Increase Window Update size

lib/src/flowcontrol/window.dart

@@ -11,13 +11,20 @@ class Window {
   /// streams is 65535).
   ///
   /// NOTE: This value can potentially become negative.
+  final int _initialSize;
   int _size;
 
-  Window({int initialSize = (1 << 16) - 1}) : _size = initialSize;
+  Window({int initialSize = (1 << 16) - 1})
+      : _size = initialSize,
+        _initialSize = initialSize;
 
   /// The current size of the flow control window.
   int get size => _size;
 
+  bool get isTooSmall => size < _initialSize / 2;
+
+  int get updateSize => _initialSize ~/ 2;
+
   void modify(int difference) {
     _size += difference;
   }

lib/src/flowcontrol/window_handler.dart

@@ -152,11 +152,15 @@ class IncomingWindowHandler {
   //  - either stop sending window update frames
   //  - or decreasing the window size
   void dataProcessed(int numberOfBytes) {
-    _localWindow.modify(numberOfBytes);
-
     // TODO: This can be optimized by delaying the window update to
     // send one update with a bigger difference than multiple small update
     // frames.
-    _frameWriter.writeWindowUpdate(numberOfBytes, streamId: _streamId);
+    if (_localWindow.isTooSmall) {
+      _frameWriter.writeWindowUpdate(
+        _localWindow.updateSize,
+        streamId: _streamId,
+      );
+    }
+    _localWindow.modify(_localWindow.updateSize);
   }
 }

test/client_test.dart

@@ -297,17 +297,6 @@ void main() {
           // Write more data on the closed stream.
           serverWriter.writeDataFrame(streamId, [42]);
 
-          // NOTE: The order of the window update frame / rst frame just
-          // happens to be like that ATM.
-
-          // Await stream/connection window update frame.
-          var win = await nextFrame() as WindowUpdateFrame;
-          expect(win.header.streamId, 1);
-          expect(win.windowSizeIncrement, 1);
-          win = await nextFrame() as WindowUpdateFrame;
-          expect(win.header.streamId, 0);
-          expect(win.windowSizeIncrement, 1);
-
           // Make sure we get a [RstStreamFrame] frame.
           expect(
               await nextFrame(),
@@ -366,20 +355,6 @@ void main() {
           await cancelDone.future;
           serverWriter.writeDataFrame(streamId, [43]);
 
-          // NOTE: The order of the window update frame / rst frame just
-          // happens to be like that ATM.
-
-          // Await stream/connection window update frame.
-          var win = await nextFrame() as WindowUpdateFrame;
-          expect(win.header.streamId, 1);
-          expect(win.windowSizeIncrement, 1);
-          win = await nextFrame() as WindowUpdateFrame;
-          expect(win.header.streamId, 0);
-          expect(win.windowSizeIncrement, 1);
-          win = await nextFrame() as WindowUpdateFrame;
-          expect(win.header.streamId, 0);
-          expect(win.windowSizeIncrement, 1);
-
           // Make sure we get a [RstStreamFrame] frame.
           expect(
               await nextFrame(),
@@ -445,20 +420,6 @@ void main() {
           serverWriter.writeRstStreamFrame(streamId, ErrorCode.STREAM_CLOSED);
           endDone.complete();
 
-          // NOTE: The order of the window update frame / rst frame just
-          // happens to be like that ATM.
-
-          // Await stream/connection window update frame.
-          var win = await nextFrame() as WindowUpdateFrame;
-          expect(win.header.streamId, 1);
-          expect(win.windowSizeIncrement, 1);
-          win = await nextFrame() as WindowUpdateFrame;
-          expect(win.header.streamId, 0);
-          expect(win.windowSizeIncrement, 1);
-          win = await nextFrame() as WindowUpdateFrame;
-          expect(win.header.streamId, 0);
-          expect(win.windowSizeIncrement, 1);
-
           await clientDone.future;
           var finFrame = await nextFrame() as DataFrame;
           expect(finFrame.hasEndStreamFlag, true);

test/src/flowcontrol/window_handler_test.dart

@@ -102,7 +102,7 @@ void main() {
       const STREAM_ID = 99;
 
       var fw = FrameWriterMock();
-      var window = Window();
+      var window = Window(initialSize: 150);
       var initialSize = window.size;
       var handler = IncomingWindowHandler.stream(fw, window, STREAM_ID);
 
@@ -112,17 +112,18 @@ void main() {
       // If the remote end sends us now 100 bytes, it reduces the local
       // incoming window by 100 bytes. Once we handled these bytes, it,
       // will send a [WindowUpdateFrame] to the remote peer to ACK it.
-      handler.gotData(100);
-      expect(handler.localWindowSize, initialSize - 100);
-      expect(window.size, initialSize - 100);
+      var numberOfBytes = 100;
+      handler.gotData(numberOfBytes);
+      expect(handler.localWindowSize, initialSize - numberOfBytes);
+      expect(window.size, initialSize - numberOfBytes);
 
       // The data might sit in a queue. Once the user drains enough data of
       // the queue, we will start ACKing the data and the window becomes
       // positive again.
-      handler.dataProcessed(100);
-      expect(handler.localWindowSize, initialSize);
-      expect(window.size, initialSize);
-      verify(fw.writeWindowUpdate(100, streamId: STREAM_ID)).called(1);
+      handler.dataProcessed(numberOfBytes);
+      expect(handler.localWindowSize, 125);
+      expect(window.size, 125);
+      verify(fw.writeWindowUpdate(75, streamId: STREAM_ID)).called(1);
       verifyNoMoreInteractions(fw);
     });
   });

test/transport_test.dart

@@ -400,7 +400,6 @@ void main() {
     group('flow-control', () {
       const kChunkSize = 1024;
       const kNumberOfMessages = 1000;
-      final headers = [Header.ascii('a', 'b')];
 
       Future testWindowSize(
           ClientTransportConnection client,
@@ -463,6 +462,7 @@ void main() {
         }
 
         Future clientFun() async {
+          final headers = [Header.ascii('a', 'b')];
           var stream = client.makeRequest(headers, endStream: true);
 
           var gotHeadersFrame = false;
@@ -502,11 +502,14 @@ void main() {
         await testWindowSize(client, server, Window().size);
       });
 
-      transportTest('fast-sender-receiver-paused--10kb-window-size',
-          (ClientTransportConnection client,
-              ServerTransportConnection server) async {
-        await testWindowSize(client, server, 8096);
-      }, clientSettings: ClientSettings(streamWindowSize: 8096));
+      transportTest(
+        'fast-sender-receiver-paused--10kb-window-size',
+        (ClientTransportConnection client,
+            ServerTransportConnection server) async {
+          await testWindowSize(client, server, 8096);
+        },
+        clientSettings: ClientSettings(streamWindowSize: 8096),
+      );
     });
   });
 }