Module buffer 

The document resource backing + the buffer-snapshot projection (plugin-host.md §4.2 / §9.6, PH7.3c).

§4.2’s borrows (&Buffer, &Path, &str inside ActiveBufferSnapshot) cannot cross the WASM boundary. The host projects the metadata into an owned [buffer::BufferSnapshot] record (project_buffer_snapshot) and hands the guest a document resource handle for the text. Bulk rope text never rides the snapshot: the guest calls get-text-range(range) and the host slices only that range out of the rope (“zero-copy at the slice level” — the bytes still cross into guest linear memory, but the whole document never does).

Decision A (locked): the resource is backed by an Arc<DocumentSnapshot> — a point-in-time immutable view. Edits landing after the handle is minted never shift byte ranges under the guest mid-read.

The end-to-end guest→host call through the canonical ABI is exercised at PH7.3d/PH7.4 (the call machinery + the <500ns bench live there); this slice proves the design at the host layer — the resource is real (wired into the linker via bindgen’s generated add_to_linker) and its methods + projection are unit-tested directly.

Structs

DocumentResource

Host-side backing for the document WIT resource (decision A): a point-in-time immutable snapshot. The bindgen with: mapping makes this the resource representation, so the Store’s ResourceTable stores it directly and [HostDocument] methods receive Resource<DocumentResource>.

Functions

project_buffer_snapshot

Project the borrow-carrying ActiveBufferSnapshot into the owned WIT [buffer::BufferSnapshot] metadata record (§4.2). Bulk text is NOT copied here — it rides the document handle. A non-UTF-8 path is a typed error (never lossy), matching the boundary convention.