SyncSection


1   /*
2    * The contents of this file are subject to the terms of the Common Development
3    * and Distribution License (the License). You may not use this file except in
4    * compliance with the License.
5    *
6    * You can obtain a copy of the License at http://www.netbeans.org/cddl.html
7    * or http://www.netbeans.org/cddl.txt.
8    *
9    * When distributing Covered Code, include this CDDL Header Notice in each file
10   * and include the License file at http://www.netbeans.org/cddl.txt.
11   * If applicable, add the following below the CDDL Header, with the fields
12   * enclosed by brackets [] replaced by your own identifying information:
13   * "Portions Copyrighted [year] [name of copyright owner]"
14   *
15   * The Original Software is NetBeans. The Initial Developer of the Original
16   * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
17   * Microsystems, Inc. All Rights Reserved.
18   */
19  
20  package org.netbeans.modules.masterfs;
21  
22  import java.util.Collections  ;
23  import java.util.WeakHashMap  ;
24  
25  /**
26   *
27   * @author  rm111737
28   */
29  final class SyncSection {
30      /** sync. purpose*/
31      private int exclusiveCounter;
32      private int normalCounter;
33      final private ThreadLocal   normalCounterPerThread = new ThreadLocal  ();
34      final private ThreadLocal   exclusiveCounterPerThread = new ThreadLocal  ();
35      final private Object   sync = new Object  ();
36      private static SyncSection instance;
37  
38  
39      static SyncSection getDefault() {
40          synchronized (Cache.class) {
41              if (instance == null) {
42                  instance = new SyncSection();
43              }
44          }
45          return instance;
46      }
47  
48      /** Creates a new instance of SyncSection */
49      private SyncSection() {
50      }
51  
52      void enterSection() {
53          synchronized (sync) {
54              try {
55                  while ((exclusiveCounter - getValue(exclusiveCounterPerThread)) > 0) {
56                      sync.wait();
57                  }
58  
59                  normalCounter++;
60                  setValue(normalCounterPerThread, getValue(normalCounterPerThread) + 1);
61              } catch (InterruptedException   iex) {
62                  iex.printStackTrace();
63              }
64          }
65      }
66  
67      void finishSection() {
68          synchronized (sync) {
69              normalCounter--;
70              setValue(normalCounterPerThread, getValue(normalCounterPerThread) - 1);
71              sync.notifyAll();
72          }
73  
74      }
75  
76      /** there should be prevented to call exclusive section from norma sectin, because of
77       * danger of deadlock. Thread, that enters exclusive section should avoid to keep
78       * locks, that could prevent to finish normal section.
79       */
80      void enterExclusiveSection() {
81          synchronized (sync) {
82              try {
83                  while ((normalCounter - getValue(normalCounterPerThread)) > 0 ||
84                          (exclusiveCounter - getValue(exclusiveCounterPerThread)) > 0) {
85                      sync.wait();
86                  }
87              } catch (InterruptedException   iex) {
88                  iex.printStackTrace();
89              }
90              exclusiveCounter++;
91              setValue(exclusiveCounterPerThread, getValue(exclusiveCounterPerThread) + 1);
92  
93          }
94      }
95  
96      void finishExclusiveSection() {
97          synchronized (sync) {
98              exclusiveCounter--;
99              setValue(exclusiveCounterPerThread, getValue(exclusiveCounterPerThread) - 1);
100             sync.notifyAll();
101         }
102     }
103 
104     private int getValue(ThreadLocal   thrVal) {
105         Integer   val = (Integer  ) thrVal.get();
106         return (val != null) ? val.intValue() : 0;
107     }
108 
109     private void setValue(ThreadLocal   thrVal, int value) {
110         thrVal.set(new Integer  (value));
111     }
112 
113 }
114
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