AtomicList

AtomicList is an experimental circular list built directly from intrusive, reference-counted nodes. The crate ships nodes and cursors only—there is no separate list container—so you keep a Node<T> (and optionally a shared cursor::Cursor) as your handle into the ring. A sync::Node<T> acts like a tiny Arc<T> that also stores strong and weak successors, letting CAS loops splice nodes in and out of a ring without locks or external hazard-pointer schemes.

Current surface area

• Node<T> / WeakNode<T>: Arc/Weak-like handles with embedded successor edges.
• Lock-free splice helpers: push_before, pop_when, and remove rearrange a ring while maintaining the self-loop invariants on detached nodes.
• Successor introspection: load_next_* plus resolve_next follow weak breadcrumbs after a node has been popped out.
• Shared traversal: cursor::Cursor is an atomic cursor that multiple holders advance together.
• Reusable atomics: atm_p exports generic atomic pointer wrappers used by the list but also usable for Arc/Weak.

Working with nodes

use atomic_list::sync::Node;

let root = Node::new("root");
root.push_before("worker-1", |cur| *cur == "root").unwrap();
root.push_before("worker-2", |_| true).unwrap();

// Remove the first node whose payload ends with "1".
let removed = Node::pop_when(&root, |cur| cur.ends_with('1')).unwrap();
assert_eq!(*removed, "worker-1");

// The ring closes back over the gap.
let worker_2 = Node::load_next_strong(&root);
assert_eq!(worker_2.to_string(), "worker-2");
assert!(Node::ptr_eq(
    &Node::load_next_strong(&worker_2),
    &root
));

// Detached nodes keep a weak breadcrumb into the live ring.
assert_eq!(
    Node::resolve_next(&removed).unwrap().to_string(),
    "root"
);
assert_eq!(Node::into_inner(removed), Some("worker-1"));

Coordinated traversal

use atomic_list::{cursor::Cursor, sync::Node};

let head = Node::new(0);
for i in 1..=3 {
    head.push_before(i, |_| true).unwrap();
}

// Multiple holders share the same atomic cursor position.
let mut cursor_a = Cursor::new(head.clone());
let mut cursor_b = cursor_a.clone();

assert_eq!(*cursor_a.next().unwrap(), 3);
assert_eq!(*cursor_b.next().unwrap(), 3);

// Advancing from either handle moves everyone forward.
assert_eq!(*cursor_a.next().unwrap(), 2);
assert_eq!(*cursor_b.next().unwrap(), 2);

Notes

• Pure atomics: no hazard pointers or epoch GC, just ref-counted nodes.
• There is no separate AtomicList struct; hang on to a Node<T> as your entry point into the ring.
• The API is experimental and may still shift as iteration ergonomics improve.

License

This project is distributed under the terms of the MIT license. See LICENSE for details.