Splits the v13 metadata wire-format knowledge out of the FILE*-bound
streaming reader into pure, buffer-based functions so the web byte-range
path (#88) can reuse it without loading the whole sidecar into the wasm
heap:
- parseSidecarHead — validates the 16-byte head, yields num_vertex_bytes
- parseSidecarTail — parses meshes/instances/georef/elements/strings
from an in-memory tail buffer, bounds-checked
- planSidecarReadRanges + SidecarReadPlan — the range-coalescing /
scatter planner, promoted out of the anonymous namespace
readSidecarMetadataOnly and the range readers now call these; desktop
behaviour is unchanged (head + tail are small, the bulk is still skipped
via seek). The metadata tail is split from the head around the bulk
sections, so a blob-backed loader just slices those two regions and
hands the bytes to the same parsers.
Closes a coverage gap: StreamingLoader had no unit tests. Adds
test_streaming_loader.cpp (7 cases: metadata round-trip, corrupt/truncated
rejection, vertex+index range scatter, head validation, tail truncation,
read-plan coalescing). 107/107 unit tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Dion Moult