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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.java;
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24
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25 import java.util.Map;
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26 import java.util.LinkedHashMap;
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27 import java.util.Iterator;
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28 import fschmidt.db.util.WeakCacheMap;
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29
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30
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31 public class TimedCacheMap<K,V> extends WeakCacheMap<K,V> {
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32
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33 private static class IdentityRef {
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34 private final Object obj;
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35
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36 IdentityRef(Object obj) {
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37 this.obj = obj;
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38 }
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39
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40 public int hashCode() {
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41 return System.identityHashCode(obj);
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42 }
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43
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44 public boolean equals(Object obj) {
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45 return obj instanceof IdentityRef
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46 && obj==((IdentityRef)obj).obj;
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47 }
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48 }
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49
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50 private final long timeLimit;
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51 private final Map<IdentityRef,Long> vals = new LinkedHashMap<IdentityRef,Long>();
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52
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53 public TimedCacheMap(long timeLimit) {
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54 this.timeLimit = timeLimit;
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55 }
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56
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57 private void add(V value,long now) {
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58 if( value==null )
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59 return;
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60 IdentityRef ref = new IdentityRef(value);
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61 vals.remove(ref);
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62 vals.put( ref, now + timeLimit );
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63 }
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64
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65 private void sweep(long now) {
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66 for( Iterator<Long> i = vals.values().iterator(); i.hasNext(); ) {
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67 long time = i.next();
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68 if( time > now )
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69 return;
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70 i.remove();
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71 }
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72 }
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73
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74 public V put(K key, V value) {
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75 long now = System.currentTimeMillis();
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76 sweep(now);
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77 add(value,now);
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78 return super.put(key,value);
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79 }
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80
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81 public V get(Object key) {
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82 long now = System.currentTimeMillis();
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83 V value = super.get(key);
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84 add(value,now);
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85 return value;
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86 }
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87 }
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