Example: To include a library such as adns, you would add IO watchers -and a timeout watcher in a prepare handler, as required by libadns, and -in a check watcher, destroy them and call into libadns. What follows is -pseudo-code only of course:
+There are a number of principal ways to embed other event loops or modules
+into libev. Here are some ideas on how to include libadns into libev
+(there is a Perl module named EV::ADNS that does this, which you could
+use for an actually working example. Another Perl module named EV::Glib
+embeds a Glib main context into libev, and finally, Glib::EV embeds EV
+into the Glib event loop).
Method 1: Add IO watchers and a timeout watcher in a prepare handler,
+and in a check watcher, destroy them and call into libadns. What follows
+is pseudo-code only of course. This requires you to either use a low
+priority for the check watcher or use ev_clear_pending explicitly, as
+the callbacks for the IO/timeout watchers might not have been called yet.
static ev_io iow [nfd];
static ev_timer tw;
static void
io_cb (ev_loop *loop, ev_io *w, int revents)
{
- // set the relevant poll flags
- // could also call adns_processreadable etc. here
- struct pollfd *fd = (struct pollfd *)w->data;
- if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
- if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
}
// create io watchers for each fd and a timer before blocking
@@ -1524,7 +1526,7 @@
ev_timer_init (&tw, 0, timeout * 1e-3);
ev_timer_start (loop, &tw);
- // create on ev_io per pollfd
+ // create one ev_io per pollfd
for (int i = 0; i < nfd; ++i)
{
ev_io_init (iow + i, io_cb, fds [i].fd,
@@ -1532,7 +1534,6 @@
| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
fds [i].revents = 0;
- iow [i].data = fds + i;
ev_io_start (loop, iow + i);
}
}
@@ -1544,11 +1545,79 @@
ev_timer_stop (loop, &tw);
for (int i = 0; i < nfd; ++i)
- ev_io_stop (loop, iow + i);
+ {
+ // set the relevant poll flags
+ // could also call adns_processreadable etc. here
+ struct pollfd *fd = fds + i;
+ int revents = ev_clear_pending (iow + i);
+ if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
+ if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
+
+ // now stop the watcher
+ ev_io_stop (loop, iow + i);
+ }
adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
}
+
+Method 2: This would be just like method 1, but you run adns_afterpoll
+in the prepare watcher and would dispose of the check watcher.
Method 3: If the module to be embedded supports explicit event +notification (adns does), you can also make use of the actual watcher +callbacks, and only destroy/create the watchers in the prepare watcher.
+ static void
+ timer_cb (EV_P_ ev_timer *w, int revents)
+ {
+ adns_state ads = (adns_state)w->data;
+ update_now (EV_A);
+
+ adns_processtimeouts (ads, &tv_now);
+ }
+
+ static void
+ io_cb (EV_P_ ev_io *w, int revents)
+ {
+ adns_state ads = (adns_state)w->data;
+ update_now (EV_A);
+
+ if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
+ if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
+ }
+
+ // do not ever call adns_afterpoll
+
+
+Method 4: Do not use a prepare or check watcher because the module you
+want to embed is too inflexible to support it. Instead, youc na override
+their poll function. The drawback with this solution is that the main
+loop is now no longer controllable by EV. The Glib::EV module does
+this.
static gint
+ event_poll_func (GPollFD *fds, guint nfds, gint timeout)
+ {
+ int got_events = 0;
+
+ for (n = 0; n < nfds; ++n)
+ // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
+
+ if (timeout >= 0)
+ // create/start timer
+
+ // poll
+ ev_loop (EV_A_ 0);
+
+ // stop timer again
+ if (timeout >= 0)
+ ev_timer_stop (EV_A_ &to);
+
+ // stop io watchers again - their callbacks should have set
+ for (n = 0; n < nfds; ++n)
+ ev_io_stop (EV_A_ iow [n]);
+
+ return got_events;
+ }
+