i2c.rs

struct Unconnected<T: I2c>(T);
struct Connected<T: I2c>(T);

impl<T: I2c> Unconnected<T> {
    #[inline(always)]
    fn start(self) -> Result<Connected<T>, T::Err> {
        self.0.start()
    }
}

impl<T: I2c> Connected<T> {
    #[inline(always)]
    fn read(&mut self) -> Result<u8, T::Err> {
        self.0.read()
    }

    #[inline(always)]
    fn stop(self) -> Result<Unconnected<T>, T::Err> {
        self.0.stop()
    }
}

trait I2c: Sized {
    type Err;

    fn start(self) -> Result<Connected<Self>, Self::Err>;
    fn stop(self) -> Result<Unconnected<Self>, Self::Err>;
    fn read(&mut self) -> Result<u8, Self::Err>;
}

struct SAMDI2c;

impl I2c for SAMDI2c {
    type Err = ();

    fn read(&mut self) -> Result<u8, Self::Err> {
        Ok(8)
    }

    fn start(self) -> Result<Connected<SAMDI2c>, ()> {
        Ok(Connected(SAMDI2c))
    }

    fn stop(self) -> Result<Unconnected<SAMDI2c>, ()> {
        Ok(Unconnected(self))
    }
}

#[allow(unused_variables)]
fn main() {
    let x = SAMDI2c;

    let mut y = x.start().unwrap();
    let r = y.read();
    let r = y.read();
    let x = y.stop().unwrap();
    let z = x.start();
}