Struct EngineBuilder 

pub struct EngineBuilder { /* private fields */ }

Builder for an Engine.

The builder is the only public construction path. New fields can gain defaults without breaking callers.

Implementations

impl EngineBuilder

pub fn data_root(self, path: impl Into<PathBuf>) -> Self

Sets the directory where durable worlds and the audit log live.

Default: ./data. The directory is created if missing.

pub fn key(self, key: SecretBytes) -> Self

Sets the HMAC key that protects the audit chain. Required.

pub fn read_token(self, token: impl Into<Vec<u8>>) -> Self

Sets the optional read-tier token.

Empty or all-whitespace bytes are treated as “unset” — they never silently grant access.

pub fn write_token(self, token: impl Into<Vec<u8>>) -> Self

Sets the optional write-tier token (covers read + write).

Empty or all-whitespace bytes are treated as “unset” — they never silently grant access.

pub fn approve_token(self, token: impl Into<Vec<u8>>) -> Self

Sets the optional approve-tier token (covers read + write + system writes + delete).

Empty or all-whitespace bytes are treated as “unset” — they never silently grant access.

pub fn max_world_bytes(self, value: usize) -> Self

Caps the per-world payload size in bytes. Defaults to 64 MiB.

pub fn max_memory_bytes(self, value: usize) -> Self

Caps the in-memory backend’s total bytes. Defaults to 256 MiB.

pub fn max_storage_bytes(self, value: Option<usize>) -> Self

Sets an optional durable storage quota in bytes.

Some(0) is treated as “no quota”. Writes that would push the total past the quota fail with EngineError::QuotaExceeded.

pub fn max_listen_connections(self, value: usize) -> Self

Sets the maximum simultaneous subscription slots. 0 reverts to the default (1024).

pub fn listen_replay_max(self, value: usize) -> Self

Sets the per-subscription replay ring depth. 0 reverts to the default (1024).

pub fn read_cache_max_entries(self, value: usize) -> Self

Sets the read cache’s maximum tracked entries. 0 reverts to the default (5000).

pub fn build(self) -> Result<Engine, EngineBuildError>

Acquires the data-root writer lock, verifies every audit chain, and returns a ready-to-serve Engine.

Errors

• EngineBuildError::HmacKeyMissing if EngineBuilder::key was never called.
• EngineBuildError::DataRootIo for filesystem errors creating data_root.
• EngineBuildError::DataRootLockHeld if another process holds the writer lock.
• EngineBuildError::AuditChainCorrupted if any existing world’s HMAC chain fails verification.
• EngineBuildError::Storage for other storage-layer failures.

Trait Implementations

impl Default for EngineBuilder

fn default() -> Self

Returns the “default value” for a type.