124 lines
2.3 KiB
C++
124 lines
2.3 KiB
C++
#ifndef VSHAREDPTR_H
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#define VSHAREDPTR_H
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#include <cassert>
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#include <memory>
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#include <atomic>
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template <typename T, typename Rc>
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class vshared_ptr {
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struct model {
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Rc mRef{1};
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model() = default;
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template <class... Args>
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explicit model(Args&&... args) : mValue(std::forward<Args>(args)...){}
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explicit model(const T& other) : mValue(other){}
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T mValue;
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};
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model* mModel{nullptr};
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public:
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using element_type = T;
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vshared_ptr() = default;
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~vshared_ptr()
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{
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unref();
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}
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template <class... Args>
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explicit vshared_ptr(Args&&... args) : mModel(new model(std::forward<Args>(args)...))
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{
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}
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vshared_ptr(const vshared_ptr& x) noexcept : vshared_ptr()
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{
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if (x.mModel) {
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mModel = x.mModel;
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++mModel->mRef;
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}
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}
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vshared_ptr(vshared_ptr&& x) noexcept : vshared_ptr()
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{
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if (x.mModel) {
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mModel = x.mModel;
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x.mModel = nullptr;
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}
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}
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auto operator=(const vshared_ptr& x) noexcept -> vshared_ptr&
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{
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unref();
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mModel = x.mModel;
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ref();
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return *this;
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}
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auto operator=(vshared_ptr&& x) noexcept -> vshared_ptr&
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{
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unref();
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mModel = x.mModel;
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x.mModel = nullptr;
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return *this;
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}
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operator bool() const noexcept {
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return mModel != nullptr;
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}
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auto operator*() const noexcept -> element_type& { return read(); }
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auto operator-> () const noexcept -> element_type* { return &read(); }
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std::size_t refCount() const noexcept
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{
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assert(mModel);
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return mModel->mRef;
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}
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bool unique() const noexcept
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{
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assert(mModel);
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return mModel->mRef == 1;
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}
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private:
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auto read() const noexcept -> element_type&
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{
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assert(mModel);
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return mModel->mValue;
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}
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void ref()
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{
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if (mModel) ++mModel->mRef;
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}
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void unref()
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{
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if (mModel && (--mModel->mRef == 0)) {
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delete mModel;
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mModel = nullptr;
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}
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}
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};
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// atomic ref counted pointer implementation.
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template < typename T>
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using arc_ptr = vshared_ptr<T, std::atomic<std::size_t>>;
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// ref counter pointer implementation.
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template < typename T>
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using rc_ptr = vshared_ptr<T, std::size_t>;
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#endif // VSHAREDPTR_H
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