1. 构造函数
shared_ptr p(u)
p从unique_ptr u中接管了对象的所有权；将u置为空
template <class _Ux, class _Dx,
enable_if_t<conjunction_v<_SP_pointer_compatible<_Ux, _Ty>,
is_convertible<typename unique_ptr<_Ux, _Dx>::pointer, element_type*>>,
int> = 0>
shared_ptr(unique_ptr<_Ux, _Dx>&& _Other) {
using _Fancy_t = typename unique_ptr<_Ux, _Dx>::pointer;
using _Raw_t = typename unique_ptr<_Ux, _Dx>::element_type*;
using _Deleter_t = conditional_t<is_reference_v<_Dx>, decltype(_STD ref(_Other.get_deleter())), _Dx>;
const _Fancy_t _Fancy = _Other.get();
if (_Fancy) {
const _Raw_t _Raw = _Fancy;
const auto _Rx = new _Ref_count_resource<_Fancy_t, _Deleter_t>(_Fancy, _Other.get_deleter());
_Set_ptr_rep_and_enable_shared(_Raw, _Rx);
_Other.release();//将u置为空
}
}
1.1 _Ref_count_resource
// CLASS TEMPLATE _Ref_count_resource
template <class _Resource, class _Dx>
class _Ref_count_resource : public _Ref_count_base {
// handle reference counting for object with deleter
public:
_Ref_count_resource(_Resource _Px, _Dx _Dt)
: _Ref_count_base(), _Mypair(_One_then_variadic_args_t{
}, _STD move(_Dt), _Px) {
}
#ifdef __EDG__ // TRANSITION, VSO-1292293
virtual ~_Ref_count_resource() noexcept override {
} // TRANSITION, should be non-virtual
#else // ^^^ workaround / no workaround vvv
virtual ~_Ref_count_resource() noexcept override = default; // TRANSITION, should be non-virtual
#endif // ^^^ no workaround ^^^
virtual void* _Get_deleter(const type_info& _Typeid) const noexcept override {
#if _HAS_STATIC_RTTI
if (_Typeid == typeid(_Dx)) {
return const_cast<_Dx*>(_STD addressof(_Mypair._Get_first()));
}
#else // _HAS_STATIC_RTTI
(void) _Typeid;
#endif // _HAS_STATIC_RTTI
return nullptr;
}
private:
virtual void _Destroy() noexcept override {
// destroy managed resource
_Mypair._Get_first()(_Mypair._Myval2);
}
virtual void _Delete_this() noexcept override {
// destroy self
delete this;
}
_Compressed_pair<_Dx, _Resource> _Mypair;
};