Symfony\Component\HttpFoundation\BinaryFileResponse::prepare PHP Method

    public function prepare(Request $request)
    {
        $this->headers->set('Content-Length', $this->file->getSize());
        if (!$this->headers->has('Accept-Ranges')) {
            // Only accept ranges on safe HTTP methods
            $this->headers->set('Accept-Ranges', $request->isMethodSafe(false) ? 'bytes' : 'none');
        }
        if (!$this->headers->has('Content-Type')) {
            $this->headers->set('Content-Type', $this->file->getMimeType() ?: 'application/octet-stream');
        }
        if ('HTTP/1.0' !== $request->server->get('SERVER_PROTOCOL')) {
            $this->setProtocolVersion('1.1');
        }
        $this->ensureIEOverSSLCompatibility($request);
        $this->offset = 0;
        $this->maxlen = -1;
        if (self::$trustXSendfileTypeHeader && $request->headers->has('X-Sendfile-Type')) {
            // Use X-Sendfile, do not send any content.
            $type = $request->headers->get('X-Sendfile-Type');
            $path = $this->file->getRealPath();
            // Fall back to scheme://path for stream wrapped locations.
            if (false === $path) {
                $path = $this->file->getPathname();
            }
            if (strtolower($type) === 'x-accel-redirect') {
                // Do X-Accel-Mapping substitutions.
                // @link http://wiki.nginx.org/X-accel#X-Accel-Redirect
                foreach (explode(',', $request->headers->get('X-Accel-Mapping', '')) as $mapping) {
                    $mapping = explode('=', $mapping, 2);
                    if (2 === count($mapping)) {
                        $pathPrefix = trim($mapping[0]);
                        $location = trim($mapping[1]);
                        if (substr($path, 0, strlen($pathPrefix)) === $pathPrefix) {
                            $path = $location . substr($path, strlen($pathPrefix));
                            break;
                        }
                    }
                }
            }
            $this->headers->set($type, $path);
            $this->maxlen = 0;
        } elseif ($request->headers->has('Range')) {
            // Process the range headers.
            if (!$request->headers->has('If-Range') || $this->hasValidIfRangeHeader($request->headers->get('If-Range'))) {
                $range = $request->headers->get('Range');
                $fileSize = $this->file->getSize();
                list($start, $end) = explode('-', substr($range, 6), 2) + array(0);
                $end = '' === $end ? $fileSize - 1 : (int) $end;
                if ('' === $start) {
                    $start = $fileSize - $end;
                    $end = $fileSize - 1;
                } else {
                    $start = (int) $start;
                }
                if ($start <= $end) {
                    if ($start < 0 || $end > $fileSize - 1) {
                        $this->setStatusCode(416);
                        $this->headers->set('Content-Range', sprintf('bytes */%s', $fileSize));
                    } elseif ($start !== 0 || $end !== $fileSize - 1) {
                        $this->maxlen = $end < $fileSize ? $end - $start + 1 : -1;
                        $this->offset = $start;
                        $this->setStatusCode(206);
                        $this->headers->set('Content-Range', sprintf('bytes %s-%s/%s', $start, $end, $fileSize));
                        $this->headers->set('Content-Length', $end - $start + 1);
                    }
                }
            }
        }
        return $this;
    }

 /**
  * @param Request $request
  * @return DecryptFileResponse
  */
 public function prepare(Request $request)
 {
     parent::prepare($request);
     $this->headers->set('Content-Length', $this->fileSize);
     $this->headers->set('Content-Type', 'application/octet-stream');
     return $this;
 }