1 | #ifndef __SINGLETON_HPP__
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2 | #define __SINGLETON_HPP__
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3 |
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4 | #include <boost/thread/mutex.hpp>
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5 | #include <boost/thread/thread.hpp>
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6 |
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7 | #include <boost/noncopyable.hpp>
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8 |
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9 | namespace boost
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10 | {
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11 | /**
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12 | Thanks to A. Alexandrescu for CTAssert concept.
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13 | */
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14 |
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15 | template<bool> class CTAssert;
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16 | template<> class CTAssert<false>{ };
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17 |
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18 | /**
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19 | See http://www.research.ibm.com/designpatterns/pubs/ph-jun96.txt
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20 | about Singletons and Destroyers.
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21 | This is destroyer for Singleton.
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22 | Singleton must not be array.
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23 | */
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24 |
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25 | template<class Doomed>
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26 | class SingletonDestroyer : boost::noncopyable
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27 | {
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28 | /**
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29 | SingletonDestroyer is only used with Singleton.
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30 | The goal of SingletonDestroyer - to delete
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31 | Singleton instance at program exit.
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32 | */
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33 |
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34 | template<class> friend class Singleton;
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35 |
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36 | private:
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37 | Doomed* doomed_;
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38 | private:
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39 | SingletonDestroyer()
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40 | {
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41 | typedef typename boost::is_array<Doomed>::type DoomedArrayType;
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42 | CTAssert<DoomedArrayType::value>
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43 | ____DOOMED_SINGLETON_MUST_NOT_BE_ARRAY____;
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44 | /**
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45 | Suppress unused variable warning
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46 | */
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47 | ____DOOMED_SINGLETON_MUST_NOT_BE_ARRAY____;
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48 | }
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49 | ~SingletonDestroyer(){ delete doomed_; }
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50 | private:
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51 | void set_doomed(Doomed* doomed){ doomed_ = doomed; }
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52 | };
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53 |
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54 | template<class T>
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55 | class Singleton : boost::noncopyable
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56 | {
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57 | private:
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58 | static T* instance_;
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59 | static SingletonDestroyer<T> destroyer_;
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60 | static boost::mutex mtx_instance_;
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61 | public:
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62 | static T& Instance()
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63 | {
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64 | /**
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65 | Perform the Double-Check pattern.
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66 | See http://www.research.ibm.com/designpatterns/pubs/ph-jun96.txt.
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67 | */
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68 |
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69 | if (instance_ == NULL)
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70 | {
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71 | boost::mutex::scoped_lock locker(mtx_instance_);
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72 | if (instance_ == NULL)
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73 | {
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74 | instance_ = new T();
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75 | destroyer_.set_doomed(instance_);
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76 | }
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77 | }
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78 |
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79 | return *instance_;
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80 | }
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81 | };
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82 |
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83 | template<typename T> T* Singleton<T>::instance_ = NULL;
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84 | template<typename T> SingletonDestroyer<T> Singleton<T>::destroyer_;
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85 | template<typename T> boost::mutex Singleton<T>::mtx_instance_;
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86 |
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87 | } // !namespace boost
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88 |
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89 | #define SINGLETON_IS_MY_FRIEND \
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90 | template<class> friend class Singleton; \
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91 | template<class> friend class SingletonDestroyer;
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92 |
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93 | #endif // __SINGLETON_HPP__
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94 |
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