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// **********************************************************************
//
// Copyright (c) 2003-2010 ZeroC, Inc. All rights reserved.
//
// This copy of Ice is licensed to you under the terms described in the
// ICE_LICENSE file included in this distribution.
//
// **********************************************************************
package IceUtilInternal;
import java.io.File;
import java.io.RandomAccessFile;
import java.io.FileWriter;
import java.nio.channels.FileChannel;
import java.nio.channels.OverlappingFileLockException;
import java.lang.management.ManagementFactory;
public final class FileLock
{
//
// The constructor opens the given file (eventually creating it)
// and acquires a lock on the file or throws FileLockException if
// the file couldn't be locked.
//
// If the lock can be acquired, the Java VM name is written to the
// file.
//
public FileLock(String path)
{
_file = new File(path);
FileChannel channel;
try
{
_randFile = new RandomAccessFile(_file, "rw");
channel = _randFile.getChannel();
}
catch(java.io.FileNotFoundException e)
{
throw new IceUtil.FileLockException(path);
}
java.nio.channels.FileLock lock;
try
{
lock = channel.tryLock();
}
catch(Exception ex)
{
throw new IceUtil.FileLockException(path, ex);
}
if(lock == null)
{
throw new IceUtil.FileLockException(path);
}
//
// In Windows we don't write the process pid to the file, as is not posible
// to read the file from other process while it is locked here.
//
if(!System.getProperty("os.name").startsWith("Windows"))
{
try
{
//
// Java doesn't provide get pid operation. This code
// writes the Java VM name instead of the pid.
//
// The output is JVM dependent. With the Sun
// implementation it's `pid@hostname'
//
_randFile.writeUTF(ManagementFactory.getRuntimeMXBean().getName());
//
// Don't close _randFile here or the lock will be released. It is called
// during release see comments there.
//
}
catch(java.io.IOException ex)
{
release();
throw new IceUtil.FileLockException(path);
}
}
}
//
// Remove the lock if it is owned by the class instance.
//
public void release()
{
if(System.getProperty("os.name").startsWith("Windows"))
{
if(_randFile != null)
{
//
// In Windows we need to close the file handler before
// we try to delete the file. Note that the call to close
// also release the file lock.
//
try
{
_randFile.close();
}
catch(java.io.IOException ex)
{
}
_randFile = null;
}
}
//
// on UNIX the call to delete remove the file and that
// release the lock.
//
// In Windows the call to delete will success if at that point
// the file has not been opened by any process.
//
if(_file != null)
{
_file.delete();
_file = null;
}
}
//
// We need to keep these refrences to delete the lock file during release
//
private File _file;
private RandomAccessFile _randFile;
}
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