mount + resolve + list + read over a BlockDevice, host-tested against a
RAM-backed image the tests build with formatExfat. mount reads the VBR,
loads the geometry, and scans the root for the Allocation Bitmap (0x81)
and Up-case Table (0x82); the up-case prefix is decompressed (0xFFFF
identity runs) into a bounded table so names fold correctly.
A directory is read as consecutive 32-byte entries via readChain, so a
File/Stream/Name SET that straddles a sector or cluster boundary
assembles cleanly; each set's checksum is validated before it counts as
a file. A stream's no_fat_chain flag picks contiguous-arithmetic vs
FAT-follow cluster walking. reads honor valid_data_length (allocated-
but-unwritten tail reads as zero) and clamp data_length to the vfs u32
offset surface.
Tests cover mount + up-case fold, listing (skipping the metadata
entries), case-insensitive resolve, and reads across a cluster boundary
on both a contiguous and a FAT-fragmented file. Wired via engine.zig
(which imports on-disk.zig) into the host-test aggregate. 12/12, bounds
green. Write path is step 3.
Daniel Samson
62eb2a748a