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use std::pin::Pin;
use std::task::{Context, Poll};
use std::{fmt, io};
use futures::stream::Stream;
use pin_project_lite::pin_project;
use tokio::io::{AsyncRead, ReadBuf};
use crate::request::Request;
use crate::response::stream::One;
use crate::response::{self, Responder, Response};
pin_project! {
/// An async reader that reads from a stream of async readers.
///
/// A `ReaderStream` can be constructed from any [`Stream`] of items of type
/// `T` where `T: AsyncRead`, or from a single `AsyncRead` type using
/// [`ReaderStream::one()`]. The `AsyncRead` implementation of
/// `ReaderStream` progresses the stream forward, returning the contents of
/// the inner readers. Thus, a `ReaderStream` can be thought of as a
/// _flattening_ of async readers.
///
/// `ReaderStream` is designed to be used as a building-block for
/// stream-based responders by acting as the `streamed_body` of a
/// `Response`, though it may also be used as a responder itself.
///
/// [`Stream`]: https://docs.rs/futures/0.3/futures/stream/trait.Stream.html
///
/// ```rust
/// use std::io::Cursor;
///
/// use rkt::{Request, Response};
/// use rkt::futures::stream::{Stream, StreamExt};
/// use rkt::response::{self, Responder, stream::ReaderStream};
/// use rkt::http::ContentType;
///
/// struct MyStream<S>(S);
///
/// impl<'r, S: Stream<Item = String>> Responder<'r, 'r> for MyStream<S>
/// where S: Send + 'r
/// {
/// fn respond_to(self, _: &'r Request<'_>) -> response::Result<'r> {
/// Response::build()
/// .header(ContentType::Text)
/// .streamed_body(ReaderStream::from(self.0.map(Cursor::new)))
/// .ok()
/// }
/// }
/// ```
///
/// # Responder
///
/// `ReaderStream` is a (potentially infinite) responder. No `Content-Type`
/// is set. The body is [unsized](crate::response::Body#unsized), and values
/// are sent as soon as they are yielded by the internal stream.
///
/// # Example
///
/// ```rust
/// # use rkt::*;
/// use rkt::response::stream::ReaderStream;
/// use rkt::futures::stream::{repeat, StreamExt};
/// use rkt::tokio::time::{self, Duration};
/// use rkt::tokio::fs::File;
///
/// // Stream the contents of `safe/path` followed by `another/safe/path`.
/// #[get("/reader/stream")]
/// fn stream() -> ReaderStream![File] {
/// ReaderStream! {
/// let paths = &["safe/path", "another/safe/path"];
/// for path in paths {
/// if let Ok(file) = File::open(path).await {
/// yield file;
/// }
/// }
/// }
/// }
///
/// // Stream the contents of the file `safe/path`. This is identical to
/// // returning `File` directly; Rocket responders stream and never buffer.
/// #[get("/reader/stream/one")]
/// async fn stream_one() -> std::io::Result<ReaderStream![File]> {
/// let file = File::open("safe/path").await?;
/// Ok(ReaderStream::one(file))
/// }
/// ```
///
/// The syntax of [`ReaderStream!`] as an expression is identical to that of
/// [`stream!`](crate::response::stream::stream).
pub struct ReaderStream<S: Stream> {
#[pin]
stream: S,
#[pin]
state: State<S::Item>,
}
}
pin_project! {
#[project = StateProjection]
#[derive(Debug)]
enum State<R> {
Pending,
Reading { #[pin] reader: R },
Done,
}
}
impl<R: Unpin> ReaderStream<One<R>> {
/// Create a `ReaderStream` that yields exactly one reader, streaming the
/// contents of the reader itself.
///
/// # Example
///
/// Stream the bytes from a remote TCP connection:
///
/// ```rust
/// # use rkt::*;
/// use std::io;
/// use std::net::SocketAddr;
///
/// use rkt::tokio::net::TcpStream;
/// use rkt::response::stream::ReaderStream;
///
/// #[get("/stream")]
/// async fn stream() -> io::Result<ReaderStream![TcpStream]> {
/// let addr = SocketAddr::from(([127, 0, 0, 1], 9999));
/// let stream = TcpStream::connect(addr).await?;
/// Ok(ReaderStream::one(stream))
/// }
/// ```
pub fn one(reader: R) -> Self {
ReaderStream::from(One::from(reader))
}
}
impl<S: Stream> From<S> for ReaderStream<S> {
fn from(stream: S) -> Self {
ReaderStream {
stream,
state: State::Pending,
}
}
}
impl<'r, S: Stream> Responder<'r, 'r> for ReaderStream<S>
where
S: Send + 'r,
S::Item: AsyncRead + Send,
{
fn respond_to(self, _: &'r Request<'_>) -> response::Result<'r> {
Response::build().streamed_body(self).ok()
}
}
impl<S: Stream> AsyncRead for ReaderStream<S>
where
S::Item: AsyncRead + Send,
{
fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>> {
let mut me = self.project();
loop {
match me.state.as_mut().project() {
StateProjection::Pending => match me.stream.as_mut().poll_next(cx) {
Poll::Pending => return Poll::Pending,
Poll::Ready(None) => me.state.set(State::Done),
Poll::Ready(Some(reader)) => me.state.set(State::Reading { reader }),
},
StateProjection::Reading { reader } => {
let init = buf.filled().len();
match reader.poll_read(cx, buf) {
Poll::Ready(Ok(())) if buf.filled().len() == init => {
me.state.set(State::Pending);
}
Poll::Ready(Ok(())) => return Poll::Ready(Ok(())),
Poll::Ready(Err(e)) => return Poll::Ready(Err(e)),
Poll::Pending => return Poll::Pending,
}
}
StateProjection::Done => return Poll::Ready(Ok(())),
}
}
}
}
impl<S: Stream + fmt::Debug> fmt::Debug for ReaderStream<S>
where
S::Item: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ReaderStream")
.field("stream", &self.stream)
.field("state", &self.state)
.finish()
}
}
crate::export! {
/// Type and stream expression macro for [`struct@ReaderStream`].
///
/// See [`stream!`](crate::response::stream::stream) for the syntax
/// supported by this macro.
///
/// See [`struct@ReaderStream`] and the [module level
/// docs](crate::response::stream#typed-streams) for usage details.
macro_rules! ReaderStream {
($($s:tt)*) => ($crate::_typed_stream!(ReaderStream, $($s)*));
}
}