private function _reloadBuffer($fp, $len)
{
if (!feof($fp) && ($bytes = fread($fp, $len)) !== false) {
$buf = array();
for ($i = 0, $len = strlen($bytes); $i < $len; ++$i) {
$buf[] = self::$_byteMap[$bytes[$i]];
}
return $buf;
}
return false;
}