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use std::fmt;
use futures::{Async, Poll, Stream};
use futures::sync::mpsc;
pub struct Body<T, E> {
inner: Inner<T, E>,
}
enum Inner<T, E> {
Once(Option<T>),
Stream(mpsc::Receiver<Result<T, E>>),
Empty,
}
impl<T, E> Body<T, E> {
pub fn empty() -> Body<T, E> {
Body { inner: Inner::Empty }
}
pub fn pair() -> (mpsc::Sender<Result<T, E>>, Body<T, E>) {
let (tx, rx) = mpsc::channel(0);
let rx = Body { inner: Inner::Stream(rx) };
(tx, rx)
}
}
impl<T, E> Stream for Body<T, E> {
type Item = T;
type Error = E;
fn poll(&mut self) -> Poll<Option<T>, E> {
match self.inner {
Inner::Once(ref mut val) => Ok(Async::Ready(val.take())),
Inner::Stream(ref mut s) => {
match s.poll().unwrap() {
Async::Ready(None) => Ok(Async::Ready(None)),
Async::Ready(Some(Ok(e))) => Ok(Async::Ready(Some(e))),
Async::Ready(Some(Err(e))) => Err(e),
Async::NotReady => Ok(Async::NotReady),
}
}
Inner::Empty => Ok(Async::Ready(None)),
}
}
}
impl<T, E> From<mpsc::Receiver<Result<T, E>>> for Body<T, E> {
fn from(src: mpsc::Receiver<Result<T, E>>) -> Body<T, E> {
Body { inner: Inner::Stream(src) }
}
}
impl<T, E> From<T> for Body<T, E> {
fn from(val: T) -> Body<T, E> {
Body { inner: Inner::Once(Some(val)) }
}
}
impl<T, E> fmt::Debug for Body<T, E> {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
write!(fmt, "Body {{ [stream of values] }}")
}
}