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/*
* Copyright (c) 2012, 2016, 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.
*
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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 java.util.concurrent.Semaphore;
import com.sun.tools.javac.util.Assert;
import com.sun.tools.sjavac.Log;
import com.sun.tools.sjavac.client.PortFileInaccessibleException;
/**
* 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.
*
* 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.
*/
public 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;
// FileLock used to solve inter JVM synchronization, lockSem used to avoid
// JVM internal OverlappingFileLockExceptions.
// Class invariant: lock.isValid() <-> lockSem.availablePermits() == 0
private FileLock lock;
private Semaphore lockSem = new Semaphore(1);
private boolean containsPortInfo;
private int serverPort;
private long serverCookie;
private int myServerPort;
private long myServerCookie;
/**
* Create a new portfile.
* @param fn is the path to the file.
*/
public PortFile(String fn) {
filename = fn;
file = new File(filename);
stopFile = new File(filename+".stop");
containsPortInfo = false;
lock = null;
}
private void initializeChannel() throws PortFileInaccessibleException {
try {
rwfile = new RandomAccessFile(file, "rw");
} catch (FileNotFoundException e) {
// Reached if file for instance already exists and is a directory
throw new PortFileInaccessibleException(e);
}
// 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();
}
/**
* Lock the port file.
*/
public void lock() throws IOException, InterruptedException {
if (channel == null) {
initializeChannel();
}
lockSem.acquire();
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 (IOException 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.check(containsPortInfo);
return serverPort;
}
/**
* If so, then we can acquire the server cookie.
*/
public long getCookie() {
Assert.check(containsPortInfo);
return serverCookie;
}
/**
* Store the values into the locked port file.
*/
public void setValues(int port, long cookie) throws IOException {
Assert.check(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, InterruptedException {
// Access to file must be closed before deleting.
rwfile.close();
file.delete();
// Wait until file has been deleted (deletes are asynchronous on Windows!) otherwise we
// might shutdown the server and prevent another one from starting.
for (int i = 0; i < 10 && file.exists(); i++) {
Thread.sleep(1000);
}
if (file.exists()) {
throw new IOException("Failed to delete file.");
}
}
/**
* 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 {
if (lock == null) {
return;
}
lock.release();
lock = null;
lockSem.release();
}
/**
* Wait for the port file to contain values that look valid.
*/
public void waitForValidValues() throws IOException, InterruptedException {
final int MS_BETWEEN_ATTEMPTS = 500;
long startTime = System.currentTimeMillis();
long timeout = startTime + getServerStartupTimeoutSeconds() * 1000;
while (true) {
Log.debug("Looking for valid port file values...");
if (exists()) {
lock();
getValues();
unlock();
}
if (containsPortInfo) {
Log.debug("Valid port file values found after " + (System.currentTimeMillis() - startTime) + " ms");
return;
}
if (System.currentTimeMillis() > timeout) {
break;
}
Thread.sleep(MS_BETWEEN_ATTEMPTS);
}
throw new IOException("No port file values materialized. Giving up after " +
(System.currentTimeMillis() - startTime) + " ms");
}
/**
* Check if the portfile still contains my values, assuming that I am the server.
*/
public boolean stillMyValues() throws IOException, FileNotFoundException, InterruptedException {
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;
}
private long getServerStartupTimeoutSeconds() {
String str = System.getProperty("serverStartupTimeout");
if (str != null) {
try {
return Integer.parseInt(str);
} catch (NumberFormatException e) {
}
}
return 60;
}
}