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use crate::io::{AsyncRead, ReadBuf};
use std::io;
use std::pin::Pin;
use std::task::{Context, Poll};
cfg_io_util! {
/// An async reader which yields one byte over and over and over and over and
/// over and...
///
/// This struct is generally created by calling [`repeat`][repeat]. Please
/// see the documentation of `repeat()` for more details.
///
/// This is an asynchronous version of [`std::io::Repeat`][std].
///
/// [repeat]: fn@repeat
/// [std]: std::io::Repeat
#[derive(Debug)]
pub struct Repeat {
byte: u8,
}
/// Creates an instance of an async reader that infinitely repeats one byte.
///
/// All reads from this reader will succeed by filling the specified buffer with
/// the given byte.
///
/// This is an asynchronous version of [`std::io::repeat`][std].
///
/// [std]: std::io::repeat
///
/// # Examples
///
/// ```
/// use tokio::io::{self, AsyncReadExt};
///
/// #[tokio::main]
/// async fn main() {
/// let mut buffer = [0; 3];
/// io::repeat(0b101).read_exact(&mut buffer).await.unwrap();
/// assert_eq!(buffer, [0b101, 0b101, 0b101]);
/// }
/// ```
pub fn repeat(byte: u8) -> Repeat {
Repeat { byte }
}
}
impl AsyncRead for Repeat {
#[inline]
fn poll_read(
self: Pin<&mut Self>,
_: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>> {
// TODO: could be faster, but should we unsafe it?
while buf.remaining() != 0 {
buf.put_slice(&[self.byte]);
}
Poll::Ready(Ok(()))
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn assert_unpin() {
crate::is_unpin::<Repeat>();
}
}