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io_inspect.rs
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io_inspect.rs
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use std::{
pin::Pin,
task::{Context, Poll},
};
use tokio::io::{AsyncRead, AsyncReadExt, ReadBuf};
use tokio_util::io::InspectReader;
/// An AsyncRead implementation that works byte-by-byte, to catch out callers
/// who don't allow for `buf` being part-filled before the call
struct SmallReader {
contents: Vec<u8>,
}
impl Unpin for SmallReader {}
impl AsyncRead for SmallReader {
fn poll_read(
mut self: Pin<&mut Self>,
_cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<std::io::Result<()>> {
if let Some(byte) = self.contents.pop() {
buf.put_slice(&[byte])
}
Poll::Ready(Ok(()))
}
}
#[tokio::test]
async fn read_tee() {
let contents = b"This could be really long, you know".to_vec();
let reader = SmallReader {
contents: contents.clone(),
};
let mut altout: Vec<u8> = Vec::new();
let mut teeout = Vec::new();
{
let mut tee = InspectReader::new(reader, |bytes| altout.extend(bytes));
tee.read_to_end(&mut teeout).await.unwrap();
}
assert_eq!(teeout, altout);
assert_eq!(altout.len(), contents.len());
}