Tackling some low hanging performance fruit (#1470)

* Tackling some low hanging performance fruit
- Use native Memory/Span APIs on Stream and WebSocket in .NET Core 2.1
- Remove double copying in formatters
- Implemented custom HttpContent over ReadOnlyBuffer<byte>

benchmarks/Microsoft.AspNetCore.SignalR.Microbenchmarks/MessageParserBenchmark.cs

@@ -23,14 +23,16 @@ namespace Microsoft.AspNetCore.SignalR.Microbenchmarks
             var buffer = new byte[MessageLength];
             Random.NextBytes(buffer);
             var output = new MemoryStream();
-            BinaryMessageFormatter.WriteMessage(buffer, output);
+            BinaryMessageFormatter.WriteLengthPrefix(buffer.Length, output);
+            output.Write(buffer, 0, buffer.Length);
 
             _binaryInput = output.ToArray();
 
             buffer = new byte[MessageLength];
             Random.NextBytes(buffer);
             output = new MemoryStream();
-            TextMessageFormatter.WriteMessage(buffer, output);
+            output.Write(buffer, 0, buffer.Length);
+            TextMessageFormatter.WriteRecordSeparator(output);
 
             _textInput = output.ToArray();
         }

src/Common/PipeWriterStream.cs

@@ -4,11 +4,10 @@
 using System;
 using System.Buffers;
 using System.IO;
-using System.IO.Pipelines;
 using System.Threading;
 using System.Threading.Tasks;
 
-namespace Microsoft.AspNetCore.Sockets.Http.Internal
+namespace System.IO.Pipelines
 {
     // Write only stream implementation for efficiently writing bytes from the request body
     internal class PipeWriterStream : Stream
@@ -62,5 +61,14 @@ namespace Microsoft.AspNetCore.Sockets.Http.Internal
             Write(buffer, offset, count);
             return Task.CompletedTask;
         }
+
+#if NETCOREAPP2_1
+        public override Task WriteAsync(ReadOnlyMemory<byte> source, CancellationToken cancellationToken = default)
+        {
+            _pipeWriter.Write(source.Span);
+            _length += source.Length;
+            return Task.CompletedTask;
+        }
+#endif
     }
 }

src/Common/StreamExtensions.cs

@@ -0,0 +1,30 @@
+// 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.Buffers;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.IO
+{
+    internal static class StreamExtensions
+    {
+        public static async Task WriteAsync(this Stream stream, ReadOnlyBuffer<byte> buffer, CancellationToken cancellationToken = default)
+        {
+            // REVIEW: Should we special case IsSingleSegment here?
+            foreach (var segment in buffer)
+            {
+#if NETCOREAPP2_1
+                await stream.WriteAsync(segment, cancellationToken);
+#else
+                var isArray = MemoryMarshal.TryGetArray(segment, out var arraySegment);
+                // We're using the managed memory pool which is backed by managed buffers
+                Debug.Assert(isArray);
+                await stream.WriteAsync(arraySegment.Array, arraySegment.Offset, arraySegment.Count, cancellationToken);
+#endif
+            }
+        }
+    }
+}

src/Common/WebSocketExtensions.cs

@@ -0,0 +1,43 @@
+// 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.Buffers;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.Net.WebSockets
+{
+    internal static class WebSocketExtensions
+    {
+        public static Task SendAsync(this WebSocket webSocket, ReadOnlyBuffer<byte> buffer, WebSocketMessageType webSocketMessageType, CancellationToken cancellationToken = default)
+        {
+            // TODO: Consider chunking writes here if we get a multi segment buffer
+#if NETCOREAPP2_1
+            if (buffer.IsSingleSegment)
+            {
+                return webSocket.SendAsync(buffer.First, webSocketMessageType, endOfMessage: true, cancellationToken);
+            }
+            else
+            {
+                return webSocket.SendAsync(buffer.ToArray(), webSocketMessageType, endOfMessage: true, cancellationToken);
+            }
+#else
+            if (buffer.IsSingleSegment)
+            {
+                var isArray = MemoryMarshal.TryGetArray(buffer.First, out var segment);
+                Debug.Assert(isArray);
+                return webSocket.SendAsync(segment, webSocketMessageType, endOfMessage: true, cancellationToken);
+            }
+            else
+            {
+                return webSocket.SendAsync(new ArraySegment<byte>(buffer.ToArray()), webSocketMessageType, true, cancellationToken);
+            }
+#endif
+        }
+    }
+}

src/Microsoft.AspNetCore.SignalR.Common/Internal/Formatters/BinaryMessageFormatter.cs

@@ -2,21 +2,23 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Buffers;
 using System.IO;
 
 namespace Microsoft.AspNetCore.SignalR.Internal.Formatters
 {
     public static class BinaryMessageFormatter
     {
-        public unsafe static void WriteMessage(ReadOnlySpan<byte> payload, Stream output)
+        public static void WriteLengthPrefix(long length, Stream output)
         {
             // This code writes length prefix of the message as a VarInt. Read the comment in
             // the BinaryMessageParser.TryParseMessage for details.
 
-            var lenBuffer = stackalloc byte[5];
+#if NETCOREAPP2_1
+            Span<byte> lenBuffer = stackalloc byte[5];
+#else
+            var lenBuffer = new byte[5];
+#endif
             var lenNumBytes = 0;
-            var length = payload.Length;
             do
             {
                 ref var current = ref lenBuffer[lenNumBytes];
@@ -30,14 +32,11 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Formatters
             }
             while (length > 0);
 
-            var buffer = ArrayPool<byte>.Shared.Rent(lenNumBytes + payload.Length);
-            var bufferSpan = buffer.AsSpan();
-
-            new ReadOnlySpan<byte>(lenBuffer, lenNumBytes).CopyTo(bufferSpan);
-            bufferSpan = bufferSpan.Slice(lenNumBytes);
-            payload.CopyTo(bufferSpan);
-            output.Write(buffer, 0, lenNumBytes + payload.Length);
-            ArrayPool<byte>.Shared.Return(buffer);
+#if NETCOREAPP2_1
+            output.Write(lenBuffer.Slice(0, lenNumBytes));
+#else
+            output.Write(lenBuffer, 0, lenNumBytes);
+#endif
         }
     }
 }

src/Microsoft.AspNetCore.SignalR.Common/Internal/Formatters/TextMessageFormatter.cs

@@ -1,8 +1,6 @@
 // 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.Buffers;
 using System.IO;
 
 namespace Microsoft.AspNetCore.SignalR.Internal.Formatters
@@ -13,11 +11,8 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Formatters
         // will not occur (is not a valid character) and therefore it is safe to not escape it
         internal static readonly byte RecordSeparator = 0x1e;
 
-        public static void WriteMessage(ReadOnlySpan<byte> payload, Stream output)
+        public static void WriteRecordSeparator(Stream output)
         {
-            var buffer = ArrayPool<byte>.Shared.Rent(payload.Length);
-            payload.CopyTo(buffer);
-            output.Write(buffer, 0, payload.Length);
             output.WriteByte(RecordSeparator);
         }
     }

src/Microsoft.AspNetCore.SignalR.Common/Internal/Protocol/JsonHubProtocol.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Runtime.ExceptionServices;
+using System.Text;
 using Microsoft.AspNetCore.SignalR.Internal.Formatters;
 using Microsoft.Extensions.Options;
 using Newtonsoft.Json;
@@ -15,6 +16,8 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
 {
     public class JsonHubProtocol : IHubProtocol
     {
+        private static readonly UTF8Encoding _utf8NoBom = new UTF8Encoding(encoderShouldEmitUTF8Identifier: false);
+
         private const string ResultPropertyName = "result";
         private const string ItemPropertyName = "item";
         private const string InvocationIdPropertyName = "invocationId";
@@ -59,13 +62,8 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
 
         public void WriteMessage(HubMessage message, Stream output)
         {
-            using (var memoryStream = new MemoryStream())
-            {
-                WriteMessageCore(message, memoryStream);
-                memoryStream.Flush();
-
-                TextMessageFormatter.WriteMessage(memoryStream.ToArray(), output);
-            }
+            WriteMessageCore(message, output);
+            TextMessageFormatter.WriteRecordSeparator(output);
         }
 
         private HubMessage ParseMessage(Stream input, IInvocationBinder binder)
@@ -135,7 +133,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
 
         private void WriteMessageCore(HubMessage message, Stream stream)
         {
-            using (var writer = new JsonTextWriter(new StreamWriter(stream)))
+            using (var writer = new JsonTextWriter(new StreamWriter(stream, _utf8NoBom, 1024, leaveOpen: true)))
             {
                 writer.WriteStartObject();
                 switch (message)

src/Microsoft.AspNetCore.SignalR.Common/Internal/Protocol/NegotiationProtocol.cs

@@ -5,6 +5,7 @@ using System;
 using System.Buffers;
 using System.Collections;
 using System.IO;
+using System.Text;
 using Microsoft.AspNetCore.SignalR.Internal.Formatters;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
@@ -13,22 +14,21 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
 {
     public static class NegotiationProtocol
     {
+        private static readonly UTF8Encoding _utf8NoBom = new UTF8Encoding(encoderShouldEmitUTF8Identifier: false);
+
         private const string ProtocolPropertyName = "protocol";
 
         public static void WriteMessage(NegotiationMessage negotiationMessage, Stream output)
         {
-            using (var memoryStream = new MemoryStream())
+            using (var writer = new JsonTextWriter(new StreamWriter(output, _utf8NoBom, 1024, leaveOpen: true)))
             {
-                using (var writer = new JsonTextWriter(new StreamWriter(memoryStream)))
-                {
-                    writer.WriteStartObject();
-                    writer.WritePropertyName(ProtocolPropertyName);
-                    writer.WriteValue(negotiationMessage.Protocol);
-                    writer.WriteEndObject();
-                }
-
-                TextMessageFormatter.WriteMessage(memoryStream.ToArray(), output);
+                writer.WriteStartObject();
+                writer.WritePropertyName(ProtocolPropertyName);
+                writer.WriteValue(negotiationMessage.Protocol);
+                writer.WriteEndObject();
             }
+
+            TextMessageFormatter.WriteRecordSeparator(output);
         }
 
         public static bool TryParseMessage(ReadOnlySpan<byte> input, out NegotiationMessage negotiationMessage)

src/Microsoft.AspNetCore.SignalR.Common/Microsoft.AspNetCore.SignalR.Common.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <Description>Common serialiation primitives for SignalR Clients Servers</Description>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;netcoreapp2.1</TargetFrameworks>
     <RootNamespace>Microsoft.AspNetCore.SignalR</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>

src/Microsoft.AspNetCore.SignalR.Protocols.MsgPack/Internal/Protocol/MessagePackHubProtocol.cs

@@ -229,10 +229,22 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Protocol
 
         public void WriteMessage(HubMessage message, Stream output)
         {
+            // We're writing data into the memoryStream so that we can get the length prefix
             using (var memoryStream = new MemoryStream())
             {
                 WriteMessageCore(message, memoryStream);
-                BinaryMessageFormatter.WriteMessage(new ReadOnlySpan<byte>(memoryStream.ToArray()), output);
+                if (memoryStream.TryGetBuffer(out var buffer))
+                {
+                    // Write the buffer directly
+                    BinaryMessageFormatter.WriteLengthPrefix(buffer.Count, output);
+                    output.Write(buffer.Array, buffer.Offset, buffer.Count);
+                }
+                else
+                {
+                    BinaryMessageFormatter.WriteLengthPrefix(memoryStream.Length, output);
+                    memoryStream.Position = 0;
+                    memoryStream.CopyTo(output);
+                }
             }
         }
 

src/Microsoft.AspNetCore.Sockets.Client.Http/LongPollingTransport.cs

@@ -123,12 +123,9 @@ namespace Microsoft.AspNetCore.Sockets.Client
                     {
                         _logger.ReceivedMessages();
 
-                        // TODO: Use CopyToAsync here
-                        var payload = await response.Content.ReadAsByteArrayAsync();
-                        if (payload.Length > 0)
-                        {
-                            await _application.Output.WriteAsync(payload);
-                        }
+                        var stream = new PipeWriterStream(_application.Output);
+                        await response.Content.CopyToAsync(stream);
+                        await _application.Output.FlushAsync();
                     }
                 }
             }

src/Microsoft.AspNetCore.Sockets.Client.Http/Microsoft.AspNetCore.Sockets.Client.Http.csproj

@@ -2,11 +2,14 @@
 
   <PropertyGroup>
     <Description>Client for ASP.NET Core SignalR</Description>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;netcoreapp2.1</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
     <Compile Include="..\Common\ForceAsyncAwaiter.cs" Link="ForceAsyncAwaiter.cs" />
+    <Compile Include="..\Common\PipeWriterStream.cs" Link="PipeWriterStream.cs" />
+    <Compile Include="..\Common\WebSocketExtensions.cs" Link="WebSocketExtensions.cs" />
+    <Compile Include="..\Common\StreamExtensions.cs" Link="StreamExtensions.cs" />
   </ItemGroup>
 
   <ItemGroup>

src/Microsoft.AspNetCore.Sockets.Client.Http/SendMessage.cs

@@ -1,19 +0,0 @@
-// 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.Threading.Tasks;
-
-namespace Microsoft.AspNetCore.Sockets.Client
-{
-    public struct SendMessage
-    {
-        public byte[] Payload { get; }
-        public TaskCompletionSource<object> SendResult { get; }
-
-        public SendMessage(byte[] payload, TaskCompletionSource<object> result)
-        {
-            Payload = payload;
-            SendResult = result;
-        }
-    }
-}

src/Microsoft.AspNetCore.Sockets.Client.Http/SendUtils.cs

@@ -2,7 +2,10 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Buffers;
+using System.IO;
 using System.IO.Pipelines;
+using System.Net;
 using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
@@ -39,8 +42,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
                             var request = new HttpRequestMessage(HttpMethod.Post, sendUrl);
                             PrepareHttpRequest(request, httpOptions);
 
-                            // TODO: Use a custom stream implementation over the ReadOnlyBuffer<byte>
-                            request.Content = new ByteArrayContent(buffer.ToArray());
+                            request.Content = new ReadOnlyBufferContent(buffer);
 
                             var response = await httpClient.SendAsync(request, transportCts.Token);
                             response.EnsureSuccessStatusCode();
@@ -96,5 +98,26 @@ namespace Microsoft.AspNetCore.Sockets.Client
                 request.Headers.Add("Authorization", $"Bearer {httpOptions.AccessTokenFactory()}");
             }
         }
+
+        private class ReadOnlyBufferContent : HttpContent
+        {
+            private readonly ReadOnlyBuffer<byte> _buffer;
+
+            public ReadOnlyBufferContent(ReadOnlyBuffer<byte> buffer)
+            {
+                _buffer = buffer;
+            }
+
+            protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
+            {
+                return stream.WriteAsync(_buffer);
+            }
+
+            protected override bool TryComputeLength(out long length)
+            {
+                length = _buffer.Length;
+                return true;
+            }
+        }
     }
 }

src/Microsoft.AspNetCore.Sockets.Client.Http/WebSocketsTransport.cs

@@ -2,8 +2,10 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Diagnostics;
 using System.IO.Pipelines;
 using System.Net.WebSockets;
+using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Sockets.Client.Http;
@@ -102,18 +104,23 @@ namespace Microsoft.AspNetCore.Sockets.Client
                 {
                     var memory = _application.Output.GetMemory();
 
-                    // REVIEW: Use new Memory<byte> websocket APIs on .NET Core 2.1
-                    memory.TryGetArray(out var arraySegment);
+#if NETCOREAPP2_1
+                    var receiveResult = await _webSocket.ReceiveAsync(memory, _receiveCts.Token);
+#else
+                    var isArray = memory.TryGetArray(out var arraySegment);
+                    Debug.Assert(isArray);
 
                     // Exceptions are handled above where the send and receive tasks are being run.
                     var receiveResult = await _webSocket.ReceiveAsync(arraySegment, _receiveCts.Token);
+#endif
+
                     if (receiveResult.MessageType == WebSocketMessageType.Close)
                     {
-                        _logger.WebSocketClosed(receiveResult.CloseStatus);
+                        _logger.WebSocketClosed(_webSocket.CloseStatus);
 
-                        if (receiveResult.CloseStatus != WebSocketCloseStatus.NormalClosure)
+                        if (_webSocket.CloseStatus != WebSocketCloseStatus.NormalClosure)
                         {
-                            throw new InvalidOperationException($"Websocket closed with error: {receiveResult.CloseStatus}.");
+                            throw new InvalidOperationException($"Websocket closed with error: {_webSocket.CloseStatus}.");
                         }
 
                         return;
@@ -162,7 +169,7 @@ namespace Microsoft.AspNetCore.Sockets.Client
                         {
                             _logger.ReceivedFromApp(buffer.Length);
 
-                            await _webSocket.SendAsync(new ArraySegment<byte>(buffer.ToArray()), webSocketMessageType, true, _transportCts.Token);
+                            await _webSocket.SendAsync(buffer, webSocketMessageType, _transportCts.Token);
                         }
                         else if (result.IsCompleted)
                         {

src/Microsoft.AspNetCore.Sockets.Http/HttpConnectionDispatcher.cs

@@ -12,7 +12,6 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Protocols;
 using Microsoft.AspNetCore.Sockets.Features;
-using Microsoft.AspNetCore.Sockets.Http.Internal;
 using Microsoft.AspNetCore.Sockets.Internal;
 using Microsoft.AspNetCore.Sockets.Internal.Transports;
 using Microsoft.Extensions.Logging;

src/Microsoft.AspNetCore.Sockets.Http/Internal/Transports/LongPollingTransport.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Diagnostics;
+using System.IO;
 using System.IO.Pipelines;
 using System.Runtime.InteropServices;
 using System.Threading;
@@ -52,13 +53,7 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Transports
 
                 try
                 {
-                    foreach (var segment in buffer)
-                    {
-                        var isArray = MemoryMarshal.TryGetArray(segment, out var arraySegment);
-                        // We're using the managed memory pool which is backed by managed buffers
-                        Debug.Assert(isArray);
-                        await context.Response.Body.WriteAsync(arraySegment.Array, arraySegment.Offset, arraySegment.Count);
-                    }
+                    await context.Response.Body.WriteAsync(buffer);
                 }
                 finally
                 {

src/Microsoft.AspNetCore.Sockets.Http/Internal/Transports/ServerSentEventsMessageFormatter.cs

@@ -3,7 +3,10 @@
 
 using System;
 using System.Buffers;
+using System.Diagnostics;
 using System.IO;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
 
 namespace Microsoft.AspNetCore.Sockets.Internal.Formatters
 {
@@ -14,7 +17,31 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Formatters
 
         private const byte LineFeed = (byte)'\n';
 
-        public static void WriteMessage(ReadOnlySpan<byte> payload, MemoryStream output)
+        public static async Task WriteMessageAsync(ReadOnlyBuffer<byte> payload, Stream output)
+        {
+            var ms = new MemoryStream();
+
+            // TODO: There are 2 improvements to be made here
+            // 1. Don't convert the entire payload into an array if if's multi-segmented.
+            // 2. Don't allocate the memory stream unless the payload contains \n. If it doesn't we can just write the buffers directly
+            // to the stream without modification. While it does mean that there will be smaller writes, should be fine for the most part
+            // since we're using reasonably sized buffers.
+
+            if (payload.IsSingleSegment)
+            {
+                WriteMessage(payload.First, ms);
+            }
+            else
+            {
+                WriteMessage(payload.ToArray(), ms);
+            }
+
+            ms.Position = 0;
+
+            await ms.CopyToAsync(output);
+        }
+
+        public static void WriteMessage(ReadOnlyMemory<byte> payload, Stream output)
         {
             // Write the payload
             WritePayload(payload, output);
@@ -23,7 +50,7 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Formatters
             output.Write(Newline, 0, Newline.Length);
         }
 
-        private static void WritePayload(ReadOnlySpan<byte> payload, Stream output)
+        private static void WritePayload(ReadOnlyMemory<byte> payload, Stream output)
         {
             // Short-cut for empty payload
             if (payload.Length == 0)
@@ -45,8 +72,9 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Formatters
             var keepWriting = true;
             while (keepWriting)
             {
+                var span = payload.Span;
                 // Seek to the end of buffer or newline
-                var sliceEnd = payload.IndexOf(LineFeed);
+                var sliceEnd = span.IndexOf(LineFeed);
                 var nextSliceStart = sliceEnd + 1;
                 if (sliceEnd < 0)
                 {
@@ -56,7 +84,7 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Formatters
                     // This is the last span
                     keepWriting = false;
                 }
-                if (sliceEnd > 0 && payload[sliceEnd - 1] == '\r')
+                if (sliceEnd > 0 && span[sliceEnd - 1] == '\r')
                 {
                     sliceEnd--;
                 }
@@ -65,7 +93,7 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Formatters
 
                 if (nextSliceStart >= payload.Length)
                 {
-                    payload = ReadOnlySpan<byte>.Empty;
+                    payload = ReadOnlyMemory<byte>.Empty;
                 }
                 else
                 {
@@ -76,15 +104,20 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Formatters
             }
         }
 
-        private static void WriteLine(ReadOnlySpan<byte> payload, Stream output)
+        private static void WriteLine(ReadOnlyMemory<byte> payload, Stream output)
         {
             output.Write(DataPrefix, 0, DataPrefix.Length);
 
-            var buffer = ArrayPool<byte>.Shared.Rent(payload.Length);
-            payload.CopyTo(buffer);
-            output.Write(buffer, 0, payload.Length);
-            ArrayPool<byte>.Shared.Return(buffer);
-
+#if NETCOREAPP2_1
+            output.Write(payload.Span);
+#else
+            if (payload.Length > 0)
+            {
+                var isArray = MemoryMarshal.TryGetArray(payload, out var segment);
+                Debug.Assert(isArray);
+                output.Write(segment.Array, segment.Offset, segment.Count);
+            }
+#endif
             output.Write(Newline, 0, Newline.Length);
         }
     }

src/Microsoft.AspNetCore.Sockets.Http/Internal/Transports/ServerSentEventsTransport.cs

@@ -53,12 +53,9 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Transports
                     {
                         if (!buffer.IsEmpty)
                         {
-                            var ms = new MemoryStream();
                             _logger.SSEWritingMessage(buffer.Length);
-                            // Don't create a copy using ToArray every time
-                            ServerSentEventsMessageFormatter.WriteMessage(buffer.ToArray(), ms);
-                            ms.Seek(0, SeekOrigin.Begin);
-                            await ms.CopyToAsync(context.Response.Body);
+
+                            await ServerSentEventsMessageFormatter.WriteMessageAsync(buffer, context.Response.Body);
                         }
                         else if (result.IsCompleted)
                         {

src/Microsoft.AspNetCore.Sockets.Http/Internal/Transports/WebSocketsTransport.cs

@@ -2,10 +2,10 @@
 // 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.Diagnostics;
 using System.IO.Pipelines;
 using System.Net.WebSockets;
+using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
@@ -105,7 +105,7 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Transports
             trigger.GetAwaiter().GetResult();
         }
 
-        private async Task<WebSocketReceiveResult> StartReceiving(WebSocket socket)
+        private async Task StartReceiving(WebSocket socket)
         {
             try
             {
@@ -113,14 +113,18 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Transports
                 {
                     var memory = _application.Output.GetMemory();
 
-                    // REVIEW: Use new Memory<byte> websocket APIs on .NET Core 2.1
-                    memory.TryGetArray(out var arraySegment);
+#if NETCOREAPP2_1
+                    var receiveResult = await socket.ReceiveAsync(memory, CancellationToken.None);
+#else
+                    var isArray = memory.TryGetArray(out var arraySegment);
+                    Debug.Assert(isArray);
 
                     // Exceptions are handled above where the send and receive tasks are being run.
                     var receiveResult = await socket.ReceiveAsync(arraySegment, CancellationToken.None);
+#endif
                     if (receiveResult.MessageType == WebSocketMessageType.Close)
                     {
-                        return receiveResult;
+                        return;
                     }
 
                     _logger.MessageReceived(receiveResult.MessageType, receiveResult.Count, receiveResult.EndOfMessage);
@@ -163,7 +167,7 @@ namespace Microsoft.AspNetCore.Sockets.Internal.Transports
 
                             if (WebSocketCanSend(ws))
                             {
-                                await ws.SendAsync(new ArraySegment<byte>(buffer.ToArray()), webSocketMessageType, endOfMessage: true, cancellationToken: CancellationToken.None);
+                                await ws.SendAsync(buffer, webSocketMessageType);
                             }
                         }
                         catch (WebSocketException socketException) when (!WebSocketCanSend(ws))

src/Microsoft.AspNetCore.Sockets.Http/Microsoft.AspNetCore.Sockets.Http.csproj

@@ -2,9 +2,15 @@
 
   <PropertyGroup>
     <Description>Components for providing real-time bi-directional communication across the Web.</Description>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;netcoreapp2.1</TargetFrameworks>
   </PropertyGroup>
 
+  <ItemGroup>
+    <Compile Include="..\Common\PipeWriterStream.cs" Link="PipeWriterStream.cs" />
+    <Compile Include="..\Common\WebSocketExtensions.cs" Link="WebSocketExtensions.cs" />
+    <Compile Include="..\Common\StreamExtensions.cs" Link="StreamExtensions.cs" />
+  </ItemGroup>
+  
   <ItemGroup>
     <ProjectReference Include="..\Microsoft.AspNetCore.Sockets\Microsoft.AspNetCore.Sockets.csproj" />
     <ProjectReference Include="..\Microsoft.AspNetCore.Sockets.Common.Http\Microsoft.AspNetCore.Sockets.Common.Http.csproj" />

test/Microsoft.AspNetCore.SignalR.Client.Tests/TestConnection.cs

@@ -115,7 +115,8 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
         private byte[] FormatMessageToArray(byte[] message)
         {
             var output = new MemoryStream();
-            TextMessageFormatter.WriteMessage(message, output);
+            output.Write(message, 0, message.Length);
+            TextMessageFormatter.WriteRecordSeparator(output);
             return output.ToArray();
         }
 

test/Microsoft.AspNetCore.SignalR.Common.Tests/Internal/Formatters/BinaryMessageFormatterTests.cs

@@ -33,7 +33,8 @@ namespace Microsoft.AspNetCore.Sockets.Tests.Internal.Formatters
             var output = new MemoryStream(); // Use small chunks to test Advance/Enlarge and partial payload writing
             foreach (var message in messages)
             {
-                BinaryMessageFormatter.WriteMessage(message, output);
+                BinaryMessageFormatter.WriteLengthPrefix(message.Length, output);
+                output.Write(message, 0, message.Length);
             }
 
             Assert.Equal(expectedEncoding, output.ToArray());
@@ -77,7 +78,8 @@ namespace Microsoft.AspNetCore.Sockets.Tests.Internal.Formatters
                 output.Seek(offset, SeekOrigin.Begin);
             }
 
-            BinaryMessageFormatter.WriteMessage(payload, output);
+            BinaryMessageFormatter.WriteLengthPrefix(payload.Length, output);
+            output.Write(payload, 0, payload.Length);
 
             Assert.Equal(encoded, output.ToArray().Skip(offset));
         }
@@ -97,7 +99,8 @@ namespace Microsoft.AspNetCore.Sockets.Tests.Internal.Formatters
                 output.Seek(offset, SeekOrigin.Begin);
             }
 
-            BinaryMessageFormatter.WriteMessage(message, output);
+            BinaryMessageFormatter.WriteLengthPrefix(message.Length, output);
+            output.Write(message, 0, message.Length);
 
             Assert.Equal(encoded, output.ToArray().Skip(offset));
         }
@@ -108,7 +111,8 @@ namespace Microsoft.AspNetCore.Sockets.Tests.Internal.Formatters
         {
             using (var ms = new MemoryStream())
             {
-                BinaryMessageFormatter.WriteMessage(payload, ms);
+                BinaryMessageFormatter.WriteLengthPrefix(payload.Length, ms);
+                ms.Write(payload, 0, payload.Length);
                 var buffer = new ReadOnlySpan<byte>(ms.ToArray());
                 Assert.True(BinaryMessageParser.TryParseMessage(ref buffer, out var roundtripped));
                 Assert.Equal(payload, roundtripped.ToArray());

test/Microsoft.AspNetCore.SignalR.Common.Tests/Internal/Formatters/TextMessageFormatterTests.cs

@@ -16,7 +16,9 @@ namespace Microsoft.AspNetCore.SignalR.Common.Tests.Internal.Formatters
         {
             using (var ms = new MemoryStream())
             {
-                TextMessageFormatter.WriteMessage(new ReadOnlySpan<byte>(Encoding.UTF8.GetBytes("ABC")), ms);
+                var buffer = Encoding.UTF8.GetBytes("ABC");
+                ms.Write(buffer, 0, buffer.Length);
+                TextMessageFormatter.WriteRecordSeparator(ms);
                 Assert.Equal("ABC\u001e", Encoding.UTF8.GetString(ms.ToArray()));
             }
         }

test/Microsoft.AspNetCore.SignalR.Common.Tests/Internal/Protocol/JsonHubProtocolTests.cs

@@ -206,7 +206,8 @@ namespace Microsoft.AspNetCore.SignalR.Common.Tests.Internal.Protocol
         private static byte[] FormatMessageToArray(byte[] message)
         {
             var output = new MemoryStream();
-            TextMessageFormatter.WriteMessage(message, output);
+            output.Write(message, 0, message.Length);
+            TextMessageFormatter.WriteRecordSeparator(output);
             return output.ToArray();
         }
     }

test/Microsoft.AspNetCore.SignalR.Common.Tests/Internal/Protocol/MessagePackHubProtocolTests.cs

@@ -485,8 +485,8 @@ namespace Microsoft.AspNetCore.SignalR.Common.Tests.Internal.Protocol
         {
             using (var stream = new MemoryStream())
             {
-                BinaryMessageFormatter.WriteMessage(input, stream);
-                stream.Flush();
+                BinaryMessageFormatter.WriteLengthPrefix(input.Length, stream);
+                stream.Write(input, 0, input.Length);
                 return stream.ToArray();
             }
         }