Avoiding serializing to MemoryStream

src/Microsoft.AspNetCore.SignalR.Common/Internal/Encoders/Base64Encoder.cs

@@ -5,7 +5,6 @@ using System;
 using System.Buffers;
 using System.Buffers.Text;
 using System.Diagnostics;
-using System.IO;
 
 namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
 {
@@ -23,18 +22,37 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
             return decoded.Slice(0, written);
         }
 
+        private const int Int32OverflowLength = 10;
+
         public byte[] Encode(byte[] payload)
         {
-            Span<byte> buffer = new byte[Base64.GetMaxEncodedToUtf8Length(payload.Length)];
+            var maxEncodedLength = Base64.GetMaxEncodedToUtf8Length(payload.Length);
 
-            var status = Base64.EncodeToUtf8(payload, buffer, out _, out var written);
+            // Int32OverflowLength + length of separator (':') + length of terminator (';')
+            if (int.MaxValue - maxEncodedLength < Int32OverflowLength + 2)
+            {
+                throw new FormatException("The encoded message exceeds the maximum supported size.");
+            }
+
+            //The format is: [{length}:{message};] so allocate enough to be able to write the entire message
+            Span<byte> buffer = new byte[Int32OverflowLength + 1 + maxEncodedLength + 1];
+
+            buffer[Int32OverflowLength] = (byte)':';
+            var status = Base64.EncodeToUtf8(payload, buffer.Slice(Int32OverflowLength + 1), out _, out var written);
             Debug.Assert(status == OperationStatus.Done);
 
-            using (var stream = new MemoryStream())
+            buffer[Int32OverflowLength + 1 + written] = (byte)';';
+            var prefixLength = 0;
+            var prefix = written;
+            do
             {
-                LengthPrefixedTextMessageWriter.WriteMessage(buffer.Slice(0, written), stream);
+                buffer[Int32OverflowLength - 1 - prefixLength] = (byte)('0' + prefix % 10);
-                return stream.ToArray();
+                prefix /= 10;
+                prefixLength++;
             }
+            while (prefix > 0);
+
+            return buffer.Slice(Int32OverflowLength - prefixLength, prefixLength + 1 + written + 1).ToArray();
         }
     }
 }

src/Microsoft.AspNetCore.SignalR.Common/Internal/Encoders/LengthPrefixedTextMessageParser.cs

@@ -9,6 +9,8 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
     public static class LengthPrefixedTextMessageParser
     {
         private const int Int32OverflowLength = 10;
+        private const char FieldDelimiter = ':';
+        private const char MessageDelimiter = ';';
 
         /// <summary>
         /// Attempts to parse a message from the buffer. Returns 'false' if there is not enough data to complete a message. Throws an
@@ -25,7 +27,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
 
             var remaining = buffer.Slice(index);
 
-            if (!TryReadDelimiter(remaining, LengthPrefixedTextMessageWriter.FieldDelimiter, "length"))
+            if (!TryReadDelimiter(remaining, FieldDelimiter, "length"))
             {
                 return false;
             }
@@ -42,7 +44,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
 
             remaining = remaining.Slice(length);
 
-            if (!TryReadDelimiter(remaining, LengthPrefixedTextMessageWriter.MessageDelimiter, "payload"))
+            if (!TryReadDelimiter(remaining, MessageDelimiter, "payload"))
             {
                 return false;
             }
@@ -56,7 +58,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
         {
             length = 0;
             // Read until the first ':' to find the length
-            index = buffer.IndexOf((byte)LengthPrefixedTextMessageWriter.FieldDelimiter);
+            index = buffer.IndexOf((byte)FieldDelimiter);
 
             if (index == -1)
             {

src/Microsoft.AspNetCore.SignalR.Common/Internal/Encoders/LengthPrefixedTextMessageWriter.cs

@@ -1,44 +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;
-using System.Buffers;
-using System.Globalization;
-using System.IO;
-using System.Text;
-
-namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
-{
-    public static class LengthPrefixedTextMessageWriter
-    {
-        private const int Int32OverflowLength = 10;
-
-        internal const char FieldDelimiter = ':';
-        internal const char MessageDelimiter = ';';
-
-        public static void WriteMessage(ReadOnlySpan<byte> payload, Stream output)
-        {
-            // Calculate the length, it's the number of characters for text messages, but number of base64 characters for binary
-
-            // Write the length as a string
-
-            // Super inefficient...
-            var lengthString = payload.Length.ToString(CultureInfo.InvariantCulture);
-            var buffer = ArrayPool<byte>.Shared.Rent(Int32OverflowLength);
-            var encodedLength = Encoding.UTF8.GetBytes(lengthString, 0, lengthString.Length, buffer, 0);
-            output.Write(buffer, 0, encodedLength);
-            ArrayPool<byte>.Shared.Return(buffer);
-
-            // Write the field delimiter ':'
-            output.WriteByte((byte)FieldDelimiter);
-
-            buffer = ArrayPool<byte>.Shared.Rent(payload.Length);
-            payload.CopyTo(buffer);
-            output.Write(buffer, 0, payload.Length);
-            ArrayPool<byte>.Shared.Return(buffer);
-
-            // Terminator
-            output.WriteByte((byte)MessageDelimiter);
-        }
-    }
-}

test/Microsoft.AspNetCore.SignalR.Common.Tests/Internal/Encoders/Base64EncoderTests.cs

@@ -0,0 +1,38 @@
+// 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 System.Text;
+using Xunit;
+
+namespace Microsoft.AspNetCore.SignalR.Internal.Encoders
+{
+    public class Base64EncoderTests
+    {
+        [Theory]
+        [MemberData(nameof(Payloads))]
+        public void VerifyDecode(string payload, string encoded)
+        {
+            var message = Encoding.UTF8.GetBytes(payload);
+            var encodedMessage = Encoding.UTF8.GetString(new Base64Encoder().Encode(message));
+            Assert.Equal(encoded, encodedMessage);
+        }
+
+        [Theory]
+        [MemberData(nameof(Payloads))]
+        public void VerifyEncode(string payload, string encoded)
+        {
+            var encodedMessage = Encoding.UTF8.GetBytes(encoded);
+            var decodedMessage = Encoding.UTF8.GetString(new Base64Encoder().Decode(encodedMessage).ToArray());
+            Assert.Equal(payload, decodedMessage);
+        }
+
+        public static IEnumerable<object[]> Payloads =>
+            new object[][]
+            {
+                new object[] { "", "0:;" },
+                new object[] { "ABC", "4:QUJD;" },
+                new object[] { "A\nR\rC\r\n;DEF1234567890", "28:QQpSDUMNCjtERUYxMjM0NTY3ODkw;" },
+            };
+    }
+}

test/Microsoft.AspNetCore.SignalR.Common.Tests/Internal/Encoders/LengthPrefixedTextMessageFormatterTests.cs

@@ -1,46 +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.IO;
-using System.Text;
-using Microsoft.AspNetCore.SignalR.Internal.Encoders;
-using Xunit;
-
-namespace Microsoft.AspNetCore.SignalR.Tests.Internal.Encoders
-{
-    public class LengthPrefixedTextMessageFormatterTests
-    {
-        [Fact]
-        public void WriteMultipleMessages()
-        {
-            const string expectedEncoding = "0:;14:Hello,\r\nWorld!;";
-            var messages = new[]
-            {
-                new byte[0],
-                Encoding.UTF8.GetBytes("Hello,\r\nWorld!")
-            };
-
-            var output = new MemoryStream();
-            foreach (var message in messages)
-            {
-                LengthPrefixedTextMessageWriter.WriteMessage(message, output);
-            }
-
-            Assert.Equal(expectedEncoding, Encoding.UTF8.GetString(output.ToArray()));
-        }
-
-        [Theory]
-        [InlineData("0:;", "")]
-        [InlineData("3:ABC;", "ABC")]
-        [InlineData("11:A\nR\rC\r\n;DEF;", "A\nR\rC\r\n;DEF")]
-        public void WriteMessage(string encoded, string payload)
-        {
-            var message = Encoding.UTF8.GetBytes(payload);
-            var output = new MemoryStream();
-
-            LengthPrefixedTextMessageWriter.WriteMessage(message, output);
-
-            Assert.Equal(encoded, Encoding.UTF8.GetString(output.ToArray()));
-        }
-    }
-}