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|
use bytes::Buf;
use futures_core::stream::Stream;
use pin_project_lite::pin_project;
use std::io;
use std::pin::Pin;
use std::task::{Context, Poll};
use tokio::io::{AsyncBufRead, AsyncRead, ReadBuf};
pin_project! {
/// Convert a [`Stream`] of byte chunks into an [`AsyncRead`].
///
/// This type performs the inverse operation of [`ReaderStream`].
///
/// # Example
///
/// ```
/// use bytes::Bytes;
/// use tokio::io::{AsyncReadExt, Result};
/// use tokio_util::io::StreamReader;
/// # #[tokio::main]
/// # async fn main() -> std::io::Result<()> {
///
/// // Create a stream from an iterator.
/// let stream = tokio_stream::iter(vec![
/// Result::Ok(Bytes::from_static(&[0, 1, 2, 3])),
/// Result::Ok(Bytes::from_static(&[4, 5, 6, 7])),
/// Result::Ok(Bytes::from_static(&[8, 9, 10, 11])),
/// ]);
///
/// // Convert it to an AsyncRead.
/// let mut read = StreamReader::new(stream);
///
/// // Read five bytes from the stream.
/// let mut buf = [0; 5];
/// read.read_exact(&mut buf).await?;
/// assert_eq!(buf, [0, 1, 2, 3, 4]);
///
/// // Read the rest of the current chunk.
/// assert_eq!(read.read(&mut buf).await?, 3);
/// assert_eq!(&buf[..3], [5, 6, 7]);
///
/// // Read the next chunk.
/// assert_eq!(read.read(&mut buf).await?, 4);
/// assert_eq!(&buf[..4], [8, 9, 10, 11]);
///
/// // We have now reached the end.
/// assert_eq!(read.read(&mut buf).await?, 0);
///
/// # Ok(())
/// # }
/// ```
///
/// [`AsyncRead`]: tokio::io::AsyncRead
/// [`Stream`]: futures_core::Stream
/// [`ReaderStream`]: crate::io::ReaderStream
#[derive(Debug)]
pub struct StreamReader<S, B> {
#[pin]
inner: S,
chunk: Option<B>,
}
}
impl<S, B, E> StreamReader<S, B>
where
S: Stream<Item = Result<B, E>>,
B: Buf,
E: Into<std::io::Error>,
{
/// Convert a stream of byte chunks into an [`AsyncRead`](tokio::io::AsyncRead).
///
/// The item should be a [`Result`] with the ok variant being something that
/// implements the [`Buf`] trait (e.g. `Vec<u8>` or `Bytes`). The error
/// should be convertible into an [io error].
///
/// [`Result`]: std::result::Result
/// [`Buf`]: bytes::Buf
/// [io error]: std::io::Error
pub fn new(stream: S) -> Self {
Self {
inner: stream,
chunk: None,
}
}
/// Do we have a chunk and is it non-empty?
fn has_chunk(&self) -> bool {
if let Some(ref chunk) = self.chunk {
chunk.remaining() > 0
} else {
false
}
}
/// Consumes this `StreamReader`, returning a Tuple consisting
/// of the underlying stream and an Option of the interal buffer,
/// which is Some in case the buffer contains elements.
pub fn into_inner_with_chunk(self) -> (S, Option<B>) {
if self.has_chunk() {
(self.inner, self.chunk)
} else {
(self.inner, None)
}
}
}
impl<S, B> StreamReader<S, B> {
/// Gets a reference to the underlying stream.
///
/// It is inadvisable to directly read from the underlying stream.
pub fn get_ref(&self) -> &S {
&self.inner
}
/// Gets a mutable reference to the underlying stream.
///
/// It is inadvisable to directly read from the underlying stream.
pub fn get_mut(&mut self) -> &mut S {
&mut self.inner
}
/// Gets a pinned mutable reference to the underlying stream.
///
/// It is inadvisable to directly read from the underlying stream.
pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut S> {
self.project().inner
}
/// Consumes this `BufWriter`, returning the underlying stream.
///
/// Note that any leftover data in the internal buffer is lost.
/// If you additionally want access to the internal buffer use
/// [`into_inner_with_chunk`].
///
/// [`into_inner_with_chunk`]: crate::io::StreamReader::into_inner_with_chunk
pub fn into_inner(self) -> S {
self.inner
}
}
impl<S, B, E> AsyncRead for StreamReader<S, B>
where
S: Stream<Item = Result<B, E>>,
B: Buf,
E: Into<std::io::Error>,
{
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>> {
if buf.remaining() == 0 {
return Poll::Ready(Ok(()));
}
let inner_buf = match self.as_mut().poll_fill_buf(cx) {
Poll::Ready(Ok(buf)) => buf,
Poll::Ready(Err(err)) => return Poll::Ready(Err(err)),
Poll::Pending => return Poll::Pending,
};
let len = std::cmp::min(inner_buf.len(), buf.remaining());
buf.put_slice(&inner_buf[..len]);
self.consume(len);
Poll::Ready(Ok(()))
}
}
impl<S, B, E> AsyncBufRead for StreamReader<S, B>
where
S: Stream<Item = Result<B, E>>,
B: Buf,
E: Into<std::io::Error>,
{
fn poll_fill_buf(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<&[u8]>> {
loop {
if self.as_mut().has_chunk() {
// This unwrap is very sad, but it can't be avoided.
let buf = self.project().chunk.as_ref().unwrap().chunk();
return Poll::Ready(Ok(buf));
} else {
match self.as_mut().project().inner.poll_next(cx) {
Poll::Ready(Some(Ok(chunk))) => {
// Go around the loop in case the chunk is empty.
*self.as_mut().project().chunk = Some(chunk);
}
Poll::Ready(Some(Err(err))) => return Poll::Ready(Err(err.into())),
Poll::Ready(None) => return Poll::Ready(Ok(&[])),
Poll::Pending => return Poll::Pending,
}
}
}
}
fn consume(self: Pin<&mut Self>, amt: usize) {
if amt > 0 {
self.project()
.chunk
.as_mut()
.expect("No chunk present")
.advance(amt);
}
}
}
|
