"shared ptr"

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#ifndef _SHAREDPTR_H_
#define _SHAREDPTR_H_

#include "GaussNumber.h"
#define NULL 0

class Storage {

private:
	GaussNumber *p_obj;
	int count;

public:
	Storage(GaussNumber *p_obj);
	~Storage();
	void increaseCount();
	void decreaseCount();
	GaussNumber *ptr() const;
	bool isNull() const;

};


class shared_ptr {

private:
	Storage *storage;

public:
	shared_ptr();
	shared_ptr(GaussNumber *p_obj);
	shared_ptr(const shared_ptr &sptr);
	~shared_ptr();
	const shared_ptr &operator=(const shared_ptr &sptr);
	GaussNumber &operator*() const;
	GaussNumber *operator->() const;
	GaussNumber *ptr() const;
	bool isNull() const;

};

#endif
#include "shared_ptr.h"

// Storage class definitions

Storage::Storage(GaussNumber *p_obj) {
	this->p_obj = p_obj;
	count = 1;
}

Storage::~Storage() {
	if (p_obj != NULL)
		delete p_obj;
}

void Storage::increaseCount() {
	count++;
}

void Storage::decreaseCount() {
	count--;

	if (count == 0)
		delete this;
}

GaussNumber *Storage::ptr() const {
	return p_obj;
}

bool Storage::isNull() const {
	if (p_obj == NULL)
		return true;
	else
		return false;
}

// shared_ptr class definitions

shared_ptr::shared_ptr() {
	storage = new Storage(NULL);
}

shared_ptr::shared_ptr(GaussNumber *p_obj) {
	storage = new Storage(p_obj);
}

shared_ptr::shared_ptr(const shared_ptr &sptr) {
	storage = sptr.storage;
	storage->increaseCount();
}

shared_ptr::~shared_ptr() {
	storage->decreaseCount();
}

const shared_ptr &shared_ptr::operator=(const shared_ptr &sptr) {
	sptr.storage->increaseCount();
	storage->decreaseCount();
	
	storage = sptr.storage;
	return *this;
}

GaussNumber &shared_ptr::operator*() const {
	return *storage->ptr();
}

GaussNumber *shared_ptr::operator->() const {
	return storage->ptr();
}

GaussNumber *shared_ptr::ptr() const {
	return storage->ptr();
}

bool shared_ptr::isNull() const {
	return storage->isNull();
}