Changelog

See the full CHANGELOG.md in the repository root.

Unreleased (v0.6.5)

AccessBuffer drain: deferred LRU/LFU updates buffered by get() are now drained on the write path. ConcurrentPulseMap::get() ties TypedPulseMap at 95.372% hit rate (peek-only control: 94.456% — counting reads is worth +0.92 points). Read latency is untouched: the drain runs inside insert(). Ships with a BucketGuard fix so the drain is Miri-clean.
Validation: cargo-fuzz shadow-map oracle (5.46M executions clean under AddressSanitizer), Miri in CI for both engine and sync configs, loom models for the MetaWord CAS and AccessBuffer, multi-threaded soak at +0.0 MB RSS drift (147.9M ops).
Embedded: 8-target cargo check matrix in CI — thumbv6m (Cortex-M0) and riscv32imc (ESP32-C3) now compile via the opt-in critical-section feature. QEMU-executed tests on Cortex-M3 and Cortex-M0: 12 assertions, heap measured at 128 B per bucket (2 KiB for a 16-bucket map).

Replaced core::sync::atomic::AtomicU64 / std::sync::atomic::AtomicU64 with portable-atomic::AtomicU64 across meta.rs and sync.rs
Enables compilation on targets without native 64-bit atomics: WASM32, ARMv7-M, 32-bit embedded
No API changes — drop-in replacement

8 PRs merged — correctness fixes, performance optimizations, and a breaking TTL type change.

TTL types widened to u64: set_ttl(u64), get_ttl() -> u64, current_epoch() -> u64, insert_ttl(..., ttl: u64)
Sentinel value for “never expire” is now u64::MAX (was u32::MAX)
SlotTTL layout updated: { epoch: u64, ttl: u64 } (16 bytes per slot)

AccessBuffer module (engine/access_buffer.rs): Lock-free lossy ring buffer for deferred LRU/LFU priority updates
Lock-free reads: MetaWord backed by AtomicU64, enabling relaxed atomic loads without dirtying cache lines
Lazy slab lock: Inline keys skip slab_pool.lock() entirely during reads

UB Fix: Removed unsafe impl Sync from PulseMapRaw — now Send only
Data loss during resize: Overflow retry loop ensures zero data loss during rehash
TTL wipe during resize: Epoch/TTL metadata properly migrated
Fingerprint entropy collapse: Shard routing no longer overlaps with h2 fingerprint bits

ShardedPulseMap — 16-shard concurrent map, 2.4–3.1x faster than ConcurrentPulseMap
Per-entry TTL — insert_ttl(key, value, ttl) on all map types
- ttl = 0: use global default, u32::MAX: never expire, N: expire after N inserts
Zero-copy key borrow — PulseKey::with_key_bytes() for read-path optimization
Competitor benchmarks — moka + quick_cache single-thread and 4-thread comparisons