libev loop_init分析

尼玛 C语言学不好真是桑心呐！

看了libev的代码有一种想死的感觉，但是还是要硬着头皮看下去，一定看完！

/* initialise a loop structure, must be zero-initialised */

static void loop_init ( unsigned int flags)

{

  if (!loop->backend)

    {

      origflags = flags;

#if EV_USE_REALTIME

      if (!have_realtime)

        {

          struct timespec ts;

          if (!clock_gettime (CLOCK_REALTIME, &ts))

            have_realtime = ;

        }

#endif

#if EV_USE_MONOTONIC

      if (!have_monotonic)

        {

          struct timespec ts;

          if (!clock_gettime (CLOCK_MONOTONIC, &ts))

            have_monotonic = ;

        }

#endif

      /* pid check not overridable via env */

#ifndef _WIN32

      if (flags & EVFLAG_FORKCHECK)

        curpid = getpid ();

#endif

      if (!(flags & EVFLAG_NOENV)

          && !enable_secure ()

          && getenv ("LIBEV_FLAGS"))

        flags = atoi (getenv ("LIBEV_FLAGS"));

      ev_rt_now          = ev_time ();

      mn_now             = get_clock ();

      now_floor          = mn_now;

      rtmn_diff          = ev_rt_now - mn_now;

#if EV_FEATURE_API

      invoke_cb          = ev_invoke_pending;

#endif

      io_blocktime       = .;

      timeout_blocktime  = .;

      backend            = ;

      backend_fd         = -;

      sig_pending        = ;

#if EV_ASYNC_ENABLE

      async_pending      = ;

#endif

      pipe_write_skipped = ;

      pipe_write_wanted  = ;

      evpipe []         = -;

      evpipe []         = -;

#if EV_USE_INOTIFY

      fs_fd              = flags & EVFLAG_NOINOTIFY ? - : -;

#endif

#if EV_USE_SIGNALFD

      sigfd              = flags & EVFLAG_SIGNALFD  ? - : -;

#endif

      if (!(flags & EVBACKEND_MASK))

        flags |= ev_recommended_backends ();

#if EV_USE_IOCP

      if (!backend && (flags & EVBACKEND_IOCP  )) backend = iocp_init   (EV_A_ flags);

#endif

#if EV_USE_PORT

      if (!backend && (flags & EVBACKEND_PORT  )) backend = port_init   (EV_A_ flags);

#endif

#if EV_USE_KQUEUE

      if (!backend && (flags & EVBACKEND_KQUEUE)) backend = kqueue_init (EV_A_ flags);

#endif

#if EV_USE_EPOLL

      if (!backend && (flags & EVBACKEND_EPOLL )) backend = epoll_init  (EV_A_ flags);

#endif

#if EV_USE_POLL

      if (!backend && (flags & EVBACKEND_POLL  )) backend = poll_init   (EV_A_ flags);

#endif

#if EV_USE_SELECT

      if (!backend && (flags & EVBACKEND_SELECT)) backend = select_init (EV_A_ flags);

#endif

      ev_prepare_init (&pending_w, pendingcb);

#if EV_SIGNAL_ENABLE || EV_ASYNC_ENABLE

      ev_init (&pipe_w, pipecb);

      ev_set_priority (&pipe_w, EV_MAXPRI);

#endif

    }

}

主要就是初始化loop中的数据成员，其中最重要的是backend的初始化，比如win32选择IOCP，Select等，获取当前时间等。

void *event_init (void)

{

#if EV_MULTIPLICITY //定义多线程，就是可以有多个loop

  if (ev_x_cur)

    ev_x_cur = (struct event_base *)ev_loop_new (EVFLAG_AUTO);

  else

    ev_x_cur = (struct event_base *)ev_default_loop (EVFLAG_AUTO);

#else

  assert (("libev: multiple event bases not supported when not compiled with EV_MULTIPLICITY", !ev_x_cur));

  ev_x_cur = (struct event_base *)(long)ev_default_loop (EVFLAG_AUTO);

#endif

  return ev_x_cur;

}

其中ev_default_loop就是把一个全局的static loop赋给ev_default_loop_ptr，然后返回。这样就可以全局用define的东东调来调去，好不羞涩。

ev_loop_new就new出来一个loop并对loop进行初始化。

ok，第一步完成！