// choose a proxy server to excute http GET/method to download
func connectByHttpProxy(p *page.Page, in_req *request.Request) (*http.Response, error) {
	request, _ := http.NewRequest("GET", in_req.GetUrl(), nil)
	proxy, err := url.Parse(in_req.GetProxyHost())
	if err != nil {
		return nil, err
	}
	client := &http.Client{
		Transport: &http.Transport{
			Proxy: http.ProxyURL(proxy),
		},
	}
	resp, err := client.Do(request)
	if err != nil {
		return nil, err
	}
	return resp, nil

}
// Download file and change the charset of page charset.
func (this *HttpDownloader) downloadFile(p *page.Page, req *request.Request) (*page.Page, string) {
	var err error
	var urlstr string
	if urlstr = req.GetUrl(); len(urlstr) == 0 {
		mlog.LogInst().LogError("url is empty")
		p.SetStatus(true, "url is empty")
		return p, ""
	}

	var resp *http.Response

	if proxystr := req.GetProxyHost(); len(proxystr) != 0 {
		//using http proxy
		//fmt.Print("HttpProxy Enter ",proxystr,"\n")
		resp, err = connectByHttpProxy(p, req)
	} else {
		//normal http download
		//fmt.Print("Http Normal Enter \n",proxystr,"\n")
		resp, err = connectByHttp(p, req)
	}

	if err != nil {
		return p, ""
	}

	//b, _ := ioutil.ReadAll(resp.Body)
	//fmt.Printf("Resp body %v \r\n", string(b))

	p.SetHeader(resp.Header)
	p.SetCookies(resp.Cookies())

	// get converter to utf-8
	var bodyStr string
	if resp.Header.Get("Content-Encoding") == "gzip" {
		bodyStr = this.changeCharsetEncodingAutoGzipSupport(resp.Header.Get("Content-Type"), resp.Body)
	} else {
		bodyStr = this.changeCharsetEncodingAuto(resp.Header.Get("Content-Type"), resp.Body)
	}
	//fmt.Printf("utf-8 body %v \r\n", bodyStr)
	defer resp.Body.Close()
	return p, bodyStr
}