Use MessagePackReader \ MessagePackWriter to implement IHubProtocol for server-side Blazor

.gitmodules

@@ -1,3 +1,7 @@
 [submodule "googletest"]
 	path = src/submodules/googletest
 	url = https://github.com/google/googletest
+
+[submodule "src/submodules/MessagePack-CSharp"]
+	path = src/submodules/MessagePack-CSharp
+	url = https://github.com/aspnet/MessagePack-CSharp.git

src/Components/Browser.JS/src/Boot.Server.ts

@@ -42,9 +42,11 @@ async function boot() {
 }
 
 async function initializeConnection(circuitHandlers: CircuitHandler[]): Promise<signalR.HubConnection> {
+  const hubProtocol = new MessagePackHubProtocol();
+  (hubProtocol as any).name = 'blazorpack';
   const connection = new signalR.HubConnectionBuilder()
     .withUrl('_blazor')
-    .withHubProtocol(new MessagePackHubProtocol())
+    .withHubProtocol(hubProtocol)
     .configureLogging(signalR.LogLevel.Information)
     .build();
 

src/Components/Server/src/BlazorPack/ArrayBufferWriter.cs

@@ -0,0 +1,193 @@
+// 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.
+
+// Copied from https://github.com/dotnet/corefx/blob/b0751dcd4a419ba6731dcaa7d240a8a1946c934c/src/System.Text.Json/src/System/Text/Json/Serialization/ArrayBufferWriter.cs
+
+using System;
+using System.Buffers;
+using System.Diagnostics;
+
+namespace Microsoft.AspNetCore.Components.Server.BlazorPack
+{
+    // Note: this is currently an internal class that will be replaced with a shared version.
+    internal sealed class ArrayBufferWriter<T> : IBufferWriter<T>, IDisposable
+    {
+        private T[] _rentedBuffer;
+        private int _index;
+
+        private const int MinimumBufferSize = 256;
+
+        public ArrayBufferWriter()
+        {
+            _rentedBuffer = ArrayPool<T>.Shared.Rent(MinimumBufferSize);
+            _index = 0;
+        }
+
+        public ArrayBufferWriter(int initialCapacity)
+        {
+            if (initialCapacity <= 0)
+            {
+                throw new ArgumentException(nameof(initialCapacity));
+            }
+
+            _rentedBuffer = ArrayPool<T>.Shared.Rent(initialCapacity);
+            _index = 0;
+        }
+
+        public ReadOnlyMemory<T> WrittenMemory
+        {
+            get
+            {
+                CheckIfDisposed();
+
+                return _rentedBuffer.AsMemory(0, _index);
+            }
+        }
+
+        public int WrittenCount
+        {
+            get
+            {
+                CheckIfDisposed();
+
+                return _index;
+            }
+        }
+
+        public int Capacity
+        {
+            get
+            {
+                CheckIfDisposed();
+
+                return _rentedBuffer.Length;
+            }
+        }
+
+        public int FreeCapacity
+        {
+            get
+            {
+                CheckIfDisposed();
+
+                return _rentedBuffer.Length - _index;
+            }
+        }
+
+        public void Clear()
+        {
+            CheckIfDisposed();
+
+            ClearHelper();
+        }
+
+        private void ClearHelper()
+        {
+            Debug.Assert(_rentedBuffer != null);
+
+            _rentedBuffer.AsSpan(0, _index).Clear();
+            _index = 0;
+        }
+
+        // Returns the rented buffer back to the pool
+        public void Dispose()
+        {
+            if (_rentedBuffer == null)
+            {
+                return;
+            }
+
+            ClearHelper();
+            ArrayPool<T>.Shared.Return(_rentedBuffer);
+            _rentedBuffer = null;
+        }
+
+        private void CheckIfDisposed()
+        {
+            if (_rentedBuffer == null)
+            {
+                ThrowObjectDisposedException();
+            }
+        }
+
+        private static void ThrowObjectDisposedException()
+        {
+            throw new ObjectDisposedException(nameof(ArrayBufferWriter<T>));
+        }
+
+        public void Advance(int count)
+        {
+            CheckIfDisposed();
+
+            if (count < 0)
+                throw new ArgumentException(nameof(count));
+
+            if (_index > _rentedBuffer.Length - count)
+            {
+                ThrowInvalidOperationException(_rentedBuffer.Length);
+            }
+
+            _index += count;
+        }
+
+        public Memory<T> GetMemory(int sizeHint = 0)
+        {
+            CheckIfDisposed();
+
+            CheckAndResizeBuffer(sizeHint);
+            return _rentedBuffer.AsMemory(_index);
+        }
+
+        public Span<T> GetSpan(int sizeHint = 0)
+        {
+            CheckIfDisposed();
+
+            CheckAndResizeBuffer(sizeHint);
+            return _rentedBuffer.AsSpan(_index);
+        }
+
+        private void CheckAndResizeBuffer(int sizeHint)
+        {
+            Debug.Assert(_rentedBuffer != null);
+
+            if (sizeHint < 0)
+            {
+                throw new ArgumentException(nameof(sizeHint));
+            }
+
+            if (sizeHint == 0)
+            {
+                sizeHint = MinimumBufferSize;
+            }
+
+            var availableSpace = _rentedBuffer.Length - _index;
+
+            if (sizeHint > availableSpace)
+            {
+                var growBy = Math.Max(sizeHint, _rentedBuffer.Length);
+
+                var newSize = checked(_rentedBuffer.Length + growBy);
+
+                var oldBuffer = _rentedBuffer;
+
+                _rentedBuffer = ArrayPool<T>.Shared.Rent(newSize);
+
+                Debug.Assert(oldBuffer.Length >= _index);
+                Debug.Assert(_rentedBuffer.Length >= _index);
+
+                var previousBuffer = oldBuffer.AsSpan(0, _index);
+                previousBuffer.CopyTo(_rentedBuffer);
+                previousBuffer.Clear();
+                ArrayPool<T>.Shared.Return(oldBuffer);
+            }
+
+            Debug.Assert(_rentedBuffer.Length - _index > 0);
+            Debug.Assert(_rentedBuffer.Length - _index >= sizeHint);
+        }
+
+        private static void ThrowInvalidOperationException(int capacity)
+        {
+            throw new InvalidOperationException($"Cannot advance past the end of the buffer, which has a size of {capacity}.");
+        }
+    }
+}