File: shared_ptr.h
///////////////////////////////////////////////////////////////////////////
//
// template class shared_ptr
// 2004-6-12
// Chengliang Shan
// [email protected]
//
///////////////////////////////////////////////////////////////////////////
#ifndef SHARED_PTR_H_
#define SHARED_PTR_H_
namespace clshan{
template<class T>
class shared_ptr;
template<class T>
class shared_data
{
private:
friend class shared_ptr<T>;
explicit shared_data(T* pT):_M_ptr(pT) {
_M_nCount = 1;
}
~shared_data() {
delete _M_ptr;
}
void operator++ () {
++_M_nCount;
}
operator-- () {
--_M_nCount;
if (_M_nCount == 0) {
delete this;
}
}
T& operator* () const {
return *_M_ptr;
}
T* operator-> () const {
return _M_ptr;
}
bool operator== (T* pT) const {
return _M_ptr == pT;
}
T* get() {
return _M_ptr;
}
int use_count() {
return _M_nCount;
}
private:
T* _M_ptr;
unsigned int _M_nCount;
};
template<class T>
class shared_ptr
{
typedef shared_data<T> element;
public:
explicit shared_ptr(T* pT):_M_pD(NULL) {
_M_pD = new element(pT);
}
explicit shared_ptr():_M_pD(NULL){
}
// copy constructor
shared_ptr(const shared_ptr<T>& rT) {
_M_pD = rT.get_element();
if (_M_pD != NULL) {
++(*_M_pD);
}
}
~shared_ptr() {
if (_M_pD != NULL) {
--(*_M_pD);
}
}
// assignment operator
shared_ptr<T>& operator = (shared_ptr<T>& rT) {
if (_M_pD != NULL) {
--(*_M_pD);
}
_M_pD = rT.get_element();
if (_M_pD != NULL){
++(*_M_pD);
}
return *this;
}
T& operator* () const {
return _M_pD->operator *();
}
T* operator-> () const {
return _M_pD->operator ->();
}
bool operator== (shared_ptr<T>& rT) const {
return rT.get_element() == _M_pD;
}
bool operator== (T* pT) const {
if (_M_pD == NULL){
return pT == NULL;
}
return *_M_pD == pT;
}
T* get() {
if (_M_pD == NULL) {
return NULL;
}
else {
return _M_pD->get();
}
}
void release() {
if (_M_pD != NULL) {
--(*_M_pD);
_M_pD = NULL;
}
}
void reset(T* pT) {
if (_M_pD != NULL) {
--(*_M_pD);
_M_pD = NULL;
}
_M_pD = new element(pT);
}
private:
element* get_element()const {
return _M_pD;
}
element* _M_pD;
};
}
#endif 
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