pub fn read_metadata_ranged<R>(reader: &R) -> Result<Option<Vec<u8>>, FileError>where
R: RangeReader,Expand description
Fetch only the metadata section (the opaque Dataset Card blob) via a
RangeReader: read the 1 KiB header, then the metadata byte range —
nothing else. This is the index-free CARD tier of the exploration model: a
remote/S3 client learns the dataset’s self-description in two small range
requests, never touching the dictionary, index, or pyramid. Returns None
when the file carries no metadata.
Companion to Rete::open_ranged (which deliberately skips the card to
keep the query path minimal); this is the explicit “I want the card” path.