上一篇讲述了eventloop的结构和创建，添加文件事件删除文件事件，派发等等。
而eventloop主要就是调用不同网络模型完成事件监听和派发的。
这一篇主要讲述epoll网络模型，redis是如何封装和调用的
下面是epoll_event的结构
/*epoll_event 结构struct epoll_event{uint32_t events; //epoll_event 要注册的事件类型epoll_data_t data; //User data //联合体用于存储用户要保存的数据}typedef union epoll_data{void * ptr;uint32_t u32;uint64_t u64;int fd; //一般存储accept后生成的socketfd}epoll_data_t*/
Ae_epoll.c文件中回传的数据结构
#include <sys/epoll.h>//该结构用于回传eventLoop->apidatatypedef struct aeApiState {int epfd; //管理epoll事件表的句柄struct epoll_event *events; //epoll events的队列} aeApiState;
Ae_epoll.c中创建epoll句柄
//epoll 创建epfd过程static int aeApiCreate(aeEventLoop *eventLoop) {//开辟存储不同网络模型的数据块aeApiState *state = zmalloc(sizeof(aeApiState));if (!state) return -1;//开辟epoll_event * size 大小的空间，这段空间是连续的state->events = zmalloc(sizeof(struct epoll_event)*eventLoop->setsize);//开辟失败if (!state->events) {zfree(state);return -1;}//创建epfd，最多关注1024个文件描述符state->epfd = epoll_create(1024); /* 1024 is just a hint for the kernel */if (state->epfd == -1) {zfree(state->events);zfree(state);return -1;}// eventLoop->apidata数据回传eventLoop->apidata = state;return 0;}
Ae_epoll.c重新设置events队列大小
//重新设置aeApiState大小static int aeApiResize(aeEventLoop *eventLoop, int setsize) {aeApiState *state = eventLoop->apidata;state->events = zrealloc(state->events, sizeof(struct epoll_event)*setsize);return 0;}
Ae_epoll.c中释放内存和回收
//释放aeApiState和 events 的内存static void aeApiFree(aeEventLoop *eventLoop) {aeApiState *state = eventLoop->apidata;//关闭文件描述符close(state->epfd);//释放events的内存zfree(state->events);//释放aeApiState 的内存zfree(state);}
Ae_epoll.c添加读写事件或者更改读写事件的函数
//epoll 注册事件，读或者写static int aeApiAddEvent(aeEventLoop *eventLoop, int fd, int mask) {//aeEventLopp 的数据域aeApiState *state = eventLoop->apidata;//epoll_event 事件struct epoll_event ee;//aeEventLoop 中注册的文件事件队列标志位如果不是AE_NONE，那么更改，否则添加int op = eventLoop->events[fd].mask == AE_NONE ?EPOLL_CTL_ADD : EPOLL_CTL_MOD;//events读写事件清零ee.events = 0;//aeEventLoop 中注册的文件事件标志位进行融合mask |= eventLoop->events[fd].mask; /* Merge old events *///如果是读事件，那么将epoll_event 注册读事件if (mask & AE_READABLE) ee.events |= EPOLLIN;//如果是写事件，那么将epoll_event 注册写事件if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;ee.data.u64 = 0; /* avoid valgrind warning *///epoll_event 文件描述符ee.data.fd = fd;//将epoll事件注册到epoll的事件表里if (epoll_ctl(state->epfd,op,fd,&ee) == -1) return -1;return 0;}
Ae_epoll.c中删除读写事件的函数
static void aeApiDelEvent(aeEventLoop *eventLoop, int fd, int delmask) {aeApiState *state = eventLoop->apidata;struct epoll_event ee;//这是创建的逆过程//按位去反，按位&,即去掉相应的标志位int mask = eventLoop->events[fd].mask & (~delmask);ee.events = 0;//判断此时文件事件是读if (mask & AE_READABLE) ee.events |= EPOLLIN;//判断此时文件事件是写if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;ee.data.u64 = 0; /* avoid valgrind warning */ee.data.fd = fd;if (mask != AE_NONE) {//更改epoll_event的事件类型epoll_ctl(state->epfd,EPOLL_CTL_MOD,fd,&ee);} else {/* Note, Kernel < 2.6.9 requires a non null event pointer even for* EPOLL_CTL_DEL. *///删除epoll_event 事件epoll_ctl(state->epfd,EPOLL_CTL_DEL,fd,&ee);}}
事件派发函数
//epoll 事件派发static int aeApiPoll(aeEventLoop *eventLoop, struct timeval *tvp) {aeApiState *state = eventLoop->apidata;int retval, numevents = 0;//epoll wait 返回就绪状态的文件描述符，后面的结构体如果为空，那么说明阻塞，不为空表示等待多少秒后返回//下面是man手册的解释//Specifying a timeout of -1 makesepoll_wait(2) wait indefinitely, while specifying//a timeout equal to zero makesepoll_wait(2) to return immediately//even if no events are available (return code equal to zero)retval = epoll_wait(state->epfd,state->events,eventLoop->setsize,tvp ? (tvp->tv_sec*1000 + tvp->tv_usec/1000) : -1);if (retval > 0) {int j;numevents = retval;//轮询处理已经就绪的文件描述符for (j = 0; j < numevents; j++) {int mask = 0;//指针+j，表示每次便宜地址为j*epoll_event个字节struct epoll_event *e = state->events+j;//可读事件if (e->events & EPOLLIN) mask |= AE_READABLE;//可写事件if (e->events & EPOLLOUT) mask |= AE_WRITABLE;//处理错误发送给客户端if (e->events & EPOLLERR) mask |= AE_WRITABLE;//对端正常关闭（程序里close()，shell下kill或ctr+c），//触发EPOLLIN和EPOLLRDHUP，但是不触发EPOLLERR和EPOLLHUP。if (e->events & EPOLLHUP) mask |= AE_WRITABLE;//添加到aeApiState 的就绪事件队列里eventLoop->fired[j].fd = e->data.fd;//就绪时间状态eventLoop->fired[j].mask = mask;}}return numevents;}
//网络模型名字static char *aeApiName(void) {return "epoll";}
以上是封装的epoll结构和解释
