从直接下载URL下载URL文件？| C++

#include <iostream>
#include <fstream>
#include <curl/curl.h>

size_t WriteCallback(void* contents, size_t size, size_t nmemb, void* userp) {
    std::ofstream* file = static_cast<std::ofstream*>(userp);
    file->write(static_cast<char*>(contents), size * nmemb);
    return size * nmemb;
}

int main() {
    std::string fileUrl = "https://example.com/file.txt";
    std::string savePath = "downloaded_file.txt";

   URL* curl = curl_easy_init();
    if (curl) {
        std::ofstream file(savePath, std::ios::binary);
        if (file) {
            curl_easy_setopt(curl,URLOPT_URL, fileUrl.c_str());
            curl_easy_setopt(curl,URLOPT_WRITEFUNCTION, WriteCallback);
            curl_easy_setopt(curl,URLOPT_WRITEDATA, &file);

           URLcode res = curl_easy_perform(curl);
            if (res !=URLE_OK) {
                std::cerr << "Failed to download file: " << curl_easy_strerror(res) << std::endl;
            }

            file.close();
        } else {
            std::cerr << "Failed to create file: " << savePath << std::endl;
        }

        curl_easy_cleanup(curl);
    } else {
        std::cerr << "Failed to initialize libcurl" << std::endl;
    }

    return 0;
}