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rewind.rs
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rewind.rs
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use std::io::{self, Read};
use std::marker::Unpin;
use bytes::{Buf, Bytes, IntoBuf};
use tokio_io::{AsyncRead, AsyncWrite};
use crate::common::{Pin, Poll, task};
/// 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> {
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,
}
}
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))
}
}
impl<T> AsyncRead for Rewind<T>
where
T: AsyncRead + Unpin,
{
#[inline]
unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool {
self.inner.prepare_uninitialized_buffer(buf)
}
fn poll_read(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>, buf: &mut [u8]) -> Poll<io::Result<usize>> {
if let Some(pre_bs) = self.pre.take() {
// If there are no remaining bytes, let the bytes get dropped.
if pre_bs.len() > 0 {
let mut pre_reader = pre_bs.into_buf().reader();
let read_cnt = pre_reader.read(buf)?;
let mut new_pre = pre_reader.into_inner().into_inner();
new_pre.advance(read_cnt);
// Put back whats left
if new_pre.len() > 0 {
self.pre = Some(new_pre);
}
return Poll::Ready(Ok(read_cnt));
}
}
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_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)
}
#[inline]
fn poll_write_buf<B: Buf>(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>, buf: &mut B) -> Poll<io::Result<usize>> {
Pin::new(&mut self.inner).poll_write_buf(cx, buf)
}
}
#[cfg(test)]
mod tests {
// FIXME: re-implement tests with `async/await`, this import should
// trigger a warning to remind us
use super::Rewind;
/*
use super::*;
use tokio_mockstream::MockStream;
use std::io::Cursor;
// Test a partial rewind
#[test]
fn async_partial_rewind() {
let bs = &mut [104, 101, 108, 108, 111];
let o1 = &mut [0, 0];
let o2 = &mut [0, 0, 0, 0, 0];
let mut stream = Rewind::new(MockStream::new(bs));
let mut o1_cursor = Cursor::new(o1);
// Read off some bytes, ensure we filled o1
match stream.read_buf(&mut o1_cursor).unwrap() {
Async::NotReady => panic!("should be ready"),
Async::Ready(cnt) => assert_eq!(2, cnt),
}
// Rewind the stream so that it is as if we never read in the first place.
let read_buf = Bytes::from(&o1_cursor.into_inner()[..]);
stream.rewind(read_buf);
// We poll 2x here since the first time we'll only get what is in the
// prefix (the rewinded part) of the Rewind.\
let mut o2_cursor = Cursor::new(o2);
stream.read_buf(&mut o2_cursor).unwrap();
stream.read_buf(&mut o2_cursor).unwrap();
let o2_final = o2_cursor.into_inner();
// At this point we should have read everything that was in the MockStream
assert_eq!(&o2_final, &bs);
}
// Test a full rewind
#[test]
fn async_full_rewind() {
let bs = &mut [104, 101, 108, 108, 111];
let o1 = &mut [0, 0, 0, 0, 0];
let o2 = &mut [0, 0, 0, 0, 0];
let mut stream = Rewind::new(MockStream::new(bs));
let mut o1_cursor = Cursor::new(o1);
match stream.read_buf(&mut o1_cursor).unwrap() {
Async::NotReady => panic!("should be ready"),
Async::Ready(cnt) => assert_eq!(5, cnt),
}
let read_buf = Bytes::from(&o1_cursor.into_inner()[..]);
stream.rewind(read_buf);
let mut o2_cursor = Cursor::new(o2);
stream.read_buf(&mut o2_cursor).unwrap();
stream.read_buf(&mut o2_cursor).unwrap();
let o2_final = o2_cursor.into_inner();
assert_eq!(&o2_final, &bs);
}
#[test]
fn partial_rewind() {
let bs = &mut [104, 101, 108, 108, 111];
let o1 = &mut [0, 0];
let o2 = &mut [0, 0, 0, 0, 0];
let mut stream = Rewind::new(MockStream::new(bs));
stream.read(o1).unwrap();
let read_buf = Bytes::from(&o1[..]);
stream.rewind(read_buf);
let cnt = stream.read(o2).unwrap();
stream.read(&mut o2[cnt..]).unwrap();
assert_eq!(&o2, &bs);
}
#[test]
fn full_rewind() {
let bs = &mut [104, 101, 108, 108, 111];
let o1 = &mut [0, 0, 0, 0, 0];
let o2 = &mut [0, 0, 0, 0, 0];
let mut stream = Rewind::new(MockStream::new(bs));
stream.read(o1).unwrap();
let read_buf = Bytes::from(&o1[..]);
stream.rewind(read_buf);
let cnt = stream.read(o2).unwrap();
stream.read(&mut o2[cnt..]).unwrap();
assert_eq!(&o2, &bs);
}
*/
}