Optimize Websocket compression for no context takeover requests

sdk/lib/io/websocket_impl.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;
 
 const String _webSocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 const String _clientNoContextTakeover = "client_no_context_takeover";
 const String _serverNoContextTakeover = "server_no_context_takeover";
 const String _clientMaxWindowBits = "client_max_window_bits";
@@ skipping 463 matching lines @@
     var extensionHeader = request.headers.value("Sec-WebSocket-Extensions");
 
     extensionHeader ??= "";
 
     var hv = HeaderValue.parse(extensionHeader, valueSeparator: ',');
     if (compression.enabled && hv.value == _WebSocketImpl.PER_MESSAGE_DEFLATE) {
       var info = compression._createHeader(hv);
 
       response.headers.add("Sec-WebSocket-Extensions", info.headerValue);
       var serverNoContextTakeover =
-          hv.parameters.containsKey(_serverNoContextTakeover);
+          (hv.parameters.containsKey(_serverNoContextTakeover) &&
+            compression.serverNoContextTakeover);
       var clientNoContextTakeover =
-          hv.parameters.containsKey(_clientNoContextTakeover);
+          (hv.parameters.containsKey(_clientNoContextTakeover) &&
+            compression.clientNoContextTakeover);
       var deflate = new _WebSocketPerMessageDeflate(
           serverNoContextTakeover: serverNoContextTakeover,
           clientNoContextTakeover: clientNoContextTakeover,
           serverMaxWindowBits: info.maxWindowBits,
           clientMaxWindowBits: info.maxWindowBits,
           serverSide: true);
 
       return deflate;
     }
 
@@ skipping 73 matching lines @@
     data.addAll(const [0x00, 0x00, 0xff, 0xff]);
 
     decoder.process(data, 0, data.length);
     var result = [];
     var out;
 
     while ((out = decoder.processed()) != null) {
       result.addAll(out);
     }
 
+    if ((serverSide && clientNoContextTakeover) ||
+        (!serverSide && serverNoContextTakeover)) {
+      decoder.end();
+      decoder = null;
+    }
+
     return new Uint8List.fromList(result);
   }
 
   List<int> processOutgoingMessage(List<int> msg) {
     _ensureEncoder();
     var result = [];
     Uint8List buffer;
     var out;
 
     if (msg is! Uint8List) {
       for (var i = 0; i < msg.length; i++) {
         if (msg[i] < 0 || 255 < msg[i]) {
           throw new ArgumentError("List element is not a byte value "
               "(value ${msg[i]} at index $i)");
         }
       }
       buffer = new Uint8List.fromList(msg);
     } else {
       buffer = msg;
     }
 
     encoder.process(buffer, 0, buffer.length);
 
     while ((out = encoder.processed()) != null) {
       result.addAll(out);
     }
 
-    if (!serverSide && clientNoContextTakeover) {
+    if ((!serverSide && clientNoContextTakeover) ||
+        (serverSide && serverNoContextTakeover)) {
       encoder.end();
       encoder = null;
     }
 
     if (result.length > 4) {
       result = result.sublist(0, result.length - 4);
     }
 
     return result;
   }
@@ skipping 616 matching lines @@
     return code != null &&
         (code < WebSocketStatus.NORMAL_CLOSURE ||
             code == WebSocketStatus.RESERVED_1004 ||
             code == WebSocketStatus.NO_STATUS_RECEIVED ||
             code == WebSocketStatus.ABNORMAL_CLOSURE ||
             (code > WebSocketStatus.INTERNAL_SERVER_ERROR &&
                 code < WebSocketStatus.RESERVED_1015) ||
             (code >= WebSocketStatus.RESERVED_1015 && code < 3000));
   }
 }