33 Concurrency support library [thread]

33.3 Stop tokens [thread.stoptoken]

33.3.3 Class stop_token [stoptoken]

33.3.3.1 General [stoptoken.general]

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The class stop_token provides an interface for querying whether a stop request has been made (stop_requested) or can ever be made (stop_possible) using an associated stop_source object ([stopsource]).
A stop_token can also be passed to a stop_callback ([stopcallback]) constructor to register a callback to be called when a stop request has been made from an associated stop_source.
namespace std { class stop_token { public: // [stoptoken.cons], 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; // [stoptoken.mem], 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; }; }

33.3.3.2 Constructors, copy, and assignment [stoptoken.cons]

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stop_token() noexcept;
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Postconditions: stop_possible() is false and stop_requested() is false.
[Note 1: 
Because the created stop_token object can never receive a stop request, no resources are allocated for a stop state.
— end note]
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stop_token(const stop_token& rhs) noexcept;
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Postconditions: *this == rhs is true.
[Note 2: 
*this and rhs share the ownership of the same stop state, if any.
— end note]
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stop_token(stop_token&& rhs) noexcept;
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Postconditions: *this contains the value of rhs prior to the start of construction and rhs.stop_possible() is false.
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~stop_token();
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Effects: Releases ownership of the stop state, if any.
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stop_token& operator=(const stop_token& rhs) noexcept;
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Effects: Equivalent to: stop_token(rhs).swap(*this).
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Returns: *this.
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stop_token& operator=(stop_token&& rhs) noexcept;
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Effects: Equivalent to: stop_token(std​::​move(rhs)).swap(*this).
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Returns: *this.
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void swap(stop_token& rhs) noexcept;
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Effects: Exchanges the values of *this and rhs.

33.3.3.3 Members [stoptoken.mem]

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[[nodiscard]] bool stop_requested() const noexcept;
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Returns: true if *this has ownership of a stop state that has received a stop request; otherwise, false.
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[[nodiscard]] bool stop_possible() const noexcept;
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Returns: false if:
  • (2.1)
    *this does not have ownership of a stop state, or
  • (2.2)
    a stop request was not made and there are no associated stop_source objects;
otherwise, true.

33.3.3.4 Non-member functions [stoptoken.nonmembers]

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[[nodiscard]] bool operator==(const stop_token& lhs, const stop_token& rhs) noexcept;
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Returns: true if lhs and rhs have ownership of the same stop state or if both lhs and rhs do not have ownership of a stop state; otherwise false.
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friend void swap(stop_token& x, stop_token& y) noexcept;
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Effects: Equivalent to: x.swap(y).