Add performance test for XmlSerializationWriter.WriteTypedPrimitive

src/benchmarks/micro/libraries/System.Private.Xml/Perf.XmlSerializationWriter.cs

@@ -0,0 +1,72 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using System.Text;
+using System.Xml.Serialization;
+using BenchmarkDotNet.Attributes;
+using MicroBenchmarks;
+
+namespace System.Xml.Tests
+{
+    [BenchmarkCategory(Categories.Libraries)]
+    public class Perf_XmlSerializationWriter
+    {
+        private const int Iterations = 10000;
+
+        private readonly MyXmlSerializationWriter _writer = new MyXmlSerializationWriter();
+
+        private static readonly DateTime Now = new DateTime(2022, 9, 30, 9, 4, 15, DateTimeKind.Utc);
+        private static readonly DateTimeOffset DtoNow = Now.AddDays(1);
+        private static readonly TimeSpan Ts = new TimeSpan(1, 2, 3, 4, 5);
+        private static readonly byte[] BArray = new byte[] { 33, 44, 55 };
+
+        [IterationSetup]
+        public void CleanWriter() => _writer.Clean();
+
+        [Benchmark(OperationsPerInvoke = Iterations)]
+        public int AddPrimitives()
+        {
+            for (int i = 0; i < Iterations; i++)
+            {
+                _writer.Write('a');
+                _writer.Write(123);
+                _writer.Write(123.45m);
+                _writer.Write(Now);
+                _writer.Write(Ts);
+                _writer.Write(DtoNow);
+                _writer.Write((short)55);
+                _writer.Write(2345324L);
+                _writer.Write((sbyte)11);
+                _writer.Write((ushort)34);
+                _writer.Write((uint)4564);
+                _writer.Write((ulong)456734767);
+                _writer.Write((byte)67);
+                _writer.Write(BArray);
+                _writer.Write(Guid.NewGuid());
+            }
+
+            return _writer.GetXmlLength();
+        }
+    }
+
+    internal class MyXmlSerializationWriter : XmlSerializationWriter
+    {
+        private readonly StringBuilder _builder = new StringBuilder();
+
+        public MyXmlSerializationWriter()
+        {
+            Writer = new XmlTextWriter(new StringWriter(_builder));
+        }
+
+        protected override void InitCallbacks()
+        {
+        }
+
+        public void Write<T>(T value) => WriteTypedPrimitive(null, null, value, false);
+
+        public void Clean() => _builder.Clear();
+        public int GetXmlLength() => _builder.Length;
+    }
+}