protected function validateCache($fileName)
    {
        $hash = $this->getHash($fileName);
        if (!file_exists($fileName) || !isset($this->cachedFiles[$hash])) {
            return false;
        }
        
        $fileChecksum = md5_file($fileName);
        $cachedChecksum = $this->cachedFiles[$hash]['checksum'];
        
        if ($fileChecksum != $cachedChecksum) {
            return false;
        }
        
        return true;
    }