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#include <iostream> |
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template <typename T> |
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class shared_ptr |
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{ |
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public: |
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shared_ptr() noexcept : mpValue(nullptr), mpRefCount(nullptr) |
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{ |
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} |
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shared_ptr(std::nullptr_t) noexcept : mpValue(nullptr), mpRefCount(nullptr) |
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{ |
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} |
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explicit shared_ptr(T* pValue) : mpValue(pValue), mpRefCount(new size_t(1)) |
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{ |
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} |
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shared_ptr(const shared_ptr<T>& sharedPtr) noexcept : mpValue(sharedPtr.mpValue), mpRefCount(sharedPtr.mpRefCount) |
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{ |
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if (mpRefCount != nullptr) |
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{ |
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++(*mpRefCount); |
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} |
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} |
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shared_ptr(shared_ptr<T>&& sharedPtr) noexcept : mpValue(sharedPtr.mpValue), mpRefCount(sharedPtr.mpRefCount) |
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{ |
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sharedPtr.mpValue = nullptr; |
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sharedPtr.mpRefCount = nullptr; |
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} |
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~shared_ptr() noexcept |
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{ |
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if (mpRefCount != nullptr) |
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{ |
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if (--(*mpRefCount) == 0) |
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{ |
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delete mpRefCount; |
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delete mpValue; |
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} |
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} |
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} |
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shared_ptr& operator=(const shared_ptr<T>& sharedPtr) noexcept |
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{ |
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if (&sharedPtr != this) { |
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shared_ptr<T>(shared_ptr).swap(*this); |
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} |
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return *this; |
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} |
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shared_ptr& operator=(shared_ptr<T>&& sharedPtr) noexcept |
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{ |
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if (&sharedPtr != this) |
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{ |
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shared_ptr<T>(std::move(sharedPtr)).swap(*this); |
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} |
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return *this; |
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} |
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T* get() noexcept |
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{ |
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return mpValue; |
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} |
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private: |
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T* mpValue; |
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size_t* mpRefCount; |
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void swap(shared_ptr<T>& sharedPtr) noexcept |
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{ |
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T* pValue = sharedPtr.mpValue; |
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sharedPtr.mpValue = mpValue; |
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mpValue = pValue; |
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size_t* pRefCount = sharedPtr.mpRefCount; |
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sharedPtr.mpRefCount = mpRefCount; |
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mpRefCount = pRefCount; |
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} |
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}; |
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class A |
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{ |
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public: |
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int mno; |
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A(int no) : mno(no) |
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{ |
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std::cout << "A(" << mno << ")" << std::endl; |
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} |
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~A() |
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{ |
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std::cout << "~A(" << mno << ")" << std::endl; |
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} |
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}; |
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int main() |
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{ |
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{ |
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std::cout << ">>>" << std::endl; |
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A* obj = new A{ 1 }; |
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A* obj2 = new A{ 2 }; |
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shared_ptr<A> a{ obj }; |
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{ |
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std::cout << ">>>" << std::endl; |
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shared_ptr<A> b{ obj2 }; |
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a = std::move(b); |
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std::cout << "<<<" << std::endl; |
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} |
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std::cout << "<<<" << std::endl; |
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} |
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} |
