WebSocket Compression

sdk/lib/io/websocket.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.io;
 
 /**
  * WebSocket status codes used when closing a WebSocket connection.
  */
 abstract class WebSocketStatus {
   static const int NORMAL_CLOSURE = 1000;
   static const int GOING_AWAY = 1001;
   static const int PROTOCOL_ERROR = 1002;
   static const int UNSUPPORTED_DATA = 1003;
-  static const int RESERVED_1004  = 1004;
+  static const int RESERVED_1004 = 1004;
   static const int NO_STATUS_RECEIVED = 1005;
   static const int ABNORMAL_CLOSURE = 1006;
   static const int INVALID_FRAME_PAYLOAD_DATA = 1007;
   static const int POLICY_VIOLATION = 1008;
   static const int MESSAGE_TOO_BIG = 1009;
   static const int MISSING_MANDATORY_EXTENSION = 1010;
   static const int INTERNAL_SERVER_ERROR = 1011;
   static const int RESERVED_1015 = 1015;
 }
 
 /**
+ * The [CompressionOptions] class allows you to control
+ * the options of WebSocket compression.
+ */
+class CompressionOptions {
+  /**
+   * Default WebSocket Compression options.
+   * Compression will be enabled with the following options:
+   * clientNoContextTakeover: false
+   * serverNoContextTakeover: false
+   * clientMaxWindowBits: 15
+   * serverMaxWindowBits: 15
+   */
+  static const CompressionOptions DEFAULT = const CompressionOptions();
+
+  /**
+   * Disables WebSocket Compression.
+   */
+  static const CompressionOptions OFF =
+      const CompressionOptions(enabled: false);
+
+  /**
+   * Control whether the client will reuse it's compression instances.
+   */
+  final bool clientNoContextTakeover;
+
+  /**
+   * Control whether the server will reuse it's compression instances.
+   */
+  final bool serverNoContextTakeover;
+
+  /**
+   * Sets the Max Window Bits for the Client.
+   */
+  final int clientMaxWindowBits;
+
+  /**
+   * Sets the Max Window Bits for the Server.
+   */
+  final int serverMaxWindowBits;
+
+  /**
+   * Enables or disables WebSocket compression.
+   */
+  final bool enabled;
+
+  const CompressionOptions(
+      {this.clientNoContextTakeover: false,
+      this.serverNoContextTakeover: false,
+      this.clientMaxWindowBits,
+      this.serverMaxWindowBits,
+      this.enabled: true});
+
+  /**
+   * Create a Compression Header

[Søren Gjesse, 2015/08/24 08:21:50]

Please add more documentation here on what requested is, and what is returned -
it doesn't just create a compression header.

As far as I can see if requested is not passed this generates a client request,
and if requested is passed it generates the server response.

Maybe add methods

String _createClientRequestHeader()
List _createServerResponseHeader(requested)

that forward to _createHeader.

+   */
+  List _createHeader([List<String> requested]) {

[Søren Gjesse, 2015/08/24 08:21:50]

Pass HeaderValue here and use its parameters (see comment in next file).

+    if (!enabled) {
+      return ["", 0];
+    }
+
+    var info = new List(2);
+
+    var header = _WebSocketImpl.PER_MESSAGE_DEFLATE;
+
+    if (clientNoContextTakeover &&
+        (requested != null &&
+            requested.contains("client_no_context_takeover"))) {

[Søren Gjesse, 2015/08/24 08:21:50]

Please make the values "server_no_context_takeover" , "server_max_window_bits",
"client_max_window_bits" and "client_no_context_takeover" constants:

const String clientNoContextTakeover = "client_no_context_takeover";
...

+      header += "; client_no_context_takeover";
+    }
+
+    if (serverNoContextTakeover &&
+        (requested != null &&
+            requested.contains("server_no_context_takeover"))) {
+      header += "; server_no_context_takeover";
+    }
+
+    if (requested != null &&
+        requested.any((x) => x.startsWith("server_max_window_bits="))) {

[Søren Gjesse, 2015/08/24 08:21:50]

This check is fragile, there can be WS on both sides of the = sign. See comments
in next file on parsing parameters.

+      var part = requested
+          .firstWhere((x) => x.startsWith("server_max_window_bits="))
+          .substring(23);
+      var mwb = serverMaxWindowBits == null
+          ? int.parse(part,

[Søren Gjesse, 2015/08/24 08:21:50]

According to
https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression-27 the value
must not have leading zeros.

+              onError: (source) => _WebSocketImpl.DEFAULT_WINDOW_BITS)
+          : serverMaxWindowBits;

[Søren Gjesse, 2015/08/24 08:21:50]

You also need to check for the allowed range 8-15.

+      header += "; server_max_window_bits=${mwb}";
+      info[1] = mwb;
+    } else {
+      info[1] = _WebSocketImpl.DEFAULT_WINDOW_BITS;
+    }
+
+    if (requested == null) {
+      header += "; client_max_window_bits";
+    } else {
+      if (requested.contains("client_max_window_bits")) {
+        var myMaxWindowBits = info[1];
+        header += "; client_max_window_bits=${myMaxWindowBits}";
+      }
+    }
+
+    info[0] = header;
+
+    return info;
+  }
+}
+
+/**
  * The [WebSocketTransformer] provides the ability to upgrade a
  * [HttpRequest] to a [WebSocket] connection. It supports both
  * upgrading a single [HttpRequest] and upgrading a stream of
  * [HttpRequest]s.
  *
  * To upgrade a single [HttpRequest] use the static [upgrade] method.
  *
  *     HttpServer server;
  *     server.listen((request) {
  *       if (...) {
  *         WebSocketTransformer.upgrade(request).then((websocket) {
  *           ...
  *         });
  *       } else {
  *         // Do normal HTTP request processing.
  *       }
  *     });
  *
  * To transform a stream of [HttpRequest] events as it implements a
  * stream transformer that transforms a stream of HttpRequest into a
  * stream of WebSockets by upgrading each HttpRequest from the HTTP or
  * HTTPS server, to the WebSocket protocol.
  *
  *     server.transform(new WebSocketTransformer()).listen((webSocket) => ...);
  *
  * This transformer strives to implement WebSockets as specified by RFC6455.
  */
 abstract class WebSocketTransformer
     implements StreamTransformer<HttpRequest, WebSocket> {
-
   /**
    * Create a new [WebSocketTransformer].
    *
    * If [protocolSelector] is provided, [protocolSelector] will be called to
    * select what protocol to use, if any were provided by the client.
    * [protocolSelector] is should return either a [String] or a [Future]
    * completing with a [String]. The [String] must exist in the list of
    * protocols.
    */
-  factory WebSocketTransformer({protocolSelector(List<String> protocols)})
-      => new _WebSocketTransformerImpl(protocolSelector);
+  factory WebSocketTransformer(
+          {protocolSelector(List<String> protocols),
+          CompressionOptions compression: CompressionOptions.DEFAULT}) =>
+      new _WebSocketTransformerImpl(protocolSelector, compression);
 
   /**
    * Upgrades a [HttpRequest] to a [WebSocket] connection. If the
    * request is not a valid WebSocket upgrade request an HTTP response
    * with status code 500 will be returned. Otherwise the returned
    * future will complete with the [WebSocket] when the upgrade pocess
    * is complete.
    *
    * If [protocolSelector] is provided, [protocolSelector] will be called to
    * select what protocol to use, if any were provided by the client.
    * [protocolSelector] is should return either a [String] or a [Future]
    * completing with a [String]. The [String] must exist in the list of
    * protocols.
    */
   static Future<WebSocket> upgrade(HttpRequest request,
-                                   {protocolSelector(List<String> protocols)}) {
-    return _WebSocketTransformerImpl._upgrade(request, protocolSelector);
+      {protocolSelector(List<String> protocols),
+      CompressionOptions compression: CompressionOptions.DEFAULT}) {
+    return _WebSocketTransformerImpl._upgrade(
+        request, protocolSelector, compression);
   }
 
   /**
    * Checks whether the request is a valid WebSocket upgrade request.
    */
   static bool isUpgradeRequest(HttpRequest request) {
     return _WebSocketTransformerImpl._isUpgradeRequest(request);
   }
 }
 
-
 /**
  * A two-way HTTP communication object for client or server applications.
  *
  * The stream exposes the messages received. A text message will be of type
  * [:String:] and a binary message will be of type [:List<int>:].
  */
 abstract class WebSocket implements Stream, StreamSink {
   /**
    * Possible states of the connection.
    */
@@ skipping 39 matching lines @@
    *   - `sec-websocket-protocol`
    *   - `sec-websocket-version`
    *   - `upgrade`
    *
    * If any of these are passed in the `headers` map they will be ignored.
    *
    * If the `url` contains user information this will be passed as basic
    * authentication when setting up the connection.
    */
   static Future<WebSocket> connect(String url,
-                                   {Iterable<String> protocols,
-                                    Map<String, dynamic> headers}) =>
-      _WebSocketImpl.connect(url, protocols, headers);
+          {Iterable<String> protocols,
+          Map<String, dynamic> headers,
+          CompressionOptions compression: CompressionOptions.DEFAULT}) =>
+      _WebSocketImpl.connect(url, protocols, headers, compression: compression);
 
   @Deprecated('This constructor will be removed in Dart 2.0. Use `implements`'
       ' instead of `extends` if implementing this abstract class.')
   WebSocket();
 
   /**
    * Creates a WebSocket from an already-upgraded socket.
    *
    * The initial WebSocket handshake must have occurred prior to this call. A
    * WebSocket client can automatically perform the handshake using
    * [WebSocket.connect], while a server can do so using
    * [WebSocketTransformer.upgrade]. To manually upgrade an [HttpRequest],
    * [HttpRequest.detachSocket] may be called.
    *
    * [protocol] should be the protocol negotiated by this handshake, if any.
    *
    * [serverSide] must be passed explicitly. If it's `false`, the WebSocket will
    * act as the client and mask the messages it sends. If it's `true`, it will
    * act as the server and will not mask its messages.
    */
-  factory WebSocket.fromUpgradedSocket(Socket socket, {String protocol,
-        bool serverSide}) {
+  factory WebSocket.fromUpgradedSocket(Socket socket,
+      {String protocol,
+      bool serverSide,
+      CompressionOptions compression: CompressionOptions.DEFAULT}) {
     if (serverSide == null) {
       throw new ArgumentError("The serverSide argument must be passed "
           "explicitly to WebSocket.fromUpgradedSocket.");
     }
-    return new _WebSocketImpl._fromSocket(socket, protocol, serverSide);
+    return new _WebSocketImpl._fromSocket(
+        socket, protocol, compression, serverSide);
   }
 
   /**
    * Returns the current state of the connection.
    */
   int get readyState;
 
   /**
    * The extensions property is initially the empty string. After the
    * WebSocket connection is established this string reflects the
@@ skipping 36 matching lines @@
   void add(data);
 
   /**
    * Sends data from a stream on WebSocket connection. Each data event from
    * [stream] will be send as a single WebSocket frame. The data from [stream]
    * must be either [:String:]s, or [:List<int>:]s holding bytes.
    */
   Future addStream(Stream stream);
 }
 
-
 class WebSocketException implements IOException {
   final String message;
+
   const WebSocketException([this.message = ""]);
+
   String toString() => "WebSocketException: $message";
 }