/*
* Copyright (c) 2012, 2013, 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
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*/
package com.sun.tools.sjavac.server;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.nio.channels.FileLockInterruptionException;
import com.sun.tools.sjavac.Log;
/**
* The PortFile class mediates access to a short binary file containing the tcp/ip port (for the localhost)
* and a cookie necessary for the server answering on that port. The file can be locked using file system
* primitives to avoid race conditions when several javac clients are started at the same. Note that file
* system locking is not always supported on a all operating systems and/or file systems.
*
* <p><b>This is NOT part of any supported API.
* If you write code that depends on this, you do so at your own
* risk. This code and its internal interfaces are subject to change
* or deletion without notice.</b></p>
*/
class PortFile {
// Port file format:
// byte ordering: high byte first = big endian
// Magic nr, 4 byte int, first in file.
private final static int magicNr = 0x1174;
// Followed by a 4 byte int, with the port nr.
// Followed by a 8 byte long, with cookie nr.
private String filename;
private File file;
private File stopFile;
private RandomAccessFile rwfile;
private FileChannel channel;
private FileLock lock;
private boolean containsPortInfo;
private int serverPort;
private long serverCookie;
private int myServerPort;
private long myServerCookie;
/**
* Create a new portfile.
* @param filename is the path to the file.
*/
public PortFile(String fn) throws FileNotFoundException
{
filename = fn;
file = new File(filename);
stopFile = new File(filename+".stop");
rwfile = new RandomAccessFile(file, "rw");
// The rwfile should only be readable by the owner of the process
// and no other! How do we do that on a RandomAccessFile?
channel = rwfile.getChannel();
containsPortInfo = false;
lock = null;
}
/**
* Lock the port file.
*/
void lock() throws IOException {
lock = channel.lock();
}
/**
* Read the values from the port file in the file system.
* Expects the port file to be locked.
*/
public void getValues() {
containsPortInfo = false;
if (lock == null) {
// Not locked, remain ignorant about port file contents.
return;
}
try {
if (rwfile.length()>0) {
rwfile.seek(0);
int nr = rwfile.readInt();
serverPort = rwfile.readInt();
serverCookie = rwfile.readLong();
if (nr == magicNr) {
containsPortInfo = true;
} else {
containsPortInfo = false;
}
}
} catch (Exception e) {
containsPortInfo = false;
}
}
/**
* Did the locking and getValues succeed?
*/
public boolean containsPortInfo() {
return containsPortInfo;
}
/**
* If so, then we can acquire the tcp/ip port on localhost.
*/
public int getPort() {
assert(containsPortInfo);
return serverPort;
}
/**
* If so, then we can acquire the server cookie.
*/
public long getCookie() {
assert(containsPortInfo);
return serverCookie;
}
/**
* Store the values into the locked port file.
*/
public void setValues(int port, long cookie) throws IOException {
assert(lock != null);
rwfile.seek(0);
// Write the magic nr that identifes a port file.
rwfile.writeInt(magicNr);
rwfile.writeInt(port);
rwfile.writeLong(cookie);
myServerPort = port;
myServerCookie = cookie;
}
/**
* Delete the port file.
*/
public void delete() throws IOException {
// Access to file must be closed before deleting.
rwfile.close();
// Now delete.
file.delete();
}
/**
* Is the port file still there?
*/
public boolean exists() throws IOException {
return file.exists();
}
/**
* Is a stop file there?
*/
public boolean markedForStop() throws IOException {
if (stopFile.exists()) {
try {
stopFile.delete();
} catch (Exception e)
{}
return true;
}
return false;
}
/**
* Unlock the port file.
*/
public void unlock() throws IOException {
assert(lock != null);
lock.release();
lock = null;
}
/**
* Wait for the port file to contain values that look valid.
* Return true, if a-ok, false if the valid values did not materialize within 5 seconds.
*/
public synchronized boolean waitForValidValues() throws IOException, FileNotFoundException {
for (int tries = 0; tries < 50; tries++) {
lock();
getValues();
unlock();
if (containsPortInfo) {
Log.debug("Found valid values in port file after waiting "+(tries*100)+"ms");
return true;
}
try {
Thread.sleep(100);
} catch (InterruptedException e)
{}
}
Log.debug("Gave up waiting for valid values in port file");
return false;
}
/**
* Check if the portfile still contains my values, assuming that I am the server.
*/
public synchronized boolean stillMyValues() throws IOException, FileNotFoundException {
for (;;) {
try {
lock();
getValues();
unlock();
if (containsPortInfo) {
if (serverPort == myServerPort &&
serverCookie == myServerCookie) {
// Everything is ok.
return true;
}
// Someone has overwritten the port file.
// Probably another javac server, lets quit.
return false;
}
// Something else is wrong with the portfile. Lets quit.
return false;
} catch (FileLockInterruptionException e) {
continue;
}
catch (ClosedChannelException e) {
// The channel has been closed since sjavac is exiting.
return false;
}
}
}
/**
* Return the name of the port file.
*/
public String getFilename() {
return filename;
}
}