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use std::marker::Unpin;
use std::{cmp, io};
use bytes::{Buf, Bytes};
use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
use crate::common::{task, Pin, Poll};
/// Combine a buffer with an IO, rewinding reads to use the buffer.
#[derive(Debug)]
pub(crate) struct Rewind<T> {
pre: Option<Bytes>,
inner: T,
}
impl<T> Rewind<T> {
#[cfg(any(all(feature = "http2", feature = "server"), test))]
pub(crate) fn new(io: T) -> Self {
Rewind {
pre: None,
inner: io,
}
}
pub(crate) fn new_buffered(io: T, buf: Bytes) -> Self {
Rewind {
pre: Some(buf),
inner: io,
}
}
#[cfg(any(all(feature = "http1", feature = "http2", feature = "server"), test))]
pub(crate) fn rewind(&mut self, bs: Bytes) {
debug_assert!(self.pre.is_none());
self.pre = Some(bs);
}
pub(crate) fn into_inner(self) -> (T, Bytes) {
(self.inner, self.pre.unwrap_or_else(Bytes::new))
}
// pub(crate) fn get_mut(&mut self) -> &mut T {
// &mut self.inner
// }
}
impl<T> AsyncRead for Rewind<T>
where
T: AsyncRead + Unpin,
{
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut task::Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>> {
if let Some(mut prefix) = self.pre.take() {
// If there are no remaining bytes, let the bytes get dropped.
if !prefix.is_empty() {
let copy_len = cmp::min(prefix.len(), buf.remaining());
// TODO: There should be a way to do following two lines cleaner...
buf.put_slice(&prefix[..copy_len]);
prefix.advance(copy_len);
// Put back what's left
if !prefix.is_empty() {
self.pre = Some(prefix);
}
return Poll::Ready(Ok(()));
}
}
Pin::new(&mut self.inner).poll_read(cx, buf)
}
}
impl<T> AsyncWrite for Rewind<T>
where
T: AsyncWrite + Unpin,
{
fn poll_write(
mut self: Pin<&mut Self>,
cx: &mut task::Context<'_>,
buf: &[u8],
) -> Poll<io::Result<usize>> {
Pin::new(&mut self.inner).poll_write(cx, buf)
}
fn poll_write_vectored(
mut self: Pin<&mut Self>,
cx: &mut task::Context<'_>,
bufs: &[io::IoSlice<'_>],
) -> Poll<io::Result<usize>> {
Pin::new(&mut self.inner).poll_write_vectored(cx, bufs)
}
fn poll_flush(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<io::Result<()>> {
Pin::new(&mut self.inner).poll_flush(cx)
}
fn poll_shutdown(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<io::Result<()>> {
Pin::new(&mut self.inner).poll_shutdown(cx)
}
fn is_write_vectored(&self) -> bool {
self.inner.is_write_vectored()
}
}
#[cfg(test)]
mod tests {
// FIXME: re-implement tests with `async/await`, this import should
// trigger a warning to remind us
use super::Rewind;
use bytes::Bytes;
use tokio::io::AsyncReadExt;
#[tokio::test]
async fn partial_rewind() {
let underlying = [104, 101, 108, 108, 111];
let mock = tokio_test::io::Builder::new().read(&underlying).build();
let mut stream = Rewind::new(mock);
// Read off some bytes, ensure we filled o1
let mut buf = [0; 2];
stream.read_exact(&mut buf).await.expect("read1");
// Rewind the stream so that it is as if we never read in the first place.
stream.rewind(Bytes::copy_from_slice(&buf[..]));
let mut buf = [0; 5];
stream.read_exact(&mut buf).await.expect("read1");
// At this point we should have read everything that was in the MockStream
assert_eq!(&buf, &underlying);
}
#[tokio::test]
async fn full_rewind() {
let underlying = [104, 101, 108, 108, 111];
let mock = tokio_test::io::Builder::new().read(&underlying).build();
let mut stream = Rewind::new(mock);
let mut buf = [0; 5];
stream.read_exact(&mut buf).await.expect("read1");
// Rewind the stream so that it is as if we never read in the first place.
stream.rewind(Bytes::copy_from_slice(&buf[..]));
let mut buf = [0; 5];
stream.read_exact(&mut buf).await.expect("read1");
}
}
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