1 /*
2  * Copyright (c) 2021-2022 Facebook, Inc. and its affiliates
3  * Copyright (c) 2021-2024 NVIDIA Corporation
4  *
5  * Licensed under the Apache License Version 2.0 with LLVM Exceptions
6  * (the "License"); you may not use this file except in compliance with
7  * the License. You may obtain a copy of the License at
8  *
9  *   https://llvm.org/LICENSE.txt
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 #pragma once
18 
19 #include "__concepts.hpp"
20 #include "__execution_fwd.hpp"
21 
22 namespace stdexec
23 {
24 namespace __stok
25 {
26 template <template <class> class>
27 struct __check_type_alias_exists;
28 } // namespace __stok
29 
30 template <class _Token, class _Callback>
31 using stop_callback_for_t = typename _Token::template callback_type<_Callback>;
32 
33 template <class _Token>
34 concept stoppable_token = __nothrow_copy_constructible<_Token>    //
35                           && __nothrow_move_constructible<_Token> //
36                           && equality_comparable<_Token>          //
37                           && requires(const _Token& __token) {
38                                  {
39                                      __token.stop_requested()
40                                  } noexcept -> __boolean_testable_;
41                                  {
42                                      __token.stop_possible()
43                                  } noexcept -> __boolean_testable_;
44     // workaround ICE in appleclang 13.1
45 #if !defined(__clang__)
46                                  typename __stok::__check_type_alias_exists<
47                                      _Token::template callback_type>;
48 #endif
49                              };
50 
51 template <class _Token, typename _Callback, typename _Initializer = _Callback>
52 concept stoppable_token_for =
53     stoppable_token<_Token>  //
54     && __callable<_Callback> //
55     && requires { typename stop_callback_for_t<_Token, _Callback>; } &&
56     constructible_from<_Callback, _Initializer> &&
57     constructible_from<stop_callback_for_t<_Token, _Callback>, const _Token&,
58                        _Initializer>;
59 
60 template <class _Token>
61 concept unstoppable_token =    //
62     stoppable_token<_Token> && //
63     requires {
64         {
65             _Token::stop_possible()
66         } -> __boolean_testable_;
67     } && (!_Token::stop_possible());
68 } // namespace stdexec
69