Enum RetentionClass 

#[non_exhaustive]
pub enum RetentionClass {
    Timed,
    Sparse,
}

Available on crate feature std only.

Which retention discipline a published entry follows once inside the Trunk’s sample ring.

Named RetentionClass, not Retention — plan step 3e’s tiered hot/cold archive policy (docs/superpowers/plans/2026-07-26-media-plane-implementation.md) owns the name Retention for an unrelated, later concept. This is the orthogonal, in-ring question of “how eagerly can this entry be evicted”, decided per TrunkWriter::publish call by whoever is feeding the writer — it reflects a track’s nature (video/audio vs. an SCTE-35 section PID), not something intrinsic to a transmux::Sample itself, so it is not a field the spec’s Sample type carries.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Timed

Regular-cadence media samples (audio, video, …): count-bounded, and ordinary eviction is reported to a lagging SampleCursor as SampleCursorItem::Lagged — a consumer that misses a video frame is gapped, not wrong; it resumes from the next sample.

Sparse

Irregular, semantically-critical entries — an SCTE-35 splice cue, a subtitle sample — where losing one leaves a consumer’s derived state wrong, not merely gapped: a missed splice cue means splicing in the wrong place, or not at all.

The retention rule

A Sparse entry lives in a ring bounded independently of the Timed ring (TrunkConfig::sparse_capacity, separate from TrunkConfig::timed_capacity). It is therefore never evicted “merely because a time window rolled” on the unrelated Timed class: no volume of video/audio publishes can push a still-live splice cue out of the trunk, because Timed publishes never touch the Sparse ring at all. A Sparse entry is only evicted once Sparse publish volume itself exceeds the Sparse ring’s own bound — and when that happens, SampleCursor::poll reports it as SampleCursorItem::Degraded, not ordinary Lagged: a distinct, stronger signal, because the consumer’s semantic state (e.g. “where the next ad break splices”) is now wrong. A consumer that sees Lagged should simply resume from the next sample; a consumer that sees Degraded should treat its derived state as unsynchronised until the next authoritative signal (a fresh cue, a manifest reload) re-establishes it — resuming silently would splice on stale information.

Trait Implementations

impl Clone for RetentionClass

fn clone(&self) -> RetentionClass

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for RetentionClass

impl Debug for RetentionClass

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

Formats the value using the given formatter.

impl Eq for RetentionClass

impl Hash for RetentionClass

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for RetentionClass

fn eq(&self, other: &RetentionClass) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for RetentionClass