Function unseal 

fn unseal<W: Write>(
    reader: impl Read,
    key: &[u8; 32],
    name: &str,
    hash: &str,
    out: W,
    local: &dyn Fn(Error) -> Fault,
) -> Result<W, Fault>

A sealed file’s pieces, past its beginning, opened into out and checked against the content’s hash: out given back once all of it opened whole and right.