expand documentation on new messagebody methods

actix-http/CHANGES.md

@@ -18,6 +18,7 @@
 * `Request::take_conn_data()`. [#2491]
 * `Request::take_req_data()`. [#2487]
 * `impl Clone` for `RequestHead`. [#2487]
+* New methods on `MessageBody` trait, `is_complete_body` and `take_complete_body`, both with default implementations, for optimisations on body types that are done in exactly one poll/chunk. [#2497]
 
 ### Changed
 * Rename `body::BoxBody::{from_body => new}`. [#2468]
@@ -45,6 +46,7 @@
 [#2487]: https://github.com/actix/actix-web/pull/2487
 [#2488]: https://github.com/actix/actix-web/pull/2488
 [#2491]: https://github.com/actix/actix-web/pull/2491
+[#2497]: https://github.com/actix/actix-web/pull/2497
 
 
 ## 3.0.0-beta.14 - 2021-11-30

actix-http/src/body/boxed.rs

@@ -53,14 +53,10 @@ impl MessageBody for BoxBody {
     }
 
     fn is_complete_body(&self) -> bool {
-        let a = self.0.is_complete_body();
+        self.0.is_complete_body()
-        eprintln!("BoxBody is complete?: {}", a);
-        a
     }
 
     fn take_complete_body(&mut self) -> Bytes {
-        eprintln!("taking box body contents");
-
         debug_assert!(
             self.is_complete_body(),
             "boxed type does not allow taking complete body; caller should make sure to \

actix-http/src/body/message_body.rs

@@ -25,18 +25,52 @@ pub trait MessageBody {
     fn size(&self) -> BodySize;
 
     /// Attempt to pull out the next chunk of body bytes.
+    // TODO: expand documentation
     fn poll_next(
         self: Pin<&mut Self>,
         cx: &mut Context<'_>,
     ) -> Poll<Option<Result<Bytes, Self::Error>>>;
 
+    /// Returns true if entire body bytes chunk is obtainable in one call to `poll_next`.
+    ///
+    /// This method's implementation should agree with [`take_complete_body`] and should always be
+    /// checked before taking the body.
+    ///
+    /// The default implementation returns `false.
+    ///
+    /// [`take_complete_body`]: MessageBody::take_complete_body
     fn is_complete_body(&self) -> bool {
         false
     }
 
+    /// Returns the complete chunk of body bytes.
+    ///
+    /// Implementors of this method should note the following:
+    /// - It is acceptable to skip the omit checks of [`is_complete_body`]. The responsibility of
+    ///   performing this check is delegated to the caller.
+    /// - If the result of [`is_complete_body`] is conditional, that condition should be given
+    ///   equivalent attention here.
+    /// - A second call call to [`take_complete_body`] should return an empty `Bytes` or panic.
+    /// - A call to [`poll_next`] after calling [`take_complete_body`] should return `None` unless
+    ///   the chunk is guaranteed to be empty.
+    ///
+    /// # Panics
+    /// With a correct implementation, panics if called without first checking [`is_complete_body`].
+    ///
+    /// [`is_complete_body`]: MessageBody::is_complete_body
+    /// [`take_complete_body`]: MessageBody::take_complete_body
+    /// [`poll_next`]: MessageBody::poll_next
     fn take_complete_body(&mut self) -> Bytes {
+        assert!(
+            self.is_complete_body(),
+            "type ({}) allows taking complete body but did not provide an implementation \
+            of `take_complete_body`",
+            std::any::type_name::<Self>()
+        );
+
         unimplemented!(
-            "type ({}) allows taking complete body but did not provide an implementation",
+            "type ({}) does not allow taking complete body; caller should make sure to \
+            check `is_complete_body` first",
             std::any::type_name::<Self>()
         );
     }
@@ -86,10 +120,12 @@ mod foreign_impls {
             Poll::Ready(None)
         }
 
+        #[inline]
         fn is_complete_body(&self) -> bool {
             true
         }
 
+        #[inline]
         fn take_complete_body(&mut self) -> Bytes {
             Bytes::new()
         }
@@ -114,10 +150,12 @@ mod foreign_impls {
             Pin::new(self.get_mut().as_mut()).poll_next(cx)
         }
 
+        #[inline]
         fn is_complete_body(&self) -> bool {
             self.as_ref().is_complete_body()
         }
 
+        #[inline]
         fn take_complete_body(&mut self) -> Bytes {
             self.as_mut().take_complete_body()
         }
@@ -142,10 +180,12 @@ mod foreign_impls {
             self.as_mut().poll_next(cx)
         }
 
+        #[inline]
         fn is_complete_body(&self) -> bool {
             self.as_ref().is_complete_body()
         }
 
+        #[inline]
         fn take_complete_body(&mut self) -> Bytes {
             debug_assert!(
                 self.is_complete_body(),

actix-http/src/encoding/encoder.rs

@@ -65,24 +65,16 @@ impl<B: MessageBody> Encoder<B> {
             return Self::none();
         }
 
-        eprintln!("body type: {}", std::any::type_name::<B>());
-
         let body = if body.is_complete_body() {
-            eprintln!("reducing allocation");
             let body = body.take_complete_body();
             EncoderBody::Full { body }
         } else {
-            eprintln!("using stream type");
             EncoderBody::Stream { body }
         };
 
         if can_encode {
-            eprintln!("I CAN ENCODE WOO");
-
             // Modify response body only if encoder is set
             if let Some(enc) = ContentEncoder::encoder(encoding) {
-                eprintln!("AND i have an encoder - lucky day");
-
                 update_head(encoding, head);
 
                 return Encoder {
@@ -92,12 +84,8 @@ impl<B: MessageBody> Encoder<B> {
                     eof: false,
                 };
             }
-
-            eprintln!("but i DONT have an encoder :(");
         }
 
-        eprintln!("rip, no compression for you");
-
         Encoder {
             body,
             encoder: None,