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use std::pin::Pin;
use atomic::{Atomic, Ordering};
use crate::stream::{PollRecv, Stream};
use crate::Context;
use pin_project::pin_project;
#[derive(Copy, Clone)]
enum State {
Left,
Right,
Closed,
}
#[pin_project]
pub struct ChainStream<Left, Right> {
state: Atomic<State>,
#[pin]
left: Left,
#[pin]
right: Right,
}
impl<Left, Right> ChainStream<Left, Right>
where
Left: Stream,
Right: Stream<Item = Left::Item>,
{
pub fn new(left: Left, right: Right) -> Self {
Self {
state: Atomic::new(State::Left),
left,
right,
}
}
}
impl<Left, Right> Stream for ChainStream<Left, Right>
where
Left: Stream,
Right: Stream<Item = Left::Item>,
{
type Item = Left::Item;
fn poll_recv(self: Pin<&mut Self>, cx: &mut Context<'_>) -> PollRecv<Self::Item> {
let this = self.project();
let mut state = this.state.load(Ordering::Acquire);
if let State::Left = state {
match this.left.poll_recv(cx) {
PollRecv::Ready(v) => return PollRecv::Ready(v),
PollRecv::Pending => return PollRecv::Pending,
PollRecv::Closed => {
this.state.store(State::Right, Ordering::Release);
state = State::Right;
}
}
}
if let State::Right = state {
match this.right.poll_recv(cx) {
PollRecv::Ready(v) => return PollRecv::Ready(v),
PollRecv::Pending => return PollRecv::Pending,
PollRecv::Closed => {
this.state.store(State::Closed, Ordering::Release);
return PollRecv::Closed;
}
}
}
if let State::Closed = state {
return PollRecv::Closed;
}
unreachable!();
}
}
#[cfg(test)]
mod tests {
use std::pin::Pin;
use crate::test::stream::*;
use crate::{
stream::{PollRecv, Stream},
Context,
};
use super::ChainStream;
#[test]
fn chain() {
let left = from_poll_iter(vec![PollRecv::Ready(1), PollRecv::Ready(2)]);
let right = from_poll_iter(vec![PollRecv::Ready(3)]);
let mut find = ChainStream::new(left, right);
let mut cx = Context::empty();
assert_eq!(PollRecv::Ready(1), Pin::new(&mut find).poll_recv(&mut cx));
assert_eq!(PollRecv::Ready(2), Pin::new(&mut find).poll_recv(&mut cx));
assert_eq!(PollRecv::Ready(3), Pin::new(&mut find).poll_recv(&mut cx));
assert_eq!(PollRecv::Closed, Pin::new(&mut find).poll_recv(&mut cx));
}
#[test]
fn waits_for_right() {
let left = from_poll_iter(vec![PollRecv::Pending]);
let right = from_poll_iter(vec![PollRecv::Ready(1)]);
let mut find = ChainStream::new(left, right);
let mut cx = Context::empty();
assert_eq!(PollRecv::Pending, Pin::new(&mut find).poll_recv(&mut cx));
assert_eq!(PollRecv::Ready(1), Pin::new(&mut find).poll_recv(&mut cx));
assert_eq!(PollRecv::Closed, Pin::new(&mut find).poll_recv(&mut cx));
}
#[test]
fn ignores_after_close() {
let left = from_poll_iter(vec![PollRecv::Closed, PollRecv::Ready(1)]);
let right = from_poll_iter(vec![PollRecv::Closed, PollRecv::Ready(2)]);
let mut find = ChainStream::new(left, right);
let mut cx = Context::empty();
assert_eq!(PollRecv::Closed, Pin::new(&mut find).poll_recv(&mut cx));
assert_eq!(PollRecv::Closed, Pin::new(&mut find).poll_recv(&mut cx));
assert_eq!(PollRecv::Closed, Pin::new(&mut find).poll_recv(&mut cx));
}
}