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using System;
using System.Collections.Generic;
namespace Jellyfin.Extensions
{
/// <summary>
/// Alphanumeric <see cref="IComparer{T}" />.
/// </summary>
public class AlphanumericComparator : IComparer<string?>
{
/// <summary>
/// Compares two objects and returns a value indicating whether one is less than, equal to, or greater than the other.
/// </summary>
/// <param name="s1">The first object to compare.</param>
/// <param name="s2">The second object to compare.</param>
/// <returns>A signed integer that indicates the relative values of <c>x</c> and <c>y</c>.</returns>
public static int CompareValues(string? s1, string? s2)
{
if (s1 == null && s2 == null)
{
return 0;
}
else if (s1 == null)
{
return -1;
}
else if (s2 == null)
{
return 1;
}
int len1 = s1.Length;
int len2 = s2.Length;
// Early return for empty strings
if (len1 == 0 && len2 == 0)
{
return 0;
}
else if (len1 == 0)
{
return -1;
}
else if (len2 == 0)
{
return 1;
}
int pos1 = 0;
int pos2 = 0;
do
{
int start1 = pos1;
int start2 = pos2;
bool isNum1 = char.IsDigit(s1[pos1++]);
bool isNum2 = char.IsDigit(s2[pos2++]);
while (pos1 < len1 && char.IsDigit(s1[pos1]) == isNum1)
{
pos1++;
}
while (pos2 < len2 && char.IsDigit(s2[pos2]) == isNum2)
{
pos2++;
}
var span1 = s1.AsSpan(start1, pos1 - start1);
var span2 = s2.AsSpan(start2, pos2 - start2);
if (isNum1 && isNum2)
{
// Trim leading zeros so we can compare the length
// of the strings to find the largest number
span1 = span1.TrimStart('0');
span2 = span2.TrimStart('0');
var span1Len = span1.Length;
var span2Len = span2.Length;
if (span1Len < span2Len)
{
return -1;
}
else if (span1Len > span2Len)
{
return 1;
}
else if (span1Len >= 20) // Number is probably too big for a ulong
{
// Trim all the first digits that are the same
int i = 0;
while (i < span1Len && span1[i] == span2[i])
{
i++;
}
// If there are no more digits it's the same number
if (i == span1Len)
{
continue;
}
// Only need to compare the most significant digit
span1 = span1.Slice(i, 1);
span2 = span2.Slice(i, 1);
}
if (!ulong.TryParse(span1, out var num1)
|| !ulong.TryParse(span2, out var num2))
{
return 0;
}
else if (num1 < num2)
{
return -1;
}
else if (num1 > num2)
{
return 1;
}
}
else
{
int result = span1.CompareTo(span2, StringComparison.InvariantCulture);
if (result != 0)
{
return result;
}
}
#pragma warning disable SA1500 // TODO remove with StyleCop.Analyzers v1.2.0 https://github.com/DotNetAnalyzers/StyleCopAnalyzers/pull/3196
} while (pos1 < len1 && pos2 < len2);
#pragma warning restore SA1500
return len1 - len2;
}
/// <inheritdoc />
public int Compare(string? x, string? y)
{
return CompareValues(x, y);
}
}
}
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