Memory Management
A simple, smart pointer class.
Data Types |
auto_ptr_ref operator |
Member Functions | |
get() operator*() operator->() operator=() release() reset() |
#include <memory> template <class X> class auto_ptr;
The template class auto_ptr holds onto a pointer obtained via new and deletes that object when the auto_ptr object itself is destroyed (such as when leaving block scope). auto_ptr can be used to make calls to operator new exception-safe. The auto_ptr class has semantics of strict ownership: an object may be safely pointed to by only one auto_ptr, so copying an auto_ptr copies the pointer and transfers ownership to the destination if the source had already had ownership.
template <class X> class auto_ptr { template <class Y> class auto_ptr_ref { public: const auto_ptr<Y>& p; auto_ptr_ref (const auto_ptr<Y>&); }; public: typedef X element_type; // constructor/copy/destroy explicit auto_ptr (X* = 0) throw(); auto_ptr (const auto_ptr<X>&) throw (); template <class Y> auto_ptr (const auto_ptr<Y>&) throw(); void operator=(const auto_ptr<X>&) throw(): template <class Y> void operator= (const auto_ptr<Y>&) throw(); ~auto_ptr (); // members X& operator* () const throw(); X* operator-> () const throw(); X* get () const throw(); X* release () throw(); void reset (X*=0) throw(); auto_ptr(auto_ptr_ref<X>) throw(); template <class Y> operator auto_ptr_ref<Y>() throw(); template <class Y> operator auto_ptr<Y>() throw(); };
template <class Y> class auto_ptr_ref;
A private class template that holds a reference to an auto_ptr. It can only be constructed within an auto_ptr using a reference to an auto_ptr. It prevents unsafe copying.
explicit auto_ptr (X* p = 0);
Constructs an object of class auto_ptr<X>, initializing the held pointer to p, and acquiring ownership of that pointer. p must point to an object of class X or a class derived from X for which delete p is defined and accessible, or p must be a null pointer.
auto_ptr (const auto_ptr<X>& a); template <class Y> auto_ptr (const auto_ptr<Y>& a);
Constructs an object of class auto_ptr<X>, and copies the argument a to *this. If a owned the underlying pointer, then *this becomes the new owner of that pointer.
auto_ptr (const auto_ptr_ref<X> r);
Constructs an auto_ptr from an auto_ptr_ref.
~auto_ptr ();
Deletes the underlying pointer.
void operator= (const auto_ptr<X>& a); template <class Y> void operator= (const auto_ptr<Y>& a);
Copies the argument a to *this. If a owned the underlying pointer, then *this becomes the new owner of that pointer. If *this already owned a pointer, then that pointer is deleted first.
X& operator* () const;
Returns a reference to the object to which the underlying pointer points.
X* operator-> () const;
Returns the underlying pointer.
template <class Y> operator auto_ptr_ref<Y> ();
Constructs an auto_ptr_ref from *this and returns it.
template <class Y> operator auto_ptr<Y> ();
Constructs a new auto_ptr using the underlying pointer held by *this. Calls release() on *this, so *this no longer possesses the pointer. Returns the new auto_ptr.
X* get () const;
Returns the underlying pointer.
X* release();
Releases ownership of the underlying pointer. Returns that pointer.
void reset(X* p)
Sets the underlying pointer to p. If non-null, deletes the old underlying pointer.
// // auto_ptr.cpp // #include <iostream> #include <memory> using namespace std; // // A simple structure. // struct X { X (int i = 0) : m_i(i) { } int get() const { return m_i; } int m_i; }; int main () { // // b will hold a pointer to an X. // auto_ptr<X> b(new X(12345)); // // a will now be the owner of the underlying pointer. // auto_ptr<X> a = b; // // Output the value contained by // the underlying pointer. // cout << a->get() << endl; // // The pointer will be deleted when a is destroyed on // leaving scope. // return 0; }
Program Output
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