libcurl学习

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函数及其作用

• CURL *curl_easy_init(); //初始化一个curl，如果成功返回一个CURL句柄
• void curl_easy_cleanup(CURL *handle); //用于结束一个curl
• CURLcode curl_easy_setopt(CURL *handle, CURLoption option, parameter); //设置一个curl上的选项
• CURLcode curl_easy_perform(CURL *easy_handle); //阻塞的执行文件传输
• CURLcode curl_easy_getinfo(CURL *curl, CURLINFO info, ... ); //从curl中获取信息

注意

• CURLcode curl_global_init(long flags); //libcurl其他所有函数被调用之前这函数至少需要被调用一次，此函数非线程安全，只需要调用一次，最好在主线程中调用

示例代码

curl使用post上传文件

    size_t write_data(void *ptr, size_t size, size_t nmemb, void *stream) //回调函数
    {
        std::string *str = (std::string*)stream;
        (*str).append((char*)ptr, realSize);
        return size * nmemb;
    }


    std::string data;
    CURL* curl = NULL;
    CURLcode res = CURLE_OK;
    //HTTP报文头
    struct curl_slist* headers = NULL;
    struct stat filestat;
    if (stat(path.c_str(), &filestat) < 0) {
        exit(-1);
    }

    if (!(filestat.st_mode & S_IROTH)) {
        exit(-1);
    }

    if (S_ISDIR(filestat.st_mode)) {  //判断用户对该文件所拥有的权限
        exit(-1);
    }

    FILE *file = fopen(path.c_str(), "rb");  //path为文件路径
    char *content = new char[filestat.st_size];
    fread(content, 1, filestat.st_size, file);
    fclose(file);
    //初始化easy handler句柄
    curl = curl_easy_init();
    if (curl)
    {
        //构建HTTP报文头
        curl_slist *http_headers = NULL;
        std::string cookie = "Set-Cookie: " + encodePassword;
        http_headers = curl_slist_append(http_headers, cookie.c_str()); //设置请求cookie
        http_headers = curl_slist_append(http_headers, "charsets: utf-8");
        //设置method为post
        curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
        //设置post请求的url地址
        std::string url = "http://192.168.88.128:8888" + path;
        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
        //设置HTTP头
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, http_headers);
        //设置发送超时时间
        curl_easy_setopt(curl, CURLOPT_TIMEOUT, 1);

        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

        //将文件内容设为请求体
        curl_easy_setopt(curl,CURLOPT_POSTFIELDS,content);
        curl_easy_setopt(curl,CURLOPT_POSTFIELDSIZE,filestat.st_size);  //因为是以二进制方式发送数据所以需要指定数据的长度

        //设置应答报文体内容解析回调函数
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&data);

        //执行单条请求
        res = curl_easy_perform(curl);
        if (res != CURLE_OK) {
            //curl_easy_strerror进行出错打印
            std::cout << "curl_easy_perform() failed:" << curl_easy_strerror(res);

        }
        std::cout<<"main data:"<<data<<std::endl;
        curl_slist_free_all(headers);
        //这个调用用来结束一个会话.与curl_easy_init配合着用
        curl_easy_cleanup(curl);
    }

curl使用GET并将返回的数据存入文件

    size_t receive_file(void *buffer, size_t size, size_t nmemb, FILE *file) {  //回调函数
        size_t r_size = fwrite(buffer, size, nmemb, file);
        return r_size;
    }


    std::string data;
    CURL* curl = NULL;
    CURLcode res = CURLE_OK;
    //HTTP报文头
    struct curl_slist* headers = NULL;



    //初始化easy handler句柄
    curl = curl_easy_init();
    if (curl)
    {
        //构建HTTP报文头
        curl_slist *http_headers = NULL;
        std::string cookie = "Set-Cookie: " + encodePassword;
        http_headers = curl_slist_append(http_headers, cookie.c_str());
        http_headers = curl_slist_append(http_headers, "charsets: utf-8");
        //设置method为GET
        curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "GET");
        //设置post请求的url地址
        std::string url = "http://192.168.88.128:8888" + path;
        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
        //设置HTTP头
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, http_headers);
        //设置发送超时时间
        curl_easy_setopt(curl, CURLOPT_TIMEOUT, 1);

        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
        
        //打开文件
        std::string route = "test.txt";
        FILE* fp;
        if ((fp = fopen(route.c_str(), "wb+")) == NULL)
        {
            printf("File.\n");

        }
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, receive_file);//设置回调函数
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);  //将文件描述符传递给回调函数

        //执行单条请求
        res = curl_easy_perform(curl);
        if (res != CURLE_OK) {
            //curl_easy_strerror进行出错打印
            std::cout << "curl_easy_perform() failed:" << curl_easy_strerror(res);
        }

        curl_slist_free_all(headers);
        //这个调用用来结束一个会话.与curl_easy_init配合着用
        curl_easy_cleanup(curl);

        fclose(fp);
    }