added benchmark for serializers

Frameworks/MQTTnet.NetStandard/Internal/MqttApplicationMessageExtensions.cs

@@ -2,7 +2,7 @@
 
 namespace MQTTnet.Internal
 {
-    internal static class MqttApplicationMessageExtensions
+    public static class MqttApplicationMessageExtensions
     {
         public static MqttApplicationMessage ToApplicationMessage(this MqttPublishPacket publishPacket)
         {

Frameworks/MQTTnet.NetStandard/Internal/TestMqttChannel.cs

@@ -3,7 +3,7 @@ using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Channel;
 
-namespace MQTTnet.Core.Tests
+namespace MQTTnet.Core.Internal
 {
     public class TestMqttChannel : IMqttChannel
     {

Tests/MQTTnet.Benchmarks/MQTTnet.Benchmarks.csproj

@@ -150,6 +150,7 @@
     <Compile Include="MessageProcessingBenchmark.cs" />
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="SerializerBenchmark.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="App.config" />

Tests/MQTTnet.Benchmarks/Program.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Threading;
 using BenchmarkDotNet.Running;
+using MQTTnet.Diagnostics;
 
 namespace MQTTnet.Benchmarks
 {
@@ -7,7 +9,23 @@ namespace MQTTnet.Benchmarks
     {
         public static void Main(string[] args)
         {
-            var summary = BenchmarkRunner.Run<MessageProcessingBenchmark>();
+            Console.WriteLine($"MQTTnet - BenchmarkApp.{TargetFrameworkInfoProvider.TargetFramework}");
+            Console.WriteLine("1 = MessageProcessingBenchmark");
+            Console.WriteLine("2 = SerializerBenchmark");
+
+            var pressedKey = Console.ReadKey(true);
+            switch (pressedKey.KeyChar)
+            {
+                case '1':
+                    BenchmarkRunner.Run<MessageProcessingBenchmark>();
+                    break;
+                case '2':
+                    BenchmarkRunner.Run<SerializerBenchmark>();
+                    break;
+                default:
+                    break;
+            }
+
             Console.ReadLine();
         }
     }

Tests/MQTTnet.Benchmarks/SerializerBenchmark.cs

@@ -0,0 +1,75 @@
+using BenchmarkDotNet.Attributes;
+using MQTTnet.Client;
+using MQTTnet.Packets;
+using MQTTnet.Serializer;
+using MQTTnet.Internal;
+using MQTTnet.Server;
+using BenchmarkDotNet.Attributes.Jobs;
+using BenchmarkDotNet.Attributes.Exporters;
+using System;
+using System.Threading;
+using System.IO;
+using MQTTnet.Core.Internal;
+
+namespace MQTTnet.Benchmarks
+{
+    [ClrJob]
+    [RPlotExporter]
+    [MemoryDiagnoser]
+    public class SerializerBenchmark
+    {
+        private MqttApplicationMessage _message;
+        private MqttBasePacket _packet;
+        private ArraySegment<byte> _serializedPacket;
+        private MqttPacketSerializer _serializer;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            _message = new MqttApplicationMessageBuilder()
+                .WithTopic("A")
+                .Build();
+
+            _packet = _message.ToPublishPacket();
+            _serializer = new MqttPacketSerializer();
+            _serializedPacket = _serializer.Serialize(_packet);
+        }
+
+        [Benchmark]
+        public void Serialize_10000_Messages()
+        {
+            for (var i = 0; i < 10000; i++)
+            {
+                _serializer.Serialize(_packet);
+            }
+        }
+
+        [Benchmark]
+        public void Deserialize_10000_Messages()
+        {
+            for (var i = 0; i < 10000; i++)
+            {
+                using (var headerStream = new MemoryStream(Join(_serializedPacket)))
+                {
+                    var header = MqttPacketReader.ReadHeaderAsync(new TestMqttChannel(headerStream), CancellationToken.None).GetAwaiter().GetResult();
+
+                    using (var bodyStream = new MemoryStream(Join(_serializedPacket), (int)headerStream.Position, header.BodyLength))
+                    {
+                        var deserializedPacket = _serializer.Deserialize(header, bodyStream);
+                    }
+                }
+            }
+        }
+        
+        private static byte[] Join(params ArraySegment<byte>[] chunks)
+        {
+            var buffer = new MemoryStream();
+            foreach (var chunk in chunks)
+            {
+                buffer.Write(chunk.Array, chunk.Offset, chunk.Count);
+            }
+
+            return buffer.ToArray();
+        }
+    }
+}

Tests/MQTTnet.Core.Tests/MqttPacketReaderTests.cs

@@ -1,6 +1,7 @@
 using System.IO;
 using System.Threading;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MQTTnet.Core.Internal;
 using MQTTnet.Serializer;
 
 namespace MQTTnet.Core.Tests