refactor(body): move channel based incoming body implementation to ChanBody type

Author: tottoto

src/body/incoming/channel.rs

@@ -0,0 +1,182 @@
+use std::fmt;
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use bytes::Bytes;
+use futures_channel::{mpsc, oneshot};
+use futures_util::ready;
+use futures_util::{stream::FusedStream, Stream}; // for mpsc::Receiver
+use http::HeaderMap;
+use http_body::{Frame, SizeHint};
+
+use crate::body::DecodedLength;
+use crate::common::watch;
+
+type BodySender = mpsc::Sender<Result<Bytes, crate::Error>>;
+type TrailersSender = oneshot::Sender<HeaderMap>;
+
+const WANT_PENDING: usize = 1;
+const WANT_READY: usize = 2;
+
+pub(super) struct ChanBody {
+    content_length: DecodedLength,
+    want_tx: watch::Sender,
+    data_rx: mpsc::Receiver<Result<Bytes, crate::Error>>,
+    trailers_rx: oneshot::Receiver<HeaderMap>,
+}
+
+impl ChanBody {
+    pub(super) fn new(content_length: DecodedLength, wanter: bool) -> (Sender, Self) {
+        let (data_tx, data_rx) = mpsc::channel(0);
+        let (trailers_tx, trailers_rx) = oneshot::channel();
+
+        // If wanter is true, `Sender::poll_ready()` won't becoming ready
+        // until the `Body` has been polled for data once.
+        let want = if wanter { WANT_PENDING } else { WANT_READY };
+
+        let (want_tx, want_rx) = watch::channel(want);
+
+        let tx = Sender {
+            want_rx,
+            data_tx,
+            trailers_tx: Some(trailers_tx),
+        };
+        let rx = Self {
+            content_length,
+            want_tx,
+            data_rx,
+            trailers_rx,
+        };
+
+        (tx, rx)
+    }
+
+    pub(super) fn poll_frame(
+        &mut self,
+        cx: &mut Context<'_>,
+    ) -> Poll<Option<Result<Frame<Bytes>, crate::Error>>> {
+        let Self {
+            content_length: ref mut len,
+            ref mut data_rx,
+            ref mut want_tx,
+            ref mut trailers_rx,
+        } = self;
+
+        want_tx.send(WANT_READY);
+
+        if !data_rx.is_terminated() {
+            if let Some(chunk) = ready!(Pin::new(data_rx).poll_next(cx)?) {
+                len.sub_if(chunk.len() as u64);
+                return Poll::Ready(Some(Ok(Frame::data(chunk))));
+            }
+        }
+
+        // check trailers after data is terminated
+        match ready!(Pin::new(trailers_rx).poll(cx)) {
+            Ok(t) => Poll::Ready(Some(Ok(Frame::trailers(t)))),
+            Err(_) => Poll::Ready(None),
+        }
+    }
+
+    pub(super) fn is_end_stream(&self) -> bool {
+        self.content_length == DecodedLength::ZERO
+    }
+
+    pub(super) fn size_hint(&self) -> SizeHint {
+        super::opt_len(self.content_length)
+    }
+}
+
+/// A sender half created through [`Body::channel()`].
+///
+/// Useful when wanting to stream chunks from another thread.
+///
+/// ## Body Closing
+///
+/// Note that the request body will always be closed normally when the sender is dropped (meaning
+/// that the empty terminating chunk will be sent to the remote). If you desire to close the
+/// connection with an incomplete response (e.g. in the case of an error during asynchronous
+/// processing), call the [`Sender::abort()`] method to abort the body in an abnormal fashion.
+///
+/// [`Body::channel()`]: struct.Body.html#method.channel
+/// [`Sender::abort()`]: struct.Sender.html#method.abort
+#[must_use = "Sender does nothing unless sent on"]
+pub(crate) struct Sender {
+    want_rx: watch::Receiver,
+    data_tx: BodySender,
+    trailers_tx: Option<TrailersSender>,
+}
+
+impl Sender {
+    /// Check to see if this `Sender` can send more data.
+    pub(crate) fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<crate::Result<()>> {
+        // Check if the receiver end has tried polling for the body yet
+        ready!(self.poll_want(cx)?);
+        self.data_tx
+            .poll_ready(cx)
+            .map_err(|_| crate::Error::new_closed())
+    }
+
+    pub(crate) fn poll_want(&mut self, cx: &mut Context<'_>) -> Poll<crate::Result<()>> {
+        match self.want_rx.load(cx) {
+            WANT_READY => Poll::Ready(Ok(())),
+            WANT_PENDING => Poll::Pending,
+            watch::CLOSED => Poll::Ready(Err(crate::Error::new_closed())),
+            unexpected => unreachable!("want_rx value: {}", unexpected),
+        }
+    }
+
+    /// Send trailers on trailers channel.
+    #[allow(unused)]
+    pub(crate) async fn send_trailers(&mut self, trailers: HeaderMap) -> crate::Result<()> {
+        let tx = match self.trailers_tx.take() {
+            Some(tx) => tx,
+            None => return Err(crate::Error::new_closed()),
+        };
+        tx.send(trailers).map_err(|_| crate::Error::new_closed())
+    }
+
+    /// Try to send data on this channel.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err(Bytes)` if the channel could not (currently) accept
+    /// another `Bytes`.
+    ///
+    /// # Note
+    ///
+    /// This is mostly useful for when trying to send from some other thread
+    /// that doesn't have an async context. If in an async context, prefer
+    /// `send_data()` instead.
+    pub(crate) fn try_send_data(&mut self, chunk: Bytes) -> Result<(), Bytes> {
+        self.data_tx
+            .try_send(Ok(chunk))
+            .map_err(|err| err.into_inner().expect("just sent Ok"))
+    }
+
+    pub(crate) fn send_error(&mut self, err: crate::Error) {
+        let _ = self
+            .data_tx
+            // clone so the send works even if buffer is full
+            .clone()
+            .try_send(Err(err));
+    }
+}
+
+impl fmt::Debug for Sender {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        #[derive(Debug)]
+        struct Open;
+        #[derive(Debug)]
+        struct Closed;
+
+        let mut builder = f.debug_tuple("Sender");
+        match self.want_rx.peek() {
+            watch::CLOSED => builder.field(&Closed),
+            _ => builder.field(&Open),
+        };
+
+        builder.finish()
+    }
+}