Function emit_top 

pub fn emit_top(
    inv: &mut Inventory,
    data: &[u8],
    parts: Vec<Cand>,
    logical_end: u64,
    gap: (Disposition, Option<String>),
) -> Result<(), InventoryError>

Push top-level parts (non-overlapping, in file order) with gaps between them: before logical_end a gap is gap (a lone odd-offset byte between parts is a word-alignment pad); the caller’s trailing fill covers the rest.