/*

    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 

*/

#include <sys/epoll.h>

//该结构用于回传eventLoop->apidata

typedef struct aeApiState {

    int epfd; //管理epoll事件表的句柄

    struct epoll_event *events; //epoll events的队列

} aeApiState;

//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 -;

    //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 -;

    }

    //创建epfd，最多关注1024个文件描述符

    state->epfd = epoll_create(); /* 1024 is just a hint for the kernel */

    if (state->epfd == -) {

        zfree(state->events);

        zfree(state);

        return -;

    }

    // eventLoop->apidata数据回传

    eventLoop->apidata = state;

    return ;

}

//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 ;

}

//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);

}

//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 = ;

    //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 = ; /* 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) == -) return -;

    return ;

}

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 = ;

    //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 = ; /* 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);

    }

}

//epoll 事件派发

static int aeApiPoll(aeEventLoop *eventLoop, struct timeval *tvp) {

    aeApiState *state = eventLoop->apidata;

    int retval, numevents = ;

    //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* + tvp->tv_usec/) : -);

    if (retval > ) {

        int j;

        numevents = retval;

        //轮询处理已经就绪的文件描述符

        for (j = ; j < numevents; j++) {

            int mask = ;

            //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";

}