Struct Stopper 

pub struct Stopper { /* private fields */ }

A cancellation primitive with unified clone semantics.

This is the recommended default for most use cases. Clone it to share the cancellation state - any clone can cancel or check status.

Converts to StopToken via From/Into with zero overhead — the existing Arc is reused, not double-wrapped.

Example

use almost_enough::{Stopper, Stop};

let stop = Stopper::new();

// Pass a clone to another thread
let stop2 = stop.clone();
std::thread::spawn(move || {
    while !stop2.should_stop() {
        // do work
        break;
    }
}).join().unwrap();

// Cancel from original
stop.cancel();

Performance

• Size: 8 bytes (one pointer)
• check(): ~1-2ns (single atomic load with Relaxed ordering)
• clone(): atomic increment
• cancel(): atomic store
• into() -> StopToken: zero-cost (Arc pointer widening)

Implementations

impl Stopper

pub fn new() -> Self

Create a new stopper.

pub fn cancelled() -> Self

Create a stopper that is already cancelled.

Useful for testing or when you want to signal immediate stop.

pub fn cancel(&self)

Signal all clones to stop.

A Release swap: writes made before a cancel() are visible to a thread whose is_cancelled returns true after it, even when several threads cancel. Calling it again changes nothing else.

pub fn is_cancelled(&self) -> bool

Whether cancellation has been requested, as an Acquire load.

When it returns true, this thread also sees every write the cancelling thread made before cancel, such as a reason code kept in an atomic. Call it after the work reports the stop. In a loop, use check or should_stop: one Relaxed load each, which see the stop just as soon but promise nothing about other writes.

Trait Implementations

impl Cancellable for Stopper

fn stop(&self)

Request stop/cancellation.

impl Clone for Stopper

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Stopper

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Stopper

fn default() -> Self

Returns the “default value” for a type.

impl From<Stopper> for StopToken

Zero-cost conversion: reuses the Stopper’s Arc. Direct atomic dispatch, no vtable.

fn from(stopper: Stopper) -> Self

Converts to this type from the input type.

impl Stop for Stopper

fn check(&self) -> Result<(), StopReason>

Check if the operation should stop.

fn should_stop(&self) -> bool

Returns true if the operation should stop.

fn may_stop(&self) -> bool

Returns true if this stop can ever signal a stop.