public function addStoredFields($storedFields)
    {
        if (!isset($this->_fdxFile)) {
            $this->_fdxFile = $this->_directory->createFile($this->_name . '.fdx');
            $this->_fdtFile = $this->_directory->createFile($this->_name . '.fdt');

            $this->_files[] = $this->_name . '.fdx';
            $this->_files[] = $this->_name . '.fdt';
        }

        $this->_fdxFile->writeLong($this->_fdtFile->tell());
        $this->_fdtFile->writeVInt(count($storedFields));
        foreach ($storedFields as $field) {
            $this->_fdtFile->writeVInt($this->_fields[$field->name]->number);
            $fieldBits = ($field->isTokenized ? 0x01 : 0x00) |
                         ($field->isBinary ?    0x02 : 0x00) |
                         0x00; /* 0x04 - third bit, compressed (ZLIB) */
            $this->_fdtFile->writeByte($fieldBits);
            if ($field->isBinary) {
                $this->_fdtFile->writeVInt(strlen($field->value));
                $this->_fdtFile->writeBytes($field->value);
            } else {
                $this->_fdtFile->writeString($field->getUtf8Value());
            }
        }

        $this->_docCount++;
    }