1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef _LIBCPP___STOP_TOKEN_STOP_CALLBACK_H
11 #define _LIBCPP___STOP_TOKEN_STOP_CALLBACK_H
12 
13 #include <__availability>
14 #include <__concepts/constructible.h>
15 #include <__concepts/destructible.h>
16 #include <__concepts/invocable.h>
17 #include <__config>
18 #include <__stop_token/intrusive_shared_ptr.h>
19 #include <__stop_token/stop_state.h>
20 #include <__stop_token/stop_token.h>
21 #include <__type_traits/is_nothrow_constructible.h>
22 #include <__utility/forward.h>
23 #include <__utility/move.h>
24 
25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
26 #  pragma GCC system_header
27 #endif
28 
29 _LIBCPP_BEGIN_NAMESPACE_STD
30 
31 #if _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)
32 
33 template <class _Callback>
34 class _LIBCPP_AVAILABILITY_SYNC stop_callback : private __stop_callback_base {
35   static_assert(invocable<_Callback>,
36                 "Mandates: stop_callback is instantiated with an argument for the template parameter Callback that "
37                 "satisfies invocable.");
38   static_assert(destructible<_Callback>,
39                 "Mandates: stop_callback is instantiated with an argument for the template parameter Callback that "
40                 "satisfies destructible.");
41 
42 public:
43   using callback_type = _Callback;
44 
45   template <class _Cb>
46     requires constructible_from<_Callback, _Cb>
47   _LIBCPP_HIDE_FROM_ABI explicit stop_callback(const stop_token& __st,
48                                                _Cb&& __cb) noexcept(is_nothrow_constructible_v<_Callback, _Cb>)
49       : stop_callback(__private_tag{}, __st.__state_, std::forward<_Cb>(__cb)) {}
50 
51   template <class _Cb>
52     requires constructible_from<_Callback, _Cb>
53   _LIBCPP_HIDE_FROM_ABI explicit stop_callback(stop_token&& __st,
54                                                _Cb&& __cb) noexcept(is_nothrow_constructible_v<_Callback, _Cb>)
55       : stop_callback(__private_tag{}, std::move(__st.__state_), std::forward<_Cb>(__cb)) {}
56 
57   _LIBCPP_HIDE_FROM_ABI ~stop_callback() {
58     if (__state_) {
59       __state_->__remove_callback(this);
60     }
61   }
62 
63   stop_callback(const stop_callback&)            = delete;
64   stop_callback(stop_callback&&)                 = delete;
65   stop_callback& operator=(const stop_callback&) = delete;
66   stop_callback& operator=(stop_callback&&)      = delete;
67 
68 private:
69   _LIBCPP_NO_UNIQUE_ADDRESS _Callback __callback_;
70   __intrusive_shared_ptr<__stop_state> __state_;
71 
72   friend __stop_callback_base;
73 
74   struct __private_tag {};
75 
76   template <class _StatePtr, class _Cb>
77   _LIBCPP_HIDE_FROM_ABI explicit stop_callback(__private_tag, _StatePtr&& __state, _Cb&& __cb) noexcept(
78       is_nothrow_constructible_v<_Callback, _Cb>)
79       : __stop_callback_base([](__stop_callback_base* __cb_base) noexcept {
80           // stop callback is supposed to only be called once
81           std::forward<_Callback>(static_cast<stop_callback*>(__cb_base)->__callback_)();
82         }),
83         __callback_(std::forward<_Cb>(__cb)),
84         __state_() {
85     if (__state && __state->__add_callback(this)) {
86       // st.stop_requested() was false and this is successfully added to the linked list
87       __state_ = std::forward<_StatePtr>(__state);
88     }
89   }
90 };
91 
92 template <class _Callback>
93 _LIBCPP_AVAILABILITY_SYNC stop_callback(stop_token, _Callback) -> stop_callback<_Callback>;
94 
95 #endif // _LIBCPP_STD_VER >= 20
96 
97 _LIBCPP_END_NAMESPACE_STD
98 
99 #endif // _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)
100