Timeline

std.hash.Crc32 is byte-at-a-time over one table (~350 MB/s here) and the open-time scan CRCs every payload byte, so it was ~93% of a cold open. Slicing-by-8 in its place: a 416 MB store opens in 292ms against 1.22s, warm reads run 3.3x, the write path 1.5x. Bit-identical by construction, so no format changes and no repository is affected. check-in: 602c2459f2 user: dmestas tags: trunk

Both consumers live in their own build roots and cannot reach crc32.zig by path, so the export is forced. Adds the differential fuzz lane against std — the only coverage that can see a self-consistent but numerically shifted implementation, which would orphan every existing .zit file.

The implementation brief prohibited this export, citing repocache as the precedent for unexported leaf modules. That precedent does not apply: repocache has no out-of-module consumer. storestat and repoimage, which do, are both exported. Overridden deliberately. closed check-in: c57c16c5cd user: dmestas tags: logstore-index

The other three on-disk formats defined in terms of this checksum: the cache image self-checksum, the bisect session trailer, the undo journal trailer. Same swap, same values. check-in: 55d6e7c7bb user: dmestas tags: logstore-index

The four frame checksums plus the file header. The open-time scan CRCs every payload byte, so this is ~93% of a cold open: 416 MB goes 1.22s to 292ms. No format change — the values are identical by construction. check-in: dd71dd3006 user: dmestas tags: logstore-index

Bit-identical to std.hash.Crc32, which every on-disk checksum in the store is already defined in terms of. std's is byte-at-a-time over one table (~350 MB/s here); this folds eight bytes per step. Nothing uses it yet. check-in: aef8f539b5 user: dmestas tags: logstore-index