feat(server): add from_tcp method

Adds the `from_tcp()` method as per
#1602.

fix clippy changes

src/server/mod.rs

@@ -54,18 +54,20 @@ pub mod conn;
 #[cfg(feature = "runtime")] mod tcp;
 
 use std::fmt;
-#[cfg(feature = "runtime")] use std::net::SocketAddr;
+#[cfg(feature = "runtime")] use std::net::{SocketAddr, TcpListener as StdTcpListener};
+
 #[cfg(feature = "runtime")] use std::time::Duration;
 
 use futures::{Future, Stream, Poll};
 use tokio_io::{AsyncRead, AsyncWrite};
+#[cfg(feature = "runtime")] use tokio_reactor;
 
 use body::{Body, Payload};
 use service::{NewService, Service};
 // Renamed `Http` as `Http_` for now so that people upgrading don't see an
 // error that `hyper::server::Http` is private...
 use self::conn::{Http as Http_, SpawnAll};
-#[cfg(feature = "runtime")] use self::tcp::{AddrIncoming};
+#[cfg(feature = "runtime")] use self::tcp::AddrIncoming;
 
 /// A listening HTTP server that accepts connections in both HTTP1 and HTTP2 by default.
 ///
@@ -117,6 +119,16 @@ impl Server<AddrIncoming, ()> {
         AddrIncoming::new(addr, None)
             .map(Server::builder)
     }
+
+    /// Create a new instance from a `std::net::TcpListener` instance.
+    pub fn from_tcp(
+        listener: StdTcpListener,
+    ) -> Result<Builder<AddrIncoming>, ::Error> {
+        let handle = tokio_reactor::Handle::current();
+        let incoming = AddrIncoming::from_tcp(listener, &handle)
+          .map_err(|err| ::Error::new_listen(err))?;
+        Ok(Self::builder(incoming))
+    }
 }
 
 #[cfg(feature = "runtime")]
@@ -275,4 +287,3 @@ impl Builder<AddrIncoming> {
         self
     }
 }
-

src/server/tcp.rs

@@ -44,6 +44,20 @@ impl AddrIncoming {
         })
     }
 
+    pub(super) fn from_tcp(std_listener: StdTcpListener, handle: &Handle) -> ::Result<Self>{
+        let listener = TcpListener::from_std(std_listener, &handle)
+            .map_err(::Error::new_listen)?;
+        let addr = listener.local_addr().map_err(::Error::new_listen)?;
+        Ok(AddrIncoming {
+            listener,
+            addr: addr,
+            sleep_on_errors: true,
+            tcp_keepalive_timeout: None,
+            tcp_nodelay: false,
+            timeout: None,
+        })
+    }
+
     /// Get the local address bound to this listener.
     pub fn local_addr(&self) -> SocketAddr {
         self.addr