c语言libcurl库的异步用法multi接口的使用会比easy 接口稍微复杂点，毕竟multi接口是依赖easy接口的，首先粗略的讲下其使用流程：curl_multi _init初始化一个multi curl对象，为了同时进行多个curl的并发访问，我们需要初始化多个easy curl对象，使用curl_easy_setopt进行相关设置，然后调用curl_multi _add_handle把easy curl对象添加到multi curl对象中，添加完毕后执行curl_multi_perform方法进行并发的访问，访问结束后curl_multi_remove_handle移除相关easy curl对象，curl_easy_cleanup清除easy curl对象，最后curl_multi_cleanup清除multi curl对象。  #include <string> #include <iostream> #include <curl/curl.h> #include <sys/time.h> #include <unistd.h> using namespace std; size_t curl_writer(void *buffer, size_t size, size_t count, void * stream) { std::string * pStream = static_cast<std::string *>(stream); (*pStream).append((char *)buffer, size * count); return size * count; }; /** * 生成一个easy curl对象，进行一些简单的设置操作 */ CURL * curl_easy_handler(const std::string & sUrl, const std::string & sProxy, std::string & sRsp, unsigned int uiTimeout) { CURL * curl = curl_easy_init(); curl_easy_setopt(curl, CURLOPT_URL, sUrl.c_str()); curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1); if (uiTimeout > 0) { curl_easy_setopt(curl, CURLOPT_TIMEOUT_MS, uiTimeout); } if (!sProxy.empty()) { curl_easy_setopt(curl, CURLOPT_PROXY, sProxy.c_str()); } // write function // curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, curl_writer); curl_easy_setopt(curl, CURLOPT_WRITEDATA, &sRsp); return curl; } /** * 使用select函数监听multi curl文件描述符的状态 * 监听成功返回0，监听失败返回-1 */ int curl_multi_select(CURLM * curl_m) { int ret = 0; struct timeval timeout_tv; fd_set fd_read; fd_set fd_write; fd_set fd_except; int max_fd = -1; // 注意这里一定要清空fdset,curl_multi_fdset不会执行fdset的清空操作 // FD_ZERO(&fd_read); FD_ZERO(&fd_write); FD_ZERO(&fd_except); // 设置select超时时间 // timeout_tv.tv_sec = 1; timeout_tv.tv_usec = 0; // 获取multi curl需要监听的文件描述符集合 fd_set // curl_multi_fdset(curl_m, &fd_read, &fd_write, &fd_except, &max_fd); /** * When max_fd returns with -1, * you need to wait a while and then proceed and call curl_multi_perform anyway. * How long to wait? I would suggest 100 milliseconds at least, * but you may want to test it out in your own particular conditions to find a suitable value. */ if (-1 == max_fd) { return -1; } /** * 执行监听，当文件描述符状态发生改变的时候返回 * 返回0，程序调用curl_multi_perform通知curl执行相应操作 * 返回-1，表示select错误 * 注意：即使select超时也需要返回0，具体可以去官网看文档说明 */ int ret_code = ::select(max_fd + 1, &fd_read, &fd_write, &fd_except, &timeout_tv); switch(ret_code) { case -1: /* select error */ ret = -1; break; case 0: /* select timeout */ default: /* one or more of curl's file descriptors say there's data to read or write*/ ret = 0; break; } return ret; } #define MULTI_CURL_NUM 3 // 这里设置你需要访问的url // std::string URL = "http://"; // 这里设置代理ip和端口 // std::string PROXY = "ip:port"; // 这里设置超时时间 // unsigned int TIMEOUT = 2000; /* ms */ /** * multi curl使用demo */ int curl_multi_demo(int num) { // 初始化一个multi curl 对象 // CURLM * curl_m = curl_multi_init(); std::string RspArray[num]; CURL * CurlArray[num]; // 设置easy curl对象并添加到multi curl对象中 // for (int idx = 0; idx < num; ++idx) { CurlArray[idx] = NULL; CurlArray[idx] = curl_easy_handler(URL, PROXY, RspArray[idx], TIMEOUT); if (CurlArray[idx] == NULL) { return -1; } curl_multi_add_handle(curl_m, CurlArray[idx]); } /* * 调用curl_multi_perform函数执行curl请求 * url_multi_perform返回CURLM_CALL_MULTI_PERFORM时，表示需要继续调用该函数直到返回值不是CURLM_CALL_MULTI_PERFORM为止 * running_handles变量返回正在处理的easy curl数量，running_handles为0表示当前没有正在执行的curl请求 */ int running_handles; while (CURLM_CALL_MULTI_PERFORM == curl_multi_perform(curl_m, &running_handles)) { cout << running_handles << endl; } /** * 为了避免循环调用curl_multi_perform产生的cpu持续占用的问题，采用select来监听文件描述符 */ while (running_handles) { if (-1 == curl_multi_select(curl_m)) { cerr << "select error" << endl; break; } else { // select监听到事件，调用curl_multi_perform通知curl执行相应的操作 // while (CURLM_CALL_MULTI_PERFORM == curl_multi_perform(curl_m, &running_handles)) { cout << "select: " << running_handles << endl; } } cout << "select: " << running_handles << endl; } // 输出执行结果 // int msgs_left; CURLMsg * msg; while((msg = curl_multi_info_read(curl_m, &msgs_left))) { if (CURLMSG_DONE == msg->msg) { int idx; for (idx = 0; idx < num; ++idx) { if (msg->easy_handle == CurlArray[idx]) break; } if (idx == num) { cerr << "curl not found" << endl; } else { cout << "curl [" << idx << "] completed with status: " << msg->data.result << endl; cout << "rsp: " << RspArray[idx] << endl; } } } // 这里要注意cleanup的顺序 // for (int idx = 0; idx < num; ++idx) { curl_multi_remove_handle(curl_m, CurlArray[idx]); } for (int idx = 0; idx < num; ++idx) { curl_easy_cleanup(CurlArray[idx]); } curl_multi_cleanup(curl_m); return 0; } /** * easy curl使用demo */ int curl_easy_demo(int num) { std::string RspArray[num]; for (int idx = 0; idx < num; ++idx) { CURL * curl = curl_easy_handler(URL, PROXY, RspArray[idx], TIMEOUT); CURLcode code = curl_easy_perform(curl); cout << "curl [" << idx << "] completed with status: " << code << endl; cout << "rsp: " << RspArray[idx] << endl; // clear handle // curl_easy_cleanup(curl); } return 0; } #define USE_MULTI_CURL struct timeval begin_tv, end_tv; int main(int argc, char * argv[]) { if (argc < 2) { return -1; } int num = atoi(argv[1]); // 获取开始时间 // gettimeofday(&begin_tv, NULL); #ifdef USE_MULTI_CURL // 使用multi接口进行访问 // curl_multi_demo(num); #else // 使用easy接口进行访问 // curl_easy_demo(num); #endif // 获取结束时间 // struct timeval end_tv; gettimeofday(&end_tv, NULL); // 计算执行延时并输出，用于比较 // int eclapsed = (end_tv.tv_sec - begin_tv.tv_sec) * 1000 + (end_tv.tv_usec - begin_tv.tv_usec) / 1000; cout << "eclapsed time:" << eclapsed << "ms" << endl; return 0; }
转载自: http://blog.csdn.net/zxgfa/article/details/8220724 |
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