fn parse<T>(bytes: &[u8], n: usize) -> File<T> {
    let bytes = bytes.into_iter();

    // Skip first byte
    let _ = bytes.next();

    // Take n next bytes and do something with them
    let vec1: Vec<T> = bytes.take(n).map(|v| f(v)).collect();

    // Continue with the rest of the byte iterator, from after the n+1 first elements
    let vec2: Vec<usize> = bytes.skip(n).map(|v| v as usize).collect();

    File{ vec1, vec2 }
}