protected function _getCacheFilePath( $sFileName = '' )
    {
        $sTmpDirFullPath          = realpath( oxRegistry::getConfig()->getConfigParam( 'sCompileDir' ) );
        $sResourceCacheFolderName = $this->getCacheFolder();
        $sResourceCachePath       = $sTmpDirFullPath . DIRECTORY_SEPARATOR . $sResourceCacheFolderName;

        // Try to create resource cache folder if it does not exist
        if ( !is_dir( $sResourceCachePath ) ) {
            @mkdir( $sResourceCachePath, 0777 );
        }

        if ( !is_dir( $sResourceCachePath ) ) {
            return null;
        }

        return empty( $sFileName )
            ? $sResourceCachePath
            : $sResourceCachePath . DIRECTORY_SEPARATOR . basename( $sFileName );
    }