首页 > 代码库 > Socket网络编程--Libev库学习(3)
Socket网络编程--Libev库学习(3)
这一小节继续讲解各个观察器(Watcher).
上一小节已经讲解了ev_io(IO可读可写观察器)，ev_stat(文件属性变化观察器)，ev_signal(信号处理观察器)，ev_timer(定时器)，ev_periodic(周期任务处理)，ev_child(子进程状态变化观察器)。这一小节准备讲ev_fork(创建的进程时的观察器)，ev_async(异步调用观察器)，ev_cleanup(event loop退出时触发事件)，ev_prepare(每次event loop之前事件),ev_check(每次event loop之后事件)，ev_idle(每次event loop空闲触发事件).
ev_async (ev_async当ev_async_send通过watcher调用时调用，触发EV_ASYNC)
1 #include <stdio.h> 2 #include <string.h> 3 #include <unistd.h> 4 #include <stdlib.h> 5 #include <ev.h> 6 7 ev_async async_watcher; 8 9 static void sigint_callback(struct ev_loop *loop,ev_signal * w,int revents)10 {11 if(revents & EV_SIGNAL)12 {13 printf("Call sigint_callback\n");14 printf("ev_async_send 调用前 %d\n",ev_async_pending(&async_watcher));15 ev_async_send(loop,&async_watcher);//这里会调用async_callback16 printf("ev_async_send 调用后 %d\n",ev_async_pending(&async_watcher));17 }18 }19 20 static void sigquit_callback(struct ev_loop *loop,ev_signal *w,int revetns)21 {22 printf("Call sigquit_callback\n");23 ev_break(loop,EVBREAK_ALL);24 }25 26 static void async_callback(struct ev_loop *loop,ev_async *w,int revents)27 {28 if(revents & EV_ASYNC)29 {30 printf("Call async_callback\n");31 }32 }33 34 int main(int argc, char **args)35 {36 struct ev_loop *main_loop=ev_default_loop(0);37 38 ev_init(&async_watcher,async_callback);39 ev_async_start(main_loop,&async_watcher);40 41 ev_signal sigint_watcher;42 ev_init(&sigint_watcher,sigint_callback);43 ev_signal_set(&sigint_watcher,SIGINT);44 ev_signal_start(main_loop,&sigint_watcher);45 46 ev_signal sigquit_watcher;//这里的ev_signal不能与上面共用,必须在声明一个变量47 ev_init(&sigquit_watcher,sigquit_callback);48 ev_signal_set(&sigquit_watcher,SIGQUIT);49 ev_signal_start(main_loop,&sigquit_watcher);50 51 ev_run(main_loop,0);52 return 0;53 }
下面这个是运行截图
可以看出程序ev_async这个是通过ev_async_send来驱动async_callback这个回调函数执行的。而且ev_async_pending这个也是可以判断ev_async是否处于pending状态。我在第15行处增加了sleep(1)后，运行的结构还是一样，可以看出ev_async所绑定的回调函数是处于pending状态而不是另外开一个线程(进程)来执行的。
从上面的处理机制看，好像就是发送一个信号，然后ev_async就调用回调函数去执行，好像跟ev_signal一样，没有什么特点啊。这里给出官方文档的解释。
This functionality is very similar to ev_signal watchers, as signals, too, are asynchronous in nature, and signals, too, will be compressed (i.e. the number of callback invocations may be less than the number of ev_async_sent calls).Unlike ev_signal watchers, ev_async works with any event loop, not just the default loop.
上面说到，不同与ev_signal watchers的是，ev_async可以在多种event loop，而不是默认的loop。前几小节已经讲到ev_loop 的创建，可以通过ev_loop_new进行创建(创建异步事件什么的)。具体的用法这里还不是很清楚，先跳过。
ev_fork (开辟进程时观察器)
1 #include <stdio.h> 2 #include <string.h> 3 #include <unistd.h> 4 #include <stdlib.h> 5 #include <ev.h> 6 7 static void fork_callback(struct ev_loop *loop,ev_fork *w,int revents) 8 { 9 printf("Call fork_callback\n");10 }11 12 static void timeout_callback(struct ev_loop*loop,ev_timer *w,int revents)13 {14 printf("Time Out\n");15 ev_break(loop,EVBREAK_ALL);16 }17 18 int main(int argc, char **args)19 {20 struct ev_loop *main_loop=ev_default_loop(0);21 22 ev_fork fork_watcher;23 ev_init(&fork_watcher,fork_callback);24 ev_fork_start(main_loop,&fork_watcher);25 26 ev_timer timer_watcher;27 ev_init(&timer_watcher,timeout_callback);28 ev_timer_set(&timer_watcher,3,0);29 ev_timer_start(main_loop,&timer_watcher);30 31 switch(fork())32 {33 case -1:34 break;35 case 0://child36 //ev_loop_fork(main_loop);37 break;38 }39 40 ev_run(main_loop,0);41 return 0;42 }
上面这个代码没有输出Call fork_callback，如果把第36行的注释去掉，就会输出Call fork_callback了，可以说明这个ev_fork不是针对fork函数创建的进程。而是要ev_loop_fork针对ev_loop 创建的loop。具体解释的不是很清楚，下面给出官方文档:
Fork watchers are called when a fork () was detected (usually because whoever is a good citizen cared to tell libev about it by calling ev_default_fork or ev_loop_fork). The invocation is done before the event loop blocks next and before ev_check watchers are being called, and only in the child after the fork. If whoever good citizen calling ev_default_fork cheats and calls it in the wrong process, the fork handlers will be invoked, too, of course.
loop的创建小解
1 struct ev_loop *ev_default_loop (unsigned int flags) 2 struct ev_loop *ev_loop_new (unsigned int flags) 3 //这两个函数都是默认原始化一个loop，区别是第一个不是线程安全的，第二个不能捕捉信号和子进程的watcher。 4 //参数flags可以为下面几种类型： 5 //引用 6 #define EVFLAG_AUTO 0x00000000U /* not quite a mask */ 7 /* flag bits */ 8 #define EVFLAG_NOENV 0x01000000U /* do NOT consult environment */ 9 #define EVFLAG_FORKCHECK 0x02000000U /* check for a fork in each iteration */ 10 /* method bits to be ored together */ 11 #define EVBACKEND_SELECT 0x00000001U /* about anywhere */ 12 #define EVBACKEND_POLL 0x00000002U /* !win */ 13 #define EVBACKEND_EPOLL 0x00000004U /* linux */ 14 #define EVBACKEND_KQUEUE 0x00000008U /* bsd */ 15 #define EVBACKEND_DEVPOLL 0x00000010U /* solaris 8 */ /* NYI */ 16 #define EVBACKEND_PORT 0x00000020U /* solaris 10 */17 ev_default_fork () 18 ev_loop_fork (loop)19 //这两个函数就是当你在子进程里须要 运用 libev的函数的之前必须要调用。他们的区别是第二个函数是当运用 ev_loop_new建立 的loop时，才用第二个函数,也就是说重用父进程建立 的loop。 20 ev_loop (loop, int flags)21 //开始事件循环。 22 ev_TYPE_init (ev_TYPE *watcher, callback, [args]) 23 //原始化一个watcher。TYPE也就是libev支持的事件类型，比如io，比如time等等。。 24 //第一个参数为一个watcher,第二个回调函数，第三个句柄，第四个事件类型。包含下面几种： 25 //引用26 #define EV_UNDEF -1 /* guaranteed to be invalid */ 27 #define EV_NONE 0x00 /* no events */ 28 #define EV_READ 0x01 /* ev_io detected read will not block */ 29 #define EV_WRITE 0x02 /* ev_io detected write will not block */ 30 #define EV_IOFDSET 0x80 /* internal use only */ 31 #define EV_TIMEOUT 0x00000100 /* timer timed out */ 32 #define EV_PERIODIC 0x00000200 /* periodic timer timed out */ 33 #define EV_SIGNAL 0x00000400 /* signal was received */ 34 #define EV_CHILD 0x00000800 /* child/pid had status change */ 35 #define EV_STAT 0x00001000 /* stat data changed */ 36 #define EV_IDLE 0x00002000 /* event loop is idling */ 37 #define EV_PREPARE 0x00004000 /* event loop about to poll */ 38 #define EV_CHECK 0x00008000 /* event loop finished poll */ 39 #define EV_EMBED 0x00010000 /* embedded event loop needs sweep */ 40 #define EV_FORK 0x00020000 /* event loop resumed in child */ 41 #define EV_ASYNC 0x00040000 /* async intra-loop signal */ 42 #define EV_ERROR 0x80000000 /* sent when an error occurs */ 43 //引用44 ev_TYPE_start (loop *, ev_TYPE *watcher)45 //启动一个watcher。
1 switch(fork()) 2 { 3 case -1: 4 break; 5 case 0://child 6 ev_loop_fork(main_loop);//使用父进程main_loop 7 ev_timer timer_watcher1; 8 ev_init(&timer_watcher1,timeout_callback); 9 ev_timer_set(&timer_watcher1,3,0);10 ev_timer_start(main_loop,&timer_watcher1);11 break;12 }
上面代码如果修改如下是可以编译通过的。就是在父进程中的main_loop中再增加一个watcher，这个程序将会输出三次Time Out。注意如果没有第六行的ev_loop_fork是编译不通过的。大概的原因是ev库设计的原因。
下面给出一个例子，用于以后可以参考用
1 #include <ev.h> 2 #include <stdio.h> 3 4 //不同的watcher 5 ev_io stdin_watcher; 6 ev_timer timeout_watcher; 7 ev_timer timeout_watcher_child; 8 9 //标准输入的回调函数10 static void stdin_cb (EV_P_ ev_io *w, int revents)11 {12 puts ("stdin ready");13 ev_io_stop (EV_A_ w);14 ev_unloop (EV_A_ EVUNLOOP_ALL);15 }16 17 //父进程的定时器回调函数18 static void timeout_cb (EV_P_ ev_timer *w, int revents)19 {20 puts ("timeout");21 ev_unloop (EV_A_ EVUNLOOP_ONE);22 }23 //子进程的定时器回调函数24 static void timeout_cb_child (EV_P_ ev_timer *w, int revents)25 {26 puts ("child timeout");27 ev_unloop (EV_A_ EVUNLOOP_ONE);28 }29 30 static void fork_callback(struct ev_loop *loop,ev_fork *w,int revents)31 {32 printf("Call fork_callback\n");33 }34 35 int main (void)36 {37 //创建一个backend为select的loop38 struct ev_loop *loop = ev_loop_new(EVBACKEND_SELECT);39 40 //初始化并启动父进程的watcher41 ev_timer_init(&timeout_watcher, timeout_cb, 10, 0.);42 ev_timer_start(loop, &timeout_watcher);43 switch (fork()) {44 case -1:45 return -1;46 case 0:47 //使用父进程loop。48 ev_loop_fork(loop);49 //子进程的loop50 struct ev_loop *loop_child = ev_loop_new (EVBACKEND_SELECT);51 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);52 ev_io_start (loop, &stdin_watcher);53 ev_timer_init(&timeout_watcher_child, timeout_cb_child, 5.5, 0.);54 ev_timer_start(loop_child, &timeout_watcher_child);55 ev_loop(loop_child,0);56 }57 58 //等待事件59 ev_loop (loop, 0);60 return 0;61 }
ev_cleanup event loop 退出触发事件
1 #include <stdio.h> 2 #include <string.h> 3 #include <unistd.h> 4 #include <stdlib.h> 5 #include <ev.h> 6 7 struct ev_loop *main_loop; 8 9 static void program_exits(void)10 {11 printf("Call AtExit\n");12 ev_loop_destroy(EV_DEFAULT);//注释掉43行处代码，该函数在这里没有调用到cleanup_callback，但是却执行没有错误13 }14 15 static void cleanup_callback(struct ev_loop *loop,ev_cleanup *w,int revents)16 {17 printf("Call cleanup_callback\n");18 }19 20 static void timer_callback(struct ev_loop *loop,ev_timer *w,int revents)21 {22 printf("Call timer_callback\n");23 }24 25 int main(int argc, char **args)26 {27 //struct ev_loop *main_loop=ev_default_loop(0);//error 注意ev_loop_destroy与ev_loop_new对应28 main_loop=ev_loop_new(EVBACKEND_EPOLL);29 30 ev_cleanup cleanup_watcher;31 ev_init(&cleanup_watcher,cleanup_callback);32 ev_cleanup_start(main_loop,&cleanup_watcher);33 34 ev_timer timer_watcher;35 ev_init(&timer_watcher,timer_callback);36 ev_timer_set(&timer_watcher,0.2,0);37 ev_timer_start(main_loop,&timer_watcher);38 39 atexit(program_exits);40 41 ev_run(main_loop,0);42 43 ev_loop_destroy(main_loop);//在这里就可以调用到cleanup_callback44 printf("END\n");45 return 0;46 }
运行时截图
ev_prepare (每次event loop之前事件)
ev_check (每次event loop之后事件)
1 #include <stdio.h> 2 #include <string.h> 3 #include <unistd.h> 4 #include <stdlib.h> 5 #include <ev.h> 6 7 static void prepare_callback(struct ev_loop *loop,ev_prepare *w,int revents) 8 { 9 printf("Prepare Callback\n");10 }11 12 static void check_callback(struct ev_loop *loop,ev_check *w,int revents)13 {14 printf("Check Callback\n");15 }16 17 static void timer_callback(struct ev_loop *loop,ev_timer *w,int revents)18 {19 printf("Timer Callback\n");20 }21 22 static void sigint_callback(struct ev_loop *loop,ev_signal *w,int revents)23 {24 printf("Sigint Callback\n");25 ev_break(loop,EVBREAK_ALL);26 }27 28 int main(int argc, char **args)29 {30 struct ev_loop *main_loop=ev_default_loop(0);31 32 ev_prepare prepare_watcher;33 ev_check check_watcher;34 ev_timer timer_watcher;35 ev_signal signal_watcher;36 37 ev_prepare_init(&prepare_watcher,prepare_callback);38 ev_check_init(&check_watcher,check_callback);39 ev_timer_init(&timer_watcher,timer_callback,2,0);40 ev_signal_init(&signal_watcher,sigint_callback,SIGINT);41 42 ev_prepare_start(main_loop,&prepare_watcher);43 ev_check_start(main_loop,&check_watcher);44 ev_timer_start(main_loop,&timer_watcher);45 ev_signal_start(main_loop,&signal_watcher);46 47 ev_run(main_loop,0);48 return 0;49 }
运行结果
看前三个为一组，我测试了几次都是这样，Timer Callback的输出都是在Check之后，这个不知道为什么不过后面的捕获SIGINT信号就没有这个问题，SIGINT信号的回调函数的输出是处于Prepare和Check之间。这个就符合预想。还有就是我们输入一个Ctrl-C时，也会触发Prepare-Check的回调函数。这个倒是没有想到，应该是一个ev_signal会向ev_loop里放入两个处理过程，一个是Linux默认的捕获SIGINT信号(signal函数)一个是我们的回调函数，大概是在默认的回调函数中调用我们的回调函数，毕竟捕获信号是系统调用。上面这个是我的猜想(理解)，不一定是正确的。
ev_idle (每次event loop空闲触发事件)
1 #include <stdio.h> 2 #include <string.h> 3 #include <unistd.h> 4 #include <stdlib.h> 5 #include <ev.h> 6 7 ev_idle idle_watcher; 8 int count=0; 9 10 static void timer_callback_start(struct ev_loop *loop,ev_timer *w,int revents)11 {12 printf("Timer Callback Start\n");13 ev_idle_start(loop,&idle_watcher);14 }15 static void timer_callback_stop(struct ev_loop *loop,ev_timer *w,int revents)16 {17 printf("Timer Callback Stop\n");18 ev_idle_stop(loop,&idle_watcher);19 }20 21 static void sigint_callback(struct ev_loop *loop,ev_signal *w,int revents)22 {23 printf("Sigint Callback\n");24 ev_break(loop,EVBREAK_ALL);25 }26 27 static void idle_callback(struct ev_loop *loop,ev_idle *w,int revents)28 {29 count++;30 }31 32 int main(int argc, char **args)33 {34 struct ev_loop *main_loop=ev_default_loop(0);35 36 ev_timer timer_watcher_start;37 ev_timer timer_watcher_stop;38 ev_signal signal_watcher;39 40 ev_idle_init(&idle_watcher,idle_callback);41 ev_timer_init(&timer_watcher_start,timer_callback_start,1,0);42 ev_timer_init(&timer_watcher_stop,timer_callback_stop,3,0);43 ev_signal_init(&signal_watcher,sigint_callback,SIGINT);44 45 ev_timer_start(main_loop,&timer_watcher_start);46 ev_timer_start(main_loop,&timer_watcher_stop);47 ev_signal_start(main_loop,&signal_watcher);48 49 ev_run(main_loop,0);50 51 printf("从第1秒到第3秒之间count计数器的累加到 %d\n",count);52 return 0;53 }
运行结果
我们的idle是可以控制开始和结束的。而这个idle的作用是但event_loop处于空闲的时候，与其在ev_run阻塞等待，不如利用这时的cpu时间来做其他事。应用的话，就是如果服务器繁忙的话就主要处理请求等，如果服务器请求不多时，可以利用cpu时间来处理备份什么的，这样就可以最大限度的利用cpu了。
观察器watcher差不多就这些了，还有个ev_embed这个还不会用。
参考资料: http://wangjunle23.blog.163.com/blog/static/11783817120124308920321/
: http://simohayha.iteye.com/blog/306712
本文地址: http://www.cnblogs.com/wunaozai/p/3955156.html
Socket网络编程--Libev库学习(3)
声明：以上内容来自用户投稿及互联网公开渠道收集整理发布，本网站不拥有所有权，未作人工编辑处理，也不承担相关法律责任，若内容有误或涉及侵权可进行投诉： 投诉/举报 工作人员会在5个工作日内联系你，一经查实，本站将立刻删除涉嫌侵权内容。