SpanTrimZBenchmarks.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Jobs;

namespace MikeysBenchmarks;

[SimpleJob(RuntimeMoniker.Net70)]
[MemoryDiagnoser()]
[MarkdownExporter]
public class SpanTrimZ
{
    private const string _withUtc = "2022-12-05T11:11:23Z";
    private const string _withoutUtc = "2022-12-05T11:11:23";

    private static readonly char[] _z = new char[1]
    {
        'Z'
    };

    [GlobalSetup]
    public void GlobalSetup()
    {
    }

    [ParamsAllValues]
    public bool WithUtc { get; set; }

    public string String => WithUtc ? _withUtc : _withoutUtc;

    [Benchmark]
    public int StringTrimEnd()
    {
        var str = String.TrimEnd('Z').TrimEnd('z');

        var isUtc = str.Length < String.Length;

        var utcOffset = isUtc ? 1 : 0;

        return str.Length + utcOffset;
    }

    [Benchmark]
    public int CompareStackalloc_TrimEnd()
    {
        var span = String.AsSpan();
        var utcOffset = 0;

        Span<char> s = stackalloc char[1]
        {
            'Z'
        };

        if (span.EndsWith(s, StringComparison.OrdinalIgnoreCase))
        {
            span = span.TrimEnd('Z').TrimEnd('z');
            utcOffset = 1;
        }

        return span.Length + utcOffset;
    }

    [Benchmark]
    public int CompareStackalloc_Range()
    {
        var span = String.AsSpan();
        var utcOffset = 0;

        Span<char> s = stackalloc char[1]
        {
            'Z'
        };

        if (span.EndsWith(s, StringComparison.OrdinalIgnoreCase))
        {
            span = span[..^1];
            utcOffset = 1;
        }

        return span.Length + utcOffset;
    }

    [Benchmark]
    public int CompareStackalloc_Length()
    {
        var span = String.AsSpan();
        var utcOffset = 0;

        Span<char> s = stackalloc char[1]
        {
            'Z'
        };

        if (span.EndsWith(s, StringComparison.OrdinalIgnoreCase))
        {
            span = span.Slice(0, span.Length - 1);
            utcOffset = 1;
        }

        return span.Length + utcOffset;
    }

    [Benchmark]
    public int CompareArray_Length()
    {
        var span = String.AsSpan();
        var utcOffset = 0;

        var c = _z.AsSpan();

        if (span.EndsWith(c, StringComparison.OrdinalIgnoreCase))
        {
            span = span.Slice(0, span.Length - 1);
            utcOffset = 1;
        }

        return span.Length + utcOffset;
    }

    [Benchmark]
    public int CompareArray_Range()
    {
        var span = String.AsSpan();
        var utcOffset = 0;

        var c = _z.AsSpan();

        if (span.EndsWith(c, StringComparison.OrdinalIgnoreCase))
        {
            span = span[..^1];
            utcOffset = 1;
        }

        return span.Length + utcOffset;
    }

    [Benchmark]
    public int CompareArray_TrimEnd()
    {
        var span = String.AsSpan();
        var utcOffset = 0;

        var c = _z.AsSpan();

        if (span.EndsWith(c, StringComparison.OrdinalIgnoreCase))
        {
            span = span.TrimEnd('Z').TrimEnd('z');
            utcOffset = 1;
        }

        return span.Length + utcOffset;
    }

    [Benchmark]
    public int StringEndsWith_Range()
    {
        var span = String.AsSpan();
        var utcOffset = 0;

        if (String.EndsWith("Z", StringComparison.OrdinalIgnoreCase))
        {
            span = span[..^1];
            utcOffset = 1;
        }

        return span.Length + utcOffset;
    }

    [Benchmark]
    public int SpanTrimEndWithCheck()
    {
        var span = String.AsSpan();

        var span2 = span.TrimEnd('Z').TrimEnd('z');

        var isUtc = span2.Length < span.Length;

        var utcOffset = isUtc ? 1 : 0;

        return span.Length + utcOffset;
    }
}

/*

// * Summary *

BenchmarkDotNet=v0.13.2, OS=Windows 10 (10.0.19043.1348/21H1/May2021Update), VM=VMware
AMD EPYC 7713P, 1 CPU, 12 logical and 12 physical cores
.NET SDK=7.0.100-rc.2.22477.23
  [Host]   : .NET 6.0.10 (6.0.1022.47605), X64 RyuJIT AVX2
  .NET 7.0 : .NET 7.0.0 (7.0.22.47203), X64 RyuJIT AVX2

Job=.NET 7.0  Runtime=.NET 7.0

|                    Method | WithUtc |      Mean |     Error |    StdDev |   Gen0 | Allocated |
|-------------------------- |-------- |----------:|----------:|----------:|-------:|----------:|
|             StringTrimEnd |   False | 10.510 ns | 0.2319 ns | 0.1936 ns |      - |         - |
| CompareStackalloc_TrimEnd |   False |  5.326 ns | 0.0705 ns | 0.0589 ns |      - |         - |
|   CompareStackalloc_Range |   False |  5.812 ns | 0.1114 ns | 0.0987 ns |      - |         - |
|  CompareStackalloc_Length |   False |  5.555 ns | 0.1105 ns | 0.1033 ns |      - |         - |
|       CompareArray_Length |   False |  5.026 ns | 0.0475 ns | 0.0371 ns |      - |         - |
|        CompareArray_Range |   False |  5.013 ns | 0.0982 ns | 0.0918 ns |      - |         - |
|      CompareArray_TrimEnd |   False |  5.426 ns | 0.1222 ns | 0.1143 ns |      - |         - |
|      StringEndsWith_Range |   False |  9.735 ns | 0.1929 ns | 0.1804 ns |      - |         - |
|      SpanTrimEndWithCheck |   False |  2.866 ns | 0.0879 ns | 0.0822 ns |      - |         - |
|             StringTrimEnd |    True | 22.666 ns | 0.3861 ns | 0.3423 ns | 0.0007 |      64 B |
| CompareStackalloc_TrimEnd |    True |  6.663 ns | 0.0746 ns | 0.0582 ns |      - |         - |
|   CompareStackalloc_Range |    True |  5.308 ns | 0.0518 ns | 0.0405 ns |      - |         - |
|  CompareStackalloc_Length |    True |  5.114 ns | 0.1376 ns | 0.1287 ns |      - |         - |
|       CompareArray_Length |    True |  4.364 ns | 0.0474 ns | 0.0420 ns |      - |         - |
|        CompareArray_Range |    True |  4.387 ns | 0.0618 ns | 0.0548 ns |      - |         - |
|      CompareArray_TrimEnd |    True |  6.434 ns | 0.1147 ns | 0.1178 ns |      - |         - |
|      StringEndsWith_Range |    True | 10.174 ns | 0.2208 ns | 0.2168 ns |      - |         - |
|      SpanTrimEndWithCheck |    True |  4.105 ns | 0.0843 ns | 0.0788 ns |      - |         - |


*/