D6 - Create a files table entry for a file
It's just done manually, e.g.:

$file = new stdClass();
$file-&gt;filename = 'foo.bar';
$file-&gt;filepath = $file;
$file-&gt;filemime = file_get_mimetype($file-&gt;filename);
$file-&gt;uid = $user-&gt;uid;
$file-&gt;status = FILE_STATUS_TEMPORARY;
$file-&gt;timestamp = time();
drupal_write_record('files', $file);


See file_save_upload() for a much broader example, including validation.