//! Timers
use nb;
use Void;
/// A count down timer
///
/// # Contract
///
/// - `self.start(count); block!(self.wait());` MUST block for AT LEAST the time specified by
/// `count`.
///
/// *Note* that the implementer doesn't necessarily have to be a *downcounting* timer; it could also
/// be an *upcounting* timer as long as the above contract is upheld.
///
/// # Examples
///
/// You can use this timer to create delays
///
/// ```
/// extern crate embedded_hal as hal;
/// #[macro_use(block)]
/// extern crate nb;
///
/// use hal::prelude::*;
///
/// fn main() {
/// let mut led: Led = {
/// // ..
/// # Led
/// };
/// let mut timer: Timer6 = {
/// // ..
/// # Timer6
/// };
///
/// Led.on();
/// timer.start(1.s());
/// block!(timer.wait()); // blocks for 1 second
/// Led.off();
/// }
///
/// # extern crate void;
/// # use void::Void;
/// # struct Seconds(u32);
/// # trait U32Ext { fn s(self) -> Seconds; }
/// # impl U32Ext for u32 { fn s(self) -> Seconds { Seconds(self) } }
/// # struct Led;
/// # impl Led {
/// # pub fn off(&mut self) {}
/// # pub fn on(&mut self) {}
/// # }
/// # struct Timer6;
/// # impl hal::timer::CountDown for Timer6 {
/// # type Time = Seconds;
/// # fn start<T>(&mut self, _: T) where T: Into<Seconds> {}
/// # fn wait(&mut self) -> ::nb::Result<(), Void> { Ok(()) }
/// # }
/// ```