Libevent源码分析—event, event_base

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;
};