Function encode_to_destination 

pub fn encode_to_destination<E: Encoder, S: Source, D: Destination, R: OperationPolicy>(
    encoder: E,
    source: S,
    writer: D,
    resolver: R,
    options: Options,
    pulse: Option<&dyn Pulse>,
) -> Result<Completed, At<Failure>>

Encode to an actual forward or seek-back destination. Layout admission occurs before policy, source reads and output publication. Patches are fully checked before final tail writes. I/O failure can leave partial overwrites; their confirmed byte count is distinct from appended extent. No automatic spooling converts a forward destination into a seekable one.