108 lines
2.3 KiB
C++
108 lines
2.3 KiB
C++
/* Copyright 2019 The Mathworks, Inc. */
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#pragma once
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#include <iostream>
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#include <assert.h>
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// Custom shared intrusive pointer. Counts the number of items pointing to an object
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// without storing a separate reference count. Requires the corresponding object to
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// store a field called "referenceCount" as well as friend this class.
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namespace coder {
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template <typename T>
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class shared_ptr {
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public:
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explicit shared_ptr(T* p = nullptr);
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shared_ptr(const shared_ptr<T>& sp);
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unsigned int use_count();
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T* get() const;
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bool unique() const;
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~shared_ptr();
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shared_ptr& operator=(shared_ptr rhs);
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shared_ptr& operator=(T* rhs);
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T& operator*() const;
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T* operator->() const;
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friend void swap(shared_ptr& lhs, shared_ptr& rhs) {
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using std::swap;
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swap(lhs.fPtr, rhs.fPtr);
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}
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private:
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T* fPtr;
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};
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template <typename T>
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shared_ptr<T>::shared_ptr(T* p)
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: fPtr(p) {
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if (fPtr != nullptr) {
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fPtr->referenceCount++;
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}
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}
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template <typename T>
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shared_ptr<T>::shared_ptr(const shared_ptr<T>& sp)
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: fPtr(sp.fPtr) {
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if (fPtr) {
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fPtr->referenceCount++;
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}
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}
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template <typename T>
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shared_ptr<T>& shared_ptr<T>::operator=(shared_ptr<T> rhs) {
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swap(*this, rhs);
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return *this;
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}
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template <typename T>
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shared_ptr<T>& shared_ptr<T>::operator=(T* rhs) {
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shared_ptr<T> temp(rhs);
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*this = temp;
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return *this;
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}
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template <typename T>
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T& shared_ptr<T>::operator*() const {
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return *fPtr;
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}
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template <typename T>
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T* shared_ptr<T>::operator->() const {
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return fPtr;
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}
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// returns the number of pointers pointing to this object
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template <typename T>
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unsigned int shared_ptr<T>::use_count() {
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return fPtr->referenceCount;
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}
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// returns the object
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template <typename T>
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T* shared_ptr<T>::get() const {
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return fPtr;
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}
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// checks whether this is the only pointer pointing to this object
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template <typename T>
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bool shared_ptr<T>::unique() const {
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return fPtr->referenceCount == 1;
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}
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// if there are no more pointers pointing to this object, delete the object
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template <typename T>
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shared_ptr<T>::~shared_ptr() {
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if (fPtr != nullptr) {
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fPtr->referenceCount--;
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if (fPtr->referenceCount == 0) {
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delete fPtr;
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}
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}
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}
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template <typename T>
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shared_ptr<T> make_shared() {
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return shared_ptr<T>(new T());
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}
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} // namespace coder
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