Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||||||
NSMultiReaderLock |
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| 2.0714285714285716;2.071 |
1 | /* |
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2 | Wotonomy: OpenStep design patterns for pure Java applications. |
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3 | Copyright (C) 2002 Israfil consulting Services Corporation |
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4 | ||
5 | This library is free software; you can redistribute it and/or |
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6 | modify it under the terms of the GNU Lesser General Public |
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7 | License as published by the Free Software Foundation; either |
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8 | version 2.1 of the License, or (at your option) any later version. |
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9 | ||
10 | This library is distributed in the hope that it will be useful, |
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11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 | Lesser General Public License for more details. |
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14 | ||
15 | You should have received a copy of the GNU Lesser General Public |
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16 | License along with this library; if not, see http://www.gnu.org |
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17 | ||
18 | $Id: NSMultiReaderLock.java 893 2006-02-16 13:22:23 +0000 (Thu, 16 Feb 2006) cgruber $ |
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19 | ||
20 | */ |
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21 | ||
22 | package net.wotonomy.foundation; |
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23 | ||
24 | import EDU.oswego.cs.dl.util.concurrent.ReentrantWriterPreferenceReadWriteLock; |
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25 | ||
26 | /** |
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27 | * A Read-Write lock that allows unlimited number of calling threads to |
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28 | * acquire read locks, but only one thread to acquire a write lock. It |
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29 | * is also reentrant, allowing each thread to re-acquire it's lock |
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30 | * recursively. For that reason it is somewhat slower, as there is a |
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31 | * hash lookup when attempting to acquire and release reader locks. Of |
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32 | * course a writer lock is quite a bit slower than a reader lock. A |
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33 | * write lock is mutally exclusive with read locks, though a thread |
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34 | * that has obtained a read-lock may be promoted to a write lock and |
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35 | * vice versa when conditions permit. |
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36 | * |
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37 | * @author cgruber@israfil.net |
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38 | * @author $Author: cgruber $ |
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39 | * @version $Revision: 893 $ |
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40 | */ |
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41 | public class NSMultiReaderLock extends ReentrantWriterPreferenceReadWriteLock implements NSLocking { |
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42 | ||
43 | 0 | NSMutableDictionary _readerSuspended = new NSMutableDictionary(); |
44 | ||
45 | 0 | public NSMultiReaderLock() { |
46 | 0 | } |
47 | ||
48 | public void lockForReading() { |
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49 | try { |
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50 | 0 | readerLock_.acquire(); |
51 | 0 | } catch (InterruptedException interruptedexception) { |
52 | // Null behavior, as notify() is already called |
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53 | // by acquire(); |
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54 | // We may want to log here. |
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55 | 0 | } |
56 | 0 | } |
57 | ||
58 | public void unlockForReading() { |
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59 | 0 | readerLock_.release(); |
60 | 0 | } |
61 | ||
62 | public void lock() { |
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63 | 0 | lockForWriting(); |
64 | 0 | } |
65 | ||
66 | public void lockForWriting() { |
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67 | try { |
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68 | 0 | writerLock_.acquire(); |
69 | 0 | } catch (InterruptedException interruptedexception) { |
70 | // Null behavior, as notify() is already called |
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71 | // by acquire(); |
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72 | // We may want to log here. |
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73 | 0 | } |
74 | 0 | } |
75 | ||
76 | public void unlock() { |
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77 | 0 | unlockForWriting(); |
78 | 0 | } |
79 | ||
80 | public void unlockForWriting() { |
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81 | 0 | writerLock_.release(); |
82 | 0 | } |
83 | ||
84 | /** @see com.webobjects.foundation.NSMultiReaderLock#suspendReaderLock() */ |
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85 | public void suspendReaderLocks() { |
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86 | 0 | Thread thisThread = Thread.currentThread(); |
87 | 0 | Integer suspendedReaders = (Integer)_readerSuspended.get(thisThread); |
88 | 0 | if (suspendedReaders != null && suspendedReaders.intValue() > 0) return; |
89 | // logic is to override startRead / endRead and ensure that the suspension |
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90 | // isn't improperly stopped. |
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91 | 0 | throw new UnsupportedOperationException("Not Yet Implemented"); |
92 | } |
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93 | ||
94 | /** @see com.webobjects.foundation.NSMultiReaderLock#retrieveReaderLock() */ |
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95 | public void retrieveReaderLocks() { |
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96 | 0 | Thread thisThread = Thread.currentThread(); |
97 | 0 | Integer suspendedReaders = (Integer)_readerSuspended.get(thisThread); |
98 | 0 | if (suspendedReaders != null && suspendedReaders.intValue() > 0) return; |
99 | // logic is to override startRead / endRead and ensure that the suspension |
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100 | // isn't improperly stopped. |
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101 | 0 | throw new UnsupportedOperationException("Not Yet Implemented"); |
102 | } |
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103 | ||
104 | public boolean tryLockForWriting() { |
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105 | try { |
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106 | 0 | return writerLock_.attempt(0); |
107 | 0 | } catch (InterruptedException interruptedexception) { |
108 | // notify() is already called by attempt(); |
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109 | // We may want to log here. |
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110 | 0 | return false; |
111 | } |
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112 | } |
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113 | ||
114 | public boolean tryLockForReading() { |
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115 | try { |
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116 | 0 | return readerLock_.attempt(0); |
117 | 0 | } catch (InterruptedException interruptedexception) { |
118 | // notify() is already called by attempt(); |
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119 | // We may want to log here. |
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120 | 0 | return false; |
121 | } |
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122 | } |
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123 | ||
124 | public String toString() { |
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125 | 0 | throw new UnsupportedOperationException("Not Yet Implemented"); |
126 | } |
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127 | ||
128 | protected String _padString(long l, int i) { |
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129 | 0 | throw new UnsupportedOperationException("Not Yet Implemented"); |
130 | } |
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131 | ||
132 | protected String _padString(String s, int i, boolean flag) { |
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133 | 0 | throw new UnsupportedOperationException("Not Yet Implemented"); |
134 | } |
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135 | ||
136 | ||
137 | } |
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138 | /* |
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139 | * $Log$ |
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140 | * Revision 1.2 2006/02/16 13:15:00 cgruber |
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141 | * Check in all sources in eclipse-friendly maven-enabled packages. |
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142 | * |
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143 | * Revision 1.2 2003/08/06 23:07:52 chochos |
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144 | * general code cleanup (mostly, removing unused imports) |
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145 | * |
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146 | * Revision 1.1 2002/07/14 21:56:16 mpowers |
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147 | * Contributions from cgruber. |
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148 | * |
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149 | * Revision 1.2 2002/06/26 00:40:22 cgruber |
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150 | * Add implementation, using ReentrantWriterPreferenceReadWriteLock |
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151 | * as a base. |
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152 | * |
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153 | * suspendReaderLocks and retreiveReaderLocks is the one |
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154 | * that's likeliest to be a pain. |
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155 | * |
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156 | * Revision 1.1 2002/06/25 07:52:57 cgruber |
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157 | * Add quite a few abstract classes, interfaces, and classes. All API consistent with WebObjects, but with no implementation, nor any private or package access members from the original. |
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158 | * |
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159 | */ |