Use C#'s ReadOnlySpan static data optimization in more places (#14447)

src/Http/WebUtilities/src/FormPipeReader.cs

@@ -29,6 +29,7 @@ namespace Microsoft.AspNetCore.WebUtilities
         private const int DefaultValueLengthLimit = 1024 * 1024 * 4;
 
         // Used for UTF8/ASCII (precalculated for fast path)
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
         private static ReadOnlySpan<byte> UTF8EqualEncoded => new byte[] { (byte)'=' };
         private static ReadOnlySpan<byte> UTF8AndEncoded => new byte[] { (byte)'&' };
 

src/Middleware/WebSockets/src/HandshakeHelpers.cs

@@ -24,7 +24,8 @@ namespace Microsoft.AspNetCore.WebSockets
         };
 
         // "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
-        private static ReadOnlySpan<byte> _encodedWebSocketKey => new byte[]
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
+        private static ReadOnlySpan<byte> EncodedWebSocketKey => new byte[]
         {
             (byte)'2', (byte)'5', (byte)'8', (byte)'E', (byte)'A', (byte)'F', (byte)'A', (byte)'5', (byte)'-',
             (byte)'E', (byte)'9', (byte)'1', (byte)'4', (byte)'-', (byte)'4', (byte)'7', (byte)'D', (byte)'A',
@@ -115,7 +116,7 @@ namespace Microsoft.AspNetCore.WebSockets
                 // so this can be hardcoded to 60 bytes for the requestKey + static websocket string
                 Span<byte> mergedBytes = stackalloc byte[60];
                 Encoding.UTF8.GetBytes(requestKey, mergedBytes);
-                _encodedWebSocketKey.CopyTo(mergedBytes.Slice(24));
+                EncodedWebSocketKey.CopyTo(mergedBytes.Slice(24));
 
                 Span<byte> hashedBytes = stackalloc byte[20];
                 var success = algorithm.TryComputeHash(mergedBytes, hashedBytes, out var written);

src/Servers/Kestrel/Core/src/Internal/Http/ChunkWriter.cs

@@ -6,12 +6,14 @@ using System.Buffers;
 using System.IO.Pipelines;
 using System.Text;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 {
     internal static class ChunkWriter
     {
-        private static readonly byte[] _hex = Encoding.ASCII.GetBytes("0123456789abcdef");
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
+        private static ReadOnlySpan<byte> Hex => new byte[16] { (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6', (byte)'7', (byte)'8', (byte)'9', (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f' };
 
         public static int BeginChunkBytes(int dataCount, Span<byte> span)
         {
@@ -28,7 +30,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             count = (total >> 2) + 3;
 
             var offset = 0;
-            ref var startHex = ref _hex[0];
+            ref var startHex = ref MemoryMarshal.GetReference(Hex);
 
             for (shift = total; shift >= 0; shift -= 4)
             {

src/Servers/Kestrel/Core/src/Internal/Http/DateHeaderValueManager.cs

@@ -14,7 +14,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
     /// </summary>
     internal class DateHeaderValueManager : IHeartbeatHandler
     {
-        private static readonly byte[] _datePreambleBytes = Encoding.ASCII.GetBytes("\r\nDate: ");
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
+        private static ReadOnlySpan<byte> DatePreambleBytes => new byte[8] { (byte)'\r', (byte)'\n', (byte)'D', (byte)'a', (byte)'t', (byte)'e', (byte)':', (byte)' ' };
 
         private DateHeaderValues _dateValues;
 
@@ -38,9 +39,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         private void SetDateValues(DateTimeOffset value)
         {
             var dateValue = HeaderUtilities.FormatDate(value);
-            var dateBytes = new byte[_datePreambleBytes.Length + dateValue.Length];
+            var dateBytes = new byte[DatePreambleBytes.Length + dateValue.Length];
-            Buffer.BlockCopy(_datePreambleBytes, 0, dateBytes, 0, _datePreambleBytes.Length);
+            DatePreambleBytes.CopyTo(dateBytes);
-            Encoding.ASCII.GetBytes(dateValue, 0, dateValue.Length, dateBytes, _datePreambleBytes.Length);
+            Encoding.ASCII.GetBytes(dateValue, dateBytes.AsSpan(DatePreambleBytes.Length));
 
             var dateValues = new DateHeaderValues
             {

src/Servers/Kestrel/Core/src/Internal/Http/HttpResponseHeaders.cs

@@ -14,6 +14,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 {
     internal sealed partial class HttpResponseHeaders : HttpHeaders
     {
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
         private static ReadOnlySpan<byte> CrLf => new[] { (byte)'\r', (byte)'\n' };
         private static ReadOnlySpan<byte> ColonSpace => new[] { (byte)':', (byte)' ' };
 

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Connection.Generated.cs

@@ -0,0 +1,23 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
+{
+    internal partial class Http2Connection
+    {
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
+     
+        private static ReadOnlySpan<byte> ClientPrefaceBytes => new byte[24] { (byte)'P', (byte)'R', (byte)'I', (byte)' ', (byte)'*', (byte)' ', (byte)'H', (byte)'T', (byte)'T', (byte)'P', (byte)'/', (byte)'2', (byte)'.', (byte)'0', (byte)'\r', (byte)'\n', (byte)'\r', (byte)'\n', (byte)'S', (byte)'M', (byte)'\r', (byte)'\n', (byte)'\r', (byte)'\n' };
+        private static ReadOnlySpan<byte> AuthorityBytes => new byte[10] { (byte)':', (byte)'a', (byte)'u', (byte)'t', (byte)'h', (byte)'o', (byte)'r', (byte)'i', (byte)'t', (byte)'y' };
+        private static ReadOnlySpan<byte> MethodBytes => new byte[7] { (byte)':', (byte)'m', (byte)'e', (byte)'t', (byte)'h', (byte)'o', (byte)'d' };
+        private static ReadOnlySpan<byte> PathBytes => new byte[5] { (byte)':', (byte)'p', (byte)'a', (byte)'t', (byte)'h' };
+        private static ReadOnlySpan<byte> SchemeBytes => new byte[7] { (byte)':', (byte)'s', (byte)'c', (byte)'h', (byte)'e', (byte)'m', (byte)'e' };
+        private static ReadOnlySpan<byte> StatusBytes => new byte[7] { (byte)':', (byte)'s', (byte)'t', (byte)'a', (byte)'t', (byte)'u', (byte)'s' };
+        private static ReadOnlySpan<byte> ConnectionBytes => new byte[10] { (byte)'c', (byte)'o', (byte)'n', (byte)'n', (byte)'e', (byte)'c', (byte)'t', (byte)'i', (byte)'o', (byte)'n' };
+        private static ReadOnlySpan<byte> TeBytes => new byte[2] { (byte)'t', (byte)'e' };
+        private static ReadOnlySpan<byte> TrailersBytes => new byte[8] { (byte)'t', (byte)'r', (byte)'a', (byte)'i', (byte)'l', (byte)'e', (byte)'r', (byte)'s' };
+        private static ReadOnlySpan<byte> ConnectBytes => new byte[7] { (byte)'C', (byte)'O', (byte)'N', (byte)'N', (byte)'E', (byte)'C', (byte)'T' };
+    }
+}

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Connection.cs

@@ -27,23 +27,13 @@ using Microsoft.Net.Http.Headers;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
 {
-    internal class Http2Connection : IHttp2StreamLifetimeHandler, IHttpHeadersHandler, IRequestProcessor
+    internal partial class Http2Connection : IHttp2StreamLifetimeHandler, IHttpHeadersHandler, IRequestProcessor
     {
-        public static byte[] ClientPreface { get; } = Encoding.ASCII.GetBytes("PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n");
+        public static ReadOnlySpan<byte> ClientPreface => ClientPrefaceBytes;
 
         private static readonly PseudoHeaderFields _mandatoryRequestPseudoHeaderFields =
             PseudoHeaderFields.Method | PseudoHeaderFields.Path | PseudoHeaderFields.Scheme;
 
-        private static readonly byte[] _authorityBytes = Encoding.ASCII.GetBytes(HeaderNames.Authority);
-        private static readonly byte[] _methodBytes = Encoding.ASCII.GetBytes(HeaderNames.Method);
-        private static readonly byte[] _pathBytes = Encoding.ASCII.GetBytes(HeaderNames.Path);
-        private static readonly byte[] _schemeBytes = Encoding.ASCII.GetBytes(HeaderNames.Scheme);
-        private static readonly byte[] _statusBytes = Encoding.ASCII.GetBytes(HeaderNames.Status);
-        private static readonly byte[] _connectionBytes = Encoding.ASCII.GetBytes("connection");
-        private static readonly byte[] _teBytes = Encoding.ASCII.GetBytes("te");
-        private static readonly byte[] _trailersBytes = Encoding.ASCII.GetBytes("trailers");
-        private static readonly byte[] _connectBytes = Encoding.ASCII.GetBytes("CONNECT");
-
         private readonly HttpConnectionContext _context;
         private readonly Http2FrameWriter _frameWriter;
         private readonly Pipe _input;
@@ -1175,7 +1165,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
 
                 if (headerField == PseudoHeaderFields.Method)
                 {
-                    _isMethodConnect = value.SequenceEqual(_connectBytes);
+                    _isMethodConnect = value.SequenceEqual(ConnectBytes);
                 }
 
                 _parsedPseudoHeaderFields |= headerField;
@@ -1217,23 +1207,23 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
                 return false;
             }
 
-            if (name.SequenceEqual(_pathBytes))
+            if (name.SequenceEqual(PathBytes))
             {
                 headerField = PseudoHeaderFields.Path;
             }
-            else if (name.SequenceEqual(_methodBytes))
+            else if (name.SequenceEqual(MethodBytes))
             {
                 headerField = PseudoHeaderFields.Method;
             }
-            else if (name.SequenceEqual(_schemeBytes))
+            else if (name.SequenceEqual(SchemeBytes))
             {
                 headerField = PseudoHeaderFields.Scheme;
             }
-            else if (name.SequenceEqual(_statusBytes))
+            else if (name.SequenceEqual(StatusBytes))
             {
                 headerField = PseudoHeaderFields.Status;
             }
-            else if (name.SequenceEqual(_authorityBytes))
+            else if (name.SequenceEqual(AuthorityBytes))
             {
                 headerField = PseudoHeaderFields.Authority;
             }
@@ -1247,7 +1237,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
 
         private static bool IsConnectionSpecificHeaderField(ReadOnlySpan<byte> name, ReadOnlySpan<byte> value)
         {
-            return name.SequenceEqual(_connectionBytes) || (name.SequenceEqual(_teBytes) && !value.SequenceEqual(_trailersBytes));
+            return name.SequenceEqual(ConnectionBytes) || (name.SequenceEqual(TeBytes) && !value.SequenceEqual(TrailersBytes));
         }
 
         private bool TryClose()

src/Servers/Kestrel/Core/src/Internal/Http2/Http2FrameWriter.cs

@@ -22,6 +22,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
     internal class Http2FrameWriter
     {
         // Literal Header Field without Indexing - Indexed Name (Index 8 - :status)
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
         private static ReadOnlySpan<byte> ContinueBytes => new byte[] { 0x08, 0x03, (byte)'1', (byte)'0', (byte)'0' };
 
         private readonly object _writeLock = new object();

src/Servers/Kestrel/Kestrel/test/GeneratedCodeTests.cs

@@ -16,14 +16,16 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
         [Flaky("https://github.com/aspnet/AspNetCore-Internal/issues/2223", FlakyOn.Helix.All)]
         public void GeneratedCodeIsUpToDate()
         {
-            var httpHeadersGeneratedPath = Path.Combine(AppContext.BaseDirectory,"shared", "GeneratedContent", "HttpHeaders.Generated.cs");
+            var httpHeadersGeneratedPath = Path.Combine(AppContext.BaseDirectory, "shared", "GeneratedContent", "HttpHeaders.Generated.cs");
-            var httpProtocolGeneratedPath = Path.Combine(AppContext.BaseDirectory,"shared", "GeneratedContent", "HttpProtocol.Generated.cs");
+            var httpProtocolGeneratedPath = Path.Combine(AppContext.BaseDirectory, "shared", "GeneratedContent", "HttpProtocol.Generated.cs");
-            var httpUtilitiesGeneratedPath = Path.Combine(AppContext.BaseDirectory,"shared", "GeneratedContent", "HttpUtilities.Generated.cs");
+            var httpUtilitiesGeneratedPath = Path.Combine(AppContext.BaseDirectory, "shared", "GeneratedContent", "HttpUtilities.Generated.cs");
-            var transportConnectionGeneratedPath = Path.Combine(AppContext.BaseDirectory,"shared", "GeneratedContent", "TransportConnection.Generated.cs");
+            var http2ConnectionGeneratedPath = Path.Combine(AppContext.BaseDirectory, "shared", "GeneratedContent", "Http2Connection.Generated.cs");
+            var transportConnectionGeneratedPath = Path.Combine(AppContext.BaseDirectory, "shared", "GeneratedContent", "TransportConnection.Generated.cs");
 
             var testHttpHeadersGeneratedPath = Path.GetTempFileName();
             var testHttpProtocolGeneratedPath = Path.GetTempFileName();
             var testHttpUtilitiesGeneratedPath = Path.GetTempFileName();
+            var testHttp2ConnectionGeneratedPath = Path.GetTempFileName();
             var testTransportConnectionGeneratedPath = Path.GetTempFileName();
 
             try
@@ -31,26 +33,29 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
                 var currentHttpHeadersGenerated = File.ReadAllText(httpHeadersGeneratedPath);
                 var currentHttpProtocolGenerated = File.ReadAllText(httpProtocolGeneratedPath);
                 var currentHttpUtilitiesGenerated = File.ReadAllText(httpUtilitiesGeneratedPath);
+                var currentHttp2ConnectionGenerated = File.ReadAllText(http2ConnectionGeneratedPath);
                 var currentTransportConnectionGenerated = File.ReadAllText(transportConnectionGeneratedPath);
 
-                CodeGenerator.Program.Run(testHttpHeadersGeneratedPath, testHttpProtocolGeneratedPath, testHttpUtilitiesGeneratedPath, testTransportConnectionGeneratedPath);
+                CodeGenerator.Program.Run(testHttpHeadersGeneratedPath, testHttpProtocolGeneratedPath, testHttpUtilitiesGeneratedPath, testTransportConnectionGeneratedPath, testHttp2ConnectionGeneratedPath);
 
                 var testHttpHeadersGenerated = File.ReadAllText(testHttpHeadersGeneratedPath);
                 var testHttpProtocolGenerated = File.ReadAllText(testHttpProtocolGeneratedPath);
                 var testHttpUtilitiesGenerated = File.ReadAllText(testHttpUtilitiesGeneratedPath);
+                var testHttp2ConnectionGenerated = File.ReadAllText(testHttp2ConnectionGeneratedPath);
                 var testTransportConnectionGenerated = File.ReadAllText(testTransportConnectionGeneratedPath);
 
                 Assert.Equal(currentHttpHeadersGenerated, testHttpHeadersGenerated, ignoreLineEndingDifferences: true);
                 Assert.Equal(currentHttpProtocolGenerated, testHttpProtocolGenerated, ignoreLineEndingDifferences: true);
                 Assert.Equal(currentHttpUtilitiesGenerated, testHttpUtilitiesGenerated, ignoreLineEndingDifferences: true);
+                Assert.Equal(currentHttp2ConnectionGenerated, testHttp2ConnectionGenerated, ignoreLineEndingDifferences: true);
                 Assert.Equal(currentTransportConnectionGenerated, testTransportConnectionGenerated, ignoreLineEndingDifferences: true);
-
             }
             finally
             {
                 File.Delete(testHttpHeadersGeneratedPath);
                 File.Delete(testHttpProtocolGeneratedPath);
                 File.Delete(testHttpUtilitiesGeneratedPath);
+                File.Delete(testHttp2ConnectionGeneratedPath);
                 File.Delete(testTransportConnectionGeneratedPath);
             }
         }

src/Servers/Kestrel/Kestrel/test/Microsoft.AspNetCore.Server.Kestrel.Tests.csproj

@@ -12,6 +12,7 @@
     <Content Include="$(KestrelRoot)Core\src\Internal\Http\HttpHeaders.Generated.cs" LinkBase="shared\GeneratedContent" CopyToOutputDirectory="PreserveNewest" />
     <Content Include="$(KestrelRoot)Core\src\Internal\Http\HttpProtocol.Generated.cs" LinkBase="shared\GeneratedContent" CopyToOutputDirectory="PreserveNewest" />
     <Content Include="$(KestrelRoot)Core\src\Internal\Infrastructure\HttpUtilities.Generated.cs" LinkBase="shared\GeneratedContent" CopyToOutputDirectory="PreserveNewest" />
+    <Content Include="$(KestrelRoot)Core\src\Internal\Http2\Http2Connection.Generated.cs" LinkBase="shared\GeneratedContent" CopyToOutputDirectory="PreserveNewest" />
     <Content Include="$(KestrelSharedSourceRoot)\TransportConnection.Generated.cs" LinkBase="shared\GeneratedContent" CopyToOutputDirectory="PreserveNewest" />
   </ItemGroup>
 

src/Servers/Kestrel/samples/http2cat/Http2Utilities.cs

@@ -340,7 +340,7 @@ namespace http2cat
             await writableBuffer.FlushAsync().AsTask().DefaultTimeout();
         }
 
-        public Task SendPreambleAsync() => SendAsync(new ArraySegment<byte>(Http2Connection.ClientPreface));
+        public Task SendPreambleAsync() => SendAsync(Http2Connection.ClientPreface);
 
         public async Task SendSettingsAsync()
         {

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

@@ -688,7 +688,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             await writableBuffer.FlushAsync().AsTask().DefaultTimeout();
         }
 
-        protected Task SendPreambleAsync() => SendAsync(new ArraySegment<byte>(Http2Connection.ClientPreface));
+        protected Task SendPreambleAsync() => SendAsync(Http2Connection.ClientPreface);
 
         protected async Task SendSettingsAsync()
         {

src/Servers/Kestrel/tools/CodeGenerator/CodeGenerator.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>$(DefaultNetCoreTargetFramework)</TargetFramework>
@@ -18,7 +18,7 @@
 
   <PropertyGroup>
     <StartWorkingDirectory>$(MSBuildThisFileDirectory)..\..\</StartWorkingDirectory>
-    <StartArguments>Core/src/Internal/Http/HttpHeaders.Generated.cs Core/src/Internal/Http/HttpProtocol.Generated.cs Core/src/Internal/Infrastructure/HttpUtilities.Generated.cs shared/TransportConnection.Generated.cs</StartArguments>
+    <StartArguments>Core/src/Internal/Http/HttpHeaders.Generated.cs Core/src/Internal/Http/HttpProtocol.Generated.cs Core/src/Internal/Infrastructure/HttpUtilities.Generated.cs shared/TransportConnection.Generated.cs Core/src/Internal/Http2/Http2Connection.Generated.cs</StartArguments>
   </PropertyGroup>
 
 </Project>

src/Servers/Kestrel/tools/CodeGenerator/Http2Connection.cs

@@ -0,0 +1,33 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using Microsoft.Net.Http.Headers;
+
+namespace CodeGenerator
+{
+    public static class Http2Connection
+    {
+        public static string GenerateFile()
+        {
+            return ReadOnlySpanStaticDataGenerator.GenerateFile(
+                namespaceName: "Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2",
+                className: "Http2Connection",
+                allProperties: GetStrings());
+        }
+
+        private static IEnumerable<(string Name, string Value)> GetStrings()
+        {
+            yield return ("ClientPreface", "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n");
+            yield return ("Authority", HeaderNames.Authority);
+            yield return ("Method", HeaderNames.Method);
+            yield return ("Path", HeaderNames.Path);
+            yield return ("Scheme", HeaderNames.Scheme);
+            yield return ("Status", HeaderNames.Status);
+            yield return ("Connection", "connection");
+            yield return ("Te", "te");
+            yield return ("Trailers", "trailers");
+            yield return ("Connect", "CONNECT");
+        }
+    }
+}

src/Servers/Kestrel/tools/CodeGenerator/Program.cs

@@ -30,8 +30,13 @@ namespace CodeGenerator
                 Console.Error.WriteLine("Missing path to TransportConnection.Generated.cs");
                 return 1;
             }
+            else if (args.Length < 5)
+            {
+                Console.Error.WriteLine("Missing path to Http2Connection.Generated.cs");
+                return 1;
+            }
 
-            Run(args[0], args[1], args[2], args[3]);
+            Run(args[0], args[1], args[2], args[3], args[4]);
 
             return 0;
         }
@@ -40,12 +45,14 @@ namespace CodeGenerator
             string knownHeadersPath,
             string httpProtocolFeatureCollectionPath,
             string httpUtilitiesPath,
-            string transportConnectionFeatureCollectionPath)
+            string transportConnectionFeatureCollectionPath,
+            string http2ConnectionPath)
         {
             var knownHeadersContent = KnownHeaders.GeneratedFile();
             var httpProtocolFeatureCollectionContent = HttpProtocolFeatureCollection.GenerateFile();
             var httpUtilitiesContent = HttpUtilities.HttpUtilities.GeneratedFile();
             var transportConnectionFeatureCollectionContent = TransportConnectionFeatureCollection.GenerateFile();
+            var http2ConnectionContent = Http2Connection.GenerateFile();
 
             var existingKnownHeaders = File.Exists(knownHeadersPath) ? File.ReadAllText(knownHeadersPath) : "";
             if (!string.Equals(knownHeadersContent, existingKnownHeaders))
@@ -70,6 +77,12 @@ namespace CodeGenerator
             {
                 File.WriteAllText(transportConnectionFeatureCollectionPath, transportConnectionFeatureCollectionContent);
             }
+
+            var existingHttp2Connection = File.Exists(http2ConnectionPath) ? File.ReadAllText(http2ConnectionPath) : "";
+            if (!string.Equals(http2ConnectionContent, existingHttp2Connection))
+            {
+                File.WriteAllText(http2ConnectionPath, http2ConnectionContent);
+            }
         }
     }
 }

src/Servers/Kestrel/tools/CodeGenerator/ReadOnlySpanStaticDataGenerator.cs

@@ -0,0 +1,78 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace CodeGenerator
+{
+    public static class ReadOnlySpanStaticDataGenerator
+    {
+        public static string GenerateFile(string namespaceName, string className, IEnumerable<(string Name, string Value)> allProperties)
+        {
+            var properties = allProperties.Select((p, index) => new Property
+            {
+                Data = p,
+                Index = index
+            });
+
+            return $@"// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace {namespaceName}
+{{
+    internal partial class {className}
+    {{
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
+     {Each(properties, p => $@"
+        private static ReadOnlySpan<byte> {p.Data.Name}Bytes => new byte[{p.Data.Value.Length}] {{ {GetDataAsBytes(p.Data.Value)} }};")}
+    }}
+}}
+";
+        }
+
+        private static string Each<T>(IEnumerable<T> values, Func<T, string> formatter)
+        {
+            return values.Any() ? values.Select(formatter).Aggregate((a, b) => a + b) : "";
+        }
+
+        private static string GetDataAsBytes(string value)
+        {
+            var stringBuilder = new StringBuilder();
+
+            for (var i = 0; i < value.Length; ++i)
+            {
+                var c = value[i];
+                if (c == '\n')
+                {
+                    stringBuilder.Append("(byte)'\\n'");
+                }
+                else if (c == '\r')
+                {
+                    stringBuilder.Append("(byte)'\\r'");
+                }
+                else
+                {
+                    stringBuilder.AppendFormat("(byte)'{0}'", c);
+                }
+
+                if (i < value.Length - 1)
+                {
+                    stringBuilder.Append(", ");
+                }
+            }
+
+            return stringBuilder.ToString();
+        }
+
+        private class Property
+        {
+            public (string Name, string Value) Data;
+            public int Index;
+        }
+    }
+}

src/Shared/Http2/Hpack/StatusCodes.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0.
 // See THIRD-PARTY-NOTICES.TXT in the project root for license information.
 
@@ -9,6 +9,8 @@ namespace System.Net.Http.HPack
 {
     internal static class StatusCodes
     {
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
+
         private static ReadOnlySpan<byte> BytesStatus100 => new byte[] { (byte)'1', (byte)'0', (byte)'0' };
         private static ReadOnlySpan<byte> BytesStatus101 => new byte[] { (byte)'1', (byte)'0', (byte)'1' };
         private static ReadOnlySpan<byte> BytesStatus102 => new byte[] { (byte)'1', (byte)'0', (byte)'2' };

src/SignalR/clients/csharp/Http.Connections.Client/src/Internal/ServerSentEventsMessageParser.cs

@@ -15,8 +15,9 @@ namespace Microsoft.AspNetCore.Http.Connections.Client.Internal
         private const byte ByteLF = (byte)'\n';
         private const byte ByteColon = (byte)':';
 
-        private static ReadOnlySpan<byte> _dataPrefix => new byte[] { (byte)'d', (byte)'a', (byte)'t', (byte)'a', (byte)':', (byte)' ' };
+        // This uses C# compiler's ability to refer to static data directly. For more information see https://vcsjones.dev/2019/02/01/csharp-readonly-span-bytes-static
-        private static ReadOnlySpan<byte> _sseLineEnding => new byte[] { (byte)'\r', (byte)'\n' };
+        private static ReadOnlySpan<byte> DataPrefix => new byte[] { (byte)'d', (byte)'a', (byte)'t', (byte)'a', (byte)':', (byte)' ' };
+        private static ReadOnlySpan<byte> SseLineEnding => new byte[] { (byte)'\r', (byte)'\n' };
         private static readonly byte[] _newLine = Encoding.UTF8.GetBytes(Environment.NewLine);
 
         private InternalParseState _internalParserState = InternalParseState.ReadMessagePayload;
@@ -74,7 +75,7 @@ namespace Microsoft.AspNetCore.Http.Connections.Client.Internal
                 // data: foo\n\bar should be encoded as
                 // data: foo\r\n
                 // data: bar\r\n
-                else if (line[line.Length - _sseLineEnding.Length] != ByteCR)
+                else if (line[line.Length - SseLineEnding.Length] != ByteCR)
                 {
                     throw new FormatException("Unexpected '\\n' in message. A '\\n' character can only be used as part of the newline sequence '\\r\\n'");
                 }
@@ -90,8 +91,8 @@ namespace Microsoft.AspNetCore.Http.Connections.Client.Internal
                         EnsureStartsWithDataPrefix(line);
 
                         // Slice away the 'data: '
-                        var payloadLength = line.Length - (_dataPrefix.Length + _sseLineEnding.Length);
+                        var payloadLength = line.Length - (DataPrefix.Length + SseLineEnding.Length);
-                        var newData = line.Slice(_dataPrefix.Length, payloadLength).ToArray();
+                        var newData = line.Slice(DataPrefix.Length, payloadLength).ToArray();
                         _data.Add(newData);
 
                         start = lineEnd;
@@ -162,7 +163,7 @@ namespace Microsoft.AspNetCore.Http.Connections.Client.Internal
 
         private void EnsureStartsWithDataPrefix(ReadOnlySpan<byte> line)
         {
-            if (!line.StartsWith(_dataPrefix))
+            if (!line.StartsWith(DataPrefix))
             {
                 throw new FormatException("Expected the message prefix 'data: '");
             }
@@ -170,7 +171,7 @@ namespace Microsoft.AspNetCore.Http.Connections.Client.Internal
 
         private bool IsMessageEnd(ReadOnlySpan<byte> line)
         {
-            return line.Length == _sseLineEnding.Length && line.SequenceEqual(_sseLineEnding);
+            return line.Length == SseLineEnding.Length && line.SequenceEqual(SseLineEnding);
         }
 
         public enum ParseResult