private function parseHttpResponse($respData, $headerSize)
  {
    // check proxy header
    foreach (self::$CONNECTION_ESTABLISHED_HEADERS as $established_header) {
      if (stripos($respData, $established_header) !== false) {
        // existed, remove it
        $respData = str_ireplace($established_header, '', $respData);
        // Subtract the proxy header size unless the cURL bug prior to 7.30.0
        // is present which prevented the proxy header size from being taken into
        // account.
        // @TODO look into this
        // if (!$this->needsQuirk()) {
        //   $headerSize -= strlen($established_header);
        // }
        break;
      }
    }

    if ($headerSize) {
      $responseBody = substr($respData, $headerSize);
      $responseHeaders = substr($respData, 0, $headerSize);
    } else {
      $responseSegments = explode("\r\n\r\n", $respData, 2);
      $responseHeaders = $responseSegments[0];
      $responseBody = isset($responseSegments[1]) ? $responseSegments[1] :
                                                    null;
    }

    $responseHeaders = $this->parseRawHeaders($responseHeaders);

    return array($responseHeaders, $responseBody);
  }