Mercurial > jdk8-mips64-public > langtools / file revision

 /*

  * 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

  * questions.

  */

 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;

     }

 }