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

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This header is part of the thread support library.

Contents

Classes

an interface for querying if a std::jthread cancellation request has been made
(class) [edit]
class representing a request to stop one or more std::jthreads
(class) [edit]
an interface for registering callbacks on std::jthread cancellation
(class template) [edit]
placeholder type for use in stop_source constructor
(class) [edit]

Constants

a std::nostopstate_t instance for use in stop_source constructor
(constant) [edit]

[edit] Synopsis

namespace std {
  // class stop_token
  class stop_token;
 
  // class stop_source
  class stop_source;
 
  // no-shared-stop-state indicator
  struct nostopstate_t {
    explicit nostopstate_t() = default;
  };
  inline constexpr nostopstate_t nostopstate{};
 
  // class stop_callback
  template<class Callback>
  class stop_callback;
}

[edit] Class std::stop_token

namespace std {
  class stop_token {
  public:
    // constructors, copy, and assignment
    stop_token() noexcept;
 
    stop_token(const stop_token&) noexcept;
    stop_token(stop_token&&) noexcept;
    stop_token& operator=(const stop_token&) noexcept;
    stop_token& operator=(stop_token&&) noexcept;
    ~stop_token();
    void swap(stop_token&) noexcept;
 
    // stop handling
    [[nodiscard]] bool stop_requested() const noexcept;
    [[nodiscard]] bool stop_possible() const noexcept;
 
    [[nodiscard]]
    friend bool operator==(const stop_token& lhs, const stop_token& rhs) noexcept;
    friend void swap(stop_token& lhs, stop_token& rhs) noexcept;
  };
}

[edit] Class std::stop_source

namespace std {
  // no-shared-stop-state indicator
  struct nostopstate_t {
    explicit nostopstate_t() = default;
  };
  inline constexpr nostopstate_t nostopstate{};
 
  class stop_source {
  public:
    // constructors, copy, and assignment
    stop_source();
    explicit stop_source(nostopstate_t) noexcept;
 
    stop_source(const stop_source&) noexcept;
    stop_source(stop_source&&) noexcept;
    stop_source& operator=(const stop_source&) noexcept;
    stop_source& operator=(stop_source&&) noexcept;
    ~stop_source();
    void swap(stop_source&) noexcept;
 
    // stop handling
    [[nodiscard]] stop_token get_token() const noexcept;
    [[nodiscard]] bool stop_possible() const noexcept;
    [[nodiscard]] bool stop_requested() const noexcept;
    bool request_stop() noexcept;
 
    [[nodiscard]] friend bool
    operator==(const stop_source& lhs, const stop_source& rhs) noexcept;
    friend void swap(stop_source& lhs, stop_source& rhs) noexcept;
  };
}

[edit] Class template std::stop_callback

namespace std {
  template<class Callback>
  class stop_callback {
  public:
    using callback_type = Callback;
 
    // constructors and destructor
    template<class C>
    explicit stop_callback(const stop_token& st, C&& cb)
        noexcept(is_nothrow_constructible_v<Callback, C>);
    template<class C>
    explicit stop_callback(stop_token&& st, C&& cb)
        noexcept(is_nothrow_constructible_v<Callback, C>);
    ~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:
    Callback callback;      // exposition only
  };
 
  template<class Callback>
  stop_callback(stop_token, Callback) -> stop_callback<Callback>;
}