CloverBootloader/rEFIt_UEFI/cpp_foundation/shared_ptr.h

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/*
* sharedptr.h
*
* Created on: Oct 17, 2020
* Author: jief
* From https://www.geeksforgeeks.org/how-to-implement-user-defined-shared-pointers-in-c/
*/
#ifndef CPP_FOUNDATION_SHARED_PTR_H_
#define CPP_FOUNDATION_SHARED_PTR_H_
// Class representing a reference counter class
class Counter {
public:
// Constructor
Counter()
: m_counter(0){};
Counter(const Counter&) = delete;
Counter& operator=(const Counter&) = delete;
// Destructor
~Counter()
{
}
void reset()
{
m_counter = 0;
}
unsigned int get()
{
return m_counter;
}
// Overload post/pre increment
Counter& operator++()
{
m_counter++;
return *this;
}
// Counter operator++(int)
// {
// Counter tmp = *this;
// m_counter++;
// return tmp;
// }
//
// // Overload post/pre decrement
Counter& operator--()
{
m_counter--;
return *this;
}
// Counter operator--(int)
// {
// Counter tmp = *this;
// m_counter--;
// return tmp;
// }
private:
unsigned int m_counter{};
};
// Class representing a shared pointer
template <typename T>
class Shared_ptr {
public:
// Constructor
explicit Shared_ptr(T* ptr = nullptr)
{
m_ptr = ptr;
m_counter = new Counter;
if (ptr) {
++(*m_counter);
}
}
// Copy constructor
Shared_ptr(Shared_ptr<T>& sp)
{
m_ptr = sp.m_ptr;
m_counter = sp.m_counter;
++(*m_counter);
}
// Reference count
unsigned int use_count()
{
return m_counter->get();
}
// Get the pointer
T* get()
{
return m_ptr;
}
// Overload * operator
T& operator*() {
return *m_ptr;
}
// Overload -> operator
T* operator->() {
return m_ptr;
}
// Destructor
~Shared_ptr()
{
--(*m_counter);
if (m_counter->get() == 0) {
delete m_counter;
delete m_ptr;
}
}
//// shared_ptr comparisons:
//template<class T, class U>
// bool operator==(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;
//template<class T, class U>
// bool operator!=(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;
//template <class T>
// bool operator==(const shared_ptr<T>& x, nullptr_t) noexcept;
//template <class T>
// bool operator==(nullptr_t, const shared_ptr<T>& y) noexcept;
//template <class T>
// bool operator!=(const shared_ptr<T>& x, nullptr_t) noexcept;
//template <class T>
// bool operator!=(nullptr_t, const shared_ptr<T>& y) noexcept;
// shared_ptr bool cast ?
//see /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/memory
private:
// Reference counter
Counter* m_counter;
// Shared pointer
T* m_ptr;
};
//int main()
//{
// // ptr1 pointing to an integer.
// Shared_ptr<int> ptr1(new int(151));
// cout << "--- Shared pointers ptr1 ---\n";
// *ptr1 = 100;
// cout << " ptr1's value now: " << *ptr1 << endl;
// cout << ptr1;
//
// {
// // ptr2 pointing to same integer
// // which ptr1 is pointing to
// // Shared pointer reference counter
// // should have increased now to 2.
// Shared_ptr<int> ptr2 = ptr1;
// cout << "--- Shared pointers ptr1, ptr2 ---\n";
// cout << ptr1;
// cout << ptr2;
//
// {
// // ptr3 pointing to same integer
// // which ptr1 and ptr2 are pointing to.
// // Shared pointer reference counter
// // should have increased now to 3.
// Shared_ptr<int> ptr3(ptr2);
// cout << "--- Shared pointers ptr1, ptr2, ptr3 ---\n";
// cout << ptr1;
// cout << ptr2;
// cout << ptr3;
// }
//
// // ptr3 is out of scope.
// // It would have been destructed.
// // So shared pointer reference counter
// // should have decreased now to 2.
// cout << "--- Shared pointers ptr1, ptr2 ---\n";
// cout << ptr1;
// cout << ptr2;
// }
//
// // ptr2 is out of scope.
// // It would have been destructed.
// // So shared pointer reference counter
// // should have decreased now to 1.
// cout << "--- Shared pointers ptr1 ---\n";
// cout << ptr1;
//
// return 0;
//}
#endif /* CPP_FOUNDATION_SHARED_PTR_H_ */