Struct HttpRangeFetcher 

pub struct HttpRangeFetcher { /* private fields */ }

HTTP Range transport against a HuggingFace-hosted file.

Opened via HttpRangeReader::open. One authenticated, redirect-free probe (reusing the chunked-download probe) resolves the file size and classifies access failures eagerly (gated repos, no Range support). Every range request then targets the HF /resolve URL and follows the redirect to a freshly-signed CDN URL; reqwest strips the Authorization header on the cross-host redirect, so the Bearer token is never sent to the CDN host.

Per-request re-resolution is required, not just convenient: Xet-backed repos sign each CDN URL for the exact Range header that minted it (a ByteRange policy condition in the signed URL), so a CDN URL stored from the probe can never serve any other range. Re-resolving also makes signed-URL expiry a non-issue — every request gets a fresh signature. Discovered live against google/gemma-scope-2b-pt-res (v0.11.0 dogfooding).

Response validation (every request)

• Status must be 206 Partial Content. A 200 (server ignoring the Range header) is rejected without reading the body — the guard against silently pulling the full file.
• Content-Range must match the requested range and the probed total size.
• The body is streamed with a hard cap of the requested length; over- or under-delivery is an error.
• The response ETag (when present) must stay identical across requests — a mid-inspect change upstream aborts with a clear error.

Trait Implementations

impl RangeFetcher for HttpRangeFetcher

fn fetch( &mut self, start: u64, end_inclusive: u64, ) -> Result<Vec<u8>, FetchError>

Fetches the inclusive byte range start..=end_inclusive.

fn total_size(&self) -> u64

Total size of the remote file in bytes.

fn extra_requests(&self) -> u32

Requests spent by the transport outside RangeFetcher::fetch (e.g. the eager probe that resolved the file size and classified access). Included in RangeReader::stats so the reported request count is honest.