1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
use futures::{Future, Async}; use std::mem; pub struct FirstOk2<A: Future, B: Future> { inner: FirstOk2Inner<A, B>, } impl<A: Future, B: Future> FirstOk2<A, B> { pub fn new(a: A, b: B) -> FirstOk2<A, B> { FirstOk2 { inner: FirstOk2Inner::BothRunning(a, b), } } } enum FirstOk2Inner<A: Future, B: Future> { BothRunning(A, B), RunningA(A, B::Error), RunningB(A::Error, B), Finished, } impl<A, B> Future for FirstOk2<A, B> where A: Future, B: Future<Item=A::Item> { type Item = A::Item; type Error = (A::Error, B::Error); fn poll(&mut self) -> Result<Async<A::Item>, (A::Error, B::Error)> { let inner = mem::replace(&mut self.inner, FirstOk2Inner::Finished); match inner { FirstOk2Inner::BothRunning(mut a, mut b) => { match a.poll() { Ok(Async::Ready(x)) => Ok(Async::Ready(x)), Ok(Async::NotReady) => { match b.poll() { Ok(Async::Ready(x)) => Ok(Async::Ready(x)), Ok(Async::NotReady) => { self.inner = FirstOk2Inner::BothRunning(a, b); Ok(Async::NotReady) }, Err(eb) => { self.inner = FirstOk2Inner::RunningA(a, eb); Ok(Async::NotReady) }, } }, Err(ea) => { match b.poll() { Ok(Async::Ready(x)) => Ok(Async::Ready(x)), Ok(Async::NotReady) => { self.inner = FirstOk2Inner::RunningB(ea, b); Ok(Async::NotReady) }, Err(eb) => Err((ea, eb)), } }, } }, FirstOk2Inner::RunningA(mut a, eb) => { match a.poll() { Ok(Async::Ready(x)) => Ok(Async::Ready(x)), Ok(Async::NotReady) => { self.inner = FirstOk2Inner::RunningA(a, eb); Ok(Async::NotReady) }, Err(ea) => Err((ea, eb)), } }, FirstOk2Inner::RunningB(ea, mut b) => { match b.poll() { Ok(Async::Ready(x)) => Ok(Async::Ready(x)), Ok(Async::NotReady) => { self.inner = FirstOk2Inner::RunningB(ea, b); Ok(Async::NotReady) }, Err(eb) => Err((ea, eb)), } }, FirstOk2Inner::Finished => { panic!("poll() called on FirstOk2 which has already finished"); }, } } }