libevent源码阅读笔记

struct event_base *base = event_base_new();

struct event *ev1, *ev2;
struct timeval five_seconds = {5,0};

ev1 = event_new(base, fd1, EV_TIMEOUT|EV_READ|EV_PERSIST, cb_func,(char*)"Reading event");
ev2 = event_new(base, fd2, EV_WRITE|EV_PERSIST, cb_func, (char*)"Writing event");

event_add(ev1, &five_seconds);
event_add(ev2, NULL);

event_base_loop(base);

struct event_base {
     /** Function pointers and other data to describe this event_base's
      * backend. */
     const struct eventop *evsel;
     /** Pointer to backend-specific data. */
     void *evbase;

     /** Number of virtual events */
     int virtual_event_count;
     /** Maximum number of virtual events active */
     int virtual_event_count_max;
     /** Number of total events added to this event_base */
     int event_count;
     /** Maximum number of total events added to this event_base */
     int event_count_max;
     /** Number of total events active in this event_base */
     int event_count_active;
     /** Maximum number of total events active in this event_base */
     int event_count_active_max;

     /** Set if we should terminate the loop once we're done processing
      * events. */
     int event_gotterm;
     /** Set if we should terminate the loop immediately */
     int event_break;
     /** Set if we should start a new instance of the loop immediately. */
     int event_continue;

     /** The currently running priority of events */
     int event_running_priority;

     /** Set if we're running the event_base_loop function, to prevent
      * reentrant invocation. */
     int running_loop;

     /** Set to the number of deferred_cbs we've made 'active' in the
      * loop.  This is a hack to prevent starvation; it would be smarter
      * to just use event_config_set_max_dispatch_interval's max_callbacks
      * feature */
     int n_deferreds_queued;

     /* Active event management. */
     /** An array of nactivequeues queues for active event_callbacks (ones
      * that have triggered, and whose callbacks need to be called).  Low
      * priority numbers are more important, and stall higher ones.
      */
     struct evcallback_list *activequeues;
     /** The length of the activequeues array */
     int nactivequeues;
     /** A list of event_callbacks that should become active the next time
      * we process events, but not this time. */
     struct evcallback_list active_later_queue;

     /** Mapping from file descriptors to enabled (added) events */
     struct event_io_map io;

     /** Mapping from signal numbers to enabled (added) events. */
     struct event_signal_map sigmap;

     /** The event whose callback is executing right now */
     struct event_callback *current_event;
};

struct eventop {
     /** The name of this backend. */
     const char *name;
     /** Function to set up an event_base to use this backend.  It should
      * create a new structure holding whatever information is needed to
      * run the backend, and return it.  The returned pointer will get
      * stored by event_init into the event_base.evbase field.  On failure,
      * this function should return NULL. */
     void *(*init)(struct event_base *);
     /** Enable reading/writing on a given fd or signal.  'events' will be
      * the events that we're trying to enable: one or more of EV_READ,
      * EV_WRITE, EV_SIGNAL, and EV_ET.  'old' will be those events that
      * were enabled on this fd previously.  'fdinfo' will be a structure
      * associated with the fd by the evmap; its size is defined by the
      * fdinfo field below.  It will be set to 0 the first time the fd is
      * added.  The function should return 0 on success and -1 on error.
      */
     int (*add)(struct event_base *, evutil_socket_t fd, short old, short events, void *fdinfo);
     /** As "add", except 'events' contains the events we mean to disable. */
     int (*del)(struct event_base *, evutil_socket_t fd, short old, short events, void *fdinfo);
     /** Function to implement the core of an event loop.  It must see which
         added events are ready, and cause event_active to be called for each
         active event (usually via event_io_active or such).  It should
         return 0 on success and -1 on error.
      */
     int (*dispatch)(struct event_base *, struct timeval *);
     /** Function to clean up and free our data from the event_base. */
     void (*dealloc)(struct event_base *);
     /** Flag: set if we need to reinitialize the event base after we fork.
      */
     int need_reinit;
     /** Bit-array of supported event_method_features that this backend can
      * provide. */
     enum event_method_feature features;
     /** Length of the extra information we should record for each fd that
         has one or more active events.  This information is recorded
         as part of the evmap entry for each fd, and passed as an argument
         to the add and del functions above.
      */
     size_t fdinfo_len;
};

struct event_io_map {
     /* An array of evmap_io * or of evmap_signal *; empty entries are
      * set to NULL. */
     void **entries;
     /* The number of entries available in entries */
     int nentries;
};

/** An entry for an evmap_io list: notes all the events that want to read or
     write on a given fd, and the number of each.
  */
struct evmap_io {
     struct event_dlist events;
     ev_uint16_t nread;
     ev_uint16_t nwrite;
     ev_uint16_t nclose;
};

struct epollop {
     struct epoll_event *events;
     int nevents;
     int epfd;
#ifdef USING_TIMERFD
     int timerfd;
#endif
};

typedef union epoll_data {
    void        *ptr;
    int          fd;
    uint32_t     u32;
    uint64_t     u64;
} epoll_data_t;

struct epoll_event {
    uint32_t     events;      /* Epoll events */
    epoll_data_t data;        /* User data variable */
};