struct event {        TAILQ_ENTRY (event) ev_next;  //I/O事件        TAILQ_ENTRY (event) ev_active_next;  //所有激活事件的链表        TAILQ_ENTRY (event) ev_signal_next;  //Signal事件        //定时事件在小根堆中的索引        unsigned int min_heap_idx;      /* for managing timeouts */        struct event_base *ev_base; //event所属的Reactor        int ev_fd; //IO事件：绑定的文件描述符；Signal事件：绑定的信号        short ev_events;  //I/O、信号、定时器        short ev_ncalls;  //调用回调函数的次数        short *ev_pncalls; //指向ev_ncalls      /* Allows deletes in callback */        struct timeval ev_timeout;  //定时事件的超时值        int ev_pri; //event优先级               /* smaller numbers are higher priority */        void (*ev_callback)(int, short, void *arg);  //回调函数:ev_fd, ev_events, ev_arg        void *ev_arg;        int ev_res;             /* result passed to event callback */        int ev_flags;  //event的当前状态};

// event.ev_events#define EV_TIMEOUT      0x01#define EV_READ         0x02#define EV_WRITE        0x04#define EV_SIGNAL       0x08//永久事件#define EV_PERSIST      0x10    /* Persistant event */

// event.ev_flags// event在time堆中#define EVLIST_TIMEOUT  0x01//event在已注册事件链表中#define EVLIST_INSERTED 0x02#define EVLIST_SIGNAL   0x04//event在激活链表中#define EVLIST_ACTIVE   0x08#define EVLIST_INTERNAL 0x10//event已被初始化#define EVLIST_INIT     0x80/* EVLIST_X_ Private space: 0x1000-0xf000 */#define EVLIST_ALL      (0xf000 | 0x9f)

struct event_base {        const struct eventop *evsel;  //I/O多路复用机制的封装,eventops[]数组中一项        void *evbase;  //I/O多路复用机制的一个实例，执行具体任务        int event_count; //该event_base上的总的event            /* counts number of total events */        int event_count_active;  //该event_base上的总的激活的event /* counts number of active events */        int event_gotterm;              /* Set to terminate loop */        int event_break;                /* Set to terminate loop immediately */        /* active event management */        struct event_list **activequeues; //指针数组，activequeues[priority]指向优先级为priority的链表        int nactivequeues;        /* signal handling info */        struct evsignal_info sig;  //管理Signal事件        struct event_list eventqueue; //链表，保存了所有注册事件event的指针        struct timeval event_tv;  //时间管理        struct min_heap timeheap;  //管理定时事件的小根堆        struct timeval tv_cache;  //时间管理};

struct eventop {        const char *name;        void *(*init)(struct event_base *);  //初始化        int (*add)(void *, struct event *);  //注册事件        int (*del)(void *, struct event *);  //删除事件        int (*dispatch)(struct event_base *, void *, struct timeval *);  //事件分发        void (*dealloc)(struct event_base *, void *);  //注销，释放资源        /* set if we need to reinitialize the event base */        int need_reinit;};