libcxx/include/__stop_token/stop_callback.h

   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 <__concepts/constructible.h>
  14 #include <__concepts/destructible.h>
  15 #include <__concepts/invocable.h>
  16 #include <__config>
  17 #include <__stop_token/intrusive_shared_ptr.h>
  18 #include <__stop_token/stop_state.h>
  19 #include <__stop_token/stop_token.h>
  20 #include <__type_traits/is_nothrow_constructible.h>
  21 #include <__utility/forward.h>
  22 #include <__utility/move.h>
  23 #include <__utility/private_constructor_tag.h>
  24
  25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  26 #  pragma GCC system_header
  27 #endif
  28
  29 _LIBCPP_PUSH_MACROS
  30 #include <__undef_macros>
  31
  32 _LIBCPP_BEGIN_NAMESPACE_STD
  33
  34 #if _LIBCPP_STD_VER >= 20 && _LIBCPP_HAS_THREADS
  35
  36 template <class _Callback>
  37 class _LIBCPP_AVAILABILITY_SYNC stop_callback : private __stop_callback_base {
  38   static_assert(invocable<_Callback>,
  39                 "Mandates: stop_callback is instantiated with an argument for the template parameter Callback that "
  40                 "satisfies invocable.");
  41   static_assert(destructible<_Callback>,
  42                 "Mandates: stop_callback is instantiated with an argument for the template parameter Callback that "
  43                 "satisfies destructible.");
  44
  45 public:
  46   using callback_type = _Callback;
  47
  48   template <class _Cb>
  49     requires constructible_from<_Callback, _Cb>
  50   _LIBCPP_HIDE_FROM_ABI explicit stop_callback(const stop_token& __st,
  51                                                _Cb&& __cb) noexcept(is_nothrow_constructible_v<_Callback, _Cb>)
  52       : stop_callback(__private_constructor_tag{}, __st.__state_, std::forward<_Cb>(__cb)) {}
  53
  54   template <class _Cb>
  55     requires constructible_from<_Callback, _Cb>
  56   _LIBCPP_HIDE_FROM_ABI explicit stop_callback(stop_token&& __st,
  57                                                _Cb&& __cb) noexcept(is_nothrow_constructible_v<_Callback, _Cb>)
  58       : stop_callback(__private_constructor_tag{}, std::move(__st.__state_), std::forward<_Cb>(__cb)) {}
  59
  60   _LIBCPP_HIDE_FROM_ABI ~stop_callback() {
  61     if (__state_) {
  62       __state_->__remove_callback(this);
  63     }
  64   }
  65
  66   stop_callback(const stop_callback&)            = delete;
  67   stop_callback(stop_callback&&)                 = delete;
  68   stop_callback& operator=(const stop_callback&) = delete;
  69   stop_callback& operator=(stop_callback&&)      = delete;
  70
  71 private:
  72   _LIBCPP_NO_UNIQUE_ADDRESS _Callback __callback_;
  73   __intrusive_shared_ptr<__stop_state> __state_;
  74
  75   friend __stop_callback_base;
  76
  77   template <class _StatePtr, class _Cb>
  78   _LIBCPP_HIDE_FROM_ABI explicit stop_callback(__private_constructor_tag, _StatePtr&& __state, _Cb&& __cb) noexcept(
  79       is_nothrow_constructible_v<_Callback, _Cb>)
  80       : __stop_callback_base([](__stop_callback_base* __cb_base) noexcept {
  81           // stop callback is supposed to only be called once
  82           std::forward<_Callback>(static_cast<stop_callback*>(__cb_base)->__callback_)();
  83         }),
  84         __callback_(std::forward<_Cb>(__cb)),
  85         __state_() {
  86     if (__state && __state->__add_callback(this)) {
  87       // st.stop_requested() was false and this is successfully added to the linked list
  88       __state_ = std::forward<_StatePtr>(__state);
  89     }
  90   }
  91 };
  92
  93 template <class _Callback>
  94 _LIBCPP_AVAILABILITY_SYNC stop_callback(stop_token, _Callback) -> stop_callback<_Callback>;
  95
  96 #endif // _LIBCPP_STD_VER >= 20 && _LIBCPP_HAS_THREADS
  97
  98 _LIBCPP_END_NAMESPACE_STD
  99
 100 _LIBCPP_POP_MACROS
 101
 102 #endif // _LIBCPP___STOP_TOKEN_STOP_CALLBACK_H