.channels.OverlappingFileLockException;
import java.util.HashMap;
import java.util.Map;
final class DirectoryLock {
private static final PlatformLogger logger =
PlatformLogger.getLogger(DirectoryLock.class.getName());
private static final Map descriptors = new HashMap<>();
private Descriptor descriptor;
DirectoryLock(File directory) throws IOException,
DirectoryAlreadyInUseException
{
directory = canonicalize(directory);
descriptor = descriptors.get(directory);
if (descriptor == null) {
File lockFile = lockFile(directory);
RandomAccessFile lockRaf = new RandomAccessFile(lockFile, "rw");
try {
FileLock lock = lockRaf.getChannel().tryLock();
if (lock == null) {
throw new DirectoryAlreadyInUseException(
directory.toString(), null);
}
descriptor = new Descriptor(directory, lockRaf, lock);
descriptors.put(directory, descriptor);
} catch (OverlappingFileLockException ex) {
throw new DirectoryAlreadyInUseException(
directory.toString(), ex);
} finally {
if (descriptor == null) { // tryLock failed
try {
lockRaf.close();
} catch (IOException ex) {
logger.warning(format("Error closing [%s]",
lockFile), ex);
}
}
}
}
descriptor.referenceCount++;
}
void close() {
if (descriptor == null) {
return;
}
descriptor.referenceCount--;
if (descriptor.referenceCount == 0) {
try {
descriptor.lock.release();
} catch (IOException ex) {
logger.warning(format("Error releasing lock on [%s]",
lockFile(descriptor.directory)), ex);
}
try {
descriptor.lockRaf.close();
} catch (IOException ex) {
logger.warning(format("Error closing [%s]",
lockFile(descriptor.directory)), ex);
}
descriptors.remove(descriptor.directory);
}
descriptor = null;
}
static int referenceCount(File directory) throws IOException {
Descriptor d = descriptors.get(canonicalize(directory));
return d == null ? 0 : d.referenceCount;
}
static File canonicalize(File directory) throws IOException {
String path = directory.getCanonicalPath();
if (path.length() > 0
&& path.charAt(path.length() - 1) != File.separatorChar)
{
path += File.separatorChar;
}
return new File(path);
}
private static File lockFile(File directory) {
return new File(directory, ".lock");
}
private static class Descriptor {
private final File directory;
private final RandomAccessFile lockRaf;
private final FileLock lock;
private int referenceCount;
private Descriptor(File directory,
RandomAccessFile lockRaf,
FileLock lock)
{
this.directory = directory;
this.lockRaf = lockRaf;
this.lock = lock;
}
}
final class DirectoryAlreadyInUseException extends Exception {
DirectoryAlreadyInUseException(String message, Throwable cause) {
super(message, cause);
}
}
}