feat(body): add body::aggregate and body::to_bytes functions

Adds utility functions to `hyper::body` to help asynchronously
collecting all the buffers of some `HttpBody` into one.

- `aggregate` will collect all into an `impl Buf` without copying the
  contents. This is ideal if you don't need a contiguous buffer.
- `to_bytes` will copy all the data into a single contiguous `Bytes`
  buffer.

Cargo.toml

@@ -98,7 +98,7 @@ required-features = ["runtime"]
 [[example]]
 name = "client_json"
 path = "examples/client_json.rs"
-required-features = ["runtime", "stream"]
+required-features = ["runtime"]
 
 [[example]]
 name = "echo"
@@ -162,6 +162,11 @@ path = "examples/web_api.rs"
 required-features = ["runtime", "stream"]
 
 
+[[bench]]
+name = "body"
+path = "benches/body.rs"
+required-features = ["runtime", "stream"]
+
 [[bench]]
 name = "connect"
 path = "benches/connect.rs"

benches/body.rs

@@ -0,0 +1,89 @@
+#![feature(test)]
+#![deny(warnings)]
+
+extern crate test;
+
+use bytes::Buf;
+use futures_util::stream;
+use futures_util::StreamExt;
+use hyper::body::Body;
+
+macro_rules! bench_stream {
+    ($bencher:ident, bytes: $bytes:expr, count: $count:expr, $total_ident:ident, $body_pat:pat, $block:expr) => {{
+        let mut rt = tokio::runtime::Builder::new()
+            .basic_scheduler()
+            .build()
+            .expect("rt build");
+
+        let $total_ident: usize = $bytes * $count;
+        $bencher.bytes = $total_ident as u64;
+        let __s: &'static [&'static [u8]] = &[&[b'x'; $bytes] as &[u8]; $count] as _;
+
+        $bencher.iter(|| {
+            rt.block_on(async {
+                let $body_pat = Body::wrap_stream(
+                    stream::iter(__s.iter()).map(|&s| Ok::<_, std::convert::Infallible>(s)),
+                );
+                $block;
+            });
+        });
+    }};
+}
+
+macro_rules! benches {
+    ($($name:ident, $bytes:expr, $count:expr;)+) => (
+        mod aggregate {
+            use super::*;
+
+            $(
+            #[bench]
+            fn $name(b: &mut test::Bencher) {
+                bench_stream!(b, bytes: $bytes, count: $count, total, body, {
+                    let buf = hyper::body::aggregate(body).await.unwrap();
+                    assert_eq!(buf.remaining(), total);
+                });
+            }
+            )+
+        }
+
+        mod manual_into_vec {
+            use super::*;
+
+            $(
+            #[bench]
+            fn $name(b: &mut test::Bencher) {
+                bench_stream!(b, bytes: $bytes, count: $count, total, mut body, {
+                    let mut vec = Vec::new();
+                    while let Some(chunk) = body.next().await {
+                        vec.extend_from_slice(&chunk.unwrap());
+                    }
+                    assert_eq!(vec.len(), total);
+                });
+            }
+            )+
+        }
+
+        mod to_bytes {
+            use super::*;
+
+            $(
+            #[bench]
+            fn $name(b: &mut test::Bencher) {
+                bench_stream!(b, bytes: $bytes, count: $count, total, body, {
+                    let bytes = hyper::body::to_bytes(body).await.unwrap();
+                    assert_eq!(bytes.len(), total);
+                });
+            }
+            )+
+        }
+    )
+}
+
+// ===== Actual Benchmarks =====
+
+benches! {
+    bytes_1_000_count_2, 1_000, 2;
+    bytes_1_000_count_10, 1_000, 10;
+    bytes_10_000_count_1, 10_000, 1;
+    bytes_10_000_count_10, 10_000, 10;
+}

examples/client.rs

@@ -40,6 +40,8 @@ async fn fetch_url(url: hyper::Uri) -> Result<()> {
     println!("Response: {}", res.status());
     println!("Headers: {:#?}\n", res.headers());
 
+    // Stream the body, writing each chunk to stdout as we get it
+    // (instead of buffering and printing at the end).
     while let Some(next) = res.body_mut().data().await {
         let chunk = next?;
         io::stdout().write_all(&chunk).await?;

examples/client_json.rs

@@ -4,7 +4,7 @@
 #[macro_use]
 extern crate serde_derive;
 
-use futures_util::StreamExt;
+use bytes::buf::BufExt as _;
 use hyper::Client;
 
 // A simple type alias so as to DRY.
@@ -27,14 +27,13 @@ async fn fetch_json(url: hyper::Uri) -> Result<Vec<User>> {
     let client = Client::new();
 
     // Fetch the url...
-    let mut res = client.get(url).await?;
-    // asynchronously concatenate chunks of the body
-    let mut body = Vec::new();
-    while let Some(chunk) = res.body_mut().next().await {
-        body.extend_from_slice(&chunk?);
-    }
+    let res = client.get(url).await?;
+
+    // asynchronously aggregate the chunks of the body
+    let body = hyper::body::aggregate(res.into_body()).await?;
+
     // try to parse as json with serde_json
-    let users = serde_json::from_slice(&body)?;
+    let users = serde_json::from_reader(body.reader())?;
 
     Ok(users)
 }

examples/echo.rs

@@ -1,12 +1,12 @@
-//#![deny(warnings)]
+#![deny(warnings)]
 
-use futures_util::{StreamExt, TryStreamExt};
+use futures_util::TryStreamExt;
 use hyper::service::{make_service_fn, service_fn};
 use hyper::{Body, Method, Request, Response, Server, StatusCode};
 
 /// This is our service handler. It receives a Request, routes on its
 /// path, and returns a Future of a Response.
-async fn echo(mut req: Request<Body>) -> Result<Response<Body>, hyper::Error> {
+async fn echo(req: Request<Body>) -> Result<Response<Body>, hyper::Error> {
     match (req.method(), req.uri().path()) {
         // Serve some instructions at /
         (&Method::GET, "/") => Ok(Response::new(Body::from(
@@ -34,10 +34,7 @@ async fn echo(mut req: Request<Body>) -> Result<Response<Body>, hyper::Error> {
         // So here we do `.await` on the future, waiting on concatenating the full body,
         // then afterwards the content can be reversed. Only then can we return a `Response`.
         (&Method::POST, "/echo/reversed") => {
-            let mut whole_body = Vec::new();
-            while let Some(chunk) = req.body_mut().next().await {
-                whole_body.extend_from_slice(&chunk?);
-            }
+            let whole_body = hyper::body::to_bytes(req.into_body()).await?;
 
             let reversed_body = whole_body.iter().rev().cloned().collect::<Vec<u8>>();
             Ok(Response::new(Body::from(reversed_body)))

examples/params.rs

@@ -4,7 +4,6 @@
 use hyper::service::{make_service_fn, service_fn};
 use hyper::{Body, Method, Request, Response, Server, StatusCode};
 
-use futures_util::StreamExt;
 use std::collections::HashMap;
 use url::form_urlencoded;
 
@@ -13,15 +12,12 @@ static MISSING: &[u8] = b"Missing field";
 static NOTNUMERIC: &[u8] = b"Number field is not numeric";
 
 // Using service_fn, we can turn this function into a `Service`.
-async fn param_example(mut req: Request<Body>) -> Result<Response<Body>, hyper::Error> {
+async fn param_example(req: Request<Body>) -> Result<Response<Body>, hyper::Error> {
     match (req.method(), req.uri().path()) {
         (&Method::GET, "/") | (&Method::GET, "/post") => Ok(Response::new(INDEX.into())),
         (&Method::POST, "/post") => {
             // Concatenate the body...
-            let mut b = Vec::new();
-            while let Some(chunk) = req.body_mut().next().await {
-                b.extend_from_slice(&chunk?);
-            }
+            let b = hyper::body::to_bytes(req.into_body()).await?;
             // Parse the request body. form_urlencoded::parse
             // always succeeds, but in general parsing may
             // fail (for example, an invalid post of json), so

examples/web_api.rs

@@ -1,6 +1,7 @@
 #![deny(warnings)]
 
-use futures_util::{StreamExt, TryStreamExt};
+use bytes::buf::BufExt;
+use futures_util::{stream, StreamExt};
 use hyper::client::HttpConnector;
 use hyper::service::{make_service_fn, service_fn};
 use hyper::{header, Body, Client, Method, Request, Response, Server, StatusCode};
@@ -24,25 +25,24 @@ async fn client_request_response(client: &Client<HttpConnector>) -> Result<Respo
 
     let web_res = client.request(req).await?;
     // Compare the JSON we sent (before) with what we received (after):
-    let body = Body::wrap_stream(web_res.into_body().map_ok(|b| {
-        format!(
-            "<b>POST request body</b>: {}<br><b>Response</b>: {}",
+    let before = stream::once(async {
+        Ok(format!(
+            "<b>POST request body</b>: {}<br><b>Response</b>: ",
             POST_DATA,
-            std::str::from_utf8(&b).unwrap()
         )
-    }));
+        .into())
+    });
+    let after = web_res.into_body();
+    let body = Body::wrap_stream(before.chain(after));
 
     Ok(Response::new(body))
 }
 
-async fn api_post_response(mut req: Request<Body>) -> Result<Response<Body>> {
-    // Concatenate the body...
-    let mut whole_body = Vec::new();
-    while let Some(chunk) = req.body_mut().next().await {
-        whole_body.extend_from_slice(&chunk?);
-    }
+async fn api_post_response(req: Request<Body>) -> Result<Response<Body>> {
+    // Aggregate the body...
+    let whole_body = hyper::body::aggregate(req.into_body()).await?;
     // Decode as JSON...
-    let mut data: serde_json::Value = serde_json::from_slice(&whole_body)?;
+    let mut data: serde_json::Value = serde_json::from_reader(whole_body.reader())?;
     // Change the JSON...
     data["test"] = serde_json::Value::from("test_value");
     // And respond with the new JSON.

src/body/aggregate.rs

@@ -0,0 +1,25 @@
+use bytes::Buf;
+
+use super::HttpBody;
+use crate::common::buf::BufList;
+
+/// Aggregate the data buffers from a body asynchronously.
+///
+/// The returned `impl Buf` groups the `Buf`s from the `HttpBody` without
+/// copying them. This is ideal if you don't require a contiguous buffer.
+pub async fn aggregate<T>(body: T) -> Result<impl Buf, T::Error>
+where
+    T: HttpBody,
+{
+    let mut bufs = BufList::new();
+
+    futures_util::pin_mut!(body);
+    while let Some(buf) = body.data().await {
+        let buf = buf?;
+        if buf.has_remaining() {
+            bufs.push(buf);
+        }
+    }
+
+    Ok(bufs)
+}

src/body/mod.rs

@@ -18,11 +18,16 @@
 pub use bytes::{Buf, Bytes};
 pub use http_body::Body as HttpBody;
 
+pub use self::aggregate::aggregate;
 pub use self::body::{Body, Sender};
+pub use self::to_bytes::to_bytes;
+
 pub(crate) use self::payload::Payload;
 
+mod aggregate;
 mod body;
 mod payload;
+mod to_bytes;
 
 /// An optimization to try to take a full body if immediately available.
 ///

src/body/to_bytes.rs

@@ -0,0 +1,36 @@
+use bytes::{Buf, BufMut, Bytes};
+
+use super::HttpBody;
+
+/// dox
+pub async fn to_bytes<T>(body: T) -> Result<Bytes, T::Error>
+where
+    T: HttpBody,
+{
+    futures_util::pin_mut!(body);
+
+    // If there's only 1 chunk, we can just return Buf::to_bytes()
+    let mut first = if let Some(buf) = body.data().await {
+        buf?
+    } else {
+        return Ok(Bytes::new());
+    };
+
+    let second = if let Some(buf) = body.data().await {
+        buf?
+    } else {
+        return Ok(first.to_bytes());
+    };
+
+    // With more than 1 buf, we gotta flatten into a Vec first.
+    let cap = first.remaining() + second.remaining() + body.size_hint().lower() as usize;
+    let mut vec = Vec::with_capacity(cap);
+    vec.put(first);
+    vec.put(second);
+
+    while let Some(buf) = body.data().await {
+        vec.put(buf?);
+    }
+
+    Ok(vec.into())
+}