devdocs-8.x-1.x-dev/src/Controller/DocsDownloadController.php

<?php

/**
 * @file
 * Contains \Drupal\devdocs\Controller\DocsDownloadController.
 */

namespace Drupal\devdocs\Controller;

use Drupal\Core\Controller\ControllerBase;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
use Symfony\Component\HttpFoundation\BinaryFileResponse;

/**
 * System file controller.
 */
class DocsDownloadController extends ControllerBase {

  /**
   * Handles private file transfers.
   *
   * Call modules that implement hook_file_download() to find out if a file is
   * accessible and what headers it should be transferred with. If one or more
   * modules returned headers the download will start with the returned headers.
   * If a module returns -1 an AccessDeniedHttpException will be thrown. If the
   * file exists but no modules responded an AccessDeniedHttpException will be
   * thrown. If the file does not exist a NotFoundHttpException will be thrown.
   *
   * @see hook_file_download()
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   The request object.
   * @param string $scheme
   *   The file scheme, defaults to 'private'.
   *
   * @return \Symfony\Component\HttpFoundation\BinaryFileResponse
   *   The transferred file as response.
   *
   * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
   *   Thrown when the requested file does not exist.
   * @throws \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
   *   Thrown when the user does not have access to the file.
   */
  public function download(Request $request, $scheme = 'docs') {
    $target = $request->query->get('file');
    // Merge remaining path arguments into relative file path.
    $uri = $scheme . '://' . $target;

    if (file_stream_wrapper_valid_scheme($scheme) && file_exists($uri)) {
      // Let other modules provide headers and controls access to the file.
      $headers = $this->moduleHandler()->invokeAll('file_download', array($uri));

      return new BinaryFileResponse($uri, 200, $headers, FALSE);

    }

    throw new NotFoundHttpException();
  }

}