Function chain_journal 

pub fn chain_journal(
    newest: StoreEntry,
    frame_len: u32,
    read: &mut dyn FnMut(BlobRef) -> DecodeResult<StoreEntry>,
) -> DecodeResult<(Vec<u8>, u64, u8)>

A run’s journal from its newest frame, reading the frames a Delta extends with read. Returns the journal (canonical records, oldest first), the frames’ total length and how many frames precede the newest.