Code Quality: Improve string comparer performance (#16523)

Author: viruseg

src/Files.App/Helpers/NaturalStringComparer.cs

@@ -7,32 +7,118 @@ public sealed class NaturalStringComparer
 	{
 		public static IComparer<object> GetForProcessor()
 		{
-			return Win32Helper.IsRunningOnArm ? new StringComparerArm64() : new StringComparerDefault();
+			return new NaturalComparer(StringComparison.CurrentCulture);
 		}
 
-		private sealed class StringComparerArm64 : IComparer<object>
+		/// <summary>
+		/// Provides functionality to compare and sort strings in a natural (human-readable) order.
+		/// </summary>
+		/// <remarks>
+		/// This class implements string comparison that respects the natural numeric order in strings,
+		/// such as "file10" being ordered after "file2".
+		/// It is designed to handle cases where alphanumeric sorting is required.
+		/// </remarks>
+		private sealed class NaturalComparer : IComparer<object?>, IComparer<string?>, IComparer<ReadOnlyMemory<char>>
 		{
-			public int Compare(object a, object b)
-			{
-				return StringComparer.CurrentCulture.Compare(a, b);
-			}
-		}
+		    private readonly StringComparison stringComparison;
 
-		private sealed class StringComparerDefault : IComparer<object>
-		{
-			public int Compare(object a, object b)
-			{
-				return Win32PInvoke.CompareStringEx(
-					Win32PInvoke.LOCALE_NAME_USER_DEFAULT,
-					Win32PInvoke.SORT_DIGITSASNUMBERS, // Add other flags if required.
-					a?.ToString(),
-					a?.ToString().Length ?? 0,
-					b?.ToString(),
-					b?.ToString().Length ?? 0,
-					IntPtr.Zero,
-					IntPtr.Zero,
-					0) - 2;
-			}
+		    public NaturalComparer(StringComparison stringComparison = StringComparison.Ordinal)
+		    {
+		        this.stringComparison = stringComparison;
+		    }
+
+		    public int Compare(object? x, object? y)
+		    {
+			    if (x == y) return 0;
+			    if (x == null) return -1;
+			    if (y == null) return 1;
+
+			    return x switch
+			    {
+				    string x1 when y is string y1 => Compare(x1.AsSpan(), y1.AsSpan(), stringComparison),
+				    IComparable comparable => comparable.CompareTo(y),
+				    _ => StringComparer.FromComparison(stringComparison).Compare(x, y)
+			    };
+		    }
+
+		    public int Compare(string? x, string? y)
+		    {
+		        if (ReferenceEquals(x, y)) return 0;
+		        if (x is null) return -1;
+		        if (y is null) return 1;
+
+		        return Compare(x.AsSpan(), y.AsSpan(), stringComparison);
+		    }
+
+		    public int Compare(ReadOnlySpan<char> x, ReadOnlySpan<char> y)
+		    {
+		        return Compare(x, y, stringComparison);
+		    }
+
+		    public int Compare(ReadOnlyMemory<char> x, ReadOnlyMemory<char> y)
+		    {
+		        return Compare(x.Span, y.Span, stringComparison);
+		    }
+
+		    public static int Compare(ReadOnlySpan<char> x, ReadOnlySpan<char> y, StringComparison stringComparison)
+		    {
+		        var length = Math.Min(x.Length, y.Length);
+
+		        for (var i = 0; i < length; i++)
+		        {
+		            if (char.IsDigit(x[i]) && char.IsDigit(y[i]))
+		            {
+		                var xOut = GetNumber(x.Slice(i), out var xNumAsSpan);
+		                var yOut = GetNumber(y.Slice(i), out var yNumAsSpan);
+
+		                var compareResult = CompareNumValues(xNumAsSpan, yNumAsSpan);
+
+		                if (compareResult != 0) return compareResult;
+
+		                i = -1;
+		                length = Math.Min(xOut.Length, yOut.Length);
+
+		                x = xOut;
+		                y = yOut;
+		                continue;
+		            }
+
+		            var charCompareResult = x.Slice(i, 1).CompareTo(y.Slice(i, 1), stringComparison);
+		            if (charCompareResult != 0) return charCompareResult;
+		        }
+
+		        return x.Length.CompareTo(y.Length);
+		    }
+
+		    private static ReadOnlySpan<char> GetNumber(ReadOnlySpan<char> span, out ReadOnlySpan<char> number)
+		    {
+		        var i = 0;
+		        while (i < span.Length && char.IsDigit(span[i]))
+		        {
+		            i++;
+		        }
+
+		        number = span.Slice(0, i);
+		        return span.Slice(i);
+		    }
+
+		    private static int CompareNumValues(ReadOnlySpan<char> numValue1, ReadOnlySpan<char> numValue2)
+		    {
+		        var num1AsSpan = numValue1.TrimStart('0');
+		        var num2AsSpan = numValue2.TrimStart('0');
+
+		        if (num1AsSpan.Length < num2AsSpan.Length) return -1;
+
+		        if (num1AsSpan.Length > num2AsSpan.Length) return 1;
+
+		        var compareResult = num1AsSpan.CompareTo(num2AsSpan, StringComparison.Ordinal);
+
+		        if (compareResult != 0) return Math.Sign(compareResult);
+
+		        if (numValue2.Length == numValue1.Length) return compareResult;
+
+		        return numValue2.Length < numValue1.Length ? -1 : 1; // "033" < "33" == true
+		    }
 		}
 	}
 }