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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.ReentrantLock;
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30
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31
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32 public final class TimedLocker<T> implements Locker<T> {
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33
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34 private static class Tracker {
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35 final ReentrantLock lock0 = new ReentrantLock();
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36 final Lock lock = new TimedLock(lock0);
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37 int waiters = 0;
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38 }
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39
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40 private final Map<T,Tracker> map = new HashMap<T,Tracker>();
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41
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42 private Tracker getTracker(T obj) {
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43 Tracker t = map.get(obj);
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44 if( t==null ) {
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45 t = new Tracker();
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46 map.put(obj,t);
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47 }
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48 return t;
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49 }
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50
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51 private Tracker getTrackerForWait(T obj) {
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52 synchronized(map) {
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53 Tracker t = getTracker(obj);
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54 t.waiters++;
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55 return t;
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56 }
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57 }
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58
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59 private void afterWait(Tracker t) {
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60 synchronized(map) {
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61 t.waiters--;
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62 }
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63 }
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64
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65 private void maybeRemove(T obj,Tracker t) {
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66 if( t.waiters==0 && !t.lock0.isHeldByCurrentThread() ) {
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67 map.remove(obj);
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68 }
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69 }
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70
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71 public void lock(T obj) {
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72 Tracker t = getTrackerForWait(obj);
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73 try {
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74 t.lock.lock();
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75 } finally {
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76 afterWait(t);
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77 }
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78 }
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79
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80 public boolean tryLock(T obj) {
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81 synchronized(map) {
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82 return getTracker(obj).lock.tryLock();
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83 }
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84 }
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85
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86 public boolean tryLock(T obj,long time,TimeUnit unit)
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87 throws InterruptedException
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88 {
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89 Tracker t = getTrackerForWait(obj);
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90 try {
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91 return t.lock.tryLock(time,unit);
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92 } finally {
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93 afterWait(t);
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94 }
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95 }
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96
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97 public void unlock(T obj) {
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98 synchronized(map) {
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99 Tracker t = map.get(obj);
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100 t.lock.unlock();
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101 maybeRemove(obj,t);
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102 }
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103 }
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104
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105 public boolean hasLock(T obj) {
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106 synchronized(map) {
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107 Tracker t = map.get(obj);
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108 return t!=null && t.lock0.isHeldByCurrentThread();
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109 }
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110 }
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111
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112 }
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