actix-ws: take the encoded buffer when yielding rather than split it (#435)

* actix-ws: take the encoded buffer when yielding rather than split it

* actix-ws: add memory reduction to changelog

---------

Co-authored-by: Rob Ede <robjtede@icloud.com>

actix-ws/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Take the encoded buffer when yielding bytes in the response stream rather than splitting the buffer, reducing memory use
 - Remove type parameters from `Session::{text, binary}()` methods, replacing with equivalent `impl Trait` parameters.
 - `Session::text()` now receives an `impl Into<ByteString>`, making broadcasting text messages more efficient.
 - Allow sending continuations via `Session::continuation()`

actix-ws/src/fut.rs

@@ -108,7 +108,7 @@ impl Stream for StreamingBody {
         }
 
         if !this.buf.is_empty() {
-            return Poll::Ready(Some(Ok(this.buf.split().freeze())));
+            return Poll::Ready(Some(Ok(std::mem::take(&mut this.buf).freeze())));
         }
 
         Poll::Pending