refactor http protocol selection procedure

examples/basics/Cargo.toml

@@ -8,4 +8,4 @@ workspace = "../.."
 futures = "*"
 env_logger = "0.4"
 actix = "0.4"
-actix-web = { git = "https://github.com/actix/actix-web" }
+actix-web = { path = "../../" }

src/server/channel.rs

@@ -2,29 +2,43 @@ use std::{ptr, mem, time, io};
 use std::rc::Rc;
 use std::net::{SocketAddr, Shutdown};
 
-use bytes::{Bytes, Buf, BufMut};
+use bytes::{Bytes, BytesMut, Buf, BufMut};
 use futures::{Future, Poll, Async};
 use tokio_io::{AsyncRead, AsyncWrite};
 use tokio_core::net::TcpStream;
 
-use super::{h1, h2, HttpHandler, IoStream};
+use super::{h1, h2, utils, HttpHandler, IoStream};
 use super::settings::WorkerSettings;
 
+const HTTP2_PREFACE: [u8; 14] = *b"PRI * HTTP/2.0";
+
+
 enum HttpProtocol<T: IoStream, H: 'static> {
     H1(h1::Http1<T, H>),
     H2(h2::Http2<T, H>),
+    Unknown(Rc<WorkerSettings<H>>, Option<SocketAddr>, T, BytesMut),
+}
+impl<T: IoStream, H: 'static> HttpProtocol<T, H> {
+    fn is_unknown(&self) -> bool {
+        match *self {
+            HttpProtocol::Unknown(_, _, _, _) => true,
+            _ => false
+        }
+    }
+}
+
+enum ProtocolKind {
+    Http1,
+    Http2,
 }
 
 #[doc(hidden)]
-pub struct HttpChannel<T, H>
+pub struct HttpChannel<T, H> where T: IoStream, H: HttpHandler + 'static {
-    where T: IoStream, H: HttpHandler + 'static
-{
     proto: Option<HttpProtocol<T, H>>,
     node: Option<Node<HttpChannel<T, H>>>,
 }
 
-impl<T, H> HttpChannel<T, H>
+impl<T, H> HttpChannel<T, H> where T: IoStream, H: HttpHandler + 'static
-    where T: IoStream, H: HttpHandler + 'static
 {
     pub(crate) fn new(settings: Rc<WorkerSettings<H>>,
                       io: T, peer: Option<SocketAddr>, http2: bool) -> HttpChannel<T, H>
@@ -38,7 +52,8 @@ impl<T, H> HttpChannel<T, H>
         } else {
             HttpChannel {
                 node: None,
-                proto: Some(HttpProtocol::H1(h1::Http1::new(settings, io, peer))) }
+                proto: Some(HttpProtocol::Unknown(
+                    settings, peer, io, BytesMut::with_capacity(4096))) }
         }
     }
 
@@ -52,7 +67,7 @@ impl<T, H> HttpChannel<T, H>
             Some(HttpProtocol::H2(ref mut h2)) => {
                 h2.shutdown()
             }
-            _ => unreachable!(),
+            _ => (),
         }
     }
 }
@@ -64,28 +79,25 @@ impl<T, H> Future for HttpChannel<T, H>
     type Error = ();
 
     fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
-        if self.node.is_none() {
+        if !self.proto.as_ref().map(|p| p.is_unknown()).unwrap_or(false) && self.node.is_none() {
             self.node = Some(Node::new(self));
             match self.proto {
-                Some(HttpProtocol::H1(ref mut h1)) => {
+                Some(HttpProtocol::H1(ref mut h1)) =>
-                    h1.settings().head().insert(self.node.as_ref().unwrap());
+                    h1.settings().head().insert(self.node.as_ref().unwrap()),
-                }
+                Some(HttpProtocol::H2(ref mut h2)) =>
-                Some(HttpProtocol::H2(ref mut h2)) => {
+                    h2.settings().head().insert(self.node.as_ref().unwrap()),
-                    h2.settings().head().insert(self.node.as_ref().unwrap());
+                _ => (),
-                }
-                _ => unreachable!(),
             }
         }
 
-        match self.proto {
+        let kind = match self.proto {
             Some(HttpProtocol::H1(ref mut h1)) => {
                 match h1.poll() {
-                    Ok(Async::Ready(h1::Http1Result::Done)) => {
+                    Ok(Async::Ready(())) => {
                         h1.settings().remove_channel();
                         self.node.as_ref().unwrap().remove();
                         return Ok(Async::Ready(()))
                     }
-                    Ok(Async::Ready(h1::Http1Result::Switch)) => (),
                     Ok(Async::NotReady) =>
                         return Ok(Async::NotReady),
                     Err(_) => {
@@ -94,7 +106,7 @@ impl<T, H> Future for HttpChannel<T, H>
                         return Err(())
                     }
                 }
-            }
+            },
             Some(HttpProtocol::H2(ref mut h2)) => {
                 let result = h2.poll();
                 match result {
@@ -105,18 +117,49 @@ impl<T, H> Future for HttpChannel<T, H>
                     _ => (),
                 }
                 return result
+            },
+            Some(HttpProtocol::Unknown(_, _, ref mut io, ref mut buf)) => {
+                match utils::read_from_io(io, buf) {
+                    Ok(Async::Ready(0)) => {
+                        debug!("Ignored premature client disconnection");
+                        return Err(())
+                    },
+                    Err(err) => {
+                        debug!("Ignored premature client disconnection {}", err);
+                        return Err(())
                     }
+                    _ => (),
+                }
+
+                if buf.len() >= 14 {
+                    if buf[..14] == HTTP2_PREFACE[..] {
+                        ProtocolKind::Http2
+                    } else {
+                        ProtocolKind::Http1
+                    }
+                } else {
+                    return Ok(Async::NotReady);
+                }
+            },
             None => unreachable!(),
-        }
+        };
 
         // upgrade to h2
         let proto = self.proto.take().unwrap();
         match proto {
-            HttpProtocol::H1(h1) => {
+            HttpProtocol::Unknown(settings, addr, io, buf) => {
-                let (h, io, addr, buf) = h1.into_inner();
+                match kind {
+                    ProtocolKind::Http1 => {
                         self.proto = Some(
-                    HttpProtocol::H2(h2::Http2::new(h, io, addr, buf)));
+                            HttpProtocol::H1(h1::Http1::new(settings, io, addr, buf)));
                         self.poll()
+                    },
+                    ProtocolKind::Http2 => {
+                        self.proto = Some(
+                            HttpProtocol::H2(h2::Http2::new(settings, io, addr, buf.freeze())));
+                        self.poll()
+                    },
+                }
             }
             _ => unreachable!()
         }

src/server/h1.rs

@@ -8,7 +8,7 @@ use actix::Arbiter;
 use httparse;
 use http::{Uri, Method, Version, HttpTryFrom, HeaderMap};
 use http::header::{self, HeaderName, HeaderValue};
-use bytes::{Bytes, BytesMut, BufMut};
+use bytes::{Bytes, BytesMut};
 use futures::{Future, Poll, Async};
 use tokio_core::reactor::Timeout;
 
@@ -18,24 +18,20 @@ use httprequest::HttpRequest;
 use error::{ParseError, PayloadError, ResponseError};
 use payload::{Payload, PayloadWriter, DEFAULT_BUFFER_SIZE};
 
-use super::Writer;
+use super::{utils, Writer};
 use super::h1writer::H1Writer;
 use super::encoding::PayloadType;
 use super::settings::WorkerSettings;
 use super::{HttpHandler, HttpHandlerTask, IoStream};
 
-const LW_BUFFER_SIZE: usize = 4096;
-const HW_BUFFER_SIZE: usize = 16_384;
 const MAX_BUFFER_SIZE: usize = 131_072;
-const MAX_HEADERS: usize = 100;
+const MAX_HEADERS: usize = 96;
 const MAX_PIPELINED_MESSAGES: usize = 16;
-const HTTP2_PREFACE: [u8; 14] = *b"PRI * HTTP/2.0";
 
 bitflags! {
     struct Flags: u8 {
         const ERROR = 0b0000_0010;
         const KEEPALIVE = 0b0000_0100;
-        const H2 = 0b0000_1000;
     }
 }
 
@@ -47,17 +43,6 @@ bitflags! {
     }
 }
 
-pub(crate) enum Http1Result {
-    Done,
-    Switch,
-}
-
-#[derive(Debug)]
-enum Item {
-    Http1(HttpRequest),
-    Http2,
-}
-
 pub(crate) struct Http1<T: IoStream, H: 'static> {
     flags: Flags,
     settings: Rc<WorkerSettings<H>>,
@@ -77,14 +62,16 @@ struct Entry {
 impl<T, H> Http1<T, H>
     where T: IoStream, H: HttpHandler + 'static
 {
-    pub fn new(h: Rc<WorkerSettings<H>>, stream: T, addr: Option<SocketAddr>) -> Self {
+    pub fn new(h: Rc<WorkerSettings<H>>, stream: T, addr: Option<SocketAddr>, buf: BytesMut)
+               -> Self
+    {
         let bytes = h.get_shared_bytes();
         Http1{ flags: Flags::KEEPALIVE,
                settings: h,
                addr: addr,
                stream: H1Writer::new(stream, bytes),
                reader: Reader::new(),
-               read_buf: BytesMut::new(),
+               read_buf: buf,
                tasks: VecDeque::new(),
                keepalive_timer: None }
     }
@@ -93,10 +80,6 @@ impl<T, H> Http1<T, H>
         self.settings.as_ref()
     }
 
-    pub fn into_inner(self) -> (Rc<WorkerSettings<H>>, T, Option<SocketAddr>, Bytes) {
-        (self.settings, self.stream.into_inner(), self.addr, self.read_buf.freeze())
-    }
-
     pub(crate) fn io(&mut self) -> &mut T {
         self.stream.get_mut()
     }
@@ -115,13 +98,13 @@ impl<T, H> Http1<T, H>
 
     // TODO: refacrtor
     #[cfg_attr(feature = "cargo-clippy", allow(cyclomatic_complexity))]
-    pub fn poll(&mut self) -> Poll<Http1Result, ()> {
+    pub fn poll(&mut self) -> Poll<(), ()> {
         // keep-alive timer
         if self.keepalive_timer.is_some() {
             match self.keepalive_timer.as_mut().unwrap().poll() {
                 Ok(Async::Ready(_)) => {
                     trace!("Keep-alive timeout, close connection");
-                    return Ok(Async::Ready(Http1Result::Done))
+                    return Ok(Async::Ready(()))
                 }
                 Ok(Async::NotReady) => (),
                 Err(_) => unreachable!(),
@@ -209,27 +192,18 @@ impl<T, H> Http1<T, H>
 
             // no keep-alive
             if !self.flags.contains(Flags::KEEPALIVE) && self.tasks.is_empty() {
-                let h2 = self.flags.contains(Flags::H2);
-
                 // check stream state
-                if !self.poll_completed(!h2)? {
+                if !self.poll_completed(true)? {
                     return Ok(Async::NotReady)
                 }
-
+                return Ok(Async::Ready(()))
-                if h2 {
-                    return Ok(Async::Ready(Http1Result::Switch))
-                } else {
-                    return Ok(Async::Ready(Http1Result::Done))
-                }
             }
 
             // read incoming data
-            while !self.flags.contains(Flags::ERROR) && !self.flags.contains(Flags::H2) &&
+            while !self.flags.contains(Flags::ERROR) && self.tasks.len() < MAX_PIPELINED_MESSAGES {
-                self.tasks.len() < MAX_PIPELINED_MESSAGES
-            {
                 match self.reader.parse(self.stream.get_mut(),
                                         &mut self.read_buf, &self.settings) {
-                    Ok(Async::Ready(Item::Http1(mut req))) => {
+                    Ok(Async::Ready(mut req)) => {
                         not_ready = false;
 
                         // set remote addr
@@ -254,9 +228,6 @@ impl<T, H> Http1<T, H>
                             Entry {pipe: pipe.unwrap_or_else(|| Pipeline::error(HTTPNotFound)),
                                    flags: EntryFlags::empty()});
                     }
-                    Ok(Async::Ready(Item::Http2)) => {
-                        self.flags.insert(Flags::H2);
-                    }
                     Err(ReaderError::Disconnect) => {
                         not_ready = false;
                         self.flags.insert(Flags::ERROR);
@@ -309,7 +280,7 @@ impl<T, H> Http1<T, H>
                                         return Ok(Async::NotReady)
                                     }
                                     // keep-alive disable, drop connection
-                                    return Ok(Async::Ready(Http1Result::Done))
+                                    return Ok(Async::Ready(()))
                                 }
                             } else if !self.poll_completed(false)? ||
                                 self.flags.contains(Flags::KEEPALIVE)
@@ -318,7 +289,7 @@ impl<T, H> Http1<T, H>
                                 // if keep-alive unset, rely on operating system
                                 return Ok(Async::NotReady)
                             } else {
-                                return Ok(Async::Ready(Http1Result::Done))
+                                return Ok(Async::Ready(()))
                             }
                         }
                         break
@@ -328,17 +299,12 @@ impl<T, H> Http1<T, H>
 
             // check for parse error
             if self.tasks.is_empty() {
-                let h2 = self.flags.contains(Flags::H2);
-
                 // check stream state
-                if !self.poll_completed(!h2)? {
+                if !self.poll_completed(true)? {
                     return Ok(Async::NotReady)
                 }
-                if h2 {
-                    return Ok(Async::Ready(Http1Result::Switch))
-                }
                 if self.flags.contains(Flags::ERROR) || self.keepalive_timer.is_none() {
-                    return Ok(Async::Ready(Http1Result::Done))
+                    return Ok(Async::Ready(()))
                 }
             }
 
@@ -351,7 +317,6 @@ impl<T, H> Http1<T, H>
 }
 
 struct Reader {
-    h1: bool,
     payload: Option<PayloadInfo>,
 }
 
@@ -373,22 +338,14 @@ enum ReaderError {
     Error(ParseError),
 }
 
-enum Message {
-    Http1(HttpRequest, Option<PayloadInfo>),
-    Http2,
-    NotReady,
-}
-
 impl Reader {
     pub fn new() -> Reader {
         Reader {
-            h1: false,
             payload: None,
         }
     }
 
-    fn decode(&mut self, buf: &mut BytesMut) -> std::result::Result<Decoding, ReaderError>
+    fn decode(&mut self, buf: &mut BytesMut) -> std::result::Result<Decoding, ReaderError> {
-    {
         if let Some(ref mut payload) = self.payload {
             if payload.tx.capacity() > DEFAULT_BUFFER_SIZE {
                 return Ok(Decoding::Paused)
@@ -416,12 +373,12 @@ impl Reader {
     
     pub fn parse<T, H>(&mut self, io: &mut T,
                        buf: &mut BytesMut,
-                       settings: &WorkerSettings<H>) -> Poll<Item, ReaderError>
+                       settings: &WorkerSettings<H>) -> Poll<HttpRequest, ReaderError>
         where T: IoStream
     {
         // read payload
         if self.payload.is_some() {
-            match self.read_from_io(io, buf) {
+            match utils::read_from_io(io, buf) {
                 Ok(Async::Ready(0)) => {
                     if let Some(ref mut payload) = self.payload {
                         payload.tx.set_error(PayloadError::Incomplete);
@@ -446,7 +403,7 @@ impl Reader {
 
         // if buf is empty parse_message will always return NotReady, let's avoid that
         let read = if buf.is_empty() {
-            match self.read_from_io(io, buf) {
+            match utils::read_from_io(io, buf) {
                 Ok(Async::Ready(0)) => {
                     // debug!("Ignored premature client disconnection");
                     return Err(ReaderError::Disconnect);
@@ -464,7 +421,7 @@ impl Reader {
 
         loop {
             match Reader::parse_message(buf, settings).map_err(ReaderError::Error)? {
-                Message::Http1(msg, decoder) => {
+                Async::Ready((msg, decoder)) => {
                     // process payload
                     if let Some(payload) = decoder {
                         self.payload = Some(payload);
@@ -473,22 +430,15 @@ impl Reader {
                             Decoding::Ready => self.payload = None,
                         }
                     }
-                    self.h1 = true;
+                    return Ok(Async::Ready(msg));
-                    return Ok(Async::Ready(Item::Http1(msg)));
                 },
-                Message::Http2 => {
+                Async::NotReady => {
-                    if self.h1 {
-                        return Err(ReaderError::Error(ParseError::Version))
-                    }
-                    return Ok(Async::Ready(Item::Http2));
-                },
-                Message::NotReady => {
                     if buf.capacity() >= MAX_BUFFER_SIZE {
                         error!("MAX_BUFFER_SIZE unprocessed data reached, closing");
                         return Err(ReaderError::Error(ParseError::TooLarge));
                     }
                     if read {
-                        match self.read_from_io(io, buf) {
+                        match utils::read_from_io(io, buf) {
                             Ok(Async::Ready(0)) => {
                                 debug!("Ignored premature client disconnection");
                                 return Err(ReaderError::Disconnect);
@@ -507,39 +457,8 @@ impl Reader {
         }
     }
 
-    fn read_from_io<T: IoStream>(&mut self, io: &mut T, buf: &mut BytesMut)
-                                 -> Poll<usize, io::Error>
-    {
-        unsafe {
-            if buf.remaining_mut() < LW_BUFFER_SIZE {
-                buf.reserve(HW_BUFFER_SIZE);
-            }
-            match io.read(buf.bytes_mut()) {
-                Ok(n) => {
-                    buf.advance_mut(n);
-                    Ok(Async::Ready(n))
-                },
-                Err(e) => {
-                    if e.kind() == io::ErrorKind::WouldBlock {
-                        Ok(Async::NotReady)
-                    } else {
-                        Err(e)
-                    }
-                }
-            }
-        }
-    }
-
     fn parse_message<H>(buf: &mut BytesMut, settings: &WorkerSettings<H>)
-                        -> Result<Message, ParseError>
+                        -> Poll<(HttpRequest, Option<PayloadInfo>), ParseError> {
-    {
-        if buf.is_empty() {
-            return Ok(Message::NotReady);
-        }
-        if buf.len() >= 14 && buf[..14] == HTTP2_PREFACE[..] {
-            return Ok(Message::Http2)
-        }
-
         // Parse http message
         let msg = {
             let bytes_ptr = buf.as_ref().as_ptr() as usize;
@@ -565,7 +484,7 @@ impl Reader {
                         };
                         (len, method, path, version, req.headers.len())
                     }
-                    httparse::Status::Partial => return Ok(Message::NotReady),
+                    httparse::Status::Partial => return Ok(Async::NotReady),
                 }
             };
 
@@ -625,9 +544,9 @@ impl Reader {
                 decoder: decoder,
             };
             msg.get_mut().payload = Some(payload);
-            Ok(Message::Http1(HttpRequest::from_message(msg), Some(info)))
+            Ok(Async::Ready((HttpRequest::from_message(msg), Some(info))))
         } else {
-            Ok(Message::Http1(HttpRequest::from_message(msg), None))
+            Ok(Async::Ready((HttpRequest::from_message(msg), None)))
         }
     }
 }
@@ -977,7 +896,7 @@ mod tests {
         ($e:expr) => ({
             let settings = WorkerSettings::<HttpApplication>::new(Vec::new(), None);
             match Reader::new().parse($e, &mut BytesMut::new(), &settings) {
-                Ok(Async::Ready(Item::Http1(req))) => req,
+                Ok(Async::Ready(req)) => req,
                 Ok(_) => panic!("Eof during parsing http request"),
                 Err(err) => panic!("Error during parsing http request: {:?}", err),
             }
@@ -987,7 +906,7 @@ mod tests {
     macro_rules! reader_parse_ready {
         ($e:expr) => (
             match $e {
-                Ok(Async::Ready(Item::Http1(req))) => req,
+                Ok(Async::Ready(req)) => req,
                 Ok(_) => panic!("Eof during parsing http request"),
                 Err(err) => panic!("Error during parsing http request: {:?}", err),
             }
@@ -1019,7 +938,7 @@ mod tests {
 
         let mut reader = Reader::new();
         match reader.parse(&mut buf, &mut readbuf, &settings) {
-            Ok(Async::Ready(Item::Http1(req))) => {
+            Ok(Async::Ready(req)) => {
                 assert_eq!(req.version(), Version::HTTP_11);
                 assert_eq!(*req.method(), Method::GET);
                 assert_eq!(req.path(), "/test");
@@ -1042,7 +961,7 @@ mod tests {
 
         buf.feed_data(".1\r\n\r\n");
         match reader.parse(&mut buf, &mut readbuf, &settings) {
-            Ok(Async::Ready(Item::Http1(req))) => {
+            Ok(Async::Ready(req)) => {
                 assert_eq!(req.version(), Version::HTTP_11);
                 assert_eq!(*req.method(), Method::PUT);
                 assert_eq!(req.path(), "/test");
@@ -1059,7 +978,7 @@ mod tests {
 
         let mut reader = Reader::new();
         match reader.parse(&mut buf, &mut readbuf, &settings) {
-            Ok(Async::Ready(Item::Http1(req))) => {
+            Ok(Async::Ready(req)) => {
                 assert_eq!(req.version(), Version::HTTP_10);
                 assert_eq!(*req.method(), Method::POST);
                 assert_eq!(req.path(), "/test2");
@@ -1076,7 +995,7 @@ mod tests {
 
         let mut reader = Reader::new();
         match reader.parse(&mut buf, &mut readbuf, &settings) {
-            Ok(Async::Ready(Item::Http1(mut req))) => {
+            Ok(Async::Ready(mut req)) => {
                 assert_eq!(req.version(), Version::HTTP_11);
                 assert_eq!(*req.method(), Method::GET);
                 assert_eq!(req.path(), "/test");
@@ -1095,7 +1014,7 @@ mod tests {
 
         let mut reader = Reader::new();
         match reader.parse(&mut buf, &mut readbuf, &settings) {
-            Ok(Async::Ready(Item::Http1(mut req))) => {
+            Ok(Async::Ready(mut req)) => {
                 assert_eq!(req.version(), Version::HTTP_11);
                 assert_eq!(*req.method(), Method::GET);
                 assert_eq!(req.path(), "/test");
@@ -1116,7 +1035,7 @@ mod tests {
 
         buf.feed_data("\r\n");
         match reader.parse(&mut buf, &mut readbuf, &settings) {
-            Ok(Async::Ready(Item::Http1(req))) => {
+            Ok(Async::Ready(req)) => {
                 assert_eq!(req.version(), Version::HTTP_11);
                 assert_eq!(*req.method(), Method::GET);
                 assert_eq!(req.path(), "/test");
@@ -1142,7 +1061,7 @@ mod tests {
 
         buf.feed_data("t: value\r\n\r\n");
         match reader.parse(&mut buf, &mut readbuf, &settings) {
-            Ok(Async::Ready(Item::Http1(req))) => {
+            Ok(Async::Ready(req)) => {
                 assert_eq!(req.version(), Version::HTTP_11);
                 assert_eq!(*req.method(), Method::GET);
                 assert_eq!(req.path(), "/test");
@@ -1163,7 +1082,7 @@ mod tests {
 
         let mut reader = Reader::new();
         match reader.parse(&mut buf, &mut readbuf, &settings) {
-            Ok(Async::Ready(Item::Http1(req))) => {
+            Ok(Async::Ready(req)) => {
                 let val: Vec<_> = req.headers().get_all("Set-Cookie")
                     .iter().map(|v| v.to_str().unwrap().to_owned()).collect();
                 assert_eq!(val[0], "c1=cookie1");
@@ -1512,17 +1431,4 @@ mod tests {
             Err(err) => panic!("{:?}", err),
         }
     }*/
-
-    #[test]
-    fn test_http2_prefix() {
-        let mut buf = Buffer::new("PRI * HTTP/2.0\r\n\r\n");
-        let mut readbuf = BytesMut::new();
-        let settings = WorkerSettings::<HttpApplication>::new(Vec::new(), None);
-
-        let mut reader = Reader::new();
-        match reader.parse(&mut buf, &mut readbuf, &settings) {
-            Ok(Async::Ready(Item::Http2)) => (),
-            Ok(_) | Err(_) => panic!("Error during parsing http request"),
-        }
-    }
 }

src/server/h1writer.rs

@@ -55,10 +55,6 @@ impl<T: AsyncWrite> H1Writer<T> {
         self.flags = Flags::empty();
     }
 
-    pub fn into_inner(self) -> T {
-        self.stream
-    }
-
     pub fn disconnected(&mut self) {
         self.encoder.get_mut().take();
     }

src/server/mod.rs

@@ -14,6 +14,7 @@ mod h2;
 mod h1writer;
 mod h2writer;
 mod settings;
+mod utils;
 
 pub use self::srv::HttpServer;
 pub use self::settings::ServerSettings;

src/server/utils.rs

@@ -0,0 +1,30 @@
+use std::io;
+use bytes::{BytesMut, BufMut};
+use futures::{Async, Poll};
+
+use super::IoStream;
+
+const LW_BUFFER_SIZE: usize = 4096;
+const HW_BUFFER_SIZE: usize = 16_384;
+
+
+pub fn read_from_io<T: IoStream>(io: &mut T, buf: &mut BytesMut) -> Poll<usize, io::Error> {
+    unsafe {
+        if buf.remaining_mut() < LW_BUFFER_SIZE {
+            buf.reserve(HW_BUFFER_SIZE);
+        }
+        match io.read(buf.bytes_mut()) {
+            Ok(n) => {
+                buf.advance_mut(n);
+                Ok(Async::Ready(n))
+            },
+            Err(e) => {
+                if e.kind() == io::ErrorKind::WouldBlock {
+                    Ok(Async::NotReady)
+                } else {
+                    Err(e)
+                }
+            }
+        }
+    }
+}