Enum StorageBackend 

pub enum StorageBackend {
    Memory,
    Sqlite {
        path: PathBuf,
        encryption_key: Option<Zeroizing<[u8; 32]>>,
    },
    AsyncBlob {
        blob_store: Arc<dyn AsyncBlobStore>,
    },
}

[CR-4] re-export so hosts can build ClientConfig { storage_backend: … } without pulling ping_mls_store in directly. AsyncBlobStore is the async single-blob trait WASM hosts implement to back StorageBackend::IndexedDb; BlobFuture is the matching future-type helper. Where the persistent provider checkpoints MemoryStorage to. Selected at MessagingClient::init time via [ping_core::ClientConfig::storage_backend].

Variants

Memory

In-memory only. Default and what tests use; loses state on process exit. Cold-start scenarios (iOS NSE, web Service Worker) MUST use Self::Sqlite or [Self::IndexedDb] instead.

Sqlite

SQLite-backed; native targets only. The SDK owns the file at path; the parent directory must exist. Pass encryption_key = Some(...) to enable SQLCipher; absence means the file is unencrypted (tests, dev only).

Fields

path: PathBuf

Absolute path. Host convention: <app_support>/ping/<account_id>/mls.sqlite for per-account isolation (CR-18); the SDK doesn’t enforce this — the host picks the path.

encryption_key: Option<Zeroizing<[u8; 32]>>

SQLCipher key. The SDK zeroes its copy on drop; the host is responsible for sourcing this from the OS keyring (Keychain / Keystore / etc.).

AsyncBlob

Host-supplied async blob storage. Available on every target.

The provider snapshots the entire MemoryStorage HashMap into a single CBOR blob and round-trips it through the AsyncBlobStore the host implements. This is the universal persistence path:

• WASM: host wraps its IndexedDB layer (PingStorageWeb, which already AES-GCM-encrypts every row under a non-extractable wrap key kept inside the same IDB).
• iOS / macOS / Android: host wraps the same Storage trait it already provides for conv metadata + cursors (typically Keychain-encrypted SQLite or AsyncStorage), so the OpenMLS snapshot sits under a reserved ("__mls", "snapshot") slot alongside the host’s other persisted KV.

Why this replaces the wasm-only IndexedDb variant: any host that already implements Storage (which every binding does) gets persistence for free, without per-platform path management, Keychain key plumbing, or SQLCipher dependency. The SQLite backend remains available for hosts that want a separate file (e.g. iOS NSE cold-start where the main app’s Storage isn’t reachable from the extension).

Fields

blob_store: Arc<dyn AsyncBlobStore>

Trait Implementations

impl Clone for StorageBackend

fn clone(&self) -> StorageBackend

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for StorageBackend

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

Formats the value using the given formatter.

impl Default for StorageBackend

fn default() -> StorageBackend

Returns the “default value” for a type.