The file name for the CSS or JS cache file is generated from the hash of the aggregated contents of the files in $data. This forces proxies and browsers to download new CSS when the CSS changes.

File

src/Asset/AssetDumper.php, line 88

Class

AssetDumper
Dumps a CSS or JavaScript asset.

Namespace

Drupal\advagg\Asset

Code

public function dump($data, $file_extension) {
    if (!isset($this->extension) || $this->extension != $file_extension) {
        $this->preparePath($file_extension);
    }
    // Prefix filename to prevent blocking by firewalls which reject files
    // starting with "ad*".
    $filename = $this->extension . '_' . Crypt::hashBase64($data) . $this->hash . $this->extension;
    $uri = $this->path . $filename;
    // Create the CSS or JS file.
    if (!file_exists($uri) && !file_unmanaged_save_data($data, $uri, FILE_EXISTS_REPLACE)) {
        return FALSE;
    }
    // If CSS/JS gzip compression is enabled and the zlib extension is available
    // then create a gzipped version of this file. This file is served
    // conditionally to browsers that accept gzip using .htaccess rules.
    // It's possible that the rewrite rules in .htaccess aren't working on this
    // server, but there's no harm (other than the time spent generating the
    // file) in generating the file anyway. Sites on servers where rewrite rules
    // aren't working can set css.gzip to FALSE in order to skip
    // generating a file that won't be used.
    if (extension_loaded('zlib') && $this->config
        ->get($file_extension . '.gzip')) {
        if (!file_exists($uri . '.gz') && !file_unmanaged_save_data(gzencode($data, 9, FORCE_GZIP), $uri . '.gz', FILE_EXISTS_REPLACE)) {
            return FALSE;
        }
    }
    return [
        $uri,
        $filename,
    ];
}