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8efa62013b
This change removes all references to `Stream` from within the `tokio` crate and moves them into a new `tokio-stream` crate. Most types have had their `impl Stream` removed as well in-favor of their inherent methods. Closes #2870
51 lines
1.3 KiB
Rust
51 lines
1.3 KiB
Rust
use tokio_stream::{Stream, StreamExt};
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use std::pin::Pin;
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use std::task::{Context, Poll};
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// a stream which alternates between Some and None
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struct Alternate {
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state: i32,
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}
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impl Stream for Alternate {
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type Item = i32;
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fn poll_next(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Option<i32>> {
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let val = self.state;
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self.state += 1;
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// if it's even, Some(i32), else None
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if val % 2 == 0 {
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Poll::Ready(Some(val))
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} else {
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Poll::Ready(None)
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}
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}
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}
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#[tokio::test]
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async fn basic_usage() {
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let mut stream = Alternate { state: 0 };
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// the stream goes back and forth
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assert_eq!(stream.next().await, Some(0));
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assert_eq!(stream.next().await, None);
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assert_eq!(stream.next().await, Some(2));
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assert_eq!(stream.next().await, None);
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// however, once it is fused
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let mut stream = stream.fuse();
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assert_eq!(stream.size_hint(), (0, None));
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assert_eq!(stream.next().await, Some(4));
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assert_eq!(stream.size_hint(), (0, None));
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assert_eq!(stream.next().await, None);
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// it will always return `None` after the first time.
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assert_eq!(stream.size_hint(), (0, Some(0)));
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assert_eq!(stream.next().await, None);
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assert_eq!(stream.size_hint(), (0, Some(0)));
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}
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