callback static dispatch

Signed-off-by: Alexey Galakhov <agalakhov@snapview.de>

Cargo.toml

@@ -7,7 +7,7 @@ authors = ["Alexey Galakhov"]
 license = "MIT/Apache-2.0"
 readme = "README.md"
 homepage = "https://github.com/snapview/tungstenite-rs"
-documentation = "https://docs.rs/tungstenite/0.4.0"
+documentation = "https://docs.rs/tungstenite/0.5.0"
 repository = "https://github.com/snapview/tungstenite-rs"
 version = "0.5.0"
 

examples/autobahn-server.rs

@@ -16,7 +16,7 @@ fn must_not_block<Role: HandshakeRole>(err: HandshakeError<Role>) -> Error {
 }
 
 fn handle_client(stream: TcpStream) -> Result<()> {
-    let mut socket = accept(stream, None).map_err(must_not_block)?;
+    let mut socket = accept(stream).map_err(must_not_block)?;
     loop {
         match socket.read_message()? {
             msg @ Message::Text(_) |

examples/server.rs

@@ -3,7 +3,7 @@ extern crate tungstenite;
 use std::thread::spawn;
 use std::net::TcpListener;
 
-use tungstenite::accept;
+use tungstenite::accept_hdr;
 use tungstenite::handshake::server::Request;
 
 fn main() {
@@ -25,7 +25,7 @@ fn main() {
                 ];
                 Ok(Some(extra_headers))
             };
-            let mut websocket = accept(stream.unwrap(), Some(Box::new(callback))).unwrap();
+            let mut websocket = accept_hdr(stream.unwrap(), callback).unwrap();
 
             loop {
                 let msg = websocket.read_message().unwrap();

src/handshake/server.rs

@@ -3,7 +3,6 @@
 use std::fmt::Write as FmtWrite;
 use std::io::{Read, Write};
 use std::marker::PhantomData;
-use std::mem::replace;
 
 use httparse;
 use httparse::Status;
@@ -71,43 +70,61 @@ impl<'h, 'b: 'h> FromHttparse<httparse::Request<'h, 'b>> for Request {
     }
 }
 
-/// The callback type, the callback is called when the server receives an incoming WebSocket
-/// handshake request from the client, specifying a callback allows you to analyze incoming headers
-/// and add additional headers to the response that server sends to the client and/or reject the
-/// connection based on the incoming headers. Due to usability problems which are caused by a
-/// static dispatch when using callbacks in such places, the callback is boxed.
+/// The callback trait.
 ///
-/// The type uses `FnMut` instead of `FnOnce` as it is impossible to box `FnOnce` in the current
-/// Rust version, `FnBox` is still unstable, this code has to be updated for `FnBox` when it gets
-/// stable.
-pub type Callback = Box<FnMut(&Request) -> Result<Option<Vec<(String, String)>>>>;
+/// The callback is called when the server receives an incoming WebSocket
+/// handshake request from the client. Specifying a callback allows you to analyze incoming headers
+/// and add additional headers to the response that server sends to the client and/or reject the
+/// connection based on the incoming headers.
+pub trait Callback: Sized {
+    /// Called whenever the server read the request from the client and is ready to reply to it.
+    /// May return additional reply headers.
+    /// Returning an error resulting in rejecting the incoming connection.
+    fn on_request(self, request: &Request) -> Result<Option<Vec<(String, String)>>>;
+}
+
+impl<F> Callback for F where F: FnOnce(&Request) -> Result<Option<Vec<(String, String)>>> {
+    fn on_request(self, request: &Request) -> Result<Option<Vec<(String, String)>>> {
+        self(request)
+    }
+}
+
+/// Stub for callback that does nothing.
+#[derive(Clone, Copy)]
+pub struct NoCallback;
+
+impl Callback for NoCallback {
+    fn on_request(self, _request: &Request) -> Result<Option<Vec<(String, String)>>> {
+        Ok(None)
+    }
+}
 
 /// Server handshake role.
 #[allow(missing_copy_implementations)]
-pub struct ServerHandshake<S> {
+pub struct ServerHandshake<S, C> {
     /// Callback which is called whenever the server read the request from the client and is ready
     /// to reply to it. The callback returns an optional headers which will be added to the reply
     /// which the server sends to the user.
-    callback: Option<Callback>,
+    callback: Option<C>,
     /// Internal stream type.
     _marker: PhantomData<S>,
 }
 
-impl<S: Read + Write> ServerHandshake<S> {
+impl<S: Read + Write, C: Callback> ServerHandshake<S, C> {
     /// Start server handshake. `callback` specifies a custom callback which the user can pass to
     /// the handshake, this callback will be called when the a websocket client connnects to the
     /// server, you can specify the callback if you want to add additional header to the client
     /// upon join based on the incoming headers.
-    pub fn start(stream: S, callback: Option<Callback>) -> MidHandshake<Self> {
+    pub fn start(stream: S, callback: C) -> MidHandshake<Self> {
         trace!("Server handshake initiated.");
         MidHandshake {
             machine: HandshakeMachine::start_read(stream),
-            role: ServerHandshake { callback, _marker: PhantomData },
+            role: ServerHandshake { callback: Some(callback), _marker: PhantomData },
         }
     }
 }
 
-impl<S: Read + Write> HandshakeRole for ServerHandshake<S> {
+impl<S: Read + Write, C: Callback> HandshakeRole for ServerHandshake<S, C> {
     type IncomingData = Request;
     type InternalStream = S;
     type FinalResult = WebSocket<S>;
@@ -121,8 +138,8 @@ impl<S: Read + Write> HandshakeRole for ServerHandshake<S> {
                     return Err(Error::Protocol("Junk after client request".into()))
                 }
                 let extra_headers = {
-                    if let Some(mut callback) = replace(&mut self.callback, None) {
-                        callback(&result)?
+                    if let Some(callback) = self.callback.take() {
+                        callback.on_request(&result)?
                     } else {
                         None
                     }

src/lib.rs

@@ -31,7 +31,7 @@ pub mod util;
 mod input_buffer;
 
 pub use client::{connect, client};
-pub use server::accept;
+pub use server::{accept, accept_hdr};
 pub use error::{Error, Result};
 pub use protocol::{WebSocket, Message};
 pub use handshake::HandshakeError;

src/server.rs

@@ -3,7 +3,8 @@
 pub use handshake::server::ServerHandshake;
 
 use handshake::HandshakeError;
-use handshake::server::Callback;
+use handshake::server::{Callback, NoCallback};
+
 use protocol::WebSocket;
 
 use std::io::{Read, Write};
@@ -13,10 +14,20 @@ use std::io::{Read, Write};
 /// This function starts a server WebSocket handshake over the given stream.
 /// If you want TLS support, use `native_tls::TlsStream` or `openssl::ssl::SslStream`
 /// for the stream here. Any `Read + Write` streams are supported, including
-/// those from `Mio` and others. You can also pass an optional `callback` which will
-/// be called when the websocket request is received from an incoming client.
-pub fn accept<S: Read + Write>(stream: S, callback: Option<Callback>)
-    -> Result<WebSocket<S>, HandshakeError<ServerHandshake<S>>>
+/// those from `Mio` and others.
+pub fn accept<S: Read + Write>(stream: S)
+    -> Result<WebSocket<S>, HandshakeError<ServerHandshake<S, NoCallback>>>
+{
+    accept_hdr(stream, NoCallback)
+}
+
+/// Accept the given Stream as a WebSocket.
+///
+/// This function does the same as `accept()` but accepts an extra callback
+/// for header processing. The callback receives headers of the incoming
+/// requests and is able to add extra headers to the reply.
+pub fn accept_hdr<S: Read + Write, C: Callback>(stream: S, callback: C)
+    -> Result<WebSocket<S>, HandshakeError<ServerHandshake<S, C>>>
 {
     ServerHandshake::start(stream, callback).handshake()
 }