gistfile1.rs

#![feature(await_macro)]
#![feature(futures_api)]
#![feature(async_await)]
use std::time::{Instant, Duration};
use std::future::Future;
use std::task::{Waker, Context,  Poll};
use std::pin::Pin;

static VTABLE: std::task::RawWakerVTable = std::task::RawWakerVTable { 
    wake: wake as unsafe fn(*const ()),
    drop: drop as unsafe fn(*const ()),
    clone: clone
};
fn wake(_a: *const ()) {
    println!("I was woken up!");
}
fn drop(_a: *const ()) {
    println!("Im being dropped!");
    
}
fn clone(_a: *const ()) -> std::task::RawWaker {
    unimplemented!()
}




struct Timer {
    start: Instant,
    time: Duration
    
}



impl Future for Timer {
    type Output = ();
    fn poll(self: Pin<&mut Self>, lw: &Waker) -> Poll<()> {
        if self.start.elapsed() >= self.time {
            Poll::Ready(())
        } 
        else { lw.wake(); Poll::Pending }
    }
}

async fn sleep_something() {
   Timer::new(1).await
}

fn main() {

    let mut fut = sleep_something();
    let mut context = Context::from_waker(unsafe { Waker::from_raw(std::task::RawWaker::new(std::ptr::null(), &VTABLE)) });
    
    while let Poll::Pending = Pin::new(&mut fut).poll(&mut context) {}
  
}