Libevent源码分析-----连接监听器evconnlistener
生活随笔
收集整理的這篇文章主要介紹了
Libevent源码分析-----连接监听器evconnlistener
小編覺(jué)得挺不錯(cuò)的,現(xiàn)在分享給大家,幫大家做個(gè)參考.
出處：http://blog.csdn.net/luotuo44/article/details/38800363
[cpp] view plaincopy print?#include<netinet/in.h>?? #include<sys/socket.h>?? #include<unistd.h>?? ?? #include<stdio.h>?? #include<string.h>?? ?? #include<event.h>?? #include<listener.h>?? #include<bufferevent.h>?? #include<thread.h>?? ?? ?? void?listener_cb(evconnlistener?*listener,?evutil_socket_t?fd,?? ?????????????????struct?sockaddr?*sock,?int?socklen,?void?*arg);?? ?? void?socket_read_cb(bufferevent?*bev,?void?*arg);?? void?socket_error_cb(bufferevent?*bev,?short?events,?void?*arg);?? ?? int?main()?? {?? ????evthread_use_pthreads();//enable?threads?? ?? ????struct?sockaddr_in?sin;?? ????memset(&sin,?0,?sizeof(struct?sockaddr_in));?? ????sin.sin_family?=?AF_INET;?? ????sin.sin_port?=?htons(8989);?? ?? ????event_base?*base?=?event_base_new();?? ????evconnlistener?*listener?? ????????????=?evconnlistener_new_bind(base,?listener_cb,?base,?? ??????????????????????????????????????LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE?|?LEV_OPT_THREADSAFE,?? ??????????????????????????????????????10,?(struct?sockaddr*)&sin,?? ??????????????????????????????????????sizeof(struct?sockaddr_in));?? ?? ????event_base_dispatch(base);?? ?? ?????evconnlistener_free(listener);?? ????event_base_free(base);?? ?? ????return?0;?? }?? ?? ?? //有新的客戶端連接到服務(wù)器?? //當(dāng)此函數(shù)被調(diào)用時(shí)，libevent已經(jīng)幫我們accept了這個(gè)客戶端。該客戶端的?? //文件描述符為fd?? void?listener_cb(evconnlistener?*listener,?evutil_socket_t?fd,?? ?????????????????struct?sockaddr?*sock,?int?socklen,?void?*arg)?? {?? ????event_base?*base?=?(event_base*)arg;?? ?? ????//下面代碼是為這個(gè)fd創(chuàng)建一個(gè)bufferevent?? ????bufferevent?*bev?=??bufferevent_socket_new(base,?fd,?? ???????????????????????????????????????????????BEV_OPT_CLOSE_ON_FREE);?? ?? ????bufferevent_setcb(bev,?socket_read_cb,?NULL,?socket_error_cb,?NULL);?? ????bufferevent_enable(bev,?EV_READ?|?EV_PERSIST);?? }?? ?? ?? void?socket_read_cb(bufferevent?*bev,?void?*arg)?? {?? ????char?msg[4096];?? ?? ????size_t?len?=?bufferevent_read(bev,?msg,?sizeof(msg)-1?);?? ?? ????msg[len]?=?'\0';?? ????printf("server?read?the?data?%s\n",?msg);?? ?? ????char?reply[]?=?"I?has?read?your?data";?? ????bufferevent_write(bev,?reply,?strlen(reply)?);?? }?? ?? ?? void?socket_error_cb(bufferevent?*bev,?short?events,?void?*arg)?? {?? ????if?(events?&?BEV_EVENT_EOF)?? ????????printf("connection?closed\n");?? ????else?if?(events?&?BEV_EVENT_ERROR)?? ????????printf("some?other?error\n");?? ?? ????//這將自動(dòng)close套接字和free讀寫緩沖區(qū)?? ????bufferevent_free(bev);?? }??
#include<netinet/in.h>
#include<sys/socket.h>
#include<unistd.h>#include<stdio.h>
#include<string.h>#include<event.h>
#include<listener.h>
#include<bufferevent.h>
#include<thread.h>void listener_cb(evconnlistener *listener, evutil_socket_t fd,struct sockaddr *sock, int socklen, void *arg);void socket_read_cb(bufferevent *bev, void *arg);
void socket_error_cb(bufferevent *bev, short events, void *arg);int main()
{evthread_use_pthreads();//enable threadsstruct sockaddr_in sin;memset(&sin, 0, sizeof(struct sockaddr_in));sin.sin_family = AF_INET;sin.sin_port = htons(8989);event_base *base = event_base_new();evconnlistener *listener= evconnlistener_new_bind(base, listener_cb, base,LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE | LEV_OPT_THREADSAFE,10, (struct sockaddr*)&sin,sizeof(struct sockaddr_in));event_base_dispatch(base);evconnlistener_free(listener);event_base_free(base);return 0;
}//有新的客戶端連接到服務(wù)器
//當(dāng)此函數(shù)被調(diào)用時(shí)，libevent已經(jīng)幫我們accept了這個(gè)客戶端。該客戶端的
//文件描述符為fd
void listener_cb(evconnlistener *listener, evutil_socket_t fd,struct sockaddr *sock, int socklen, void *arg)
{event_base *base = (event_base*)arg;//下面代碼是為這個(gè)fd創(chuàng)建一個(gè)buffereventbufferevent *bev = bufferevent_socket_new(base, fd,BEV_OPT_CLOSE_ON_FREE);bufferevent_setcb(bev, socket_read_cb, NULL, socket_error_cb, NULL);bufferevent_enable(bev, EV_READ | EV_PERSIST);
}void socket_read_cb(bufferevent *bev, void *arg)
{char msg[4096];size_t len = bufferevent_read(bev, msg, sizeof(msg)-1 );msg[len] = '\0';printf("server read the data %s\n", msg);char reply[] = "I has read your data";bufferevent_write(bev, reply, strlen(reply) );
}void socket_error_cb(bufferevent *bev, short events, void *arg)
{if (events & BEV_EVENT_EOF)printf("connection closed\n");else if (events & BEV_EVENT_ERROR)printf("some other error\n");//這將自動(dòng)close套接字和free讀寫緩沖區(qū)bufferevent_free(bev);
}
//listener.h文件?? typedef?void?(*evconnlistener_cb)(struct?evconnlistener?*,?evutil_socket_t,?struct?sockaddr?*,?int?socklen,?void?*);?? ?? struct?evconnlistener?*evconnlistener_new_bind(struct?event_base?*base,?? ????evconnlistener_cb?cb,?void?*ptr,?unsigned?flags,?int?backlog,?? ????const?struct?sockaddr?*sa,?int?socklen);??
//listener.h文件
typedef void (*evconnlistener_cb)(struct evconnlistener *, evutil_socket_t, struct sockaddr *, int socklen, void *);struct evconnlistener *evconnlistener_new_bind(struct event_base *base,evconnlistener_cb cb, void *ptr, unsigned flags, int backlog,const struct sockaddr *sa, int socklen);
//listener.c文件?? struct?evconnlistener_ops?{//一系列的工作函數(shù)?? ????int?(*enable)(struct?evconnlistener?*);?? ????int?(*disable)(struct?evconnlistener?*);?? ????void?(*destroy)(struct?evconnlistener?*);?? ????void?(*shutdown)(struct?evconnlistener?*);?? ????evutil_socket_t?(*getfd)(struct?evconnlistener?*);?? ????struct?event_base?*(*getbase)(struct?evconnlistener?*);?? };?? ?? struct?evconnlistener?{?? ????const?struct?evconnlistener_ops?*ops;//操作函數(shù)?? ????void?*lock;?//鎖變量，用于線程安全?? ????evconnlistener_cb?cb;//用戶的回調(diào)函數(shù)?? ????evconnlistener_errorcb?errorcb;//發(fā)生錯(cuò)誤時(shí)的回調(diào)函數(shù)?? ????void?*user_data;//回調(diào)函數(shù)的參數(shù)?? ????unsigned?flags;//屬性標(biāo)志?? ????short?refcnt;//引用計(jì)數(shù)?? ????unsigned?enabled?:?1;//位域?yàn)?.即只需一個(gè)比特位來(lái)存儲(chǔ)這個(gè)成員?? };?? ?? struct?evconnlistener_event?{?? ????struct?evconnlistener?base;?? ????struct?event?listener;?//內(nèi)部event,插入到event_base?? };??
//listener.c文件
struct evconnlistener_ops {//一系列的工作函數(shù)int (*enable)(struct evconnlistener *);int (*disable)(struct evconnlistener *);void (*destroy)(struct evconnlistener *);void (*shutdown)(struct evconnlistener *);evutil_socket_t (*getfd)(struct evconnlistener *);struct event_base *(*getbase)(struct evconnlistener *);
};struct evconnlistener {const struct evconnlistener_ops *ops;//操作函數(shù)void *lock; //鎖變量，用于線程安全evconnlistener_cb cb;//用戶的回調(diào)函數(shù)evconnlistener_errorcb errorcb;//發(fā)生錯(cuò)誤時(shí)的回調(diào)函數(shù)void *user_data;//回調(diào)函數(shù)的參數(shù)unsigned flags;//屬性標(biāo)志short refcnt;//引用計(jì)數(shù)unsigned enabled : 1;//位域?yàn)?.即只需一個(gè)比特位來(lái)存儲(chǔ)這個(gè)成員
};struct evconnlistener_event {struct evconnlistener base;struct event listener; //內(nèi)部event,插入到event_base
};
//listener.c文件?? struct?evconnlistener?*?? evconnlistener_new_bind(struct?event_base?*base,?evconnlistener_cb?cb,?? ????void?*ptr,?unsigned?flags,?int?backlog,?const?struct?sockaddr?*sa,?? ????int?socklen)?? {?? ????struct?evconnlistener?*listener;?? ????evutil_socket_t?fd;?? ????int?on?=?1;?? ????int?family?=?sa???sa->sa_family?:?AF_UNSPEC;?? ?? ????//監(jiān)聽(tīng)個(gè)數(shù)不能為0?? ????if?(backlog?==?0)?? ????????return?NULL;?? ?? ????fd?=?socket(family,?SOCK_STREAM,?0);?? ????if?(fd?==?-1)?? ????????return?NULL;?? ?? ????//LEV_OPT_LEAVE_SOCKETS_BLOCKING選項(xiàng)是應(yīng)用于accept到的客戶端socket?? ????//所以對(duì)于服務(wù)器端的socket，直接將之設(shè)置為非阻塞的?? ????if?(evutil_make_socket_nonblocking(fd)?<?0)?{?? ????????evutil_closesocket(fd);?? ????????return?NULL;?? ????}?? ?? ????if?(flags?&?LEV_OPT_CLOSE_ON_EXEC)?{?? ????????if?(evutil_make_socket_closeonexec(fd)?<?0)?{?? ????????????evutil_closesocket(fd);?? ????????????return?NULL;?? ????????}?? ????}?? ?? ????if?(setsockopt(fd,?SOL_SOCKET,?SO_KEEPALIVE,?(void*)&on,?sizeof(on))<0)?{?? ????????evutil_closesocket(fd);?? ????????return?NULL;?? ????}?? ????if?(flags?&?LEV_OPT_REUSEABLE)?{?? ????????if?(evutil_make_listen_socket_reuseable(fd)?<?0)?{?? ????????????evutil_closesocket(fd);?? ????????????return?NULL;?? ????????}?? ????}?? ?? ????if?(sa)?{?? ????????if?(bind(fd,?sa,?socklen)<0)?{//綁定?? ????????????evutil_closesocket(fd);?? ????????????return?NULL;?? ????????}?? ????}?? ?? ????listener?=?evconnlistener_new(base,?cb,?ptr,?flags,?backlog,?fd);?? ????if?(!listener)?{?? ????????evutil_closesocket(fd);?? ????????return?NULL;?? ????}?? ?? ????return?listener;?? }??
//listener.c文件
struct evconnlistener *
evconnlistener_new_bind(struct event_base *base, evconnlistener_cb cb,void *ptr, unsigned flags, int backlog, const struct sockaddr *sa,int socklen)
{struct evconnlistener *listener;evutil_socket_t fd;int on = 1;int family = sa ? sa->sa_family : AF_UNSPEC;//監(jiān)聽(tīng)個(gè)數(shù)不能為0if (backlog == 0)return NULL;fd = socket(family, SOCK_STREAM, 0);if (fd == -1)return NULL;//LEV_OPT_LEAVE_SOCKETS_BLOCKING選項(xiàng)是應(yīng)用于accept到的客戶端socket//所以對(duì)于服務(wù)器端的socket，直接將之設(shè)置為非阻塞的if (evutil_make_socket_nonblocking(fd) < 0) {evutil_closesocket(fd);return NULL;}if (flags & LEV_OPT_CLOSE_ON_EXEC) {if (evutil_make_socket_closeonexec(fd) < 0) {evutil_closesocket(fd);return NULL;}}if (setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, (void*)&on, sizeof(on))<0) {evutil_closesocket(fd);return NULL;}if (flags & LEV_OPT_REUSEABLE) {if (evutil_make_listen_socket_reuseable(fd) < 0) {evutil_closesocket(fd);return NULL;}}if (sa) {if (bind(fd, sa, socklen)<0) {//綁定evutil_closesocket(fd);return NULL;}}listener = evconnlistener_new(base, cb, ptr, flags, backlog, fd);if (!listener) {evutil_closesocket(fd);return NULL;}return listener;
}
[cpp] view plaincopy print?//listener.c文件?? static?const?struct?evconnlistener_ops?evconnlistener_event_ops?=?{?? ????event_listener_enable,?? ????event_listener_disable,?? ????event_listener_destroy,?? ????NULL,?/*?shutdown?*/?? ????event_listener_getfd,?? ????event_listener_getbase?? };?? ?? ?? struct?evconnlistener?*?? evconnlistener_new(struct?event_base?*base,?? ????evconnlistener_cb?cb,?void?*ptr,?unsigned?flags,?int?backlog,?? ????evutil_socket_t?fd)?? {?? ????struct?evconnlistener_event?*lev;?? ?? ????if?(backlog?>?0)?{?? ????????if?(listen(fd,?backlog)?<?0)?? ????????????return?NULL;?? ????}?else?if?(backlog?<?0)?{?? ????????if?(listen(fd,?128)?<?0)?? ????????????return?NULL;?? ????}?? ?? ????lev?=?mm_calloc(1,?sizeof(struct?evconnlistener_event));?? ????if?(!lev)?? ????????return?NULL;?? ?? ????//賦值?? ????lev->base.ops?=?&evconnlistener_event_ops;?? ????lev->base.cb?=?cb;?? ????lev->base.user_data?=?ptr;?? ????lev->base.flags?=?flags;?? ????lev->base.refcnt?=?1;?? ?? ????if?(flags?&?LEV_OPT_THREADSAFE)?{//線程安全就需要分配鎖?? ????????EVTHREAD_ALLOC_LOCK(lev->base.lock,?EVTHREAD_LOCKTYPE_RECURSIVE);?? ????}?? ?? ????//在多路IO復(fù)用函數(shù)中，新客戶端的連接請(qǐng)求也被當(dāng)作讀事件?? ????event_assign(&lev->listener,?base,?fd,?EV_READ|EV_PERSIST,?? ????????listener_read_cb,?lev);?? ?? ????//會(huì)調(diào)用event_add，把event加入到event_base中?? ????evconnlistener_enable(&lev->base);?? ?? ????return?&lev->base;?? }?? ?? int?? evconnlistener_enable(struct?evconnlistener?*lev)?? {?? ????int?r;?? ????LOCK(lev);?? ????lev->enabled?=?1;?? ????if?(lev->cb)?? ????????r?=?lev->ops->enable(lev);//實(shí)際上是調(diào)用下面的event_listener_enable函數(shù)?? ????else?? ????????r?=?0;?? ????UNLOCK(lev);?? ????return?r;?? }?? ?? static?int?? event_listener_enable(struct?evconnlistener?*lev)?? {?? ????struct?evconnlistener_event?*lev_e?=?? ????????EVUTIL_UPCAST(lev,?struct?evconnlistener_event,?base);?? ?? ????//加入到event_base，完成監(jiān)聽(tīng)工作。?? ????return?event_add(&lev_e->listener,?NULL);?? }??
//listener.c文件
static const struct evconnlistener_ops evconnlistener_event_ops = {event_listener_enable,event_listener_disable,event_listener_destroy,NULL, /* shutdown */event_listener_getfd,event_listener_getbase
};struct evconnlistener *
evconnlistener_new(struct event_base *base,evconnlistener_cb cb, void *ptr, unsigned flags, int backlog,evutil_socket_t fd)
{struct evconnlistener_event *lev;if (backlog > 0) {if (listen(fd, backlog) < 0)return NULL;} else if (backlog < 0) {if (listen(fd, 128) < 0)return NULL;}lev = mm_calloc(1, sizeof(struct evconnlistener_event));if (!lev)return NULL;//賦值lev->base.ops = &evconnlistener_event_ops;lev->base.cb = cb;lev->base.user_data = ptr;lev->base.flags = flags;lev->base.refcnt = 1;if (flags & LEV_OPT_THREADSAFE) {//線程安全就需要分配鎖EVTHREAD_ALLOC_LOCK(lev->base.lock, EVTHREAD_LOCKTYPE_RECURSIVE);}//在多路IO復(fù)用函數(shù)中，新客戶端的連接請(qǐng)求也被當(dāng)作讀事件event_assign(&lev->listener, base, fd, EV_READ|EV_PERSIST,listener_read_cb, lev);//會(huì)調(diào)用event_add，把event加入到event_base中evconnlistener_enable(&lev->base);return &lev->base;
}int
evconnlistener_enable(struct evconnlistener *lev)
{int r;LOCK(lev);lev->enabled = 1;if (lev->cb)r = lev->ops->enable(lev);//實(shí)際上是調(diào)用下面的event_listener_enable函數(shù)elser = 0;UNLOCK(lev);return r;
}static int
event_listener_enable(struct evconnlistener *lev)
{struct evconnlistener_event *lev_e =EVUTIL_UPCAST(lev, struct evconnlistener_event, base);//加入到event_base，完成監(jiān)聽(tīng)工作。return event_add(&lev_e->listener, NULL);
}
//listener.c文件?? static?void?? listener_read_cb(evutil_socket_t?fd,?short?what,?void?*p)?? {?? ????struct?evconnlistener?*lev?=?p;?? ????int?err;?? ????evconnlistener_cb?cb;?? ????evconnlistener_errorcb?errorcb;?? ????void?*user_data;?? ????LOCK(lev);?? ????while?(1)?{?//可能有多個(gè)客戶端同時(shí)請(qǐng)求連接?? ????????struct?sockaddr_storage?ss;?? #ifdef?WIN32?? ????????int?socklen?=?sizeof(ss);?? #else?? ????????socklen_t?socklen?=?sizeof(ss);?? #endif?? ????????evutil_socket_t?new_fd?=?accept(fd,?(struct?sockaddr*)&ss,?&socklen);?? ????????if?(new_fd?<?0)?? ????????????break;?? ????????if?(socklen?==?0)?{?? ????????????/*?This?can?happen?with?some?older?linux?kernels?in? ?????????????*?response?to?nmap.?*/?? ????????????evutil_closesocket(new_fd);?? ????????????continue;?? ????????}?? ?? ????????if?(!(lev->flags?&?LEV_OPT_LEAVE_SOCKETS_BLOCKING))?? ????????????evutil_make_socket_nonblocking(new_fd);?? ?? ????????//用戶還沒(méi)設(shè)置連接監(jiān)聽(tīng)器的回調(diào)函數(shù)?? ????????if?(lev->cb?==?NULL)?{?? ????????????UNLOCK(lev);?? ????????????return;?? ????????}?? ?? ????????//由于refcnt被初始化為1.這里有++了，所以一般情況下并不會(huì)進(jìn)入下面的?? ????????//if判斷里面。但如果程在下面UNLOCK之后，第二個(gè)線調(diào)用evconnlistener_free?? ????????//釋放這個(gè)evconnlistener時(shí)，就有可能使得refcnt為1了。即進(jìn)入那個(gè)判斷體里?? ????????//執(zhí)行l(wèi)istener_decref_and_unlock。在下面會(huì)討論這個(gè)問(wèn)題。?? ????????++lev->refcnt;?? ????????cb?=?lev->cb;?? ????????user_data?=?lev->user_data;?? ????????UNLOCK(lev);?? ????????cb(lev,?new_fd,?(struct?sockaddr*)&ss,?(int)socklen,?? ????????????user_data);//調(diào)用用戶設(shè)置的回調(diào)函數(shù)，讓用戶處理這個(gè)fd?? ????????LOCK(lev);?? ????????if?(lev->refcnt?==?1)?{?? ????????????int?freed?=?listener_decref_and_unlock(lev);?? ????????????EVUTIL_ASSERT(freed);?? ????????????return;?? ????????}?? ????????--lev->refcnt;?? ????}?? ?????? ????err?=?evutil_socket_geterror(fd);?? ????if?(EVUTIL_ERR_ACCEPT_RETRIABLE(err))?{//還可以accept?? ????????UNLOCK(lev);?? ????????return;?? ????}?? ?? ????//當(dāng)有錯(cuò)誤發(fā)生時(shí)才會(huì)運(yùn)行到這里?? ????if?(lev->errorcb?!=?NULL)?{?? ????????++lev->refcnt;?? ????????errorcb?=?lev->errorcb;?? ????????user_data?=?lev->user_data;?? ????????UNLOCK(lev);?? ????????errorcb(lev,?user_data);//調(diào)用用戶設(shè)置的錯(cuò)誤回調(diào)函數(shù)?? ????????LOCK(lev);?? ????????listener_decref_and_unlock(lev);?? ????}?? }??
//listener.c文件
static void
listener_read_cb(evutil_socket_t fd, short what, void *p)
{struct evconnlistener *lev = p;int err;evconnlistener_cb cb;evconnlistener_errorcb errorcb;void *user_data;LOCK(lev);while (1) { //可能有多個(gè)客戶端同時(shí)請(qǐng)求連接struct sockaddr_storage ss;
#ifdef WIN32int socklen = sizeof(ss);
#elsesocklen_t socklen = sizeof(ss);
#endifevutil_socket_t new_fd = accept(fd, (struct sockaddr*)&ss, &socklen);if (new_fd < 0)break;if (socklen == 0) {/* This can happen with some older linux kernels in* response to nmap. */evutil_closesocket(new_fd);continue;}if (!(lev->flags & LEV_OPT_LEAVE_SOCKETS_BLOCKING))evutil_make_socket_nonblocking(new_fd);//用戶還沒(méi)設(shè)置連接監(jiān)聽(tīng)器的回調(diào)函數(shù)if (lev->cb == NULL) {UNLOCK(lev);return;}//由于refcnt被初始化為1.這里有++了，所以一般情況下并不會(huì)進(jìn)入下面的//if判斷里面。但如果程在下面UNLOCK之后，第二個(gè)線調(diào)用evconnlistener_free//釋放這個(gè)evconnlistener時(shí)，就有可能使得refcnt為1了。即進(jìn)入那個(gè)判斷體里//執(zhí)行l(wèi)istener_decref_and_unlock。在下面會(huì)討論這個(gè)問(wèn)題。++lev->refcnt;cb = lev->cb;user_data = lev->user_data;UNLOCK(lev);cb(lev, new_fd, (struct sockaddr*)&ss, (int)socklen,user_data);//調(diào)用用戶設(shè)置的回調(diào)函數(shù)，讓用戶處理這個(gè)fdLOCK(lev);if (lev->refcnt == 1) {int freed = listener_decref_and_unlock(lev);EVUTIL_ASSERT(freed);return;}--lev->refcnt;}err = evutil_socket_geterror(fd);if (EVUTIL_ERR_ACCEPT_RETRIABLE(err)) {//還可以acceptUNLOCK(lev);return;}//當(dāng)有錯(cuò)誤發(fā)生時(shí)才會(huì)運(yùn)行到這里if (lev->errorcb != NULL) {++lev->refcnt;errorcb = lev->errorcb;user_data = lev->user_data;UNLOCK(lev);errorcb(lev, user_data);//調(diào)用用戶設(shè)置的錯(cuò)誤回調(diào)函數(shù)LOCK(lev);listener_decref_and_unlock(lev);}
}
//listener.h文件?? typedef?void?(*evconnlistener_errorcb)(struct?evconnlistener?*,?void?*);?? ?? //listener.c文件?? void?? evconnlistener_set_error_cb(struct?evconnlistener?*lev,?? ????evconnlistener_errorcb?errorcb)?? {?? ????LOCK(lev);?? ????lev->errorcb?=?errorcb;?? ????UNLOCK(lev);?? }??
//listener.h文件
typedef void (*evconnlistener_errorcb)(struct evconnlistener *, void *);//listener.c文件
void
evconnlistener_set_error_cb(struct evconnlistener *lev,evconnlistener_errorcb errorcb)
{LOCK(lev);lev->errorcb = errorcb;UNLOCK(lev);
}
//listener.c文件?? void?? evconnlistener_free(struct?evconnlistener?*lev)?? {?? ????LOCK(lev);?? ????lev->cb?=?NULL;?? ????lev->errorcb?=?NULL;?? ????if?(lev->ops->shutdown)//這里的shutdown為NULL?? ????????lev->ops->shutdown(lev);?? ?? ????//引用次數(shù)減一，并解鎖?? ????listener_decref_and_unlock(lev);?? }?? ?? static?int?? listener_decref_and_unlock(struct?evconnlistener?*listener)?? {?? ????int?refcnt?=?--listener->refcnt;?? ????if?(refcnt?==?0)?{?? ????????//實(shí)際調(diào)用event_listener_destroy?? ????????listener->ops->destroy(listener);?? ????????UNLOCK(listener);?? ????????//釋放鎖?? ????????EVTHREAD_FREE_LOCK(listener->lock,?EVTHREAD_LOCKTYPE_RECURSIVE);?? ????????mm_free(listener);?? ????????return?1;?? ????}?else?{?? ????????UNLOCK(listener);?? ????????return?0;?? ????}?? }?? ?? static?void?? event_listener_destroy(struct?evconnlistener?*lev)?? {?? ????struct?evconnlistener_event?*lev_e?=?? ????????EVUTIL_UPCAST(lev,?struct?evconnlistener_event,?base);?? ?? ????//把event從event_base中刪除?? ????event_del(&lev_e->listener);?? ????if?(lev->flags?&?LEV_OPT_CLOSE_ON_FREE)//如果用戶設(shè)置了這個(gè)選項(xiàng)，那么要關(guān)閉socket?? ????????evutil_closesocket(event_get_fd(&lev_e->listener));?? }??
//listener.c文件
void
evconnlistener_free(struct evconnlistener *lev)
{LOCK(lev);lev->cb = NULL;lev->errorcb = NULL;if (lev->ops->shutdown)//這里的shutdown為NULLlev->ops->shutdown(lev);//引用次數(shù)減一，并解鎖listener_decref_and_unlock(lev);
}static int
listener_decref_and_unlock(struct evconnlistener *listener)
{int refcnt = --listener->refcnt;if (refcnt == 0) {//實(shí)際調(diào)用event_listener_destroylistener->ops->destroy(listener);UNLOCK(listener);//釋放鎖EVTHREAD_FREE_LOCK(listener->lock, EVTHREAD_LOCKTYPE_RECURSIVE);mm_free(listener);return 1;} else {UNLOCK(listener);return 0;}
}static void
event_listener_destroy(struct evconnlistener *lev)
{struct evconnlistener_event *lev_e =EVUTIL_UPCAST(lev, struct evconnlistener_event, base);//把event從event_base中刪除event_del(&lev_e->listener);if (lev->flags & LEV_OPT_CLOSE_ON_FREE)//如果用戶設(shè)置了這個(gè)選項(xiàng)，那么要關(guān)閉socketevutil_closesocket(event_get_fd(&lev_e->listener));
}
使用evconnlistener：
? ? ? ? 基于event和event_base已經(jīng)可以寫一個(gè)CS模型了。但是對(duì)于服務(wù)器端來(lái)說(shuō)，仍然需要用戶自行調(diào)用socket、bind、listen、accept等步驟。這個(gè)過(guò)程有點(diǎn)繁瑣，為此在2.0.2-alpha版本的Libevent推出了一些對(duì)應(yīng)的封裝函數(shù)。
? ? ? ??用戶只需初始化struct sockaddr_in結(jié)構(gòu)體變量，然后把它作為參數(shù)傳給函數(shù)evconnlistener_new_bind即可。該函數(shù)會(huì)完成上面說(shuō)到的那4個(gè)過(guò)程。下面的代碼是一個(gè)使用例子。[cpp] view plaincopy print?
? ? ? ??上面的代碼是一個(gè)服務(wù)器端的例子，客戶端代碼可以使用《Libevent使用例子，從簡(jiǎn)單到復(fù)雜》博文中的客戶端。這里就不貼客戶端代碼了。
?
? ? ? ??從上面代碼可以看到，當(dāng)服務(wù)器端監(jiān)聽(tīng)到一個(gè)客戶端的連接請(qǐng)求后，就會(huì)調(diào)用listener_cb這個(gè)回調(diào)函數(shù)。這個(gè)回調(diào)函數(shù)是在evconnlistener_new_bind函數(shù)中設(shè)置的。現(xiàn)在來(lái)看一下這個(gè)函數(shù)的參數(shù)有哪些，下面是其函數(shù)原型。 [cpp] view plaincopy print?? ? ? ??第一個(gè)參數(shù)是很熟悉的event_base，無(wú)論怎么樣都是離不開(kāi)event_base這個(gè)發(fā)動(dòng)機(jī)的。
? ? ? ??第二個(gè)參數(shù)是一個(gè)函數(shù)指針，該函數(shù)指針的格式如代碼所示。當(dāng)有新的客戶端請(qǐng)求連接時(shí)，該函數(shù)就會(huì)調(diào)用。要注意的是：當(dāng)這個(gè)回調(diào)函數(shù)被調(diào)用時(shí)，Libevent已經(jīng)幫我們accept了這個(gè)客戶端。所以，該回調(diào)函數(shù)有一個(gè)參數(shù)是文件描述符fd。我們直接使用這個(gè)fd即可。真是方便。這個(gè)參數(shù)是可以為NULL的，此時(shí)用戶并不能接收到客戶端。當(dāng)用戶調(diào)用evconnlistener_set_cb函數(shù)設(shè)置回調(diào)函數(shù)后，就可以了。
? ? ? ??第三個(gè)參數(shù)是傳給回調(diào)函數(shù)的用戶參數(shù)，作用就像event_new函數(shù)的最后一個(gè)參數(shù)。
? ? ? ??參數(shù)flags是一些標(biāo)志值，有下面這些：
- LEV_OPT_LEAVE_SOCKETS_BLOCKING：默認(rèn)情況下，當(dāng)連接監(jiān)聽(tīng)器接收到新的客戶端socket連接后，會(huì)把該socket設(shè)置為非阻塞的。如果設(shè)置該選項(xiàng)，那么就把之客戶端socket保留為阻塞的
- LEV_OPT_CLOSE_ON_FREE：當(dāng)連接監(jiān)聽(tīng)器釋放時(shí)，會(huì)自動(dòng)關(guān)閉底層的socket
- LEV_OPT_CLOSE_ON_EXEC：為底層的socket設(shè)置close-on-exec標(biāo)志
- LEV_OPT_REUSEABLE:?在某些平臺(tái)，默認(rèn)情況下當(dāng)一個(gè)監(jiān)聽(tīng)socket被關(guān)閉時(shí)，其他socket不能馬上綁定到同一個(gè)端口，要等一會(huì)兒才行。設(shè)置該標(biāo)志后，Libevent會(huì)把該socket設(shè)置成reuseable。這樣，關(guān)閉該socket后，其他socket就能馬上使用同一個(gè)端口
- LEV_OPT_THREADSAFE：為連接監(jiān)聽(tīng)器分配鎖。這樣可以確保線程安全
? ? ? ??參數(shù)backlog是系統(tǒng)調(diào)用listen的第二個(gè)參數(shù)。最后兩個(gè)參數(shù)就不多說(shuō)了。
evconnlistener的封裝：
? ? ? ??接下來(lái)看一下Libevent是怎么封裝evconnlistener的。
用到的結(jié)構(gòu)體：
[cpp] view plaincopy print?? ? ? ??在evconnlistener_event結(jié)構(gòu)體有一個(gè)event結(jié)構(gòu)體。可以想象，在實(shí)現(xiàn)時(shí)必然是將服務(wù)器端的socket fd賦值給struct event 類型變量listener的fd成員。然后將listener加入到event_base，這樣就完成了自動(dòng)監(jiān)聽(tīng)工作。這也回歸到之前學(xué)過(guò)的內(nèi)容。
初始化服務(wù)器socket：
[cpp] view plaincopy print?? ? ? ??evconnlistener_new_bind函數(shù)申請(qǐng)一個(gè)socket，然后對(duì)之進(jìn)行一些有關(guān)非阻塞、重用、保持連接的處理、綁定到特定的IP和端口。最后把業(yè)務(wù)邏輯交給evconnlistener_new處理。
[cpp] view plaincopy print?
? ? ? ??幾個(gè)函數(shù)的一路調(diào)用，思路還是挺清晰的。就是申請(qǐng)一個(gè)socket，進(jìn)行一些處理，然后用之賦值給event。最后把之a(chǎn)dd到event_base中。event_base會(huì)對(duì)新客戶端的請(qǐng)求連接進(jìn)行監(jiān)聽(tīng)。
? ? ? ??在evconnlistener_enable函數(shù)里面，如果用戶沒(méi)有設(shè)置回調(diào)函數(shù)，那么就不會(huì)調(diào)用event_listener_enable。也就是說(shuō)并不會(huì)add到event_base中。
? ? ? ??event_listener_enable函數(shù)里面的宏EVUTIL_UPCAST可以根據(jù)結(jié)構(gòu)體成員變量的地址推算出結(jié)構(gòu)體的起始地址。有關(guān)這個(gè)宏，可以查看”結(jié)構(gòu)體偏移量”。
處理客戶端的連接請(qǐng)求：
? ? ? ??現(xiàn)在來(lái)看一下event的回調(diào)函數(shù)listener_read_cb。
[cpp] view plaincopy print?? ? ? ??這個(gè)函數(shù)所做的工作也比較簡(jiǎn)單，就是accept客戶端，然后調(diào)用用戶設(shè)置的回調(diào)函數(shù)。所以，用戶回調(diào)函數(shù)的參數(shù)fd是一個(gè)已經(jīng)連接好了的socket。
? ? ? ??上面函數(shù)說(shuō)到了錯(cuò)誤回調(diào)函數(shù)，可以通過(guò)下面的函數(shù)設(shè)置連接監(jiān)聽(tīng)器的錯(cuò)誤監(jiān)聽(tīng)函數(shù)。
[cpp] view plaincopy print?釋放evconnlistener：
? ? ? ??調(diào)用evconnlistener_free可以釋放一個(gè)evconnlistener。由于evconnlistener擁有一些系統(tǒng)資源，在釋放evconnlistener_free的時(shí)候會(huì)釋放這些系統(tǒng)資源。
[cpp] view plaincopy print?
? ? ? ??要注意一點(diǎn)，LEV_OPT_CLOSE_ON_FREE選項(xiàng)關(guān)閉的是服務(wù)器端的監(jiān)聽(tīng)socket，而非那些連接客戶端的socket。
? ? ? ??現(xiàn)在來(lái)說(shuō)一下那個(gè)listener_decref_and_unlock。前面注釋說(shuō)到，在函數(shù)listener_read_cb中，一般情況下是不會(huì)調(diào)用listener_decref_and_unlock，但在多線程的時(shí)候可能會(huì)調(diào)用。這種特殊情況是：當(dāng)主線程accept到一個(gè)新客戶端時(shí)，會(huì)解鎖，并調(diào)用用戶設(shè)置的回調(diào)函數(shù)。此時(shí)，引用計(jì)數(shù)等于2。就在這個(gè)時(shí)候，第二個(gè)線程執(zhí)行evconnlistener_free函數(shù)。該函數(shù)會(huì)執(zhí)行l(wèi)istener_decref_and_unlock。明顯主線程還在用這個(gè)evconnlistener，肯定不能刪除。此時(shí)引用計(jì)數(shù)也等于2也不會(huì)刪除。但用戶已經(jīng)調(diào)用了evconnlistener_free。Libevent必須要響應(yīng)。當(dāng)?shù)诙€(gè)線程執(zhí)行完后，主線程搶到CPU，此時(shí)引用計(jì)數(shù)就變成1了，也就進(jìn)入到if判斷里面了。在判斷體里面執(zhí)行函數(shù)listener_decref_and_unlock，并且完成刪除工作。
?
? ? ? ??總得來(lái)說(shuō)，Libevent封裝的這個(gè)evconnlistener和一系列操作函數(shù)，還是比較簡(jiǎn)單的。思路也比較清晰。
總結(jié)
以上是生活随笔為你收集整理的Libevent源码分析-----连接监听器evconnlistener的全部?jī)?nèi)容，希望文章能夠幫你解決所遇到的問(wèn)題。
- 上一篇： （转）Mat, vectorpoint2
- 下一篇： MySQL如何查询两个日期之间的记录