#[derive(Debug)]
struct Peripherals {
    serial1: Option<u32>,
    serial2: Option<u32>
}

impl Peripherals {
    fn take_serial(&mut self, idx: usize) -> u32 {
        match idx {
            0 => self.serial1.take().unwrap(),
            _ => self.serial2.take().unwrap()
        }
    }
}

static mut PERIPHERALS: Peripherals = Peripherals {
    serial1: Some(1),
    serial2: Some(2)
};

fn main() {
    println!("PERIPHERALS:{:?}", unsafe { &PERIPHERALS });
    let s1 = foo();
    let s2 = bar();
    println!("s1:{}, s2:{}", s1, s2);
    println!("PERIPHERALS:{:?}", unsafe { &PERIPHERALS });
}

fn foo() -> u32 {
    unsafe { PERIPHERALS.take_serial(0) }
}

fn bar() -> u32 {
    unsafe { PERIPHERALS.take_serial(0) }
}