1 /*
   2  * Copyright (c) 2005, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package java.io;
  26 
  27 import java.util.*;
  28 
  29 import jdk.internal.access.SharedSecrets;
  30 
  31 /**
  32  * This class holds a set of filenames to be deleted on VM exit through a shutdown hook.
  33  * A set is used both to prevent double-insertion of the same file as well as offer
  34  * quick removal.
  35  */
  36 
  37 class DeleteOnExitHook {
  38     private static class OrderCount {
  39         long order;
  40         int count;
  41     }
  42     private static long nextOrder;
  43     private static HashMap<String, OrderCount> files = new HashMap<>();
  44     static {
  45         // DeleteOnExitHook must be the last shutdown hook to be invoked.
  46         // Application shutdown hooks may add the first file to the
  47         // delete on exit list and cause the DeleteOnExitHook to be
  48         // registered during shutdown in progress. So set the
  49         // registerShutdownInProgress parameter to true.
  50         SharedSecrets.getJavaLangAccess()
  51             .registerShutdownHook(2 /* Shutdown hook invocation order */,
  52                 true /* register even if shutdown in progress */,
  53                 new Runnable() {
  54                     public void run() {
  55                        runHooks();
  56                     }
  57                 }
  58         );
  59     }
  60 
  61     private DeleteOnExitHook() {}
  62 
  63     static synchronized void deleteOnExit(String file) {
  64         if(files == null) {
  65             // DeleteOnExitHook is running. Too late to add a file
  66             throw new IllegalStateException("Shutdown in progress");
  67         }
  68 
  69         OrderCount oc = files.computeIfAbsent(file, f -> new OrderCount());
  70         oc.order = nextOrder++;
  71         oc.count++;
  72     }
  73 
  74     static synchronized void cancelDeleteOnExit(String file) {
  75         if(files != null) {
  76             files.compute(file, (f, oc) -> {
  77                 if (oc == null) {
  78                     throw new IllegalStateException(
  79                         "Unbalanced cancelDeleteOnExit for missing deleteOnExit");
  80                 }
  81                 return --oc.count <= 0 ? null : oc;
  82             });
  83         }
  84     }
  85 
  86     static void runHooks() {
  87         HashMap<String, OrderCount> theFiles;
  88 
  89         synchronized (DeleteOnExitHook.class) {
  90             theFiles = files;
  91             files = null;
  92         }
  93 
  94         theFiles
  95             .entrySet()
  96             .stream()
  97             // last registered -> first deleted
  98             .sorted(Comparator.comparing(e -> -e.getValue().order))
  99             .map(e -> new File(e.getKey()))
 100             .forEach(File::delete);
 101     }
 102 }