protected function getMaskOffset()
    {
        if (!isset($this->offset_mask)) {
            $offset = self::BYTE_INITIAL_LENGTH + 1;
            $offset += $this->getLengthSize();

            $this->offset_mask = $offset;
        }
        return $this->offset_mask;
    }
protected function getMaskOffset()
    {
        if (!isset($this->offset_mask)) {
            $offset = self::BYTE_INITIAL_LENGTH + 1;
            $offset += $this->getLengthSize();

            $this->offset_mask = $offset;
        }
        return $this->offset_mask;
    }
protected function getMaskOffset ( ) { if ( ! isset ( $ this -> offset_mask ) ) { $ offset = self :: BYTE_INITIAL_LENGTH + 1 ; $ offset += $ this -> getLengthSize ( ) ; $ this -> offset_mask = $ offset ; } return $ this -> offset_mask ; }
Gets the offset in the frame to the masking bytes

@return int
Gets the offset in the frame to the masking bytes