tokio/io/util/
repeat.rs

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1use bytes::BufMut;
2
3use crate::io::util::poll_proceed_and_make_progress;
4use crate::io::{AsyncRead, ReadBuf};
5
6use std::io;
7use std::pin::Pin;
8use std::task::{ready, Context, Poll};
9
10cfg_io_util! {
11    /// An async reader which yields one byte over and over and over and over and
12    /// over and...
13    ///
14    /// This struct is generally created by calling [`repeat`][repeat]. Please
15    /// see the documentation of `repeat()` for more details.
16    ///
17    /// This is an asynchronous version of [`std::io::Repeat`][std].
18    ///
19    /// [repeat]: fn@repeat
20    /// [std]: std::io::Repeat
21    #[derive(Debug)]
22    pub struct Repeat {
23        byte: u8,
24    }
25
26    /// Creates an instance of an async reader that infinitely repeats one byte.
27    ///
28    /// All reads from this reader will succeed by filling the specified buffer with
29    /// the given byte.
30    ///
31    /// This is an asynchronous version of [`std::io::repeat`][std].
32    ///
33    /// [std]: std::io::repeat
34    ///
35    /// # Examples
36    ///
37    /// ```
38    /// use tokio::io::{self, AsyncReadExt};
39    ///
40    /// #[tokio::main]
41    /// async fn main() {
42    ///     let mut buffer = [0; 3];
43    ///     io::repeat(0b101).read_exact(&mut buffer).await.unwrap();
44    ///     assert_eq!(buffer, [0b101, 0b101, 0b101]);
45    /// }
46    /// ```
47    pub fn repeat(byte: u8) -> Repeat {
48        Repeat { byte }
49    }
50}
51
52impl AsyncRead for Repeat {
53    #[inline]
54    fn poll_read(
55        self: Pin<&mut Self>,
56        cx: &mut Context<'_>,
57        buf: &mut ReadBuf<'_>,
58    ) -> Poll<io::Result<()>> {
59        ready!(crate::trace::trace_leaf(cx));
60        ready!(poll_proceed_and_make_progress(cx));
61        buf.put_bytes(self.byte, buf.remaining());
62        Poll::Ready(Ok(()))
63    }
64}
65
66#[cfg(test)]
67mod tests {
68    use super::*;
69
70    #[test]
71    fn assert_unpin() {
72        crate::is_unpin::<Repeat>();
73    }
74}
tokio/io/util/repeat.rs

tokio/io/util/
repeat.rs
