WebSocket Compression

sdk/lib/io/websocket.dart

Index: sdk/lib/io/websocket.dart
diff --git a/sdk/lib/io/websocket.dart b/sdk/lib/io/websocket.dart
index 599e295c60ac92923dc620303830b986b8522f96..41be2b2af11b4954086b59af503121496d8be3d4 100644
--- a/sdk/lib/io/websocket.dart
+++ b/sdk/lib/io/websocket.dart
@@ -12,7 +12,7 @@ abstract class WebSocketStatus {
   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;
@@ -24,6 +24,113 @@ abstract class WebSocketStatus {
 }
 
 /**
+ * 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
@@ -53,7 +160,6 @@ abstract class WebSocketStatus {
  */
 abstract class WebSocketTransformer
     implements StreamTransformer<HttpRequest, WebSocket> {
-
   /**
    * Create a new [WebSocketTransformer].
    *
@@ -63,8 +169,10 @@ abstract class WebSocketTransformer
    * 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
@@ -80,8 +188,10 @@ abstract class WebSocketTransformer
    * 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);
   }
 
   /**
@@ -92,7 +202,6 @@ abstract class WebSocketTransformer
   }
 }
 
-
 /**
  * A two-way HTTP communication object for client or server applications.
  *
@@ -152,9 +261,10 @@ abstract class WebSocket implements Stream, StreamSink {
    * 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.')
@@ -175,13 +285,16 @@ abstract class WebSocket implements Stream, StreamSink {
    * 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);
   }
 
   /**
@@ -238,9 +351,10 @@ abstract class WebSocket implements Stream, StreamSink {
   Future addStream(Stream stream);
 }
 
-
 class WebSocketException implements IOException {
   final String message;
+
   const WebSocketException([this.message = ""]);
+
   String toString() => "WebSocketException: $message";
 }