libevent（一）

libevent官网 http://libevent.org/
libevent api http://www.monkey.org/~provos/libevent/doxygen-2.0.1/index.html

简单介绍libevent关键api

struct event_base* event_base_new   (void)

初始化一个新的事件，但这个不是一个全局事件，如果想使用全局事件，使用event_init(void)
如果使用这个api创建一个新的事件，那么在之后的每次set一个事件之后都需要调用event_set_base()
如果使用event_init(void)则不需要调用event_set_base()

void event_set ( struct event *  ,        evutil_socket_t  ,        short  ,        void(*)(evutil_socket_t, short, void *) ,        void *           );

参数解释

ev  an event struct to be modifiedfd  the file descriptor to be monitoredevent   desired events to monitor; can be EV_READ and/or EV_WRITEfn  callback function to be invoked when the event occursarg     an argument to be passed to the callback function

引用的官网api的解释，很容易理解，主要就是事件的类型以及回调函数。

int event_add (struct event * ,const struct timeval * )
添加事件，前一个set的api设置完需要添加到主循环的事件响应里面。

int event_dispatch(void)    

启动主消息监听循环。本质上使用的select，epoll这一套，所以需要主循环监听事件。

参考其他人的文章写了一个简单的demo

#include <iostream>#include <cstdlib>#include <cstdio>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <unistd.h>#include <netdb.h>#include <cstring>#include <event.h>using namespace std;void Read(int iCliFd, short iEvent, void *arg) {  int iLen;   char buf[1500];   iLen = recv(iCliFd, buf, 1500, 0);   if (iLen <= 0) {      cout << "Client Close" << endl;      struct event *pEvRead = (struct event*)arg;      event_del(pEvRead);      delete pEvRead;      close(iCliFd);      return;   }   buf[iLen] = 0;   cout << "Client Info:" << buf << endl; }void onAccept(int iSvrFd, short iEvent, void *arg) {  int iCliFd;   struct sockaddr_in sCliAddr;   event_base* base = (event_base *)arg;  cout << "in onAccept" << endl; //>>>>  socklen_t iSinSize = sizeof(sCliAddr);   iCliFd = accept(iSvrFd, (struct sockaddr*)&sCliAddr, &iSinSize);   struct event *pEvRead = new event;   event_set(pEvRead, iCliFd, EV_READ|EV_PERSIST, Read, pEvRead);   event_base_set(base, pEvRead);   event_add(pEvRead, NULL);  }class LVServer {private:   struct event_base* base;   int serv_sock;   sockaddr_in sCliAddr;   sockaddr_in sSvrAddr;public:   bool init() {      memset(&sSvrAddr, 0, sizeof(sSvrAddr));      sSvrAddr.sin_family = AF_INET;      sSvrAddr.sin_addr.s_addr = inet_addr("127.0.0.1");      sSvrAddr.sin_port = htons(8888);      sSvrAddr.sin_addr.s_addr = htonl(INADDR_ANY);      serv_sock = socket(AF_INET, SOCK_STREAM, 0);      if (!serv_sock) return false;      int ret = bind(serv_sock, (struct sockaddr*)&sSvrAddr, sizeof(sSvrAddr));      //if (!ret) return false;      ret = listen(serv_sock, 10); //      //if (!ret) return false;      // can print log.      return true;   }   int start() {      base = event_base_new();      struct event evListen;      event_set(&evListen, serv_sock, EV_READ|EV_PERSIST, onAccept, (void *)base);      event_base_set(base, &evListen);      event_add(&evListen, NULL);      event_base_dispatch(base);       return 0;   }};int main() {   LVServer myServer;   int ret = myServer.init();   if (!ret) {      cout << "error in init" << endl;      return -1;   }   return myServer.start();}