Copyright (c) 2004, 2013 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
    Danail Nachev (Prosyst) - bug 185654
    Andrei Loskutov - bug 44735
/*******************************************************************************
 * Copyright (c) 2004, 2013 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Danail Nachev (Prosyst) - bug 185654
 *     Andrei Loskutov - bug 44735
 *******************************************************************************/
package org.eclipse.osgi.internal.location;

import java.io.*;
import java.nio.channels.FileLock;
import java.nio.channels.OverlappingFileLockException;
import org.eclipse.osgi.internal.messages.Msg;
import org.eclipse.osgi.util.NLS;

Internal class.
/**
 * Internal class.
 */
public class Locker_JavaNio implements Locker {
	private final File lockFile;
	private final boolean debug;
	private FileLock fileLock;
	private RandomAccessFile raFile;

	public Locker_JavaNio(File lockFile, boolean debug) {
		this.lockFile = lockFile;
		this.debug = debug;
	}

	@Override
	public synchronized boolean lock() throws IOException {
		raFile = new RandomAccessFile(lockFile, "rw"); //$NON-NLS-1$
		try {
			/*
			 * fix for bug http://bugs.sun.com/view_bug.do?bug_id=6628575 and
			 * https://bugs.eclipse.org/bugs/show_bug.cgi?id=44735#c17
			 */
			fileLock = raFile.getChannel().tryLock(0, 1, false);
		} catch (IOException ioe) {
			// print exception if debugging
			if (debug)
				System.out.println(NLS.bind(Msg.location_cannotLock, lockFile));
			// produce a more specific message for clients
			String specificMessage = NLS.bind(Msg.location_cannotLockNIO, new Object[] {lockFile, ioe.getMessage(), "\"-D" + LocationHelper.PROP_OSGI_LOCKING + "=none\""}); //$NON-NLS-1$ //$NON-NLS-2$
			throw new IOException(specificMessage);
		} catch (OverlappingFileLockException e) {
			// handle it as null result
			fileLock = null;
		} finally {
			if (fileLock != null)
				return true;
			raFile.close();
			raFile = null;
		}
		return false;
	}

	@Override
	public synchronized void release() {
		if (fileLock != null) {
			try {
				fileLock.release();
			} catch (IOException e) {
				//don't complain, we're making a best effort to clean up
			}
			fileLock = null;
		}
		if (raFile != null) {
			try {
				raFile.close();
			} catch (IOException e) {
				//don't complain, we're making a best effort to clean up
			}
			raFile = null;
		}
	}

	@Override
	public synchronized boolean isLocked() throws IOException {
		if (fileLock != null)
			return true;
		try {
			RandomAccessFile temp = new RandomAccessFile(lockFile, "rw"); //$NON-NLS-1$
			FileLock tempLock = null;
			try {
				/*
				 * fix for bug http://bugs.sun.com/view_bug.do?bug_id=6628575 and
				 * https://bugs.eclipse.org/bugs/show_bug.cgi?id=44735#c17
				 */
				try {
					tempLock = temp.getChannel().tryLock(0, 1, false);
				} catch (IOException ioe) {
					if (debug)
						System.out.println(NLS.bind(Msg.location_cannotLock, lockFile));
					// produce a more specific message for clients
					String specificMessage = NLS.bind(Msg.location_cannotLockNIO, new Object[] {lockFile, ioe.getMessage(), "\"-D" + LocationHelper.PROP_OSGI_LOCKING + "=none\""}); //$NON-NLS-1$ //$NON-NLS-2$
					throw new IOException(specificMessage);
				}
				if (tempLock != null) {
					tempLock.release(); // allow IOException to propagate because that would mean it is still locked
					return false;
				}
				return true;
			} catch (OverlappingFileLockException e) {
				return true;
			} finally {
				temp.close();
			}
		} catch (FileNotFoundException e) {
			return false;
		}
	}
}