rust async await std

async.rs

// futures-executor = "0.3.1"


use std::pin::Pin;
use std::thread;
use std::time;
use std::future::Future;
use std::task::Poll;


pub struct Waiter {
    state : u32,
}

impl Waiter {
    pub fn new() -> Waiter {
        Waiter {
            state: 0
        }
    }
}

impl Future for Waiter {
    type Output = i32;
    fn poll(self: Pin<&mut Self>, cx: &mut std::task::Context) -> Poll<Self::Output> {
        println!("poll");

        if self.state == 0 {
            unsafe {
                self.get_unchecked_mut().state = self.state + 1;
            }
            let wk = cx.waker().clone();
            thread::spawn(move || {
                thread::sleep(time::Duration::from_secs(1));
                wk.wake();
            });
            Poll::Pending
        } else {
            Poll::Ready(1)
        }
    }
}

fn main() {
    println!("Hello, world!");

    thread::spawn(move || {
        thread::sleep(time::Duration::from_secs(1));
        println!("thread")
    });

    let a = async {
        println!("await...");
        let w = Waiter::new().await;
        println!("awaited {}", w);
        w
    };
    futures_executor::block_on(a);


    thread::sleep(time::Duration::from_secs(3));
}