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 (!pty())
{
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;
case0:
/* 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    = "website";
// 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]);
}
/*switch的用法c语言
* 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-&sult << 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);
return0;
}
/**
* 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);
}
return0;
}
#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  //
// 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;
return0;
}

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