feat(server): make Http compatible with TcpServer

This implements `From<Message> for Request` and `Into<Message> for
Response`, allowing an `Http` instance to be used with a `TcpServer`
from tokio-proto.

Closes #1036

BREAKING CHANGE: This makes `Request.remote_addr` an
  `Option<SocketAddr>`, instead of `SocketAddr`.

src/server/mod.rs

@@ -265,20 +265,32 @@ impl<T: Io + 'static, B> Future for __ProtoBindTransport<T, B> {
     }
 }
 
+impl From<Message<__ProtoRequest, http::TokioBody>> for Request {
+    fn from(message: Message<__ProtoRequest, http::TokioBody>) -> Request {
+        let (head, body) = match message {
+            Message::WithoutBody(head) => (head.0, http::Body::empty()),
+            Message::WithBody(head, body) => (head.0, body.into()),
+        };
+        request::new(None, head, body)
+    }
+}
+
+impl<B> Into<Message<__ProtoResponse, B>> for Response<B> {
+    fn into(self) -> Message<__ProtoResponse, B> {
+        let (head, body) = response::split(self);
+        if let Some(body) = body {
+            Message::WithBody(__ProtoResponse(head), body.into())
+        } else {
+            Message::WithoutBody(__ProtoResponse(head))
+        }
+    }
+}
+
 struct HttpService<T> {
     inner: T,
     remote_addr: SocketAddr,
 }
 
-fn map_response_to_message<B>(res: Response<B>) -> Message<__ProtoResponse, B> {
-    let (head, body) = response::split(res);
-    if let Some(body) = body {
-        Message::WithBody(__ProtoResponse(head), body.into())
-    } else {
-        Message::WithoutBody(__ProtoResponse(head))
-    }
-}
-
 type ResponseHead = http::MessageHead<::StatusCode>;
 
 impl<T, B> Service for HttpService<T>
@@ -296,8 +308,8 @@ impl<T, B> Service for HttpService<T>
             Message::WithoutBody(head) => (head.0, http::Body::empty()),
             Message::WithBody(head, body) => (head.0, body.into()),
         };
-        let req = request::new(self.remote_addr, head, body);
-        self.inner.call(req).map(map_response_to_message)
+        let req = request::new(Some(self.remote_addr), head, body);
+        self.inner.call(req).map(Into::into)
     }
 }
 

src/server/request.rs

@@ -18,7 +18,7 @@ pub struct Request {
     uri: Uri,
     version: HttpVersion,
     headers: Headers,
-    remote_addr: SocketAddr,
+    remote_addr: Option<SocketAddr>,
     body: Body,
 }
 
@@ -40,8 +40,11 @@ impl Request {
     pub fn version(&self) -> &HttpVersion { &self.version }
 
     /// The remote socket address of this request
+    ///
+    /// This is an `Option`, because some underlying transports may not have
+    /// a socket address, such as Unix Sockets.
     #[inline]
-    pub fn remote_addr(&self) -> &SocketAddr { &self.remote_addr }
+    pub fn remote_addr(&self) -> Option<&SocketAddr> { self.remote_addr.as_ref() }
 
     /// The target path of this Request.
     #[inline]
@@ -82,9 +85,9 @@ impl fmt::Debug for Request {
     }
 }
 
-pub fn new(addr: SocketAddr, incoming: RequestHead, body: Body) -> Request {
+pub fn new(addr: Option<SocketAddr>, incoming: RequestHead, body: Body) -> Request {
     let MessageHead { version, subject: RequestLine(method, uri), headers } = incoming;
-    debug!("Request::new: addr={}, req=\"{} {} {}\"", addr, method, uri, version);
+    debug!("Request::new: addr={}, req=\"{} {} {}\"", MaybeAddr(&addr), method, uri, version);
     debug!("Request::new: headers={:?}", headers);
 
     Request {
@@ -96,3 +99,15 @@ pub fn new(addr: SocketAddr, incoming: RequestHead, body: Body) -> Request {
         body: body,
     }
 }
+
+struct MaybeAddr<'a>(&'a Option<SocketAddr>);
+
+impl<'a> fmt::Display for MaybeAddr<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self.0 {
+            Some(ref addr) => fmt::Display::fmt(addr, f),
+            None => f.write_str("None"),
+        }
+    }
+}
+