dirSetFilePermissions

fn dirSetFilePermissions(
    userdata: ?*anyopaque,
    dir: Dir,
    sub_path: []const u8,
    permissions: Dir.Permissions,
    options: Dir.SetFilePermissionsOptions,
) Dir.SetFilePermissionsError!void {
    const ev: *Evented = @ptrCast(@alignCast(userdata));
    _ = ev;

    var path_buffer: [c.PATH_MAX]u8 = undefined;
    const sub_path_posix = try pathToPosix(sub_path, &path_buffer);

    const mode = permissions.toMode();
    const flags: u32 = if (options.follow_symlinks) 0 else c.AT.SYMLINK_NOFOLLOW;

    while (true) switch (c.errno(c.fchmodat(dir.handle, sub_path_posix, mode, flags))) {
        .SUCCESS => return,
        .INTR => {},
        .BADF => |err| return errnoBug(err),
        .FAULT => |err| return errnoBug(err),
        .INVAL => |err| return errnoBug(err),
        .ACCES => return error.AccessDenied,
        .IO => return error.InputOutput,
        .LOOP => return error.SymLinkLoop,
        .MFILE => return error.ProcessFdQuotaExceeded,
        .NAMETOOLONG => return error.NameTooLong,
        .NFILE => return error.SystemFdQuotaExceeded,
        .NOENT => return error.FileNotFound,
        .NOTDIR => return error.FileNotFound,
        .NOMEM => return error.SystemResources,
        .OPNOTSUPP => return error.OperationUnsupported,
        .PERM => return error.PermissionDenied,
        .ROFS => return error.ReadOnlyFileSystem,
        else => |err| return unexpectedErrno(err),
    };
}