70 lines
1.8 KiB
Rust
70 lines
1.8 KiB
Rust
use futures_core::FusedStream;
|
|
use tokio_stream::{Stream, StreamExt};
|
|
|
|
use std::pin::Pin;
|
|
use std::task::{Context, Poll};
|
|
|
|
// a stream which alternates between Some and None
|
|
struct Alternate {
|
|
state: i32,
|
|
}
|
|
|
|
impl Stream for Alternate {
|
|
type Item = i32;
|
|
|
|
fn poll_next(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Option<i32>> {
|
|
let val = self.state;
|
|
self.state += 1;
|
|
|
|
// if it's even, Some(i32), else None
|
|
if val % 2 == 0 {
|
|
Poll::Ready(Some(val))
|
|
} else {
|
|
Poll::Ready(None)
|
|
}
|
|
}
|
|
}
|
|
|
|
#[tokio::test]
|
|
async fn basic_usage() {
|
|
let mut stream = Alternate { state: 0 };
|
|
|
|
// the stream goes back and forth
|
|
assert_eq!(stream.next().await, Some(0));
|
|
assert_eq!(stream.next().await, None);
|
|
assert_eq!(stream.next().await, Some(2));
|
|
assert_eq!(stream.next().await, None);
|
|
|
|
// however, once it is fused
|
|
let mut stream = stream.fuse();
|
|
|
|
assert!(!stream.is_terminated());
|
|
assert_eq!(stream.size_hint(), (0, None));
|
|
assert_eq!(stream.next().await, Some(4));
|
|
|
|
assert!(!stream.is_terminated());
|
|
assert_eq!(stream.size_hint(), (0, None));
|
|
assert_eq!(stream.next().await, None);
|
|
|
|
assert!(stream.is_terminated());
|
|
|
|
// it will always return `None` after the first time.
|
|
assert_eq!(stream.size_hint(), (0, Some(0)));
|
|
assert_eq!(stream.next().await, None);
|
|
assert_eq!(stream.size_hint(), (0, Some(0)));
|
|
|
|
assert!(stream.is_terminated());
|
|
}
|
|
|
|
#[tokio::test]
|
|
#[cfg(feature = "time")]
|
|
async fn interval_stream_is_never_terminated() {
|
|
use futures_core::stream::FusedStream;
|
|
use tokio_stream::wrappers::IntervalStream;
|
|
|
|
let interval = tokio::time::interval(std::time::Duration::from_millis(1));
|
|
let stream = IntervalStream::new(interval);
|
|
|
|
assert!(!stream.is_terminated());
|
|
}
|