From 2693073babef1ae5f40686864bc1a64747fd0319 Mon Sep 17 00:00:00 2001
From: Jan Kotas <jkotas@microsoft.com>
Date: Fri, 20 Oct 2023 23:58:28 -0700
Subject: [PATCH] Add microbenchmark for core UnmanagedMemoryStream scenario

Related to https://github.com/dotnet/runtime/pull/93766
---
 .../System.IO/UnmanagedMemoryStreamTests.cs   | 53 +++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 src/benchmarks/micro/libraries/System.IO/UnmanagedMemoryStreamTests.cs

diff --git a/src/benchmarks/micro/libraries/System.IO/UnmanagedMemoryStreamTests.cs b/src/benchmarks/micro/libraries/System.IO/UnmanagedMemoryStreamTests.cs
new file mode 100644
index 0000000000..7c87bec5c9
--- /dev/null
+++ b/src/benchmarks/micro/libraries/System.IO/UnmanagedMemoryStreamTests.cs
@@ -0,0 +1,53 @@
+// 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.Runtime.InteropServices;
+using BenchmarkDotNet.Attributes;
+using MicroBenchmarks;
+
+namespace System.IO.Tests
+{
+    [BenchmarkCategory(Categories.Libraries)]
+    public unsafe class UnmanagedMemoryStreamTests
+    {
+        private const int Length = 10000;
+        private byte* buffer;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            buffer = (byte*)Marshal.AllocCoTaskMem(Length);
+        }
+
+        [GlobalCleanup]
+        public void Cleanup()
+        {
+            Marshal.FreeCoTaskMem((IntPtr)buffer);
+        }
+
+        [Benchmark]
+        public void ReadAsBytes()
+        {
+            using (var ums = new UnmanagedMemoryStream(buffer, Length))
+            {
+                while (ums.ReadByte() >= 0)
+                {
+                }
+            }
+        }
+
+        [Benchmark]
+        public void ReadAsArrays()
+        {
+            var array = new byte[1];
+            using (var ums = new UnmanagedMemoryStream(buffer, Length))
+            {
+                while (ums.Read(array, 0, array.Length) != 0)
+                {
+                }
+            }
+        }
+    }
+}