Struct ReaderRegistry 

pub struct ReaderRegistry { /* private fields */ }

Lock-free reader registration for tracking active epochs.

Replaces the original RwLock<HashMap<u64, u64>> with a fixed-size array of cache-line-aligned AtomicU64 slots. Every operation is O(1) amortised and fully lock-free:

• register() — CAS-loop to claim an empty slot
• unregister() — single atomic store (SLOT_EMPTY)
• min_active_epoch() — relaxed scan of all slots, no locking

Implementations

impl ReaderRegistry

pub fn new() -> Self

pub fn register(&self, epoch: u64) -> Option<u64>

Register a reader at epoch. Returns the slot index (used as reader_id).

Cost: O(MAX_READER_SLOTS) worst-case scan, O(1) amortised with low occupancy. Fully lock-free — uses compare_exchange to claim an empty slot.

Returns None if all slots are exhausted. Callers must back-pressure or retry after a brief yield — silently overwriting a slot would allow the GC watermark to advance past a still-active reader’s epoch, leading to use-after-free on version data.

pub fn unregister(&self, reader_id: u64)

Unregister a reader by slot index.

Cost: O(1), lock-free.

pub fn min_active_epoch(&self) -> Option<u64>

Compute the minimum epoch across all active readers, lock-free.

Cost: O(MAX_READER_SLOTS) with relaxed loads — no locking, no contention.

pub fn active_count(&self) -> usize

Get count of active readers.

Trait Implementations

impl Debug for ReaderRegistry

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

Formats the value using the given formatter.

impl Default for ReaderRegistry

fn default() -> Self

Returns the “default value” for a type.