From 3b4c16d7ca1d1e77cdf86520ece2c8e97d3f66e9 Mon Sep 17 00:00:00 2001
From: jakcron <jkrcarr@gmail.com>
Date: Sun, 23 Sep 2018 11:27:42 +0800
Subject: [PATCH] [fnd] Add SharedPtr template class.

---
 lib/libfnd/include/fnd/SharedPtr.h | 141 +++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 lib/libfnd/include/fnd/SharedPtr.h

diff --git a/lib/libfnd/include/fnd/SharedPtr.h b/lib/libfnd/include/fnd/SharedPtr.h
new file mode 100644
index 0000000..e976d4e
--- /dev/null
+++ b/lib/libfnd/include/fnd/SharedPtr.h
@@ -0,0 +1,141 @@
+#pragma once
+#include <fnd/types.h>
+#include <cstdio>
+
+namespace fnd
+{
+	template <class T>
+	class SharedPtr
+	{
+	public:
+		SharedPtr();
+
+		// constructor for creating owner object
+		SharedPtr(T* ptr);
+
+		// copy constructor
+		SharedPtr(const SharedPtr<T>& other);
+
+		// destructor
+		~SharedPtr();
+
+		// own operator
+		void operator=(T* ptr);
+
+		// copy operator
+		void operator=(const SharedPtr<T>& other);
+
+		// access ptr
+		const T* operator*() const;
+		T* operator*();
+
+	private:
+		T* mPtr;
+		size_t* mRefCnt;
+
+		void deletePtr();
+	};
+
+	template <class T>
+	inline SharedPtr<T>::SharedPtr() :
+		mPtr(nullptr),
+		mRefCnt(new size_t)
+	{
+		*mRefCnt = 0;
+	}
+
+	template <class T>
+	inline SharedPtr<T>::SharedPtr(T* ptr) :
+		SharedPtr()
+	{
+		*this = ptr;
+	}
+
+	template <class T>
+	inline SharedPtr<T>::SharedPtr(const SharedPtr<T>& other) :
+		SharedPtr()
+	{
+		*this = other;
+	}
+
+	template <class T>
+	inline SharedPtr<T>::~SharedPtr()
+	{
+		deletePtr();
+	}
+
+	template <class T>
+	inline void SharedPtr<T>::operator=(T* ptr)
+	{
+		deletePtr();
+		if (ptr != nullptr)
+		{
+			mPtr = ptr;
+			mRefCnt = new size_t;
+			*mRefCnt = 1;
+		}
+		else
+		{
+			mPtr = nullptr;
+			mRefCnt = new size_t;
+			*mRefCnt = 0;
+		}
+		
+	}
+
+	template <class T>
+	inline void SharedPtr<T>::operator=(const SharedPtr<T>& other)
+	{
+		deletePtr();
+
+		mPtr = other.mPtr;
+		mRefCnt = other.mRefCnt;
+		*mRefCnt += 1;
+	}
+
+	template <class T>
+	inline const T* SharedPtr<T>::operator*() const
+	{
+		return mPtr;
+	}
+
+	template <class T>
+	inline T* SharedPtr<T>::operator*()
+	{
+		return mPtr;
+	}
+
+	template <class T>
+	inline void SharedPtr<T>::deletePtr()
+	{
+		// if this is not the last reference
+		if (*mRefCnt > 1)
+		{
+			// decrement reference count
+			*mRefCnt -= 1;
+
+			// make ptrs null
+			mPtr = nullptr;
+			mRefCnt = nullptr;
+		}
+		// if this is the last refeference
+		else if (*mRefCnt == 1)
+		{
+			// delete memory
+			delete mPtr;
+			delete mRefCnt;
+
+			// make ptrs null
+			mPtr = nullptr;
+			mRefCnt = nullptr;
+		}
+		// else if this is an empty refernce
+		else if (*mRefCnt == 0)
+		{
+			delete mRefCnt;
+
+			mPtr = nullptr;
+			mRefCnt = nullptr;
+		}
+	}
+}
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