Enum OriginRangeFetch 

pub enum OriginRangeFetch {
    Ranged {
        data: Bytes,
    },
    NotFound,
    Unsupported,
}

Result of an Origin::fetch_range_data call (ADR 037 §Origin-tier pull-through, #823).

A range-scoped origin pull fetches the small sibling {H}.obao4 outboard once (Origin::fetch_outboard), then fetches the requested byte span in windows of at most crate::RANGE_PULL_WINDOW_BYTES, verifying them against the root H before any byte is imported or served — avoiding whole-blob origin egress to serve a byte range on a cache miss, with memory bounded by the window rather than the span (#2065). The verifier is the engine: one bao_tree::io::fsm::encode_ranges_validated pass on the crate::CacheEngine::origin_range_wire path.

The optimization is best-effort: when the origin does not honor Range, or the object is absent or shorter than the span, the adapter returns Self::Unsupported and the engine degrades to the existing whole-blob Origin::fetch pull. That fallback is never a correctness or availability failure — it only forgoes the cost reduction (ADR 037 §“Fallback is always correct”).

Variants

Ranged

The origin served the requested byte span. data covers exactly [req.fetch_start, req.fetch_end) (the chunk-group-aligned span the engine asked for) and is untrusted until the engine verifies it against H.

Fields

data: Bytes

The aligned data bytes, exactly req.len() long.

NotFound

The origin reported the object (data key) does not exist.

Unsupported

The range optimization is not available for this fetch — no Range/206 support, or a span the object does not hold (a stale or short copy). The engine degrades to a whole-blob Origin::fetch pull. This is an expected answer, not an error. A missing {H}.obao4 is reported by Origin::fetch_outboard, not here.

Trait Implementations

impl Debug for OriginRangeFetch

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

Formats the value using the given formatter.