Module file 

Filesystem-backed kv backend (M4.C — DS-14-storage Audit 4).

FileBackend maps each key to a .bin file under a configured directory. Keys are percent-encoded so any UTF-8 string can be stored safely: [a-zA-Z0-9_-] pass through; everything else is UTF-8 encoded with each byte formatted as lowercase %xx. The encoded filename for any given key is byte-identical to the TS fileBackend impl (packages/pure-ts/src/extra/storage/tiers-node.ts — D159) so a TS-written file can be loaded by a Rust reader on the same directory.

Writes are atomic via tempfile::NamedTempFile::persist: a tempfile is created in the target directory, written in full, then renamed onto the key path. A partially-written file is never visible at the final path, even on process crash. The NamedTempFile Drop impl deletes any tempfile that never made it through persist (covers panics between create and commit).

flush() is a no-op — durability is on per-write basis via the rename. read / delete / list tolerate missing directory + missing key by returning Ok(None) / Ok(()) / Ok(vec![]) respectively (D158).

Cargo feature: gated behind file (default-on).

Structs

FileBackend

Filesystem-backed StorageBackend.

Functions

file_append_log

Convenience: append-log tier over a fresh file backend rooted at dir.

file_append_log_default

Convenience: append-log tier over a fresh file backend with AppendLogStorageOptions::default + a JsonCodec.

file_backend

Convenience constructor returning an Arc<FileBackend>. Use this when sharing a single backend across multiple tiers (the paired { snapshot, wal } pattern from DS-14-storage §a). For non-default configuration use Arc::new(FileBackend::new(dir).with_include_hidden(true)).

file_kv

Convenience: kv tier over a fresh file backend rooted at dir.

file_kv_default

Convenience: kv tier over a fresh file backend with KvStorageOptions::default + a JsonCodec.

file_snapshot

Convenience: snapshot tier over a fresh file backend rooted at dir. Mirror of crate::memory_snapshot for filesystem persistence.

file_snapshot_default

Convenience: snapshot tier over a fresh file backend with SnapshotStorageOptions::default + a JsonCodec.