Headers HasX checks to fast check

Author: benaadams

src/Microsoft.AspNet.Server.Kestrel/Http/Frame.cs

@@ -640,7 +640,7 @@ private Task CreateResponseHeader(
         {
             var begin = SocketOutput.ProducingStart();
             var end = begin;
-            if (_keepAlive)
+            if (_keepAlive && _responseHeaders.HasConnection)
             {
                 var count = _responseHeaders.HeaderConnection.Count;
                 if (count == 1)

src/Microsoft.AspNet.Server.Kestrel/Http/FrameHeaders.Generated.cs

@@ -56,6 +56,7 @@ public partial class FrameRequestHeaders
         private StringValues _UserAgent;
 
 
+        
         public StringValues HeaderCacheControl
         {
             get
@@ -5109,6 +5110,10 @@ public partial class FrameResponseHeaders
         private byte[] _rawContentLength;
         private byte[] _rawServer;
 
+        public bool HasConnection => ((_bits & 2L) != 0);
+        public bool HasTransferEncoding => ((_bits & 64L) != 0);
+        public bool HasContentLength => ((_bits & 2048L) != 0);
+        
         public StringValues HeaderCacheControl
         {
             get

src/Microsoft.AspNet.Server.Kestrel/Http/FrameResponseHeaders.cs

@@ -13,13 +13,6 @@ public partial class FrameResponseHeaders : FrameHeaders
         private static byte[] _CrLf = new[] { (byte)'\r', (byte)'\n' };
         private static byte[] _colonSpace = new[] { (byte)':', (byte)' ' };
 
-        public bool HasConnection => HeaderConnection.Count != 0;
-
-        public bool HasTransferEncoding => HeaderTransferEncoding.Count != 0;
-
-        public bool HasContentLength => HeaderContentLength.Count != 0;
-
-
         public Enumerator GetEnumerator()
         {
             return new Enumerator(this);

tools/Microsoft.AspNet.Server.Kestrel.GeneratedCode/KnownHeaders.cs

@@ -25,6 +25,7 @@ class KnownHeader
             public int BytesOffset { get; set; }
             public int BytesCount { get; set; }
             public bool EnhancedSetter { get; set; }
+            public bool FastCheck { get; set; }
             public string TestBit() => $"((_bits & {1L << Index}L) != 0)";
             public string SetBit() => $"_bits |= {1L << Index}L";
             public string ClearBit() => $"_bits &= ~{1L << Index}L";
@@ -139,6 +140,12 @@ public static string GeneratedFile()
                 "Transfer-Encoding",
                 "Content-Length",
             };
+            var fastCheckHeaders = new[]
+            {
+                "Connection",
+                "Transfer-Encoding",
+                "Content-Length",
+            };
             var responseHeaders = commonHeaders.Concat(new[]
             {
                 "Accept-Ranges",
@@ -155,7 +162,8 @@ public static string GeneratedFile()
             {
                 Name = header,
                 Index = index,
-                EnhancedSetter = enhancedHeaders.Contains(header)
+                EnhancedSetter = enhancedHeaders.Contains(header),
+                FastCheck = fastCheckHeaders.Contains(header)
             }).ToArray();
             var loops = new[]
             {
@@ -208,6 +216,8 @@ public partial class {loop.ClassName}
         private StringValues _" + header.Identifier + ";")}
         {Each(loop.Headers.Where(header => header.EnhancedSetter), header => @"
         private byte[] _raw" + header.Identifier + ";")}
+        {Each(loop.Headers.Where(header => header.FastCheck), header => @"
+        public bool Has" + header.Identifier + $" => {header.TestBit()};")}
         {Each(loop.Headers, header => $@"
         public StringValues Header{header.Identifier}
         {{