rt

The real-time packages provide the allocation-free, lock-free primitives that a #[realtime] function can call without breaking its contract. Every method below carries #[no_alloc] and #[no_block], so it is usable from a hot path. See the Real-time page for the contracts themselves.

The capacities are currently fixed at 1024 because C+ does not yet have const-generic struct parameters, and the elements are u64 (store an index or a tagged handle when you need to carry more).

SpscRingU64: lock-free single-producer / single-consumer ring

Full and empty are reported as values, never as a block:

import "rt/rt" as rt;

let mut ring: rt::SpscRingU64 = rt::SpscRingU64::new();

// Producer side:
let ok: bool = ring.push(42 as u64);     // false if the ring is full

// Consumer side:
guard let option::Option::Some(v) = ring.pop() else { return 0; };   // None if empty

Other methods: capacity(), len(), is_empty(), is_full().

FixedPoolU64: fixed-capacity free-list object pool

acquire hands back a slot index or None when the pool is full; release returns it:

let mut pool: rt::FixedPoolU64 = rt::FixedPoolU64::new();

guard let option::Option::Some(idx) = pool.acquire() else { return 1; };   // None if full
pool.set(idx, 7 as u64);
let v: u64 = pool.get(idx);
pool.release(idx);

Other methods: capacity(), in_use_count(), available(), is_full().

rt_darwin: macOS platform controls

The platform package configures the host thread and memory before the hot path. Every fallible call returns a Result rather than throwing:

import "rt_darwin/clock" as clock;
import "rt_darwin/thread" as rt_thread;
import "rt_darwin/mem" as rt_mem;

// Raise the current thread to audio QoS before the loop.
let _ = rt_thread::set_current_priority(rt_thread::Priority::RealtimeAudio);

// Lock pages so they are not paged out under load.
let _ = rt_mem::lock_pages(buf_ptr, buf_len);

// Monotonic, high-resolution timing for per-frame latency.
let start: u64 = clock::now_monotonic_ns();
// ... run the callback ...
let took: u64 = clock::elapsed_ns(start, clock::now_monotonic_ns());

rt_darwin ships today; rt_linux and rt_posix will mirror the same surface with their own syscalls.