split up http body module

actix-http/src/body/sized_stream.rs

@@ -0,0 +1,59 @@
+use std::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+
+use bytes::Bytes;
+use futures_core::{ready, Stream};
+
+use crate::error::Error;
+
+use super::{BodySize, MessageBody};
+
+/// Known sized streaming response wrapper.
+///
+/// This body implementation should be used if total size of stream is known. Data get sent as is
+/// without using transfer encoding.
+pub struct SizedStream<S: Unpin> {
+    size: u64,
+    stream: S,
+}
+
+impl<S> SizedStream<S>
+where
+    S: Stream<Item = Result<Bytes, Error>> + Unpin,
+{
+    pub fn new(size: u64, stream: S) -> Self {
+        SizedStream { size, stream }
+    }
+}
+
+impl<S> MessageBody for SizedStream<S>
+where
+    S: Stream<Item = Result<Bytes, Error>> + Unpin,
+{
+    fn size(&self) -> BodySize {
+        BodySize::Sized(self.size as u64)
+    }
+
+    /// Attempts to pull out the next value of the underlying [`Stream`].
+    ///
+    /// Empty values are skipped to prevent [`SizedStream`]'s transmission being
+    /// ended on a zero-length chunk, but rather proceed until the underlying
+    /// [`Stream`] ends.
+    fn poll_next(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+    ) -> Poll<Option<Result<Bytes, Error>>> {
+        loop {
+            let stream = &mut self.as_mut().stream;
+
+            let chunk = match ready!(Pin::new(stream).poll_next(cx)) {
+                Some(Ok(ref bytes)) if bytes.is_empty() => continue,
+                val => val,
+            };
+
+            return Poll::Ready(chunk);
+        }
+    }
+}