127 lines
2.7 KiB
C++
127 lines
2.7 KiB
C++
#ifndef MBGL_UTIL_SINGLETON_HPP
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#define MBGL_UTIL_SINGLETON_HPP
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// stl
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#include <stdexcept> // std::runtime_error
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#include <cstdlib> // std::atexit
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#include <new> // operator new
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#define SINGLETON_THREADSAFE
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#ifdef SINGLETON_THREADSAFE
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#include <mutex>
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#endif
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namespace mbgl { namespace util {
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template <typename T>
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class CreateUsingNew
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{
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public:
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static T* create()
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{
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return new T;
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}
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static void destroy(T* obj)
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{
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delete obj;
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}
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};
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template <typename T>
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class CreateStatic
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{
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private:
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union MaxAlign
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{
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char t_[sizeof(T)];
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short int shortInt_;
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int int_;
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long int longInt_;
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float float_;
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double double_;
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long double longDouble_;
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struct Test;
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int Test::* pMember_;
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int (Test::*pMemberFn_)(int);
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};
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public:
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static T* create()
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{
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static MaxAlign staticMemory;
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return new(&staticMemory) T;
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}
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static void destroy(volatile T* obj)
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{
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obj->~T();
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}
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};
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template <typename T,
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template <typename U> class CreatePolicy=CreateStatic> class singleton
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{
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friend class CreatePolicy<T>;
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static T* pInstance_;
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static bool destroyed_;
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singleton(const singleton &rhs);
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singleton& operator=(const singleton&);
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static void onDeadReference()
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{
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throw std::runtime_error("dead reference!");
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}
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static void DestroySingleton()
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{
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CreatePolicy<T>::destroy(pInstance_);
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pInstance_ = 0;
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destroyed_ = true;
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}
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protected:
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#ifdef SINGLETON_THREADSAFE
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static std::mutex mutex_;
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#endif
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singleton() {}
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public:
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static T& instance()
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{
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if (! pInstance_)
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{
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#ifdef SINGLETON_THREADSAFE
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std::unique_lock<std::mutex> lock(mutex_);
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#endif
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if (! pInstance_)
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{
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if (destroyed_)
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{
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destroyed_ = false;
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onDeadReference();
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}
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else
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{
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pInstance_ = CreatePolicy<T>::create();
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// register destruction
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std::atexit(&DestroySingleton);
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}
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}
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}
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return *pInstance_;
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}
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};
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#ifdef SINGLETON_THREADSAFE
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template <typename T,
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template <typename U> class CreatePolicy> std::mutex singleton<T,CreatePolicy>::mutex_;
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#endif
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template <typename T,
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template <typename U> class CreatePolicy> T* singleton<T,CreatePolicy>::pInstance_=0;
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template <typename T,
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template <typename U> class CreatePolicy> bool singleton<T,CreatePolicy>::destroyed_=false;
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}}
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#endif //
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