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Diffstat (limited to 'ev.html')
| -rw-r--r-- | ev.html | 95 |
1 files changed, 82 insertions, 13 deletions
@@ -6,7 +6,7 @@ <meta name="description" content="Pod documentation for libev" /> <meta name="inputfile" content="<standard input>" /> <meta name="outputfile" content="<standard output>" /> - <meta name="created" content="Sat Dec 8 15:31:35 2007" /> + <meta name="created" content="Sat Dec 8 16:30:24 2007" /> <meta name="generator" content="Pod::Xhtml 1.57" /> <link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> <body> @@ -1494,21 +1494,23 @@ parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check macros, but using them is utterly, utterly and completely pointless.</p> </dd> </dl> -<p>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:</p> +<p>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 <code>EV::ADNS</code> that does this, which you could +use for an actually working example. Another Perl module named <code>EV::Glib</code> +embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV +into the Glib event loop).</p> +<p>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 <code>ev_clear_pending</code> explicitly, as +the callbacks for the IO/timeout watchers might not have been called yet.</p> <pre> 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 @@ pseudo-code only of course:</p> 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 @@ pseudo-code only of course:</p> | (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 @@ pseudo-code only of course:</p> 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)); } +</pre> +<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code> +in the prepare watcher and would dispose of the check watcher.</p> +<p>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.</p> +<pre> 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 + +</pre> +<p>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 <code>Glib::EV</code> module does +this.</p> +<pre> 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; + } + |