PathInternal.cs

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using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
 
namespace System.IO;
 
internal static class PathInternal
{
    internal static StringComparison StringComparison
    {
        get
        {
            if (!IsCaseSensitive)
            {
                return StringComparison.OrdinalIgnoreCase;
            }
            return StringComparison.Ordinal;
        }
    }
 
    internal static bool IsCaseSensitive
    {
        get
        {
            if (!OperatingSystem.IsWindows() && !OperatingSystem.IsMacOS() && !OperatingSystem.IsIOS() && !OperatingSystem.IsTvOS())
            {
                return !OperatingSystem.IsWatchOS();
            }
            return false;
        }
    }
 
    internal static bool IsValidDriveChar(char value)
    {
        if (value < 'A' || value > 'Z')
        {
            if (value >= 'a')
            {
                return value <= 'z';
            }
            return false;
        }
        return true;
    }
 
    private static bool EndsWithPeriodOrSpace(string path)
    {
        if (string.IsNullOrEmpty(path))
        {
            return false;
        }
        char c = path[path.Length - 1];
        if (c != ' ')
        {
            return c == '.';
        }
        return true;
    }
 
    [return: NotNullIfNotNull("path")]
    internal static string EnsureExtendedPrefixIfNeeded(string path)
    {
        if (path != null && (path.Length >= 260 || EndsWithPeriodOrSpace(path)))
        {
            return EnsureExtendedPrefix(path);
        }
        return path;
    }
 
    internal static string EnsureExtendedPrefix(string path)
    {
        if (IsPartiallyQualified(path) || IsDevice(path))
        {
            return path;
        }
        if (path.StartsWith("\\\\", StringComparison.OrdinalIgnoreCase))
        {
            return path.Insert(2, "?\\UNC\\");
        }
        return "\\\\?\\" + path;
    }
 
    internal static bool IsDevice(string path)
    {
        if (!IsExtended(path))
        {
            if (path.Length >= 4 && IsDirectorySeparator(path[0]) && IsDirectorySeparator(path[1]) && (path[2] == '.' || path[2] == '?'))
            {
                return IsDirectorySeparator(path[3]);
            }
            return false;
        }
        return true;
    }
 
    internal static bool IsExtended(string path)
    {
        if (path.Length >= 4 && path[0] == '\\' && (path[1] == '\\' || path[1] == '?') && path[2] == '?')
        {
            return path[3] == '\\';
        }
        return false;
    }
 
    internal static bool IsPartiallyQualified(string path)
    {
        if (path.Length < 2)
        {
            return true;
        }
        if (IsDirectorySeparator(path[0]))
        {
            if (path[1] != '?')
            {
                return !IsDirectorySeparator(path[1]);
            }
            return false;
        }
        if (path.Length >= 3 && path[1] == Path.VolumeSeparatorChar && IsDirectorySeparator(path[2]))
        {
            return !IsValidDriveChar(path[0]);
        }
        return true;
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    internal static bool IsDirectorySeparator(char c)
    {
        if (c != Path.DirectorySeparatorChar)
        {
            return c == Path.AltDirectorySeparatorChar;
        }
        return true;
    }
}