UrlGenerator::doGenerate

protected UrlGenerator::doGenerate(array $variables, array $defaults, array $tokens, array $parameters, array $query_params, $name)

protected function doGenerate(array $variables, array $defaults, array $tokens, array $parameters, array $query_params, $name) {
  $variables = array_flip($variables);
  $mergedParams = array_replace($defaults, $this->context->getParameters(), $parameters);

  // all params must be given
  if ($diff = array_diff_key($variables, $mergedParams)) {
    throw new MissingMandatoryParametersException(sprintf('Some mandatory parameters are missing ("%s") to generate a URL for route "%s".', implode('", "', array_keys($diff)), $name));
  }

  $url = '';
  // Tokens start from the end of the path and work to the beginning. The
  // first one or several variable tokens may be optional, but once we find a
  // supplied token or a static text portion of the path, all remaining
  // variables up to the start of the path must be supplied to there is no gap.
  $optional = TRUE;
  // Structure of $tokens from the compiled route:
  // If the path is /admin/config/user-interface/shortcut/manage/{shortcut_set}/add-link-inline
  // [ [ 0 => 'text', 1 => '/add-link-inline' ], [ 0 => 'variable', 1 => '/', 2 => '[^/]++', 3 => 'shortcut_set' ], [ 0 => 'text', 1 => '/admin/config/user-interface/shortcut/manage' ] ]
  //
  // For a simple fixed path, there is just one token.
  // If the path is /admin/config
  // [ [ 0 => 'text', 1 => '/admin/config' ] ]
  foreach ($tokens as $token) {
    if ('variable' === $token[0]) {
      if (!$optional || !array_key_exists($token[3], $defaults) || (isset($mergedParams[$token[3]]) && (string) $mergedParams[$token[3]] !== (string) $defaults[$token[3]])) {
        // check requirement
        if (!preg_match('#^' . $token[2] . '$#', $mergedParams[$token[3]])) {
          $message = sprintf('Parameter "%s" for route "%s" must match "%s" ("%s" given) to generate a corresponding URL.', $token[3], $name, $token[2], $mergedParams[$token[3]]);
          throw new InvalidParameterException($message);
        }

        $url = $token[1] . $mergedParams[$token[3]] . $url;
        $optional = FALSE;
      }
    }
    else {
      // Static text
      $url = $token[1] . $url;
      $optional = FALSE;
    }
  }

  if ('' === $url) {
    $url = '/';
  }

  // The contexts base URL is already encoded (see Symfony\Component\HttpFoundation\Request)
  $url = str_replace($this->decodedChars[0], $this->decodedChars[1], rawurlencode($url));

  // Drupal paths rarely include dots, so skip this processing if possible.
  if (strpos($url, '/.') !== FALSE) {
    // the path segments "." and ".." are interpreted as relative reference when
    // resolving a URI; see http://tools.ietf.org/html/rfc3986#section-3.3
    // so we need to encode them as they are not used for this purpose here
    // otherwise we would generate a URI that, when followed by a user agent
    // (e.g. browser), does not match this route
    $url = strtr($url, array('/../' => '/%2E%2E/', '/./' => '/%2E/'));
    if ('/..' === substr($url, -3)) {
      $url = substr($url, 0, -2) . '%2E%2E';
    }
    elseif ('/.' === substr($url, -2)) {
      $url = substr($url, 0, -1) . '%2E';
    }
  }

  // Add a query string if needed, including extra parameters.
  $query_params += array_diff_key($parameters, $variables, $defaults);
  if ($query_params && $query = UrlHelper::buildQuery($query_params)) {
    $url .= '?' . $query;
  }

  return $url;
}