Save and load from binary in Rust

main.rs

fn write_binary(vector: Vec<u8>) -> Result<(), std::io::Error> {
    let mut f = OpenOptions::new()
        .create(true)
        .write(true)
        .read(true)
        .open("foo.bin")
        .unwrap();

    println!("The file: {:?}", f);

    println!("Writing: {:?}", &vector[..]);
    let write_result = f.write(&vector[..]).unwrap();

    Ok(())
}

fn load_binary() -> Result<(), std::io::Error> {
    let mut f = OpenOptions::new()
        .read(true)
        .open("foo.bin")
        .unwrap();

    println!("The file: {:?}", f);

    let num_bytes = f.metadata().unwrap().len() as usize;

    println!("Metadata: {:?}", f.metadata());

    let mut buffer = vec![0; num_bytes];

    // read up to 10 bytes
    let read_result = f.read_to_end(&mut buffer).unwrap();
    println!("Read Buffer: {:?}", &buffer[..]);

    let decoded: World = deserialize(&buffer[..]).unwrap();
    println!("Decoded: {:?}", decoded);

    Ok(())
}