curl 获取ip

#include <iconv.h>
#include <curl/curl.h>
#include <nlohmann/json.hpp>
#define GLOG_NO_ABBREVIATED_SEVERITIES
#include <glog/logging.h>

using namespace std;

int char_code_convert(
  const string& from, const string& to,
  const string& in, string& out)
{
  const iconv_t cd = iconv_open(to.c_str(),
                                from.c_str());
  if (cd == nullptr)
  {
    return -1;
  }
  out.resize(in.size() * 2, 0);
  char* pin = const_cast<char*>(in.data());
  size_t in_len = in.size();
  char* pout = const_cast<char*>(out.data());
  size_t out_len = out.size();
  if (iconv(cd, &pin, &in_len, &pout, &out_len) == -1)
  {
    return -1;
  }
  iconv_close(cd);
  return 0;
}

int writer(char* data, const size_t size, const size_t nmemb, string* writerData)
{
  const unsigned long sizes = size * nmemb;
  if (writerData == nullptr)
    return -1;

  writerData->append(data, sizes);
  return sizes;
}

int GetData(string& ip, string& city)
{
  string buffer;
  try
  {
    curl_global_init(CURL_GLOBAL_ALL);
    const string url_str = "http://pv.sohu.com/cityjson?ie=utf-8";

    CURL* p_curl = curl_easy_init();
    if (nullptr != p_curl)
    {
      curl_easy_setopt(p_curl, CURLOPT_TIMEOUT, 10);
      curl_easy_setopt(p_curl, CURLOPT_URL, url_str.c_str());
      curl_easy_setopt(p_curl, CURLOPT_WRITEFUNCTION, writer);
      curl_easy_setopt(p_curl, CURLOPT_WRITEDATA, &buffer);
      const CURLcode res = curl_easy_perform(p_curl);
      LOG_IF(ERROR, res != CURLE_OK) << "curl_easy_perform() failed " << curl_easy_strerror(res);
      curl_easy_cleanup(p_curl);
    }
    curl_global_cleanup();
  }
  catch (std::exception& ex)
  {
    LOG(ERROR) << "curl exception=" << ex.what();
    return -1;
  }
  if (buffer.empty())
  {
    LOG(ERROR) << "!!! ERROR The sever response NULL";
    return -1;
  }

  try
  {
    const auto it1 = buffer.find('{');
    const auto it2 = buffer.find('}') + 1;
    const auto json_content = buffer.substr(it1, it2 - it1);
    nlohmann::json obj = nlohmann::json::parse(json_content);
    ip = obj["cip"].get<string>();
    city = obj["cname"].get<string>();
  }
  catch (std::exception& e)
  {
    LOG(ERROR) << "PARSE ERROR. exception=" << e.what();
    return -1;
  }

  return 0;
}

int main(int argc, char const* argv[])
{
  string ip, city, chn_city;
  const int ret = GetData(ip, city);
  char_code_convert("UTF-8", "GB2312", city, chn_city);
  LOG_IF(ERROR, ret != 0) << "get data error";
  LOG(INFO) << "ip=" << ip << " city=" << chn_city;
  return 0;
}