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| 1 | +// edition:2018 |
| 2 | +// aux-build:arc_wake.rs |
| 3 | + |
| 4 | +#![feature(async_await, await_macro)] |
| 5 | + |
| 6 | +extern crate arc_wake; |
| 7 | + |
| 8 | +use std::pin::Pin; |
| 9 | +use std::future::Future; |
| 10 | +use std::sync::{ |
| 11 | + Arc, |
| 12 | + atomic::{self, AtomicUsize}, |
| 13 | +}; |
| 14 | +use std::task::{Context, Poll}; |
| 15 | +use arc_wake::ArcWake; |
| 16 | + |
| 17 | +struct Counter { |
| 18 | + wakes: AtomicUsize, |
| 19 | +} |
| 20 | + |
| 21 | +impl ArcWake for Counter { |
| 22 | + fn wake(self: Arc<Self>) { |
| 23 | + Self::wake_by_ref(&self) |
| 24 | + } |
| 25 | + fn wake_by_ref(arc_self: &Arc<Self>) { |
| 26 | + arc_self.wakes.fetch_add(1, atomic::Ordering::SeqCst); |
| 27 | + } |
| 28 | +} |
| 29 | + |
| 30 | +struct WakeOnceThenComplete(bool, u8); |
| 31 | + |
| 32 | +impl Future for WakeOnceThenComplete { |
| 33 | + type Output = u8; |
| 34 | + fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<u8> { |
| 35 | + if self.0 { |
| 36 | + Poll::Ready(self.1) |
| 37 | + } else { |
| 38 | + cx.waker().wake_by_ref(); |
| 39 | + self.0 = true; |
| 40 | + Poll::Pending |
| 41 | + } |
| 42 | + } |
| 43 | +} |
| 44 | + |
| 45 | +fn wait(fut: impl Future<Output = u8>) -> u8 { |
| 46 | + let mut fut = Box::pin(fut); |
| 47 | + let counter = Arc::new(Counter { wakes: AtomicUsize::new(0) }); |
| 48 | + let waker = ArcWake::into_waker(counter.clone()); |
| 49 | + let mut cx = Context::from_waker(&waker); |
| 50 | + loop { |
| 51 | + match fut.as_mut().poll(&mut cx) { |
| 52 | + Poll::Ready(out) => return out, |
| 53 | + Poll::Pending => (), |
| 54 | + } |
| 55 | + } |
| 56 | +} |
| 57 | + |
| 58 | +fn base() -> WakeOnceThenComplete { WakeOnceThenComplete(false, 1) } |
| 59 | + |
| 60 | +async fn await1_level1() -> u8 { |
| 61 | + await!(base()) |
| 62 | +} |
| 63 | + |
| 64 | +async fn await2_level1() -> u8 { |
| 65 | + await!(base()) + await!(base()) |
| 66 | +} |
| 67 | + |
| 68 | +async fn await3_level1() -> u8 { |
| 69 | + await!(base()) + await!(base()) + await!(base()) |
| 70 | +} |
| 71 | + |
| 72 | +async fn await3_level2() -> u8 { |
| 73 | + await!(await3_level1()) + await!(await3_level1()) + await!(await3_level1()) |
| 74 | +} |
| 75 | + |
| 76 | +async fn await3_level3() -> u8 { |
| 77 | + await!(await3_level2()) + await!(await3_level2()) + await!(await3_level2()) |
| 78 | +} |
| 79 | + |
| 80 | +async fn await3_level4() -> u8 { |
| 81 | + await!(await3_level3()) + await!(await3_level3()) + await!(await3_level3()) |
| 82 | +} |
| 83 | + |
| 84 | +async fn await3_level5() -> u8 { |
| 85 | + await!(await3_level4()) + await!(await3_level4()) + await!(await3_level4()) |
| 86 | +} |
| 87 | + |
| 88 | +fn main() { |
| 89 | + assert_eq!(2, std::mem::size_of_val(&base())); |
| 90 | + assert_eq!(8, std::mem::size_of_val(&await1_level1())); |
| 91 | + assert_eq!(12, std::mem::size_of_val(&await2_level1())); |
| 92 | + assert_eq!(12, std::mem::size_of_val(&await3_level1())); |
| 93 | + assert_eq!(20, std::mem::size_of_val(&await3_level2())); |
| 94 | + assert_eq!(28, std::mem::size_of_val(&await3_level3())); |
| 95 | + assert_eq!(36, std::mem::size_of_val(&await3_level4())); |
| 96 | + assert_eq!(44, std::mem::size_of_val(&await3_level5())); |
| 97 | + |
| 98 | + assert_eq!(1, wait(base())); |
| 99 | + assert_eq!(1, wait(await1_level1())); |
| 100 | + assert_eq!(2, wait(await2_level1())); |
| 101 | + assert_eq!(3, wait(await3_level1())); |
| 102 | + assert_eq!(9, wait(await3_level2())); |
| 103 | + assert_eq!(27, wait(await3_level3())); |
| 104 | + assert_eq!(81, wait(await3_level4())); |
| 105 | + assert_eq!(243, wait(await3_level5())); |
| 106 | +} |
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