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]

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]

stop_token() noexcept;
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]
stop_token(const stop_token& rhs) noexcept;
Postconditions: *this == rhs is true.
[Note 2:
*this and rhs share the ownership of the same stop state, if any.
— end note]
stop_token(stop_token&& rhs) noexcept;
Postconditions: *this contains the value of rhs prior to the start of construction and rhs.stop_­possible() is false.
~stop_token();
Effects: Releases ownership of the stop state, if any.
stop_token& operator=(const stop_token& rhs) noexcept;
Effects: Equivalent to: stop_­token(rhs).swap(*this).
Returns: *this.
stop_token& operator=(stop_token&& rhs) noexcept;
Effects: Equivalent to: stop_­token(std​::​move(rhs)).swap(*this).
Returns: *this.
void swap(stop_token& rhs) noexcept;
Effects: Exchanges the values of *this and rhs.

33.3.3.3 Members [stoptoken.mem]

[[nodiscard]] bool stop_requested() const noexcept;
Returns: true if *this has ownership of a stop state that has received a stop request; otherwise, false.
[[nodiscard]] bool stop_possible() const noexcept;
Returns: false if:
  • *this does not have ownership of a stop state, or
  • 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]

[[nodiscard]] bool operator==(const stop_token& lhs, const stop_token& rhs) noexcept;
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.
friend void swap(stop_token& x, stop_token& y) noexcept;
Effects: Equivalent to: x.swap(y).