Constant HURRAY_ERR_CORE_UNUSABLE 

pub const HURRAY_ERR_CORE_UNUSABLE: HurrayStatus = -17;

A transport moved bytes whose count was lost, so the handle’s position no longer matches the transport’s and nothing can recover it (ADR-041 § 6).

Unreachable from a conforming transport vtable, which reports a count for every transfer; the code exists because the state does.