Buffer2D_DangerousGetRowSpan benchmark

tests/ImageSharp.Benchmarks/General/Buffer2D_DangerousGetRowSpan.cs

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+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using BenchmarkDotNet.Attributes;
+using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace SixLabors.ImageSharp.Benchmarks.General
+{
+    public class Buffer2D_DangerousGetRowSpan
+    {
+        [Params(true, false)]
+        public bool IsDiscontiguousBuffer { get; set; }
+
+        private Buffer2D<Rgba32> buffer;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            MemoryAllocator allocator = Configuration.Default.MemoryAllocator;
+            this.buffer = this.IsDiscontiguousBuffer
+                ? allocator.Allocate2D<Rgba32>(4000, 1000)
+                : allocator.Allocate2D<Rgba32>(500, 1000);
+        }
+
+        [GlobalCleanup]
+        public void Cleanup() => this.buffer.Dispose();
+
+        [Benchmark]
+        public int DangerousGetRowSpan() =>
+            this.buffer.DangerousGetRowSpan(1).Length +
+            this.buffer.DangerousGetRowSpan(999).Length;
+
+        // BenchmarkDotNet=v0.13.0, OS=Windows 10.0.19044
+        // Intel Core i9-10900X CPU 3.70GHz, 1 CPU, 20 logical and 10 physical cores
+        //
+        // |              Method | IsDiscontiguousBuffer |     Mean |    Error |   StdDev |
+        // |-------------------- |---------------------- |---------:|---------:|---------:|
+        // | DangerousGetRowSpan |                 False | 74.96 ns | 1.505 ns | 1.478 ns |
+        // | DangerousGetRowSpan |                  True | 71.49 ns | 1.446 ns | 2.120 ns |
+    }
+}