Function check_snapshot_integrity 

pub fn check_snapshot_integrity(
    cache_dir: &Path,
    id: &str,
    hasher: &dyn Hasher,
) -> Result<(), CacheError>

Verifies a cached snapshot by its id — mirrors _snapdir_check_integrity.

First asserts the manifest for id is present locally (loading it from <cache_dir>/.manifests/<id…>), then, for every file entry of the manifest (directory entries — whose path ends / — are excluded, exactly as the oracle’s grep -v "/$"), verifies that the cached object at its sharded path hashes via hasher to the checksum it is filed under (column 3 of the manifest line, i.e. the object’s content address).

The oracle pipes checksum path pairs into b3sum --check; this reproduces that check in-process. The first corrupt or missing object short-circuits with an error, matching b3sum --check’s non-zero exit.

Errors

• CacheError::ManifestNotFound if the snapshot’s manifest is absent.
• CacheError::ObjectNotFound if a referenced file object is missing.
• CacheError::Integrity if a cached object does not hash to its address.
• CacheError::Parse / CacheError::Io on read/parse failure.