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1 package jp.ac.u_ryukyu.ie.cr.shoshi.jungle.transaction;
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2
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3 import java.util.concurrent.atomic.AtomicBoolean;
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4 import java.util.concurrent.atomic.AtomicReference;
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5
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6 public class AtomicReservableReference<V>
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7 {
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8 public static void main(String _args[])
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9 {
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10 String hoge = "hoge";
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11 String fuga = "fuga";
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12 AtomicReservableReference<String> arr = new AtomicReservableReference<String>(hoge);
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13 AtomicReservableReference<String>.Reservation r1 = arr.makeReservation(hoge,fuga);
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14 //AtomicReservableReference<String>.Reservation r2 = arr.makeReservation(hoge,fuga);
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45
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15
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16 System.out.println(arr.get());
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17 r1.confirm();
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18 System.out.println(arr.get());
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19 }
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20
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21 private AtomicReference<Reservation> reservation;
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22 private AtomicBoolean flagReservation;
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23
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24 public AtomicReservableReference(V _ref)
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25 {
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26 reservation = new AtomicReference<Reservation>(new Reservation(_ref,null,true));
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27 flagReservation = new AtomicBoolean(false);
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28 }
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29
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30 public Reservation makeReservation(V _expect,V _update)
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31 {
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32 if(flagReservation.compareAndSet(false,true)){
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33 V value = get();
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34 if(value == _expect){
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35 Reservation expect = reservation.get();
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36 return new Reservation(_update,expect,false);
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37 }
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38 flagReservation.set(false);
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39 }
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40
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41 return null;
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42 }
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43
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44 public void set(V _value)
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45 {
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46 reservation.set(new Reservation(_value,null,true));
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47 }
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48
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49 public V get()
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50 {
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51 Reservation r = reservation.get();
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52 return r.get();
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53 }
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54
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55 public class Reservation
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56 {
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57 public final Reservation expect;
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58 public final AtomicReference<V> ref;
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59 public final AtomicBoolean flagConfirmed;
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60
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61 public Reservation(V _object,Reservation _expect,boolean _confirmed)
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62 {
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63 expect = _expect;
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64 ref = new AtomicReference<V>(_object);
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65 flagConfirmed = new AtomicBoolean(_confirmed);
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66 }
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67
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68 public V get()
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69 {
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70 return ref.get();
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71 }
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72
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73 public void confirm()
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74 {
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75 if(flagConfirmed.compareAndSet(false,true)){
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76 if(reservation.compareAndSet(expect,this) == false){
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77 throw new IllegalStateException("foo!");
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78 }
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79 flagReservation.set(false);
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80 }
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81 }
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82
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83 public void cancel()
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84 {
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85 if(flagConfirmed.compareAndSet(false,true)){
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86 flagReservation.set(true);
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87 }
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88 }
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89 }
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90 }
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