#include <iostream>
#include <memory>
using std::cout;
using std::endl;

struct holder
{
    int val;
};

void grab_autoptr(std::auto_ptr<holder> arg)
{
    cout << "func arg = " << arg.get() << endl;
    if ( arg.get() ) cout << "arg->val = " << arg->val << endl << endl;
}

std::auto_ptr<holder> give_autoptr()
{
    std::auto_ptr<holder> x(new holder);
    x->val = 4;
    return x;
}

int main(int argc, char** argv)
{
    // do not need to delete the holder object that is allocated 
    std::auto_ptr<holder> p1(new holder);
    std::auto_ptr<holder> p2;

    p1->val = 3;

    cout << "p1 = " << p1.get() << endl << "p2 = " << p2.get() << endl;
    if ( p1.get() ) cout << "p1->val = " << p1->val << endl;
    if ( p2.get() ) cout << "p2->val = " << p2->val << endl;
    cout << endl;

    // transfer ownership of the pointer
    p2 = p1;

    cout << "p1 = " << p1.get() << endl << "p2 = " << p2.get() << endl;
    if ( p1.get() ) cout << "p1->val = " << p1->val << endl;
    if ( p2.get() ) cout << "p2->val = " << p2->val << endl;
    cout << endl;

    // transfer ownership of the pointer
    std::auto_ptr<holder> p3(p2);

    cout << "p1 = " << p1.get() << endl << "p2 = " << p2.get() << endl << "p3 = " << p3.get() << endl;
    if ( p1.get() ) cout << "p1->val = " << p1->val << endl;
    if ( p2.get() ) cout << "p2->val = " << p2->val << endl;
    if ( p3.get() ) cout << "p3->val = " << p3->val << endl;
    cout << endl;

    // this function will take over ownership of pointer
    grab_autoptr(p3);

    cout << "p1 = " << p1.get() << endl << "p2 = " << p2.get() << endl << "p3 = " << p3.get() << endl;
    if ( p1.get() ) cout << "p1->val = " << p1->val << endl;
    if ( p2.get() ) cout << "p2->val = " << p2->val << endl;
    if ( p3.get() ) cout << "p3->val = " << p3->val << endl;
    cout << endl;

    // this function will give ownership of a new pointer
    p1 = give_autoptr();

    cout << "p1 = " << p1.get() << endl << "p2 = " << p2.get() << endl << "p3 = " << p3.get() << endl;
    if ( p1.get() ) cout << "p1->val = " << p1->val << endl;
    if ( p2.get() ) cout << "p2->val = " << p2->val << endl;
    if ( p3.get() ) cout << "p3->val = " << p3->val << endl;
    cout << endl;

    return 0;
}