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1 /*
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2 Copyright (c) 2008 Franklin Schmidt <fschmidt@gmail.com>
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3
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4 Permission is hereby granted, free of charge, to any person obtaining a copy
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5 of this software and associated documentation files (the "Software"), to deal
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6 in the Software without restriction, including without limitation the rights
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7 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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8 copies of the Software, and to permit persons to whom the Software is
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9 furnished to do so, subject to the following conditions:
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10
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11 The above copyright notice and this permission notice shall be included in
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12 all copies or substantial portions of the Software.
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13
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14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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15 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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16 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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17 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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18 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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19 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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20 THE SOFTWARE.
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21 */
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22
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23 package fschmidt.util.locks;
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24
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25 import java.util.Map;
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26 import java.util.HashMap;
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27 import java.util.concurrent.TimeUnit;
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28 import java.util.concurrent.locks.Lock;
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29 import java.util.concurrent.locks.ReadWriteLock;
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30 import java.util.concurrent.locks.ReentrantReadWriteLock;
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31
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32
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33 public final class TimedReadWriteLocker<T> implements ReadWriteLocker<T> {
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34
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35 private static class Tracker {
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36 final ReentrantReadWriteLock lock0 = new ReentrantReadWriteLock();
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37 final ReadWriteLock lock = new TimedReadWriteLock(lock0);
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38 int waiters = 0;
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39 }
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40
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41 private final Map<T,Tracker> map = new HashMap<T,Tracker>();
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42
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43 private Tracker getTracker(T obj) {
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44 Tracker t = map.get(obj);
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45 if( t==null ) {
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46 t = new Tracker();
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47 map.put(obj,t);
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48 }
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49 return t;
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50 }
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51
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52 private Tracker getTrackerForWait(T obj) {
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53 synchronized(map) {
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54 Tracker t = getTracker(obj);
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55 t.waiters++;
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56 return t;
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57 }
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58 }
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59
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60 private void afterWait(Tracker t) {
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61 synchronized(map) {
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62 t.waiters--;
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63 }
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64 }
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65
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66 private void maybeRemove(T obj,Tracker t) {
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67 if( t.waiters==0 && !t.lock0.isWriteLocked() && t.lock0.getReadLockCount()==0 ) {
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68 map.remove(obj);
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69 }
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70 }
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71
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72 private final Locker<T> writeLocker = new Locker<T>() {
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73
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74 public void lock(T obj) {
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75 Tracker t = getTrackerForWait(obj);
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76 try {
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77 t.lock.writeLock().lock();
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78 } finally {
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79 afterWait(t);
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80 }
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81 }
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82
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83 public boolean tryLock(T obj) {
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84 synchronized(map) {
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85 return getTracker(obj).lock.writeLock().tryLock();
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86 }
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87 }
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88
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89 public boolean tryLock(T obj,long time,TimeUnit unit)
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90 throws InterruptedException
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91 {
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92 Tracker t = getTrackerForWait(obj);
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93 try {
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94 return t.lock.writeLock().tryLock(time,unit);
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95 } finally {
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96 afterWait(t);
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97 }
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98 }
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99
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100 public void unlock(T obj) {
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101 synchronized(map) {
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102 Tracker t = map.get(obj);
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103 t.lock.writeLock().unlock();
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104 maybeRemove(obj,t);
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105 }
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106 }
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107 };
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108
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109 private final Locker<T> readLocker = new Locker<T>() {
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110
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111 public void lock(T obj) {
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112 Tracker t = getTrackerForWait(obj);
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113 try {
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114 t.lock.readLock().lock();
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115 } finally {
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116 afterWait(t);
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117 }
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118 }
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119
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120 public boolean tryLock(T obj) {
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121 synchronized(map) {
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122 return getTracker(obj).lock.readLock().tryLock();
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123 }
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124 }
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125
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126 public boolean tryLock(T obj,long time,TimeUnit unit)
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127 throws InterruptedException
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128 {
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129 Tracker t = getTrackerForWait(obj);
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130 try {
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131 return t.lock.readLock().tryLock(time,unit);
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132 } finally {
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133 afterWait(t);
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134 }
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135 }
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136
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137 public void unlock(T obj) {
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138 synchronized(map) {
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139 Tracker t = map.get(obj);
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140 t.lock.readLock().unlock();
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141 maybeRemove(obj,t);
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142 }
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143 }
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144 };
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145
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146 public Locker<T> readLocker() {
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147 return readLocker;
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148 }
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149
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150 public Locker<T> writeLocker() {
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151 return writeLocker;
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152 }
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153
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154 }
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