Web Socket compression - take two

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..5170bde89e6e45766c476c44122db6333be93f6f 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 +24,141 @@ 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: _WebSocketImpl.DEFAULT_WINDOW_BITS,
+      this.serverMaxWindowBits: _WebSocketImpl.DEFAULT_WINDOW_BITS,
+      this.enabled: true});
+
+  /// Parses list of requested server headers to return server compression
+  /// response headers. Uses [serverMaxWindowBits] value if set, otherwise will
+  /// attempt to use value from headers. Defaults to
+  /// [WebSocket.DEFAULT_WINDOW_BITS]
+  List _createServerResponseHeader(HeaderValue requested) {
+    var info = new List(2);
+
+    int mwb;
+    var part = requested.parameters[_serverMaxWindowBits];
+    if (part != null) {
+      if (part.length >= 2 && part.startsWith('0')) {
+        throw new ArgumentError("Illegal 0 padding on value.");
+      } else {
+        mwb = serverMaxWindowBits == null
+            ? int.parse(part,
+                        onError: (source) => _WebSocketImpl.DEFAULT_WINDOW_BITS)
+            : serverMaxWindowBits;
+        info[0] = "; server_max_window_bits=${mwb}";
+        info[1] = mwb;
+      }
+    } else {
+      info[1] = _WebSocketImpl.DEFAULT_WINDOW_BITS;
+    }
+    return info;
+  }
+
+  /// Returns default values for client compression request headers.
+  List _createClientRequestHeader(HeaderValue requested) {
+    var info = new List(2);
+
+    info[1] = _WebSocketImpl.DEFAULT_WINDOW_BITS;
+    if (requested != null &&
+        requested.parameters[_clientMaxWindowBits] != null) {
+      info[0] = "; client_max_window_bits=${info[1]}";
+    } else {
+      info[0] = "; client_max_window_bits";
+    }
+
+    return info;
+  }
+
+  /// Create a Compression Header. If [requested] is null or contains
+  /// client request headers, returns Client compression request headers.
+  /// If [requested] contains server response headers this method returns
+  /// a Server compression response header.
+  List _createHeader([HeaderValue requested]) {
+    if (!enabled) {
+      return ["", 0];
+    }
+
+    var info = new List(2);
+    var header = _WebSocketImpl.PER_MESSAGE_DEFLATE;
+
+    if (clientNoContextTakeover &&
+        (requested != null &&
+            requested.parameters.containsKey(_clientNoContextTakeover))) {
+      header += "; client_no_context_takeover";
+    }
+
+    if (serverNoContextTakeover &&
+        (requested != null &&
+            requested.parameters.containsKey(_serverNoContextTakeover))) {
+      header += "; server_no_context_takeover";
+    }
+
+    if (requested == null ||
+        requested.parameters.containsKey(_clientMaxWindowBits)) {
+      var clientList = _createClientRequestHeader(requested);
+      header += clientList[0];
+      info[1] = clientList[1];
+    } else {
+      var headerList = _createServerResponseHeader(requested);
+      header += headerList[0];
+      info[1] = headerList[1];
+    }
+
+    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 +188,6 @@ abstract class WebSocketStatus {
  */
 abstract class WebSocketTransformer
     implements StreamTransformer<HttpRequest, WebSocket> {
-
   /**
    * Create a new [WebSocketTransformer].
    *
@@ -62,9 +196,15 @@ abstract class WebSocketTransformer
    * [protocolSelector] is should return either a [String] or a [Future]
    * completing with a [String]. The [String] must exist in the list of
    * protocols.
+   *
+   * If [compression] is provided, the [WebSocket] created will be configured
+   * to negotiate with the specified [CompressionOptions]. If none is specified
+   * then the [WebSocket] will be created with the default [CompressionOptions].
    */
-  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
@@ -78,10 +218,16 @@ abstract class WebSocketTransformer
    * [protocolSelector] is should return either a [String] or a [Future]
    * completing with a [String]. The [String] must exist in the list of
    * protocols.
+   *
+   * If [compression] is provided, the [WebSocket] created will be configured
+   * to negotiate with the specified [CompressionOptions]. If none is specified
+   * then the [WebSocket] will be created with the default [CompressionOptions].
    */
   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 +238,6 @@ abstract class WebSocketTransformer
   }
 }
 
-
 /**
  * A two-way HTTP communication object for client or server applications.
  *
@@ -152,9 +297,10 @@ 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.')
@@ -174,14 +320,21 @@ abstract class WebSocket implements Stream, StreamSink {
    * [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.
+   *
+   * If [compression] is provided, the [WebSocket] created will be configured
+   * to negotiate with the specified [CompressionOptions]. If none is specified
+   * then the [WebSocket] will be created with the default [CompressionOptions].
    */
-  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 +391,10 @@ 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";
 }