Function packed_rows 

pub fn packed_rows(
    file: &[u8],
    offset: usize,
    p: PackedParams,
    out: &mut [u16],
    parallel: bool,
) -> Result<()>

Decode a “packed” payload. file is the whole file (the interlaced layout addresses its second field relative to the file size), offset the payload start. Rows past the end of the data are zero-filled.