class NativeFileSessionHandler

NativeFileSessionHandlerTest.php in drupal/core/vendor/symfony/http-foundation/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/NativeFileSessionHandlerTest.php

NativeSessionStorageTest.php in drupal/core/vendor/symfony/http-foundation/Symfony/Component/HttpFoundation/Tests/Session/Storage/NativeSessionStorageTest.php

class NativeFileSessionHandler extends NativeSessionHandler {

  /**
   * Constructor.
   *
   * @param string $savePath Path of directory to save session files.
   *                         Default null will leave setting as defined by PHP.
   *                         '/path', 'N;/path', or 'N;octal-mode;/path
   *
   * @see http://php.net/session.configuration.php#ini.session.save-path for further details.
   *
   * @throws \InvalidArgumentException On invalid $savePath
   */
  public function __construct($savePath = null) {
    if (null === $savePath) {
      $savePath = ini_get('session.save_path');
    }
    $baseDir = $savePath;
    if ($count = substr_count($savePath, ';')) {
      if ($count > 2) {
        throw new \InvalidArgumentException(sprintf('Invalid argument $savePath \'%s\'', $savePath));
      }

      // characters after last ';' are the path
      $baseDir = ltrim(strrchr($savePath, ';'), ';');
    }
    if ($baseDir && !is_dir($baseDir)) {
      mkdir($baseDir, 0777, true);
    }
    ini_set('session.save_path', $savePath);
    ini_set('session.save_handler', 'files');
  }

}