public DirectoryInfo CreateSubdirectory(string path)
{
if (path == null)
{
throw new ArgumentNullException(nameof(path));
}
if (PathInternal.IsEffectivelyEmpty(path.AsSpan()))
{
throw new ArgumentException(SR.Argument_PathEmpty, nameof(path));
}
if (Path.IsPathRooted(path))
{
throw new ArgumentException(SR.Arg_Path2IsRooted, nameof(path));
}
string newPath = Path.GetFullPath(Path.Combine(FullPath, path));
ReadOnlySpan <char> trimmedNewPath = Path.TrimEndingDirectorySeparator(newPath.AsSpan());
ReadOnlySpan <char> trimmedCurrentPath = Path.TrimEndingDirectorySeparator(FullPath.AsSpan());
// We want to make sure the requested directory is actually under the subdirectory.
if (trimmedNewPath.StartsWith(trimmedCurrentPath, PathInternal.StringComparison)
// Allow the exact same path, but prevent allowing "..\FooBar" through when the directory is "Foo"
&& ((trimmedNewPath.Length == trimmedCurrentPath.Length) || PathInternal.IsDirectorySeparator(newPath[trimmedCurrentPath.Length])))
{
FileSystem.CreateDirectory(newPath);
return(new DirectoryInfo(newPath));
}
// We weren't nested
throw new ArgumentException(SR.Format(SR.Argument_InvalidSubPath, path, FullPath), nameof(path));
}
