260 lines
7.9 KiB
Java
260 lines
7.9 KiB
Java
/*
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* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package com.sun.tools.sjavac.server;
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import java.io.File;
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import java.io.FileNotFoundException;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.nio.channels.ClosedChannelException;
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import java.nio.channels.FileChannel;
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import java.nio.channels.FileLock;
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import java.nio.channels.FileLockInterruptionException;
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import com.sun.tools.sjavac.Log;
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/**
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* The PortFile class mediates access to a short binary file containing the tcp/ip port (for the localhost)
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* and a cookie necessary for the server answering on that port. The file can be locked using file system
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* primitives to avoid race conditions when several javac clients are started at the same. Note that file
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* system locking is not always supported on a all operating systems and/or file systems.
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*
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* <p><b>This is NOT part of any supported API.
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* If you write code that depends on this, you do so at your own
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* risk. This code and its internal interfaces are subject to change
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* or deletion without notice.</b></p>
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*/
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class PortFile {
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// Port file format:
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// byte ordering: high byte first = big endian
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// Magic nr, 4 byte int, first in file.
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private final static int magicNr = 0x1174;
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// Followed by a 4 byte int, with the port nr.
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// Followed by a 8 byte long, with cookie nr.
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private String filename;
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private File file;
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private File stopFile;
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private RandomAccessFile rwfile;
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private FileChannel channel;
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private FileLock lock;
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private boolean containsPortInfo;
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private int serverPort;
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private long serverCookie;
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private int myServerPort;
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private long myServerCookie;
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/**
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* Create a new portfile.
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* @param filename is the path to the file.
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*/
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public PortFile(String fn) throws FileNotFoundException
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{
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filename = fn;
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file = new File(filename);
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stopFile = new File(filename+".stop");
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rwfile = new RandomAccessFile(file, "rw");
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// The rwfile should only be readable by the owner of the process
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// and no other! How do we do that on a RandomAccessFile?
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channel = rwfile.getChannel();
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containsPortInfo = false;
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lock = null;
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}
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/**
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* Lock the port file.
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*/
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void lock() throws IOException {
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lock = channel.lock();
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}
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/**
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* Read the values from the port file in the file system.
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* Expects the port file to be locked.
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*/
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public void getValues() {
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containsPortInfo = false;
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if (lock == null) {
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// Not locked, remain ignorant about port file contents.
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return;
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}
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try {
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if (rwfile.length()>0) {
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rwfile.seek(0);
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int nr = rwfile.readInt();
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serverPort = rwfile.readInt();
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serverCookie = rwfile.readLong();
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if (nr == magicNr) {
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containsPortInfo = true;
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} else {
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containsPortInfo = false;
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}
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}
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} catch (Exception e) {
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containsPortInfo = false;
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}
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}
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/**
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* Did the locking and getValues succeed?
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*/
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public boolean containsPortInfo() {
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return containsPortInfo;
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}
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/**
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* If so, then we can acquire the tcp/ip port on localhost.
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*/
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public int getPort() {
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assert(containsPortInfo);
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return serverPort;
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}
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/**
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* If so, then we can acquire the server cookie.
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*/
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public long getCookie() {
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assert(containsPortInfo);
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return serverCookie;
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}
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/**
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* Store the values into the locked port file.
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*/
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public void setValues(int port, long cookie) throws IOException {
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assert(lock != null);
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rwfile.seek(0);
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// Write the magic nr that identifes a port file.
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rwfile.writeInt(magicNr);
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rwfile.writeInt(port);
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rwfile.writeLong(cookie);
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myServerPort = port;
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myServerCookie = cookie;
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}
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/**
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* Delete the port file.
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*/
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public void delete() throws IOException {
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// Access to file must be closed before deleting.
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rwfile.close();
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// Now delete.
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file.delete();
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}
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/**
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* Is the port file still there?
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*/
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public boolean exists() throws IOException {
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return file.exists();
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}
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/**
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* Is a stop file there?
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*/
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public boolean markedForStop() throws IOException {
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if (stopFile.exists()) {
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try {
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stopFile.delete();
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} catch (Exception e)
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{}
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return true;
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}
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return false;
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}
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/**
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* Unlock the port file.
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*/
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public void unlock() throws IOException {
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assert(lock != null);
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lock.release();
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lock = null;
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}
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/**
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* Wait for the port file to contain values that look valid.
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* Return true, if a-ok, false if the valid values did not materialize within 5 seconds.
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*/
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public synchronized boolean waitForValidValues() throws IOException, FileNotFoundException {
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for (int tries = 0; tries < 50; tries++) {
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lock();
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getValues();
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unlock();
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if (containsPortInfo) {
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Log.debug("Found valid values in port file after waiting "+(tries*100)+"ms");
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return true;
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}
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try {
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Thread.sleep(100);
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} catch (InterruptedException e)
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{}
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}
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Log.debug("Gave up waiting for valid values in port file");
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return false;
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}
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/**
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* Check if the portfile still contains my values, assuming that I am the server.
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*/
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public synchronized boolean stillMyValues() throws IOException, FileNotFoundException {
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for (;;) {
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try {
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lock();
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getValues();
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unlock();
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if (containsPortInfo) {
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if (serverPort == myServerPort &&
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serverCookie == myServerCookie) {
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// Everything is ok.
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return true;
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}
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// Someone has overwritten the port file.
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// Probably another javac server, lets quit.
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return false;
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}
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// Something else is wrong with the portfile. Lets quit.
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return false;
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} catch (FileLockInterruptionException e) {
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continue;
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}
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catch (ClosedChannelException e) {
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// The channel has been closed since sjavac is exiting.
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return false;
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}
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}
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}
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/**
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* Return the name of the port file.
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*/
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public String getFilename() {
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return filename;
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}
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}
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