byte 列の16進ダンプ文字列化

result.md

Method	Mean	Error	StdDev	Gen0	Gen1	Allocated
A1	88.28 us	1.739 us	2.953 us	31.1279	4.3945	399.68 KB
A2	84.18 us	1.644 us	2.137 us	30.5176	4.0283	390.72 KB
A3	120.11 us	0.894 us	0.836 us	5.9814	0.7324	78.22 KB
B1	124.21 us	0.311 us	0.243 us	2.9297	-	39.09 KB
B2	122.88 us	0.612 us	0.543 us	2.9297	-	39.09 KB
B3	123.91 us	0.480 us	0.426 us	2.9297	-	39.09 KB
C1	109.96 us	0.325 us	0.272 us	2.9297	-	39.09 KB
A4	10.72 us	0.208 us	0.195 us	6.8207	1.1292	87.18 KB
B4	10.88 us	0.126 us	0.105 us	3.0365	-	39.09 KB
C2	10.31 us	0.197 us	0.193 us	3.0365	-	39.09 KB

ToHexString.cs

using BenchmarkDotNet.Attributes;
using System.Runtime.CompilerServices;
using System.Text;
using C = System.Globalization.CultureInfo;

#if DEBUG
var data = ToHexStringBenchmark.StaticData;

var s = data.A1();
Console.WriteLine(data.A1() == s);
Console.WriteLine(data.A2() == s);
Console.WriteLine(data.A3() == s);
Console.WriteLine(data.B1() == s);
Console.WriteLine(data.B2() == s);
Console.WriteLine(data.B3() == s);
Console.WriteLine(data.C1() == s);
Console.WriteLine(data.A4() == s);
Console.WriteLine(data.B4() == s);
Console.WriteLine(data.C2() == s);
#else
BenchmarkDotNet.Running.BenchmarkRunner.Run<ToHexStringBenchmark>();
#endif

public static class ToHexExtensions
{
    public static string A1(this ReadOnlySpan<byte> data)
    {
        var x = new StringBuilder();
        foreach (var b in data)
        {
            x.Append(b.ToString("X2", C.InvariantCulture));
        }
        return x.ToString();
    }

    public static string A2(this ReadOnlySpan<byte> data)
    {
        var x = new StringBuilder(data.Length * 2); // capacity 追加
        foreach (var b in data)
        {
            x.Append(b.ToString("X2", C.InvariantCulture));
        }
        return x.ToString();
    }

    public static string A3(this ReadOnlySpan<byte> data)
    {
        var x = new StringBuilder(data.Length * 2);
        foreach (var b in data)
        {
            x.Append(C.InvariantCulture, $"{b:X2}"); // interpolation に
        }
        return x.ToString();
    }

    public static string B1(this ReadOnlySpan<byte> data)
    {
        var x = new DefaultInterpolatedStringHandler(0, 0, C.InvariantCulture);
        foreach (var b in data)
        {
            x.AppendFormatted(b, 0, "X2");
        }
        return x.ToStringAndClear();
    }

    public static string B2(this ReadOnlySpan<byte> data)
    {
        var x = new DefaultInterpolatedStringHandler(data.Length * 2, 0, C.InvariantCulture); // literalLength に文字数追加
        foreach (var b in data)
        {
            x.AppendFormatted(b, 0, "X2");
        }
        return x.ToStringAndClear();
    }

    [SkipLocalsInit]
    public static string B3(this ReadOnlySpan<byte> data)
    {
        var x = new DefaultInterpolatedStringHandler(0, 0, C.InvariantCulture, stackalloc char[data.Length * 2]); // initialBufer 追加
        foreach (var b in data)
        {
            x.AppendFormatted(b, 0, "X2");
        }
        return x.ToStringAndClear();
    }

    // .NET 9 必須(allows ref struct が必須)。
    // でないと、SpanAction デリゲートに ReadOnlySpan を渡せない。
    public static string C1(this ReadOnlySpan<byte> data)
        => string.Create(data.Length * 2, data, static (buffer, data) =>
        {
            foreach (var b in data)
            {
                b.TryFormat(buffer, out _, "X2", C.InvariantCulture);
                buffer = buffer[2..];
            }
        });

    private const string _hexChars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

    public static string A4(this ReadOnlySpan<byte> data)
    {
        var x = new StringBuilder();
        foreach (var b in data)
        {
            x.Append(_hexChars.AsSpan(2 * b, 2));
        }
        return x.ToString();
    }

    public static string B4(this ReadOnlySpan<byte> data)
    {
        var x = new DefaultInterpolatedStringHandler(data.Length * 2, 0, C.InvariantCulture, stackalloc char[data.Length * 2]); // initialBufer 追加
        foreach (var b in data)
        {
            x.AppendFormatted(_hexChars.AsSpan(2 * b, 2));
        }
        return x.ToStringAndClear();
    }

    // .NET 9 必須(allows ref struct が必須)。
    public static string C2(this ReadOnlySpan<byte> data)
        => string.Create(data.Length * 2, data, static (buffer, data) =>
        {
            foreach (var b in data)
            {
                _hexChars.AsSpan(2 * b, 2).CopyTo(buffer);
                buffer = buffer[2..];
            }
        });
}

[MemoryDiagnoser]
public class ToHexStringBenchmark
{
    public static ReadOnlySpan<byte> StaticData => [
        0,1,2,3,4,5,6,7,8,9,
        10,11,12,13,14,15,16,17,18,19,
        20,21,22,23,24,25,26,27,28,29,
        30,31,32,33,34,35,36,37,38,39,
        40,41,42,43,44,45,46,47,48,49,
        50,51,52,53,54,55,56,57,58,59,
        60,61,62,63,64,65,66,67,68,69,
        70,71,72,73,74,75,76,77,78,79,
        80,81,82,83,84,85,86,87,88,89,
        90,91,92,93,94,95,96,97,98,99,
    ];

    private ReadOnlySpan<byte> Data => _data ??= Enumerable.Range(0, 10000).Select(x => (byte)x).ToArray();
    private byte[]? _data;

    [GlobalSetup]
    public void Setup()
    {
        _ = Data;
    }

    [Benchmark] public string A1() => Data.A1();
    [Benchmark] public string A2() => Data.A2();
    [Benchmark] public string A3() => Data.A3();
    [Benchmark] public string B1() => Data.B1();
    [Benchmark] public string B2() => Data.B2();
    [Benchmark] public string B3() => Data.B3();
    [Benchmark] public string C1() => Data.C1();
    [Benchmark] public string A4() => Data.A4();
    [Benchmark] public string B4() => Data.B4();
    [Benchmark] public string C2() => Data.C2();
}