Struct DiskCacheConfig 

pub struct DiskCacheConfig {
    pub dir: PathBuf,
    pub hmac_key: [u8; 32],
}

Configuration for the on-disk L2 cache.

The cache directory must be writable by the runtime user and SHOULD be owned exclusively by that user (mode 0700 on Unix) — operators on a hardened deployment can additionally chattr +i files after first write so a parallel attacker process cannot tamper with cached entries even with the same UID.

hmac_key is the secret that gates load: the writer HMACs each persisted entry with the key, and the reader rejects any file whose recomputed HMAC does not match. Without the key (or with a different key) the loader treats every existing entry as a miss, so rotating the key invalidates the disk cache without requiring an rm -rf.

The caller-supplied hmac_key field is plain [u8; 32] for ergonomic construction; once handed to KernelCache::with_disk_persistence the bytes are copied into a private Zeroizing<[u8; 32]> inside DiskCache which wipes them on drop. The caller’s own copy is the caller’s responsibility (e.g. construct via Zeroizing::new upstream and let it drop after the call).

jit S-3 hardening (T13): Debug is implemented manually so the hmac_key bytes are redacted in any {:?} formatting, panic message, or tracing field expansion — the derived Debug would have dumped the raw 32-byte array. Drop zeroizes hmac_key on drop so the construction-time copy does not survive in freed memory.

Fields

dir: PathBuf

Directory where the L2 cache files live. Created lazily on first put.

hmac_key: [u8; 32]

32-byte HMAC-keyed-BLAKE3 key. MUST be process-stable across the cache’s lifetime and SHOULD be treated as a server-side secret. The long-lived copy held by the cache is zeroized on drop; this field is the construction-time hand-off only.

jit S-3 (T13): redacted in the manual std::fmt::Debug impl below and zeroized in Drop so the construction-time copy does not linger in freed memory after the value is moved into the long-lived DiskCache.

Trait Implementations

impl Clone for DiskCacheConfig

fn clone(&self) -> DiskCacheConfig

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DiskCacheConfig

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Drop for DiskCacheConfig

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.