IO多路复用之epoll全面总结(必看篇)
<p><span><strong>1、基本知识</strong></span></p>
<p>
epoll是在2.6内核中提出的，是之前的select和poll的增强版本。相对于select和poll来说，epoll更加灵活，没有描述符限制。epoll使用一个文件描述符管理多个描述符，将用户关系的文件描述符的事件存放到内核的一个事件表中，这样在用户空间和内核空间的copy只需一次。</p>
<p>
<span><strong>2、epoll接口</strong></span></p>
<p>
epoll操作过程需要三个接口，分别如下：</p>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">sys</code><code class="xhtml plain">/epoll.h></code>
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<code class="xhtml plain">int epoll_create(int size);</code>
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<code class="xhtml plain">int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);</code>
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<code class="xhtml plain">int epoll_wait(int epfd, struct epoll_event * events, int maxevents, int timeout);</code>
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<p>
<span><strong>（1） int epoll_create(int size);</strong></span></p>
<p>
创建一个epoll的句柄，size用来告诉内核这个监听的数目一共有多大。这个参数不同于select()中的第一个参数，给出最大监听的fd+1的值。需要注意的是，当创建好epoll句柄后，它就是会占用一个fd值，在linux下如果查看/proc/进程id/fd/，是能够看到这个fd的，所以在使用完epoll后，必须调用close()关闭，否则可能导致fd被耗尽。</p>
<p>
<span><strong>（2）int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);</strong></span></p>
<p>
epoll的事件注册函数，它不同与select()是在监听事件时告诉内核要监听什么类型的事件epoll的事件注册函数，它不同与select()是在监听事件时告诉内核要监听什么类型的事件，而是在这里先注册要监听的事件类型。第一个参数是epoll_create()的返回值，第二个参数表示动作，用三个宏来表示：</p>
<p>
epoll_ctl_add：注册新的fd到epfd中；<br>
epoll_ctl_mod：修改已经注册的fd的监听事件；<br>
epoll_ctl_del：从epfd中删除一个fd；</p>
<p>
第三个参数是需要监听的fd，第四个参数是告诉内核需要监听什么事，struct epoll_event结构如下：</p>
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<code class="xhtml plain">struct epoll_event {</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">__uint32_t events; /* epoll events */</code>
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<code class="xhtml spaces"> </code><code class="xhtml plain">epoll_data_t data; /* user data variable */</code>
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<code class="xhtml plain">};</code>
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<span><strong>events可以是以下几个宏的集合：</strong></span></p>
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epollin ：表示对应的文件描述符可以读（包括对端socket正常关闭）；</p>
<p>
epollout：表示对应的文件描述符可以写；</p>
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epollpri：表示对应的文件描述符有紧急的数据可读（这里应该表示有带外数据到来）；</p>
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epollerr：表示对应的文件描述符发生错误；</p>
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epollhup：表示对应的文件描述符被挂断；</p>
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epollet： 将epoll设为边缘触发(edge triggered)模式，这是相对于水平触发(level triggered)来说的。</p>
<p>
epolloneshot：只监听一次事件，当监听完这次事件之后，如果还需要继续监听这个socket的话，需要再次把这个socket加入到epoll队列里</p>
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<span><strong>（3） int epoll_wait(int epfd, struct epoll_event * events, int maxevents, int timeout);</strong></span></p>
<p>
等待事件的产生，类似于select()调用。参数events用来从内核得到事件的集合，maxevents告之内核这个events有多大，这个maxevents的值不能大于创建epoll_create()时的size，参数timeout是超时时间（毫秒，0会立即返回，-1将不确定，也有说法说是永久阻塞）。该函数返回需要处理的事件数目，如返回0表示已超时。</p>
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<span><strong>3、工作模式</strong></span></p>
<p>
epoll对文件描述符的操作有两种模式：lt（level trigger）和et（edge trigger）。lt模式是默认模式，lt模式与et模式的区别如下：</p>
<p>
<span><span><strong>lt模式：</strong></span></span>当epoll_wait检测到描述符事件发生并将此事件通知应用程序，应用程序可以不立即处理该事件。下次调用epoll_wait时，会再次响应应用程序并通知此事件。</p>
<p>
<span><span><strong>et模式：</strong></span></span>当epoll_wait检测到描述符事件发生并将此事件通知应用程序，应用程序必须立即处理该事件。如果不处理，下次调用epoll_wait时，不会再次响应应用程序并通知此事件。</p>
<p>
et模式在很大程度上减少了epoll事件被重复触发的次数，因此效率要比lt模式高。epoll工作在et模式的时候，必须使用非阻塞套接口，以避免由于一个文件句柄的阻塞读/阻塞写操作把处理多个文件描述符的任务饿死。</p>
<p>
<span><strong>4、测试程序</strong></span></p>
<p>
编写一个服务器回射程序echo，练习epoll过程。</p>
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服务器代码如下所示：</p>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">stdio.h</code><code class="xhtml plain">></code>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">stdlib.h</code><code class="xhtml plain">></code>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">string.h</code><code class="xhtml plain">></code>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">errno.h</code><code class="xhtml plain">></code>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">netinet</code><code class="xhtml plain">/in.h></code>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">sys</code><code class="xhtml plain">/socket.h></code>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">arpa</code><code class="xhtml plain">/inet.h></code>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">sys</code><code class="xhtml plain">/epoll.h></code>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">unistd.h</code><code class="xhtml plain">></code>
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<code class="xhtml plain">#include <</code><code class="xhtml keyword">sys</code><code class="xhtml plain">/types.h></code>
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<code class="xhtml plain">#define ipaddress "127.0.0.1"</code>
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<code class="xhtml plain">#define port 8787</code>
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<code class="xhtml plain">#define maxsize 1024</code>
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<code class="xhtml plain">#define listenq 5</code>
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<code class="xhtml plain">#define fdsize 1000</code>
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<code class="xhtml plain">#define epollevents 100</code>
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<code class="xhtml plain">//函数声明</code>
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<code class="xhtml plain">//创建套接字并进行绑定</code>
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<code class="xhtml plain">static int socket_bind(const char* ip,int port);</code>
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<code class="xhtml plain">//io多路复用epoll</code>
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<code class="xhtml plain">static void do_epoll(int listenfd);</code>
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<code class="xhtml plain">//事件处理函数</code>
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<code class="xhtml plain">static void</code>
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<code class="xhtml plain">handle_events(int epollfd,struct epoll_event *events,int num,int listenfd,char *buf);</code>
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<code class="xhtml plain">//处理接收到的连接</code>
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<code class="xhtml plain">static void handle_accpet(int epollfd,int listenfd);</code>
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<code class="xhtml plain">//读处理</code>
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<code class="xhtml plain">static void do_read(int epollfd,int fd,char *buf);</code>
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<code class="xhtml plain">//写处理</code>
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<code class="xhtml plain">static void do_write(int epollfd,int fd,char *buf);</code>
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<code class="xhtml plain">//添加事件</code>
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<code class="xhtml plain">static void add_event(int epollfd,int fd,int state);</code>
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<code class="xhtml plain">//修改事件</code>
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<div class="line number37 index36 alt2">
<code class="xhtml plain">static void modify_event(int epollfd,int fd,int state);</code>
</div>
<div class="line number38 index37 alt1">
<code class="xhtml plain">//删除事件</code>
</div>
<div class="line number39 index38 alt2">
<code class="xhtml plain">static void delete_event(int epollfd,int fd,int state);</code>
</div>
<div class="line number40 index39 alt1">
</div>
<div class="line number41 index40 alt2">
<code class="xhtml plain">int main(int argc,char *argv[])</code>
</div>
<div class="line number42 index41 alt1">
<code class="xhtml plain">{</code>
</div>
<div class="line number43 index42 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">int listenfd;</code>
</div>
<div class="line number44 index43 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">listenfd = socket_bind(ipaddress,port);</code>
</div>
<div class="line number45 index44 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">listen(listenfd,listenq);</code>
</div>
<div class="line number46 index45 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">do_epoll(listenfd);</code>
</div>
<div class="line number47 index46 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">return 0;</code>
</div>
<div class="line number48 index47 alt1">
<code class="xhtml plain">}</code>
</div>
<div class="line number49 index48 alt2">
</div>
<div class="line number50 index49 alt1">
<code class="xhtml plain">static int socket_bind(const char* ip,int port)</code>
</div>
<div class="line number51 index50 alt2">
<code class="xhtml plain">{</code>
</div>
<div class="line number52 index51 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int listenfd;</code>
</div>
<div class="line number53 index52 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct sockaddr_in servaddr;</code>
</div>
<div class="line number54 index53 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">listenfd = socket(af_inet,sock_stream,0);</code>
</div>
<div class="line number55 index54 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (listenfd == -1)</code>
</div>
<div class="line number56 index55 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number57 index56 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">perror("socket error:");</code>
</div>
<div class="line number58 index57 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">exit(1);</code>
</div>
<div class="line number59 index58 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number60 index59 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">bzero(&servaddr,sizeof(servaddr));</code>
</div>
<div class="line number61 index60 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">servaddr.sin_family = af_inet;</code>
</div>
<div class="line number62 index61 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">inet_pton(af_inet,ip,&servaddr.sin_addr);</code>
</div>
<div class="line number63 index62 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">servaddr.sin_port = htons(port);</code>
</div>
<div class="line number64 index63 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (bind(listenfd,(struct sockaddr*)&servaddr,sizeof(servaddr)) == -1)</code>
</div>
<div class="line number65 index64 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number66 index65 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">perror("bind error: ");</code>
</div>
<div class="line number67 index66 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">exit(1);</code>
</div>
<div class="line number68 index67 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number69 index68 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">return listenfd;</code>
</div>
<div class="line number70 index69 alt1">
<code class="xhtml plain">}</code>
</div>
<div class="line number71 index70 alt2">
</div>
<div class="line number72 index71 alt1">
<code class="xhtml plain">static void do_epoll(int listenfd)</code>
</div>
<div class="line number73 index72 alt2">
<code class="xhtml plain">{</code>
</div>
<div class="line number74 index73 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int epollfd;</code>
</div>
<div class="line number75 index74 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct epoll_event events;</code>
</div>
<div class="line number76 index75 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int ret;</code>
</div>
<div class="line number77 index76 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">char buf;</code>
</div>
<div class="line number78 index77 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">memset(buf,0,maxsize);</code>
</div>
<div class="line number79 index78 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">//创建一个描述符</code>
</div>
<div class="line number80 index79 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">epollfd = epoll_create(fdsize);</code>
</div>
<div class="line number81 index80 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">//添加监听描述符事件</code>
</div>
<div class="line number82 index81 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">add_event(epollfd,listenfd,epollin);</code>
</div>
<div class="line number83 index82 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">for ( ; ; )</code>
</div>
<div class="line number84 index83 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number85 index84 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">//获取已经准备好的描述符事件</code>
</div>
<div class="line number86 index85 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">ret = epoll_wait(epollfd,events,epollevents,-1);</code>
</div>
<div class="line number87 index86 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">handle_events(epollfd,events,ret,listenfd,buf);</code>
</div>
<div class="line number88 index87 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number89 index88 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">close(epollfd);</code>
</div>
<div class="line number90 index89 alt1">
<code class="xhtml plain">}</code>
</div>
<div class="line number91 index90 alt2">
</div>
<div class="line number92 index91 alt1">
<code class="xhtml plain">static void</code>
</div>
<div class="line number93 index92 alt2">
<code class="xhtml plain">handle_events(int epollfd,struct epoll_event *events,int num,int listenfd,char *buf)</code>
</div>
<div class="line number94 index93 alt1">
<code class="xhtml plain">{</code>
</div>
<div class="line number95 index94 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">int i;</code>
</div>
<div class="line number96 index95 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int fd;</code>
</div>
<div class="line number97 index96 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">//进行选好遍历</code>
</div>
<div class="line number98 index97 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">for (i = 0;i < num;i++)</code>
</div>
<div class="line number99 index98 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number100 index99 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">fd = events.data.fd;</code>
</div>
<div class="line number101 index100 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">//根据描述符的类型和事件类型进行处理</code>
</div>
<div class="line number102 index101 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">if ((fd == listenfd) &&(events.events & epollin))</code>
</div>
<div class="line number103 index102 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">handle_accpet(epollfd,listenfd);</code>
</div>
<div class="line number104 index103 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">else if (events.events & epollin)</code>
</div>
<div class="line number105 index104 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">do_read(epollfd,fd,buf);</code>
</div>
<div class="line number106 index105 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">else if (events.events & epollout)</code>
</div>
<div class="line number107 index106 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">do_write(epollfd,fd,buf);</code>
</div>
<div class="line number108 index107 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number109 index108 alt2">
<code class="xhtml plain">}</code>
</div>
<div class="line number110 index109 alt1">
<code class="xhtml plain">static void handle_accpet(int epollfd,int listenfd)</code>
</div>
<div class="line number111 index110 alt2">
<code class="xhtml plain">{</code>
</div>
<div class="line number112 index111 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int clifd;</code>
</div>
<div class="line number113 index112 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct sockaddr_in cliaddr;</code>
</div>
<div class="line number114 index113 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">socklen_t cliaddrlen;</code>
</div>
<div class="line number115 index114 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">clifd = accept(listenfd,(struct sockaddr*)&cliaddr,&cliaddrlen);</code>
</div>
<div class="line number116 index115 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (clifd == -1)</code>
</div>
<div class="line number117 index116 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">perror("accpet error:");</code>
</div>
<div class="line number118 index117 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">else</code>
</div>
<div class="line number119 index118 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number120 index119 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">printf("accept a new client: %s:%d\n",inet_ntoa(cliaddr.sin_addr),cliaddr.sin_port);</code>
</div>
<div class="line number121 index120 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">//添加一个客户描述符和事件</code>
</div>
<div class="line number122 index121 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">add_event(epollfd,clifd,epollin);</code>
</div>
<div class="line number123 index122 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number124 index123 alt1">
<code class="xhtml plain">}</code>
</div>
<div class="line number125 index124 alt2">
</div>
<div class="line number126 index125 alt1">
<code class="xhtml plain">static void do_read(int epollfd,int fd,char *buf)</code>
</div>
<div class="line number127 index126 alt2">
<code class="xhtml plain">{</code>
</div>
<div class="line number128 index127 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int nread;</code>
</div>
<div class="line number129 index128 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">nread = read(fd,buf,maxsize);</code>
</div>
<div class="line number130 index129 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (nread == -1)</code>
</div>
<div class="line number131 index130 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number132 index131 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">perror("read error:");</code>
</div>
<div class="line number133 index132 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">close(fd);</code>
</div>
<div class="line number134 index133 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">delete_event(epollfd,fd,epollin);</code>
</div>
<div class="line number135 index134 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number136 index135 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">else if (nread == 0)</code>
</div>
<div class="line number137 index136 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number138 index137 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">fprintf(stderr,"client close.\n");</code>
</div>
<div class="line number139 index138 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">close(fd);</code>
</div>
<div class="line number140 index139 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">delete_event(epollfd,fd,epollin);</code>
</div>
<div class="line number141 index140 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number142 index141 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">else</code>
</div>
<div class="line number143 index142 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number144 index143 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">printf("read message is : %s",buf);</code>
</div>
<div class="line number145 index144 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">//修改描述符对应的事件，由读改为写</code>
</div>
<div class="line number146 index145 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">modify_event(epollfd,fd,epollout);</code>
</div>
<div class="line number147 index146 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number148 index147 alt1">
<code class="xhtml plain">}</code>
</div>
<div class="line number149 index148 alt2">
</div>
<div class="line number150 index149 alt1">
<code class="xhtml plain">static void do_write(int epollfd,int fd,char *buf)</code>
</div>
<div class="line number151 index150 alt2">
<code class="xhtml plain">{</code>
</div>
<div class="line number152 index151 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int nwrite;</code>
</div>
<div class="line number153 index152 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">nwrite = write(fd,buf,strlen(buf));</code>
</div>
<div class="line number154 index153 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (nwrite == -1)</code>
</div>
<div class="line number155 index154 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number156 index155 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">perror("write error:");</code>
</div>
<div class="line number157 index156 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">close(fd);</code>
</div>
<div class="line number158 index157 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">delete_event(epollfd,fd,epollout);</code>
</div>
<div class="line number159 index158 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number160 index159 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">else</code>
</div>
<div class="line number161 index160 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">modify_event(epollfd,fd,epollin);</code>
</div>
<div class="line number162 index161 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">memset(buf,0,maxsize);</code>
</div>
<div class="line number163 index162 alt2">
<code class="xhtml plain">}</code>
</div>
<div class="line number164 index163 alt1">
</div>
<div class="line number165 index164 alt2">
<code class="xhtml plain">static void add_event(int epollfd,int fd,int state)</code>
</div>
<div class="line number166 index165 alt1">
<code class="xhtml plain">{</code>
</div>
<div class="line number167 index166 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct epoll_event ev;</code>
</div>
<div class="line number168 index167 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.events = state;</code>
</div>
<div class="line number169 index168 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.data.fd = fd;</code>
</div>
<div class="line number170 index169 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">epoll_ctl(epollfd,epoll_ctl_add,fd,&ev);</code>
</div>
<div class="line number171 index170 alt2">
<code class="xhtml plain">}</code>
</div>
<div class="line number172 index171 alt1">
</div>
<div class="line number173 index172 alt2">
<code class="xhtml plain">static void delete_event(int epollfd,int fd,int state)</code>
</div>
<div class="line number174 index173 alt1">
<code class="xhtml plain">{</code>
</div>
<div class="line number175 index174 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct epoll_event ev;</code>
</div>
<div class="line number176 index175 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.events = state;</code>
</div>
<div class="line number177 index176 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.data.fd = fd;</code>
</div>
<div class="line number178 index177 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">epoll_ctl(epollfd,epoll_ctl_del,fd,&ev);</code>
</div>
<div class="line number179 index178 alt2">
<code class="xhtml plain">}</code>
</div>
<div class="line number180 index179 alt1">
</div>
<div class="line number181 index180 alt2">
<code class="xhtml plain">static void modify_event(int epollfd,int fd,int state)</code>
</div>
<div class="line number182 index181 alt1">
<code class="xhtml plain">{</code>
</div>
<div class="line number183 index182 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct epoll_event ev;</code>
</div>
<div class="line number184 index183 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.events = state;</code>
</div>
<div class="line number185 index184 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.data.fd = fd;</code>
</div>
<div class="line number186 index185 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">epoll_ctl(epollfd,epoll_ctl_mod,fd,&ev);</code>
</div>
<div class="line number187 index186 alt2">
<code class="xhtml plain">}</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
</div>
<p>
客户端也用epoll实现，控制stdin_fileno、stdout_fileno、和sockfd三个描述符，程序如下所示：</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterxhtml" id="highlighter_423279">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
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</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">netinet</code><code class="xhtml plain">/in.h></code>
</div>
<div class="line number2 index1 alt1">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">sys</code><code class="xhtml plain">/socket.h></code>
</div>
<div class="line number3 index2 alt2">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">stdio.h</code><code class="xhtml plain">></code>
</div>
<div class="line number4 index3 alt1">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">string.h</code><code class="xhtml plain">></code>
</div>
<div class="line number5 index4 alt2">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">stdlib.h</code><code class="xhtml plain">></code>
</div>
<div class="line number6 index5 alt1">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">sys</code><code class="xhtml plain">/epoll.h></code>
</div>
<div class="line number7 index6 alt2">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">time.h</code><code class="xhtml plain">></code>
</div>
<div class="line number8 index7 alt1">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">unistd.h</code><code class="xhtml plain">></code>
</div>
<div class="line number9 index8 alt2">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">sys</code><code class="xhtml plain">/types.h></code>
</div>
<div class="line number10 index9 alt1">
<code class="xhtml plain">#include <</code><code class="xhtml keyword">arpa</code><code class="xhtml plain">/inet.h></code>
</div>
<div class="line number11 index10 alt2">
</div>
<div class="line number12 index11 alt1">
<code class="xhtml plain">#define maxsize 1024</code>
</div>
<div class="line number13 index12 alt2">
<code class="xhtml plain">#define ipaddress "127.0.0.1"</code>
</div>
<div class="line number14 index13 alt1">
<code class="xhtml plain">#define serv_port 8787</code>
</div>
<div class="line number15 index14 alt2">
<code class="xhtml plain">#define fdsize 1024</code>
</div>
<div class="line number16 index15 alt1">
<code class="xhtml plain">#define epollevents 20</code>
</div>
<div class="line number17 index16 alt2">
</div>
<div class="line number18 index17 alt1">
<code class="xhtml plain">static void handle_connection(int sockfd);</code>
</div>
<div class="line number19 index18 alt2">
<code class="xhtml plain">static void</code>
</div>
<div class="line number20 index19 alt1">
<code class="xhtml plain">handle_events(int epollfd,struct epoll_event *events,int num,int sockfd,char *buf);</code>
</div>
<div class="line number21 index20 alt2">
<code class="xhtml plain">static void do_read(int epollfd,int fd,int sockfd,char *buf);</code>
</div>
<div class="line number22 index21 alt1">
<code class="xhtml plain">static void do_read(int epollfd,int fd,int sockfd,char *buf);</code>
</div>
<div class="line number23 index22 alt2">
<code class="xhtml plain">static void do_write(int epollfd,int fd,int sockfd,char *buf);</code>
</div>
<div class="line number24 index23 alt1">
<code class="xhtml plain">static void add_event(int epollfd,int fd,int state);</code>
</div>
<div class="line number25 index24 alt2">
<code class="xhtml plain">static void delete_event(int epollfd,int fd,int state);</code>
</div>
<div class="line number26 index25 alt1">
<code class="xhtml plain">static void modify_event(int epollfd,int fd,int state);</code>
</div>
<div class="line number27 index26 alt2">
</div>
<div class="line number28 index27 alt1">
<code class="xhtml plain">int main(int argc,char *argv[])</code>
</div>
<div class="line number29 index28 alt2">
<code class="xhtml plain">{</code>
</div>
<div class="line number30 index29 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int sockfd;</code>
</div>
<div class="line number31 index30 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct sockaddr_in servaddr;</code>
</div>
<div class="line number32 index31 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">sockfd = socket(af_inet,sock_stream,0);</code>
</div>
<div class="line number33 index32 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">bzero(&servaddr,sizeof(servaddr));</code>
</div>
<div class="line number34 index33 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">servaddr.sin_family = af_inet;</code>
</div>
<div class="line number35 index34 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">servaddr.sin_port = htons(serv_port);</code>
</div>
<div class="line number36 index35 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">inet_pton(af_inet,ipaddress,&servaddr.sin_addr);</code>
</div>
<div class="line number37 index36 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">connect(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr));</code>
</div>
<div class="line number38 index37 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">//处理连接</code>
</div>
<div class="line number39 index38 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">handle_connection(sockfd);</code>
</div>
<div class="line number40 index39 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">close(sockfd);</code>
</div>
<div class="line number41 index40 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">return 0;</code>
</div>
<div class="line number42 index41 alt1">
<code class="xhtml plain">}</code>
</div>
<div class="line number43 index42 alt2">
</div>
<div class="line number44 index43 alt1">
</div>
<div class="line number45 index44 alt2">
<code class="xhtml plain">static void handle_connection(int sockfd)</code>
</div>
<div class="line number46 index45 alt1">
<code class="xhtml plain">{</code>
</div>
<div class="line number47 index46 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">int epollfd;</code>
</div>
<div class="line number48 index47 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct epoll_event events;</code>
</div>
<div class="line number49 index48 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">char buf;</code>
</div>
<div class="line number50 index49 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int ret;</code>
</div>
<div class="line number51 index50 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">epollfd = epoll_create(fdsize);</code>
</div>
<div class="line number52 index51 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">add_event(epollfd,stdin_fileno,epollin);</code>
</div>
<div class="line number53 index52 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">for ( ; ; )</code>
</div>
<div class="line number54 index53 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number55 index54 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">ret = epoll_wait(epollfd,events,epollevents,-1);</code>
</div>
<div class="line number56 index55 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">handle_events(epollfd,events,ret,sockfd,buf);</code>
</div>
<div class="line number57 index56 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number58 index57 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">close(epollfd);</code>
</div>
<div class="line number59 index58 alt2">
<code class="xhtml plain">}</code>
</div>
<div class="line number60 index59 alt1">
</div>
<div class="line number61 index60 alt2">
<code class="xhtml plain">static void</code>
</div>
<div class="line number62 index61 alt1">
<code class="xhtml plain">handle_events(int epollfd,struct epoll_event *events,int num,int sockfd,char *buf)</code>
</div>
<div class="line number63 index62 alt2">
<code class="xhtml plain">{</code>
</div>
<div class="line number64 index63 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int fd;</code>
</div>
<div class="line number65 index64 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">int i;</code>
</div>
<div class="line number66 index65 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">for (i = 0;i < num;i++)</code>
</div>
<div class="line number67 index66 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number68 index67 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">fd = events.data.fd;</code>
</div>
<div class="line number69 index68 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (events.events & epollin)</code>
</div>
<div class="line number70 index69 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">do_read(epollfd,fd,sockfd,buf);</code>
</div>
<div class="line number71 index70 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">else if (events.events & epollout)</code>
</div>
<div class="line number72 index71 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">do_write(epollfd,fd,sockfd,buf);</code>
</div>
<div class="line number73 index72 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number74 index73 alt1">
<code class="xhtml plain">}</code>
</div>
<div class="line number75 index74 alt2">
</div>
<div class="line number76 index75 alt1">
<code class="xhtml plain">static void do_read(int epollfd,int fd,int sockfd,char *buf)</code>
</div>
<div class="line number77 index76 alt2">
<code class="xhtml plain">{</code>
</div>
<div class="line number78 index77 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int nread;</code>
</div>
<div class="line number79 index78 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">nread = read(fd,buf,maxsize);</code>
</div>
<div class="line number80 index79 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (nread == -1)</code>
</div>
<div class="line number81 index80 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number82 index81 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">perror("read error:");</code>
</div>
<div class="line number83 index82 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">close(fd);</code>
</div>
<div class="line number84 index83 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number85 index84 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">else if (nread == 0)</code>
</div>
<div class="line number86 index85 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number87 index86 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">fprintf(stderr,"server close.\n");</code>
</div>
<div class="line number88 index87 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">close(fd);</code>
</div>
<div class="line number89 index88 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number90 index89 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">else</code>
</div>
<div class="line number91 index90 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number92 index91 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (fd == stdin_fileno)</code>
</div>
<div class="line number93 index92 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">add_event(epollfd,sockfd,epollout);</code>
</div>
<div class="line number94 index93 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">else</code>
</div>
<div class="line number95 index94 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number96 index95 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">delete_event(epollfd,sockfd,epollin);</code>
</div>
<div class="line number97 index96 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">add_event(epollfd,stdout_fileno,epollout);</code>
</div>
<div class="line number98 index97 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number99 index98 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number100 index99 alt1">
<code class="xhtml plain">}</code>
</div>
<div class="line number101 index100 alt2">
</div>
<div class="line number102 index101 alt1">
<code class="xhtml plain">static void do_write(int epollfd,int fd,int sockfd,char *buf)</code>
</div>
<div class="line number103 index102 alt2">
<code class="xhtml plain">{</code>
</div>
<div class="line number104 index103 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">int nwrite;</code>
</div>
<div class="line number105 index104 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">nwrite = write(fd,buf,strlen(buf));</code>
</div>
<div class="line number106 index105 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (nwrite == -1)</code>
</div>
<div class="line number107 index106 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number108 index107 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">perror("write error:");</code>
</div>
<div class="line number109 index108 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">close(fd);</code>
</div>
<div class="line number110 index109 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number111 index110 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">else</code>
</div>
<div class="line number112 index111 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">{</code>
</div>
<div class="line number113 index112 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">if (fd == stdout_fileno)</code>
</div>
<div class="line number114 index113 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">delete_event(epollfd,fd,epollout);</code>
</div>
<div class="line number115 index114 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">else</code>
</div>
<div class="line number116 index115 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">modify_event(epollfd,fd,epollin);</code>
</div>
<div class="line number117 index116 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">}</code>
</div>
<div class="line number118 index117 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">memset(buf,0,maxsize);</code>
</div>
<div class="line number119 index118 alt2">
<code class="xhtml plain">}</code>
</div>
<div class="line number120 index119 alt1">
</div>
<div class="line number121 index120 alt2">
<code class="xhtml plain">static void add_event(int epollfd,int fd,int state)</code>
</div>
<div class="line number122 index121 alt1">
<code class="xhtml plain">{</code>
</div>
<div class="line number123 index122 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct epoll_event ev;</code>
</div>
<div class="line number124 index123 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.events = state;</code>
</div>
<div class="line number125 index124 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.data.fd = fd;</code>
</div>
<div class="line number126 index125 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">epoll_ctl(epollfd,epoll_ctl_add,fd,&ev);</code>
</div>
<div class="line number127 index126 alt2">
<code class="xhtml plain">}</code>
</div>
<div class="line number128 index127 alt1">
</div>
<div class="line number129 index128 alt2">
<code class="xhtml plain">static void delete_event(int epollfd,int fd,int state)</code>
</div>
<div class="line number130 index129 alt1">
<code class="xhtml plain">{</code>
</div>
<div class="line number131 index130 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct epoll_event ev;</code>
</div>
<div class="line number132 index131 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.events = state;</code>
</div>
<div class="line number133 index132 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.data.fd = fd;</code>
</div>
<div class="line number134 index133 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">epoll_ctl(epollfd,epoll_ctl_del,fd,&ev);</code>
</div>
<div class="line number135 index134 alt2">
<code class="xhtml plain">}</code>
</div>
<div class="line number136 index135 alt1">
</div>
<div class="line number137 index136 alt2">
<code class="xhtml plain">static void modify_event(int epollfd,int fd,int state)</code>
</div>
<div class="line number138 index137 alt1">
<code class="xhtml plain">{</code>
</div>
<div class="line number139 index138 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">struct epoll_event ev;</code>
</div>
<div class="line number140 index139 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.events = state;</code>
</div>
<div class="line number141 index140 alt2">
<code class="xhtml spaces"> </code><code class="xhtml plain">ev.data.fd = fd;</code>
</div>
<div class="line number142 index141 alt1">
<code class="xhtml spaces"> </code><code class="xhtml plain">epoll_ctl(epollfd,epoll_ctl_mod,fd,&ev);</code>
</div>
<div class="line number143 index142 alt2">
<code class="xhtml plain">}</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
</div>
<p>
<strong>5、测试结果</strong></p>
<p>
<img title="IO多路复用之epoll全面总结(必看篇)" alt="IO多路复用之epoll全面总结(必看篇)" src="https://zhuji.jb51.net/uploads/img/202305/99bcbff36e13ffcb236d12ac0827f80c.jpg"></p>
<p>
<img title="IO多路复用之epoll全面总结(必看篇)" alt="IO多路复用之epoll全面总结(必看篇)" src="https://zhuji.jb51.net/uploads/img/202305/c247a52f92aae322b1ede132b74b3b0c.jpg"></p>
<p>
<img title="IO多路复用之epoll全面总结(必看篇)" alt="IO多路复用之epoll全面总结(必看篇)" src="https://zhuji.jb51.net/uploads/img/202305/f2b3eea8b1f640b4d9cd6d3b86c2262c.jpg"></p>
<p>
以上就是小编为大家带来的io多路复用之epoll全面总结(必看篇)全部内容了，希望大家多多支持~</p>
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