{

public:

/// Construct to a new cancellation source.

cancellation_source();

/// Create a new reference to the same underlying cancellation

/// source as \p other.

cancellation_source(const cancellation_source& other) noexcept;

cancellation_source(cancellation_source&& other) noexcept;

~cancellation_source();

cancellation_source& operator=(const cancellation_source& other) noexcept;

cancellation_source& operator=(cancellation_source&& other) noexcept;

/// Query if this cancellation source can be cancelled.

///

/// A cancellation source object will not be cancellable if it has

/// previously been moved into another cancellation_source instance

/// or was copied from a cancellation_source that was not cancellable.

bool can_be_cancelled() const noexcept;

/// Obtain a cancellation token that can be used to query if

/// cancellation has been requested on this source.

///

/// The cancellation token can be passed into functions that you

/// may want to later be able to request cancellation.

cancellation_token token() const noexcept;

/// Request cancellation of operations that were passed an associated

/// cancellation token.

///

/// Any cancellation callback registered via a cancellation_registration

/// object will be called inside this function by the first thread to

/// call this method.

///

/// This operation is a no-op if can_be_cancelled() returns false.

void request_cancellation();

/// Query if some thread has called 'request_cancellation()' on this

/// cancellation_source.

bool is_cancellation_requested() const noexcept;

private:

detail::cancellation_state* m_state;