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Standard library header <stop_token> (C++20)

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C++
Standard library headers

此头文件是 线程支持 库的组成部分。

目录

类

(C++20)
用于查询 std::jthread 取消请求是否已发出的接口
(类)
(C++20)
表示停止一个或多个 std::jthread 请求的类
(类)
(C++20)
用于在 std::jthread 取消时注册回调的接口
(类模板)
(C++26)
提供停止令牌接口，表示停止既不可能也不会被请求
(类)
(C++26)
引用其关联 std::inplace_stop_source 对象停止状态的停止令牌
(类)
(C++26)
作为停止状态唯一所有者的 可停止源
(类)
(C++26)
用于 std::inplace_stop_token 的停止回调
(类模板)

别名模板

(C++26)
获取给定停止令牌类型的回调类型
(别名模板)

概念

(C++26)
指定停止令牌的基本接口，允许查询停止请求以及停止请求是否可能
(概念)
(C++26)
指定不允许停止的停止令牌
(概念)

标签

(C++20)
用于 stop_source 的标签，指示构造时不关联停止状态
(标签)

概要 

namespace std {
  // 停止令牌概念
  template<class CallbackFn, class Token, class Init = CallbackFn>
    concept /*stoppable-callback-for*/ = /* see description */; // 仅用于说明
  template<class Token>
    concept stoppable_token = /* see description */;
  template<class Token>
    concept unstoppable_token = /* see description */;
  template<class Source>
    concept /*stoppable-source*/ = /* see description */; // 仅用于说明
  // 类 stop_token
  class stop_token;
  // 类 stop_source
  class stop_source;
  // 无共享停止状态指示器
  struct nostopstate_t {
    explicit nostopstate_t() = default;
  };
  inline constexpr nostopstate_t nostopstate{};
  // 类模板 stop_callback
  template<class Callback>
  class stop_callback;
  // 类 never_stop_token
  class never_stop_token;
  // 类 inplace_stop_token
  class inplace_stop_token;
  // 类 inplace_stop_source
  class inplace_stop_source;
  // 类模板 inplace_stop_callback
  template<class CallbackFn>
    class inplace_stop_callback;
  template<class T, class CallbackFn>
    using stop_callback_for_t = T::template callback_type<CallbackFn>;
}

Stop token 概念 

namespace std {
  template<class CallbackFn, class Token, class Init = CallbackFn>
    concept /*stoppable-callback-for*/ =                         // 仅用于说明
      invocable<CallbackFn> &&
      constructible_from<CallbackFn, Init> &&
      requires { typename stop_callback_for_t<Token, CallbackFn>; } &&
      constructible_from<stop_callback_for_t<Token, CallbackFn>, const Token&, Init>;
  template<template<class> class>
    struct /*check-type-alias-exists*/;                          // 仅用于说明
  template<class Token>
    concept stoppable_token = 
      requires (const Token tok) {
        typename /*check-type-alias-exists*/<Token::template callback_type>;
        { tok.stop_requested() } noexcept -> same_as<bool>;
        { tok.stop_possible() } noexcept -> same_as<bool>;
        { Token(tok) } noexcept; // 参见隐式表达式变体
      } &&
      copyable<Token> &&
      equality_comparable<Token>;
  template<class Token>
    concept unstoppable_token = 
      stoppable_token<Token> &&
      requires (const Token tok) {
        requires bool_constant<(!tok.stop_possible())>::value;
      };
  template<class Source>
    concept /*stoppable-source*/ =                               // 仅用于说明
      requires (Source& src, const Source csrc) {
        { csrc.get_token() } -> stoppable_token;
        { csrc.stop_possible() } noexcept -> same_as<bool>;
        { csrc.stop_requested() } noexcept -> same_as<bool>;
        { src.request_stop() } -> same_as<bool>;
      };
}

类 std::stop_token 

namespace std {
  class stop_token {
  public:
    template<class CallbackFn>
      using callback_type = stop_callback<CallbackFn>;
    // 构造函数、复制和赋值
    stop_token() noexcept = default;
    // 成员函数
    void swap(stop_token&) noexcept;
    // 停止处理
    bool stop_requested() const noexcept;
    bool stop_possible() const noexcept;
    friend bool operator==(const stop_token& lhs, const stop_token& rhs) noexcept;
    friend void swap(stop_token& lhs, stop_token& rhs) noexcept;
  private:
    shared_ptr</*unspecified*/> stop_state_; // 仅用于说明
  };
}

类 std::stop_source 

namespace std {
  class stop_source {
  public:
    // 构造函数、复制和赋值
    stop_source();
    explicit stop_source(nostopstate_t) noexcept {}
    // 成员函数
    void swap(stop_source&) noexcept;
    // 停止处理
    stop_token get_token() const noexcept;
    bool stop_possible() const noexcept;
    bool stop_requested() const noexcept;
    bool request_stop() noexcept;
    friend bool
    operator==(const stop_source& lhs, const stop_source& rhs) noexcept;
    friend void swap(stop_source& lhs, stop_source& rhs) noexcept;
  private:
    shared_ptr</*unspecified*/> stop_state_; // 仅用于说明
  };
}

类模板 std::stop_callback 

namespace std {
  template<class CallbackFn>
  class stop_callback {
  public:
    using callback_type = CallbackFn;
    // 构造函数与析构函数
    template<class Init>
    explicit stop_callback(const stop_token& st, Init&& init)
        noexcept(is_nothrow_constructible_v<CallbackFn, Init>);
    template<class Init>
    explicit stop_callback(stop_token&& st, Init&& init)
        noexcept(is_nothrow_constructible_v<CallbackFn, Init>);
    ~stop_callback();
    stop_callback(const stop_callback&) = delete;
    stop_callback(stop_callback&&) = delete;
    stop_callback& operator=(const stop_callback&) = delete;
    stop_callback& operator=(stop_callback&&) = delete;
  private:
    CallbackFn callback_fn_;      // 仅用于说明
  };
  template<class CallbackFn>
  stop_callback(stop_token, CallbackFn) -> stop_callback<CallbackFn>;
}

类模板 std::never_stop_token 

namespace std {
  class never_stop_token {
    struct /*callback-type*/ {       // 仅用于说明
      explicit /*callback-type*/(never_stop_token, auto&&) noexcept {}
    };
  public:
    template<class>
      using callback_type = /*callback-type*/;
    static constexpr bool stop_requested() noexcept { return false; }
    static constexpr bool stop_posible() noexcept { return false; }
    bool operator==(const never_stop_token&) const = default;
  };
}

类模板 std::inplace_stop_token 

namespace std {
  class inplace_stop_token {
  public:
    template<class CallbackFn>
      using callback_type = inplace_stop_callback<CallbackFn>;
    inplace_stop_token() = default;
    bool operator==(const inplace_stop_token&) const = default;
    // 成员函数
    bool stop_requested() const noexcept;
    bool stop_possible() const noexcept;
    void swap(inplace_stop_token&) noexcept;
  private:
    const inplace_stop_source* stop_source_ = nullptr; // 仅用于说明
  };
}

类模板 std::inplace_stop_source 

namespace std {
  class inplace_stop_source {
    // 构造函数、赋值运算符和析构函数
    constexpr inplace_stop_source() noexcept;
    inplace_stop_source(inplace_stop_source&&) = delete;
    inplace_stop_source(const inplace_stop_source&) = delete;
    inplace_stop_source& operator=(inplace_stop_source&&) = delete;
    inplace_stop_source& operator=(const inplace_stop_source&) = delete;
    ~inplace_stop_source();
    // 停止处理
    constexpr inplace_stop_token get_token() const noexcept;
    static constexpr bool stop_possible() noexcept { return true; }
    bool stop_requested() const noexcept;
    bool request_stop() noexcept;
  };
}

类模板 std::inplace_stop_callback 

namespace std {
  template<class CallbackFn>
  class inplace_stop_callback {
  public:
    using callback_type = CallbackFn;
    // 构造函数与析构函数
    template<class Init>
    explicit inplace_stop_callback(inplace_stop_token st, Init&& init)
        noexcept(is_nothrow_constructible_v<CallbackFn, Init>);
    ~inplace_stop_callback();
    inplace_stop_callback(const inplace_stop_callback&) = delete;
    inplace_stop_callback(inplace_stop_callback&&) = delete;
    inplace_stop_callback& operator=(const inplace_stop_callback&) = delete;
    inplace_stop_callback& operator=(inplace_stop_callback&&) = delete;
  private:
    CallbackFn callback_fn_;      // 仅用于说明
  };
  template<class CallbackFn>
  inplace_stop_callback(inplace_stop_token, CallbackFn) 
    -> inplace_stop_callback<CallbackFn>;
}