Merge fixes

Author: JamesNK

src/Servers/Kestrel/perf/Kestrel.Performance/Http2ConnectionBenchmark.cs

@@ -28,6 +28,7 @@ public class Http2ConnectionBenchmark
         private Pipe _pipe;
         private HttpRequestHeaders _httpRequestHeaders;
         private Http2Connection _connection;
+        private Http2HeadersEnumerator _requestHeadersEnumerator;
         private int _currentStreamId;
         private HPackEncoder _hpackEncoder;
         private byte[] _headersBuffer;
@@ -70,6 +71,8 @@ public void GlobalSetup()
                 TimeoutControl = new MockTimeoutControl(),
             });
 
+            _requestHeadersEnumerator = new Http2HeadersEnumerator();
+
             _currentStreamId = 1;
 
             _ = _connection.ProcessRequestsAsync(new DummyApplication());
@@ -82,7 +85,8 @@ public void GlobalSetup()
         [Benchmark]
         public async Task EmptyRequest()
         {
-            PipeWriterHttp2FrameExtensions.WriteStartStream(_pipe.Writer, streamId: _currentStreamId, EnumerateHeaders(_httpRequestHeaders), _hpackEncoder, _headersBuffer, endStream: true);
+            _requestHeadersEnumerator.Initialize(_httpRequestHeaders);
+            PipeWriterHttp2FrameExtensions.WriteStartStream(_pipe.Writer, streamId: _currentStreamId, _requestHeadersEnumerator, _hpackEncoder, _headersBuffer, endStream: true);
             _currentStreamId += 2;
             await _pipe.Writer.FlushAsync();
         }

src/Servers/Kestrel/shared/test/PipeWriterHttp2FrameExtensions.cs

@@ -24,7 +24,7 @@ public static void WriteSettings(this PipeWriter writer, Http2PeerSettings clien
             writer.Write(payload);
         }
 
-        public static void WriteStartStream(this PipeWriter writer, int streamId, IEnumerable<KeyValuePair<string, string>> headers, HPackEncoder hpackEncoder, byte[] headerEncodingBuffer, bool endStream)
+        public static void WriteStartStream(this PipeWriter writer, int streamId, Http2HeadersEnumerator headers, HPackEncoder hpackEncoder, byte[] headerEncodingBuffer, bool endStream)
         {
             var frame = new Http2Frame();
             frame.PrepareHeaders(Http2HeadersFrameFlags.NONE, streamId);

src/Servers/Kestrel/test/InMemory.FunctionalTests/Http2/Http2TestBase.cs

@@ -501,7 +501,7 @@ protected Task StartStreamAsync(int streamId, IEnumerable<KeyValuePair<string, s
             var tcs = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
             _runningStreams[streamId] = tcs;
 
-            PipeWriterHttp2FrameExtensions.WriteStartStream(writableBuffer, streamId, headers, _hpackEncoder, _headerEncodingBuffer, endStream);
+            PipeWriterHttp2FrameExtensions.WriteStartStream(writableBuffer, streamId, GetHeadersEnumerator(headers), _hpackEncoder, _headerEncodingBuffer, endStream);
             return FlushAsync(writableBuffer);
         }
 
@@ -837,6 +837,13 @@ internal async Task<bool> SendContinuationAsync(int streamId, Http2ContinuationF
             return done;
         }
 
+        private Http2HeadersEnumerator GetHeadersEnumerator(IEnumerable<KeyValuePair<string, string>> headers)
+        {
+            var headersEnumerator = new Http2HeadersEnumerator();
+            headersEnumerator.Initialize(headers.ToDictionary(h => h.Key, h => new StringValues(h.Value)));
+            return headersEnumerator;
+        }
+
         internal Task SendEmptyContinuationFrameAsync(int streamId, Http2ContinuationFrameFlags flags)
         {
             var outputWriter = _pair.Application.Output;