libcxx/include/__thread/jthread.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___THREAD_JTHREAD_H
  11 #define _LIBCPP___THREAD_JTHREAD_H
  12
  13 #include <__availability>
  14 #include <__config>
  15 #include <__functional/invoke.h>
  16 #include <__stop_token/stop_source.h>
  17 #include <__stop_token/stop_token.h>
  18 #include <__thread/thread.h>
  19 #include <__threading_support>
  20 #include <__type_traits/decay.h>
  21 #include <__type_traits/is_constructible.h>
  22 #include <__type_traits/is_same.h>
  23 #include <__type_traits/remove_cvref.h>
  24 #include <__utility/forward.h>
  25 #include <__utility/move.h>
  26
  27 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  28 #  pragma GCC system_header
  29 #endif
  30
  31 #if _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)
  32
  33 _LIBCPP_BEGIN_NAMESPACE_STD
  34
  35 class _LIBCPP_AVAILABILITY_SYNC jthread {
  36 public:
  37   // types
  38   using id                 = thread::id;
  39   using native_handle_type = thread::native_handle_type;
  40
  41   // [thread.jthread.cons], constructors, move, and assignment
  42   _LIBCPP_HIDE_FROM_ABI jthread() noexcept : __stop_source_(std::nostopstate) {}
  43
  44   template <class _Fun, class... _Args>
  45   _LIBCPP_HIDE_FROM_ABI explicit jthread(_Fun&& __fun, _Args&&... __args)
  46     requires(!std::is_same_v<remove_cvref_t<_Fun>, jthread>)
  47       : __stop_source_(),
  48         __thread_(__init_thread(__stop_source_, std::forward<_Fun>(__fun), std::forward<_Args>(__args)...)) {
  49     static_assert(is_constructible_v<decay_t<_Fun>, _Fun>);
  50     static_assert((is_constructible_v<decay_t<_Args>, _Args> && ...));
  51     static_assert(is_invocable_v<decay_t<_Fun>, decay_t<_Args>...> ||
  52                   is_invocable_v<decay_t<_Fun>, stop_token, decay_t<_Args>...>);
  53   }
  54
  55   _LIBCPP_HIDE_FROM_ABI ~jthread() {
  56     if (joinable()) {
  57       request_stop();
  58       join();
  59     }
  60   }
  61
  62   jthread(const jthread&) = delete;
  63
  64   _LIBCPP_HIDE_FROM_ABI jthread(jthread&&) noexcept = default;
  65
  66   jthread& operator=(const jthread&) = delete;
  67
  68   _LIBCPP_HIDE_FROM_ABI jthread& operator=(jthread&& __other) noexcept {
  69     if (this != &__other) {
  70       if (joinable()) {
  71         request_stop();
  72         join();
  73       }
  74       __stop_source_ = std::move(__other.__stop_source_);
  75       __thread_      = std::move(__other.__thread_);
  76     }
  77
  78     return *this;
  79   }
  80
  81   // [thread.jthread.mem], members
  82   _LIBCPP_HIDE_FROM_ABI void swap(jthread& __other) noexcept {
  83     std::swap(__stop_source_, __other.__stop_source_);
  84     std::swap(__thread_, __other.__thread_);
  85   }
  86
  87   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool joinable() const noexcept { return get_id() != id(); }
  88
  89   _LIBCPP_HIDE_FROM_ABI void join() { __thread_.join(); }
  90
  91   _LIBCPP_HIDE_FROM_ABI void detach() { __thread_.detach(); }
  92
  93   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI id get_id() const noexcept { return __thread_.get_id(); }
  94
  95   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() { return __thread_.native_handle(); }
  96
  97   // [thread.jthread.stop], stop token handling
  98   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI stop_source get_stop_source() noexcept { return __stop_source_; }
  99
 100   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI stop_token get_stop_token() const noexcept { return __stop_source_.get_token(); }
 101
 102   _LIBCPP_HIDE_FROM_ABI bool request_stop() noexcept { return __stop_source_.request_stop(); }
 103
 104   // [thread.jthread.special], specialized algorithms
 105   _LIBCPP_HIDE_FROM_ABI friend void swap(jthread& __lhs, jthread& __rhs) noexcept { __lhs.swap(__rhs); }
 106
 107   // [thread.jthread.static], static members
 108   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static unsigned int hardware_concurrency() noexcept {
 109     return thread::hardware_concurrency();
 110   }
 111
 112 private:
 113   template <class _Fun, class... _Args>
 114   _LIBCPP_HIDE_FROM_ABI static thread __init_thread(const stop_source& __ss, _Fun&& __fun, _Args&&... __args) {
 115     if constexpr (is_invocable_v<decay_t<_Fun>, stop_token, decay_t<_Args>...>) {
 116       return thread(std::forward<_Fun>(__fun), __ss.get_token(), std::forward<_Args>(__args)...);
 117     } else {
 118       return thread(std::forward<_Fun>(__fun), std::forward<_Args>(__args)...);
 119     }
 120   }
 121
 122   stop_source __stop_source_;
 123   thread __thread_;
 124 };
 125
 126 _LIBCPP_END_NAMESPACE_STD
 127
 128 #endif // _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)
 129
 130 #endif // _LIBCPP___THREAD_JTHREAD_H