// cont/countptr.hpp
#ifndef COUNTED_PTR_HPP
#define COUNTED_PTR_HPP
/*class for counted reference semantics
*-deletes the object to which it refers when the last CountedPtr
* that refers to it is destroyed
*/
template <class T>
class CountedPtr {
private:
T* ptr; // pointer to the value
long* count; // shared number of owners
public:
//initialize pointer with existing pointer
//-requires that the pointer p is a return value of new
explicit CountedPtr (T* p=0)
: ptr(p), count(new long(1)) {
}
//copy pointer (one more owner)
CountedPtr (const CountedPtr<T>& p) throw()
: ptr(p.ptr), count(p.count) {
++*count;
}
//destructor (delete value if this was the last owner)
~CountedPtr () throw() {
dispose();
}
//assignment (unshare old and share new value)
CountedPtr<T>& operator= (const CountedPtr<T>& p) throw() {
if (this != &p) {
dispose();
ptr = p.ptr;
count = p.count;
++*count;
}
return *this;
}
//access the value to which the pointer refers
T& operator*() const throw() {
return *ptr;
}
T* operator->() const throw() {
return ptr;
}
private:
void dispose() {
if (--*count == 0) {
delete count;
delete ptr;
}
}
};
#endif /*COUNTED_PTR_HPP*/