68 lines
1.1 KiB
C++
68 lines
1.1 KiB
C++
#pragma once
|
|
|
|
#include <memory>
|
|
#include <exception>
|
|
#include <stdexcept>
|
|
|
|
namespace nix {
|
|
|
|
/* A simple non-nullable reference-counted pointer. Actually a wrapper
|
|
around std::shared_ptr that prevents non-null constructions. */
|
|
template<typename T>
|
|
class ref
|
|
{
|
|
private:
|
|
|
|
std::shared_ptr<T> p;
|
|
|
|
public:
|
|
|
|
ref<T>(const ref<T> & r)
|
|
: p(r.p)
|
|
{ }
|
|
|
|
explicit ref<T>(const std::shared_ptr<T> & p)
|
|
: p(p)
|
|
{
|
|
if (!p)
|
|
throw std::invalid_argument("null pointer cast to ref");
|
|
}
|
|
|
|
T* operator ->() const
|
|
{
|
|
return &*p;
|
|
}
|
|
|
|
T& operator *() const
|
|
{
|
|
return *p;
|
|
}
|
|
|
|
operator std::shared_ptr<T> ()
|
|
{
|
|
return p;
|
|
}
|
|
|
|
template<typename T2>
|
|
operator ref<T2> ()
|
|
{
|
|
return ref<T2>((std::shared_ptr<T2>) p);
|
|
}
|
|
|
|
private:
|
|
|
|
template<typename T2, typename... Args>
|
|
friend ref<T2>
|
|
make_ref(Args&&... args);
|
|
|
|
};
|
|
|
|
template<typename T, typename... Args>
|
|
inline ref<T>
|
|
make_ref(Args&&... args)
|
|
{
|
|
auto p = std::make_shared<T>(std::forward<Args>(args)...);
|
|
return ref<T>(p);
|
|
}
|
|
|
|
}
|