220 34969 <68690e5c-f466-4fbe-ab41-80be58257259@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Aleksey Loginov Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Idea about "std::pmr::memory_resource" Date: Mon, 16 Oct 2017 10:39:33 -0700 (PDT) Lines: 310 Approved: news@gmane.org Message-ID: <68690e5c-f466-4fbe-ab41-80be58257259@isocpp.org> References: <0a8293b4-3246-47a5-9881-bc1ca4b91772@isocpp.org> <07ddb1f6-d3af-43df-bf96-8975c1ab4313@isocpp.org> <2e191a96-1952-479b-b78b-22e31f8e03de@isocpp.org> <0e37b5ae-64f6-4a8a-86bd-f44b119ed40a@isocpp.org> <15f8c5ba-3a6a-4441-9620-92e157c66094@isocpp.org> <26fe4cb4-98ca-41cc-ac96-5c51851799d1@isocpp.org> <784ffce8-ace7-449d-a13d-a99d7336117a@isocpp.org> <6d0ad98b-87d5-43dd-ac54-2b7d3e03e31b@isocpp.org> <4af80cf7-244c-4137-9133-1a36a209e4ca@isocpp.org> <7f22751b-91d1-4de4-81d2-421046ceb963@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; 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Mon, 16 Oct 2017 10:39:34 -0700 (PDT) X-Received: by 10.31.69.204 with SMTP id s195mr788700vka.12.1508175573987; Mon, 16 Oct 2017 10:39:33 -0700 (PDT) In-Reply-To: <7f22751b-91d1-4de4-81d2-421046ceb963@isocpp.org> X-Original-Sender: Aleksey.Loginov@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:34969 Archived-At: ------=_Part_17984_1292694928.1508175573386 Content-Type: multipart/alternative; boundary="----=_Part_17985_2069008231.1508175573386" ------=_Part_17985_2069008231.1508175573386 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =D0=BF=D0=BE=D0=BD=D0=B5=D0=B4=D0=B5=D0=BB=D1=8C=D0=BD=D0=B8=D0=BA, 16 =D0= =BE=D0=BA=D1=82=D1=8F=D0=B1=D1=80=D1=8F 2017 =D0=B3., 18:11:02 UTC+3 =D0=BF= =D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0=B0=D1=82=D0=B5=D0=BB=D1=8C Mingxin = Wang=20 =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB: > > On Monday, October 16, 2017 at 8:26:57 PM UTC+8, Aleksey Loginov wrote: >> >> =D0=BF=D0=BE=D0=BD=D0=B5=D0=B4=D0=B5=D0=BB=D1=8C=D0=BD=D0=B8=D0=BA, 16 = =D0=BE=D0=BA=D1=82=D1=8F=D0=B1=D1=80=D1=8F 2017 =D0=B3., 15:08:45 UTC+3 =D0= =BF=D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0=B0=D1=82=D0=B5=D0=BB=D1=8C Mingx= in Wang=20 >> =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB: >>> >>> On Monday, October 16, 2017 at 6:55:41 PM UTC+8, Aleksey Loginov wrote: >>>> >>>> Let's look at a more applied example: >>>> =20 >>>> >>> template=20 >>>> struct static_resource : memory_resource { aligned_storage_t=20 >>>> m_data; }; >>>> >>>> template >>>> struct my_any; >>>> >>>> >>>> my_any x1; >>>> my_any> x2; >>>> >>>> x1 =3D 1; >>>> x2 =3D x1; >>>> >>>> assert(x2 =3D=3D 1); >>>> >>>> >>>> How can you do this without RTTI? >>>> >>> >>> The class template `my_any` may declare any `my_any` types as friend=20 > have overloads of `operator=3D` for them: > > template > friend class my_any; > > template > my_any& operator=3D(const my_any<_MR>&); > > template > my_any& operator=3D(my_any<_MR>&&); > > In order to prove that the class template `my_any` is implementable, I=20 > have roughly implemented one that supports various of constructors,=20 > `operator=3D`, `type()` and `get()`. You may use `type()` and `get()` to= =20 > implement those non-member function templates like `any_cast`. > > struct manager_t { > public: > template > constexpr explicit manager_t(std::in_place_type_t) > : type(typeid(T)), > do_copy(do_copy_impl), > do_move(do_move_impl), > do_destroy(do_destroy_impl), > size(sizeof(T)) {} > > template > void copy(void** from, void** to, MR& mr) const { > if (soo_activated()) { > do_copy(from, to); > } else { > *to =3D mr.allocate(size, ALIGNMENT); > do_copy(*from, *to); > } > } > > const std::type_info& type; > > private: > void(*do_copy)(void*, void*); > void(*do_move)(void*, void*); > void(*do_destroy)(void*); > std::size_t size; > > template > static inline void do_copy_impl(void* from, void* to) { > new (reinterpret_cast(to)) T(*reinterpret_cast(from)); > } > > }; > > template > inline constexpr manager_t MANAGER{std::in_place_type}; > > template > struct memory_resource_user { > MR mr_; > }; > > template > class my_any : public memory_resource_user { > template > friend class my_any; > > public: > my_any(const my_any& rhs) { copy_init(rhs); } > > template > my_any(const my_any<_MR>& rhs) { copy_init(rhs); } > > ~my_any() { deinit(); } > > private: > void init() { manager_ =3D &NULL_MANAGER; } > > template > void copy_init(const my_any<_MR>& rhs) { > manager_ =3D rhs.manager_; > manager_->copy(&rhs.data_, &data_, this->mr_); > } > > void deinit() { > manager_->destroy(&data_, this->mr_); > } > > const manager_t* manager_; > mutable void* data_; > }; > > Mingxin Wang > > In other words, by hand-made RTTI, and only for fixed allocation=20 starategies (for example, data_ can not be a shared_ptr or cow_ptr) =20 --=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/68690e5c-f466-4fbe-ab41-80be58257259%40isocpp.or= g. ------=_Part_17985_2069008231.1508175573386 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


=D0=BF=D0=BE=D0=BD=D0=B5=D0=B4=D0=B5=D0=BB=D1=8C= =D0=BD=D0=B8=D0=BA, 16 =D0=BE=D0=BA=D1=82=D1=8F=D0=B1=D1=80=D1=8F 2017 =D0= =B3., 18:11:02 UTC+3 =D0=BF=D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0=B0=D1=82= =D0=B5=D0=BB=D1=8C Mingxin Wang =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB:=
On Monday, Oc= tober 16, 2017 at 8:26:57 PM UTC+8, Aleksey Loginov wrote:
=D0=BF=D0=BE=D0=BD=D0=B5=D0=B4=D0= =B5=D0=BB=D1=8C=D0=BD=D0=B8=D0=BA, 16 =D0=BE=D0=BA=D1=82=D1=8F=D0=B1=D1=80= =D1=8F 2017 =D0=B3., 15:08:45 UTC+3 =D0=BF=D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0= =B2=D0=B0=D1=82=D0=B5=D0=BB=D1=8C Mingxin Wang =D0=BD=D0=B0=D0=BF=D0=B8=D1= =81=D0=B0=D0=BB:
On= Monday, October 16, 2017 at 6:55:41 PM UTC+8, Aleksey Loginov wrote:
Let's look at a= more applied example:
=C2=A0
<= /blockquote>
<= div style=3D"background-color:rgb(250,250,250);border-color:rgb(187,187,187= );border-style:solid;border-width:1px;word-wrap:break-word">
template<size_t Size>
= struct = static_resource : memory_resource { aligned_storage_t<Size><= /span> m_data; };

te= mplate<typename MR>
struct=C2=A0my_any;


my_any<default_<= span style=3D"color:rgb(0,0,0)">memory_resource> x1;
my_any<static_resource<32>> x2;

x1 =3D 1;
x2 =3D x1;=

assert(x2 =3D=3D 1);


How can you=C2=A0= do this without RTTI?

The class template `my_any` may declare any `m= y_any` types as friend have overloads of `operator=3D` for them:
=
template <class _MR>
friend class my_= any;

template <class _MR>
my_any&a= mp; operator=3D(const my_any<_MR>&);

tem= plate <class _MR>
my_any& operator=3D(my_any<_MR>= &&);

In order to prove that the c= lass template `my_any` is implementable, I have roughly implemented one tha= t supports various of constructors, `operator=3D`, `type()` and `get()`. Yo= u may use `type()` and `get()` to implement those=C2=A0non-member function = templates like `any_cast`.

st= ruct manager_t {
=C2=A0public:
=C2=A0 template <clas= s T>
=C2=A0 constexpr explicit manager_t(std::in_place_type_t<T>)
=C2=A0 =C2=A0 =C2=A0 : type(typeid(T)),
= =C2=A0 =C2=A0 =C2=A0 =C2=A0 do_copy(do_copy_impl<T>),
=C2= =A0 =C2=A0 =C2=A0 =C2=A0 do_move(do_move_impl<T>),
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 do_destroy(do_destroy_impl<T>),
= =C2=A0 =C2=A0 =C2=A0 =C2=A0 size(sizeof(T)) {}

=C2=A0 =C2=A0 templ= ate <class MR>
=C2=A0 void copy(void** from, voi= d** to, MR& mr) const {
=C2=A0 =C2=A0 if (soo_activated()) {<= /div>
=C2=A0 =C2=A0 =C2=A0 do_copy(from, to);
=C2=A0 =C2=A0 }= else {
=C2=A0 =C2=A0 =C2=A0 *to =3D mr.allocate(size, ALIGNMENT)= ;
=C2=A0 =C2=A0 =C2=A0 do_copy(*from, *to);
=C2=A0 =C2= =A0 }
=C2=A0 }

=C2=A0 =C2=A0 const std::type_info& t= ype;

=C2=A0private:
=C2=A0 void(*d= o_copy)(void*, void*);
=C2=A0 void(*do_move)(void*, void*);
=
=C2=A0 void(*do_destroy)(void*);
=C2=A0 std::size_t size;

=C2=A0 template <class T>
=C2=A0 sta= tic inline void do_copy_impl(void* from, void* to) {
=C2=A0 =C2= =A0 new (reinterpret_cast<T*>(to)) T(*reinterpret_cast<const T*>= ;(from));
=C2=A0 }

};

template <class T>
inline constexpr manager_t MANAGER{std= ::in_place_type<T>};

template <class MR>
struct memory_resource_user {
=C2=A0 MR mr_;
};

template <class MR>
class my_any = : public memory_resource_user<MR> {
=C2=A0 template <cla= ss>
=C2=A0 friend class my_any;

=C2= =A0public:
=C2=A0 =C2=A0 my_any(const my_any& rhs) { copy_init(rhs); }=

=C2=A0 template <class _MR>
= =C2=A0 my_any(const my_any<_MR>& rhs) { copy_init(rhs); }

=C2=A0=C2=A0 ~my_any() { deinit(); }

=C2= =A0private:
=C2=A0 void init() { manager_ =3D &NULL_MANAGER; = }

=C2=A0 =C2=A0 template <class _MR>
= =C2=A0 void copy_init(const my_any<_MR>& rhs) {
=C2=A0 = =C2=A0 manager_ =3D rhs.manager_;
=C2=A0 =C2=A0 manager_->copy= (&rhs.data_, &data_, this->mr_);
=C2=A0 }
=C2=A0 void deinit() {
=C2=A0 =C2=A0 manager_->de= stroy(&data_, this->mr_);
=C2=A0 }

=C2=A0 const manager_t* manager_;
=C2=A0 mutable void* data_;
};

Mingxin Wang


In other words, by hand-made RTTI= , and only for fixed allocation starategies (for example, data_ can not be = a shared_ptr<T> or cow_ptr<T>)
=C2=A0

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To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/68690e5c-f466-4fbe-ab41-80be58257259= %40isocpp.org.
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