FileSystemName.cs

Go to the documentation of this file.

using System.Text;
 
namespace System.IO.Enumeration;
 
public static class FileSystemName
{
    private static readonly char[] s_wildcardChars = new char[5] { '"', '<', '>', '*', '?' };
 
    private static readonly char[] s_simpleWildcardChars = new char[2] { '*', '?' };
 
    public static string TranslateWin32Expression(string? expression)
    {
        if (string.IsNullOrEmpty(expression) || expression == "*" || expression == "*.*")
        {
            return "*";
        }
        bool flag = false;
        Span<char> initialBuffer = stackalloc char[32];
        ValueStringBuilder valueStringBuilder = new ValueStringBuilder(initialBuffer);
        int length = expression.Length;
        for (int i = 0; i < length; i++)
        {
            char c = expression[i];
            switch (c)
            {
            case '.':
                flag = true;
                if (i >= 1 && i == length - 1 && expression[i - 1] == '*')
                {
                    valueStringBuilder[valueStringBuilder.Length - 1] = '<';
                }
                else if (i < length - 1 && (expression[i + 1] == '?' || expression[i + 1] == '*'))
                {
                    valueStringBuilder.Append('"');
                }
                else
                {
                    valueStringBuilder.Append('.');
                }
                break;
            case '?':
                flag = true;
                valueStringBuilder.Append('>');
                break;
            default:
                valueStringBuilder.Append(c);
                break;
            }
        }
        if (!flag)
        {
            return expression;
        }
        return valueStringBuilder.ToString();
    }
 
    public static bool MatchesWin32Expression(ReadOnlySpan<char> expression, ReadOnlySpan<char> name, bool ignoreCase = true)
    {
        return MatchPattern(expression, name, ignoreCase, useExtendedWildcards: true);
    }
 
    public static bool MatchesSimpleExpression(ReadOnlySpan<char> expression, ReadOnlySpan<char> name, bool ignoreCase = true)
    {
        return MatchPattern(expression, name, ignoreCase, useExtendedWildcards: false);
    }
 
    private static bool MatchPattern(ReadOnlySpan<char> expression, ReadOnlySpan<char> name, bool ignoreCase, bool useExtendedWildcards)
    {
        if (expression.Length == 0 || name.Length == 0)
        {
            return false;
        }
        if (expression[0] == '*')
        {
            if (expression.Length == 1)
            {
                return true;
            }
            ReadOnlySpan<char> readOnlySpan = expression.Slice(1);
            if (readOnlySpan.IndexOfAny(useExtendedWildcards ? s_wildcardChars : s_simpleWildcardChars) == -1)
            {
                if (name.Length < readOnlySpan.Length)
                {
                    return false;
                }
                return name.EndsWith(readOnlySpan, ignoreCase ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal);
            }
        }
        int num = 0;
        int num2 = 1;
        char c = '\0';
        Span<int> span = default(Span<int>);
        Span<int> span2 = stackalloc int[16];
        Span<int> span3 = stackalloc int[16];
        span3[0] = 0;
        int num3 = expression.Length * 2;
        bool flag = false;
        int num6;
        while (!flag)
        {
            if (num < name.Length)
            {
                c = name[num++];
            }
            else
            {
                if (span3[num2 - 1] == num3)
                {
                    break;
                }
                flag = true;
            }
            int i = 0;
            int num4 = 0;
            int j = 0;
            while (i < num2)
            {
                int num5 = (span3[i++] + 1) / 2;
                while (num5 < expression.Length)
                {
                    num6 = num5 * 2;
                    char c2 = expression[num5];
                    if (num4 >= span2.Length - 2)
                    {
                        int num7 = span2.Length * 2;
                        span = new int[num7];
                        span2.CopyTo(span);
                        span2 = span;
                        span = new int[num7];
                        span3.CopyTo(span);
                        span3 = span;
                    }
                    if (c2 != '*')
                    {
                        if (!useExtendedWildcards || c2 != '<')
                        {
                            num6 += 2;
                            if (useExtendedWildcards && c2 == '>')
                            {
                                if (!flag && c != '.')
                                {
                                    span2[num4++] = num6;
                                    break;
                                }
                            }
                            else
                            {
                                if (!useExtendedWildcards || c2 != '"')
                                {
                                    if (c2 == '\\')
                                    {
                                        if (++num5 == expression.Length)
                                        {
                                            span2[num4++] = num3;
                                            break;
                                        }
                                        num6 = num5 * 2 + 2;
                                        c2 = expression[num5];
                                    }
                                    if (!flag)
                                    {
                                        if (c2 == '?')
                                        {
                                            span2[num4++] = num6;
                                        }
                                        else if (ignoreCase ? (char.ToUpperInvariant(c2) == char.ToUpperInvariant(c)) : (c2 == c))
                                        {
                                            span2[num4++] = num6;
                                        }
                                    }
                                    break;
                                }
                                if (!flag)
                                {
                                    if (c == '.')
                                    {
                                        span2[num4++] = num6;
                                    }
                                    break;
                                }
                            }
                            goto IL_02e4;
                        }
                        bool flag2 = false;
                        if (!flag && c == '.')
                        {
                            for (int k = num; k < name.Length; k++)
                            {
                                if (name[k] == '.')
                                {
                                    flag2 = true;
                                    break;
                                }
                            }
                        }
                        if (!(flag || c != '.' || flag2))
                        {
                            goto IL_02d3;
                        }
                    }
                    span2[num4++] = num6;
                    goto IL_02d3;
                    IL_02e4:
                    if (++num5 == expression.Length)
                    {
                        span2[num4++] = num3;
                    }
                    continue;
                    IL_02d3:
                    span2[num4++] = num6 + 1;
                    goto IL_02e4;
                }
                if (i >= num2 || j >= num4)
                {
                    continue;
                }
                for (; j < num4; j++)
                {
                    for (int length = span3.Length; i < length && span3[i] < span2[j]; i++)
                    {
                    }
                }
            }
            if (num4 == 0)
            {
                return false;
            }
            span = span3;
            span3 = span2;
            span2 = span;
            num2 = num4;
        }
        num6 = span3[num2 - 1];
        return num6 == num3;
    }
}