场景
    当HTTP交互中，服务器端指定了application/x-www-form-urlencoded的Content-Type类型，需要对Body报文实体进行url编码。libcurl提供了curl_easy_escape

例子
 static void TestPostOfRestfulInterfaceByUrlEncode()
 {
  CURL *pCurlHandle = curl_easy_init();
  curl_easy_setopt(pCurlHandle, CURLOPT_CUSTOMREQUEST, "POST");
  curl_easy_setopt(pCurlHandle, CURLOPT_URL, "http://192.168.10.163:80/cs/restfull/excuteSqlByCode");
  struct curl_slist *pCurlList = NULL;
  pCurlList = curl_slist_append(pCurlList, "Content-Type: application/x-www-form-urlencoded");//指定文本url编码
  curl_easy_setopt(pCurlHandle, CURLOPT_HTTPHEADER, pCurlList);
  Json::Value jsonAuthen;
  jsonAuthen["loginAccount"] = "root";
  std::string strAuth = jsonAuthen.toStyledString();
//对参数authorJson的内容:{ "loginAccount" : "root"}  ,进行url编码
char* pszEncodeAuth = curl_easy_escape(pCurlHandle, strAuth.c_str(), strAuth.length());
  std::string strEncodeAuth = pszEncodeAuth;
//释放申请的内存
  curl_free(pszEncodeAuth);
  Json::Value jsonContent;
  jsonContent["operatorname"] = "PostName";
  Json::Value jsonParams;
  jsonParams["name"] = "fengyuzaitu";
  jsonContent["params"] = jsonParams;
  std::string strParams = jsonContent.toStyledString();
  char* pszParams = curl_easy_escape(pCurlHandle, strParams.c_str(), strParams.length());
  std::string strEncodeParams = pszParams;
  curl_free(pszParams);
  std::string strPostData = "authorJson=" + strAuth + "&parmJson=" + strParams;
  curl_easy_setopt(pCurlHandle, CURLOPT_POSTFIELDS, strPostUrlEncodeData.c_str());
  CURLcode nRet = curl_easy_perform(pCurlHandle);
  if (0 == nRet)
  {
   std::cout << "Post message successfully" << std::endl;
  }
  curl_slist_free_all(pCurlList);
  curl_easy_cleanup(pCurlHandle);
 }

内容分析：
/*
没有经过url编码的原始数据如下:
authorJson={
   "loginAccount" : "root"
}
&parmJson={
   "operatorname" : "PostName",
   "params" : {
      "name" : "fengyuzaitu"
   }
}
*/
  std::string strPostUrlEncodeData = "authorJson=" + strEncodeAuth + "&parmJson=" + strEncodeParams;
/*
经过url编码的数据如下:authorJson=%7B%0A%20%20%20%22loginAccount%22%20%3A%20%22root%22%0A%7D%0A&parmJson=%7B%0A%20%20%20%22operatorname%22%20%3A%20%22PostName%22%2C%0A%20%20%20%22params%22%20%3A%20%7B%0A%20%20%20%20%20%20%22name%22%20%3A%20%22fengyuzaitu%22%0A%20%20%20%7D%0A%7D%0A
*/