hyper/common/io/
rewind.rs

1use std::pin::Pin;
2use std::task::{Context, Poll};
3use std::{cmp, io};
4
5use bytes::{Buf, Bytes};
6
7use crate::rt::{Read, ReadBufCursor, Write};
8
9/// Combine a buffer with an IO, rewinding reads to use the buffer.
10#[derive(Debug)]
11pub(crate) struct Rewind<T> {
12    pre: Option<Bytes>,
13    inner: T,
14}
15
16impl<T> Rewind<T> {
17    #[cfg(all(
18        test,
19        any(feature = "client", feature = "server"),
20        any(feature = "http1", feature = "http2")
21    ))]
22    pub(crate) fn new(io: T) -> Self {
23        Rewind {
24            pre: None,
25            inner: io,
26        }
27    }
28
29    pub(crate) fn new_buffered(io: T, buf: Bytes) -> Self {
30        Rewind {
31            pre: Some(buf),
32            inner: io,
33        }
34    }
35
36    #[cfg(all(
37        test,
38        any(feature = "client", feature = "server"),
39        any(feature = "http1", feature = "http2")
40    ))]
41    pub(crate) fn rewind(&mut self, bs: Bytes) {
42        debug_assert!(self.pre.is_none());
43        self.pre = Some(bs);
44    }
45
46    pub(crate) fn into_inner(self) -> (T, Bytes) {
47        (self.inner, self.pre.unwrap_or_default())
48    }
49}
50
51impl<T> Read for Rewind<T>
52where
53    T: Read + Unpin,
54{
55    fn poll_read(
56        mut self: Pin<&mut Self>,
57        cx: &mut Context<'_>,
58        mut buf: ReadBufCursor<'_>,
59    ) -> Poll<io::Result<()>> {
60        if let Some(mut prefix) = self.pre.take() {
61            // If there are no remaining bytes, let the bytes get dropped.
62            if !prefix.is_empty() {
63                let copy_len = cmp::min(prefix.len(), buf.remaining());
64                // TODO: There should be a way to do following two lines cleaner...
65                buf.put_slice(&prefix[..copy_len]);
66                prefix.advance(copy_len);
67                // Put back what's left
68                if !prefix.is_empty() {
69                    self.pre = Some(prefix);
70                }
71
72                return Poll::Ready(Ok(()));
73            }
74        }
75        Pin::new(&mut self.inner).poll_read(cx, buf)
76    }
77}
78
79impl<T> Write for Rewind<T>
80where
81    T: Write + Unpin,
82{
83    fn poll_write(
84        mut self: Pin<&mut Self>,
85        cx: &mut Context<'_>,
86        buf: &[u8],
87    ) -> Poll<io::Result<usize>> {
88        Pin::new(&mut self.inner).poll_write(cx, buf)
89    }
90
91    fn poll_write_vectored(
92        mut self: Pin<&mut Self>,
93        cx: &mut Context<'_>,
94        bufs: &[io::IoSlice<'_>],
95    ) -> Poll<io::Result<usize>> {
96        Pin::new(&mut self.inner).poll_write_vectored(cx, bufs)
97    }
98
99    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
100        Pin::new(&mut self.inner).poll_flush(cx)
101    }
102
103    fn poll_shutdown(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
104        Pin::new(&mut self.inner).poll_shutdown(cx)
105    }
106
107    fn is_write_vectored(&self) -> bool {
108        self.inner.is_write_vectored()
109    }
110}
111
112#[cfg(all(
113    any(feature = "client", feature = "server"),
114    any(feature = "http1", feature = "http2"),
115))]
116#[cfg(test)]
117mod tests {
118    use super::super::Compat;
119    use super::Rewind;
120    use bytes::Bytes;
121    use tokio::io::AsyncReadExt;
122
123    #[cfg(not(miri))]
124    #[tokio::test]
125    async fn partial_rewind() {
126        let underlying = [104, 101, 108, 108, 111];
127
128        let mock = tokio_test::io::Builder::new().read(&underlying).build();
129
130        let mut stream = Compat::new(Rewind::new(Compat::new(mock)));
131
132        // Read off some bytes, ensure we filled o1
133        let mut buf = [0; 2];
134        stream.read_exact(&mut buf).await.expect("read1");
135
136        // Rewind the stream so that it is as if we never read in the first place.
137        stream.0.rewind(Bytes::copy_from_slice(&buf[..]));
138
139        let mut buf = [0; 5];
140        stream.read_exact(&mut buf).await.expect("read1");
141
142        // At this point we should have read everything that was in the MockStream
143        assert_eq!(&buf, &underlying);
144    }
145
146    #[cfg(not(miri))]
147    #[tokio::test]
148    async fn full_rewind() {
149        let underlying = [104, 101, 108, 108, 111];
150
151        let mock = tokio_test::io::Builder::new().read(&underlying).build();
152
153        let mut stream = Compat::new(Rewind::new(Compat::new(mock)));
154
155        let mut buf = [0; 5];
156        stream.read_exact(&mut buf).await.expect("read1");
157
158        // Rewind the stream so that it is as if we never read in the first place.
159        stream.0.rewind(Bytes::copy_from_slice(&buf[..]));
160
161        let mut buf = [0; 5];
162        stream.read_exact(&mut buf).await.expect("read1");
163
164        assert_eq!(&buf, &underlying);
165    }
166}
hyper/common/io/rewind.rs

hyper/common/io/
rewind.rs
