The full backing bytes (the notional server-side file). Not copied; treated as read-only.
Optional fetch granularity: reads are rounded out to a
multiple of this so bytesFetched reflects whole-block transfer. Omit (or
pass 0) for exact, unaligned fetches.
Total size of the stored byte sequence.
The byte length.
A snapshot of the fetch counters.
The current stats.
Read a range, accounting for the (block-aligned) fetch it would incur.
Returns exactly the requested length bytes as a standalone array, even
though the underlying fetch may have pulled a wider aligned span.
Absolute offset of the first byte to read.
Number of bytes to read.
The requested bytes (byteOffset 0).
An asynchronous StepExternalByteStore that models a range-fetched source — an HTTP server honouring
Range:requests, or an OPFS/blob store read block-by-block — so the index-first open path (M4) can be exercised and measured without a network. It wraps a fully-resident buffer (the "server") but never assumes the client holds it: everyreadis counted as a fetch, and with ablockBytesgrid the fetch is rounded out to whole blocks, so stats reports the real transfer an aligned store would incur.This is the source a sidecar-driven open pairs with: reconstruct the entity index from the sidecar (no scan), then pull only the byte ranges demand asks for through a source like this — and read back from
statshow little of the file that touched.