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// unique_ptr deleter with state
#include <iostream>
#include <memory>
class state_deleter { // a deleter class with state
int count_;
public:
state_deleter() : count_(0) {}
template <class T>
void operator()(T* p) {
std::cout << "[deleted #" << ++count_ << "]\n";
delete p;
}
};
int main () {
state_deleter del;
std::unique_ptr<int> p; // uses default deleter
// alpha and beta use independent copies of the deleter:
std::unique_ptr<int,state_deleter> alpha (new int);
std::unique_ptr<int,state_deleter> beta (new int,alpha.get_deleter());
// gamma and delta share the deleter "del" (deleter type is a reference!):
std::unique_ptr<int,state_deleter&> gamma (new int,del);
std::unique_ptr<int,state_deleter&> delta (new int,gamma.get_deleter());
std::cout << "resetting alpha..."; alpha.reset(new int);
std::cout << "resetting beta..."; beta.reset(new int);
std::cout << "resetting gamma..."; gamma.reset(new int);
std::cout << "resetting delta..."; delta.reset(new int);
std::cout << "calling gamma/delta deleter...";
gamma.get_deleter()(new int);
alpha.get_deleter() = state_deleter(); // a brand new deleter for alpha
// additional deletions when unique_ptr objects reach out of scope
// (in inverse order of declaration)
return 0;
}
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