Libevent 簡介

Libevent是一款事件驅動的網絡開發包，由于采用C語言開發體積小巧，跨平臺，速度極快。大量開源項目使用了Libevent比如谷歌的瀏覽器和分布式的高速緩存系統memcached。libevent支持kqueue,select,poll,epoll,iocp。內部事件機制完全獨立于公開事件API，libevent支持跨平臺可以在Linux，*BSD，MacOSX,Solaris,Windows等平臺上編譯。

學習條件：具有一定的C/C++基礎，熟悉Linux

環境搭建

• 配置zlib庫

# 1. 解壓zlib 1.2.11 tar xvf zlib-1.2.11.tar.gz # 2. 編譯 cd zlib-1.2.11/ ./configure make make install

• 配置openssl庫

# 1. 解壓openssl-1.1.1.tar.gz tar xvf openssl-1.1.1.tar.gz # 2. 編譯 cd openssl-1.1.1/ ./configure make make install

• 配置libevent環境

# 1.加壓liebevent 2.1.8 unzip libevent-master.zip # 2. 編譯 cd libevent-master/ ./autogen.sh ./configure make make install # 3.將動態路來連接到 /usr/lib 下或者執行以下 ldconfig sudo ln -s /usr/local/lib/libevent-2.2.so.1 /usr/lib/libevent-2.2.so.1

實戰實例

創建event_base

僅僅實現創建上下文

/**** 創建event base* */#include <event2/event.h> #include <iostream> using namespace std; int main() {std::cout << "test libevent!\n"; //創建libevent的上下文event_base * base = event_base_new();if (base){cout << "event_base_new success!" << endl;}return 0; }

創建test_server

test_server中說明了如何使用libevent創建一個socket監聽

evconnlistener_new_bind一個接口完成了socket的創建，綁定和監聽。

/**** 創建event base* */#include <event2/event.h> #include <iostream> #include <signal.h> #include <event2/listener.h> #include <string.h> #include "event_interface.h"using namespace std;/**A callback that we invoke when a listener has a new connection.@param listener The evconnlistener@param fd The new file descriptor@param addr The source address of the connection@param socklen The length of addr@param user_arg the pointer passed to evconnlistener_new()*/ void listen_cb(struct evconnlistener * evConnListener, evutil_socket_t evUtilSockFd, struct sockaddr * sockAddr, int socklen, void *data) {cout << "listen cb is called" << endl; }int main(int argc, char *argv[]) {//1. 忽略管道信號,發送數據給已關閉的socket//一些socket程序莫名宕掉的原因if(signal(SIGPIPE, SIG_IGN) == SIG_ERR){cout << "ignal pipe signal" << endl;}std::cout << "test libevent!\n"; //創建libevent的上下文event_base * base = event_base_new();if (!base){cout << "event_base_new failed." << endl;return -1;}else{cout << "event_base_new success!" << endl;}//監聽端口//socket, bind, listensockaddr_in sockIn;memset(&sockIn, 0, sizeof(sockIn));sockIn.sin_family = AF_INET;sockIn.sin_port = htons(SERVER_PORT);/* 地址沒有指定因為對sockIn進行了了memset，地址賦值為0代表著可以為任意可以用的地址 */struct evconnlistener *pEvListener = evconnlistener_new_bind(base, /* libevent的上下文 */listen_cb, /* 接收到連接的回調 */base, /* 回調函數參數 */LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE, /* 地址重用，evconnlistenner關閉同時關閉socket */10, /* 連接隊列的大小，對應的listen函數 */(sockaddr *)&sockIn, /* 綁定地址和端口 */sizeof(sockIn));//事件分發處理if(base)event_base_dispatch(base);if(pEvListener)evconnlistener_free(pEvListener);if(base)event_base_free(base);return 0; }

創建test_conf

test_conf主要是實現了，測試當前系統中支持的方法類型和事件特征的支持情況。

support methods epoll poll selectEV_FEATURE_ET events are supported. EV_FEATURE_O1 events are supported. EV_FEATURE_FDS events are not supports. EV_FEATURE_EARLY_CLOSE events are supported. event base new with config sucess #include <event2/event.h> #include <event2/thread.h> #include <event2/listener.h> #include <signal.h> #include <iostream> #include <string.h> #include "event_interface.h"using namespace std;int main() {//忽略管道信號，發送數據給已關閉的socketif (signal(SIGPIPE, SIG_IGN) == SIG_ERR)return 1;//創建配置上下文event_config *config = event_config_new();//顯示支持的網絡模式const char **methods = event_get_supported_methods();cout << "support methods " << endl;for(int i = 0; methods[i] != NULL; i++){cout << methods[i] << endl;}//設置特征，確認特征時候生效//這個features在linux中設置沒有效果，因為linux中本來就是支持ET模式的，邊緣觸發模式// 設置了EV_FEATURE_FDS其他特征嗯就無法設置//也就是所支持了EV_FEATURE_FDS 其他的特征都是無法支持的int ret = event_config_require_features(config, EV_FEATURE_ET|EV_FEATURE_EARLY_CLOSE);if(OK != ret){cerr << "event config require features failed." << endl;return ERROR; }//初始化libevent上下文event_base *base = event_base_new_with_config(config);//config一旦配置好就不需要在使用了event_config_free(config);if(!base){cerr << "event base new with config failed!" << endl;//首次失敗就創建一個base取默認值，若是再次失敗就返回失敗base = event_base_new();if(!base){cerr << "event base new failed." << endl; return ERROR;}}else{//確認特征那些生效int f = event_base_get_features(base);if(f&EV_FEATURE_ET){cout << "EV_FEATURE_ET events are supported." << endl;}else{cout << "EV_FEATURE_ET events are not supports." << endl;}if(f&EV_FEATURE_O1){cout << "EV_FEATURE_O1 events are supported." << endl;}else{cout << "EV_FEATURE_O1 events are not supports." << endl;}if(f&EV_FEATURE_FDS){cout << "EV_FEATURE_FDS events are supported." << endl;}else{cout << "EV_FEATURE_FDS events are not supports." << endl;}if(f&EV_FEATURE_EARLY_CLOSE){cout << "EV_FEATURE_EARLY_CLOSE events are supported." << endl;}else{cout << "EV_FEATURE_EARLY_CLOSE events are not supports." << endl;}cout << "event base new with config sucess" << endl;event_base_free(base);}return 0; }

總結

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