… | |
… | |
4 | <head> |
4 | <head> |
5 | <title>libev</title> |
5 | <title>libev</title> |
6 | <meta name="description" content="Pod documentation for libev" /> |
6 | <meta name="description" content="Pod documentation for libev" /> |
7 | <meta name="inputfile" content="<standard input>" /> |
7 | <meta name="inputfile" content="<standard input>" /> |
8 | <meta name="outputfile" content="<standard output>" /> |
8 | <meta name="outputfile" content="<standard output>" /> |
9 | <meta name="created" content="Sat Dec 8 15:27:35 2007" /> |
9 | <meta name="created" content="Sun Dec 9 20:30:11 2007" /> |
10 | <meta name="generator" content="Pod::Xhtml 1.57" /> |
10 | <meta name="generator" content="Pod::Xhtml 1.57" /> |
11 | <link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> |
11 | <link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> |
12 | <body> |
12 | <body> |
13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
… | |
… | |
529 | one iteration of the loop. This is useful if you are waiting for some |
529 | one iteration of the loop. This is useful if you are waiting for some |
530 | external event in conjunction with something not expressible using other |
530 | external event in conjunction with something not expressible using other |
531 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
531 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
532 | usually a better approach for this kind of thing.</p> |
532 | usually a better approach for this kind of thing.</p> |
533 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
533 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
|
|
534 | <pre> - Before the first iteration, call any pending watchers. |
534 | <pre> * If there are no active watchers (reference count is zero), return. |
535 | * If there are no active watchers (reference count is zero), return. |
535 | - Queue prepare watchers and then call all outstanding watchers. |
536 | - Queue all prepare watchers and then call all outstanding watchers. |
536 | - If we have been forked, recreate the kernel state. |
537 | - If we have been forked, recreate the kernel state. |
537 | - Update the kernel state with all outstanding changes. |
538 | - Update the kernel state with all outstanding changes. |
538 | - Update the "event loop time". |
539 | - Update the "event loop time". |
539 | - Calculate for how long to block. |
540 | - Calculate for how long to block. |
540 | - Block the process, waiting for any events. |
541 | - Block the process, waiting for any events. |
… | |
… | |
1096 | but on wallclock time (absolute time). You can tell a periodic watcher |
1097 | but on wallclock time (absolute time). You can tell a periodic watcher |
1097 | to trigger "at" some specific point in time. For example, if you tell a |
1098 | to trigger "at" some specific point in time. For example, if you tell a |
1098 | periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () |
1099 | periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () |
1099 | + 10.</code>) and then reset your system clock to the last year, then it will |
1100 | + 10.</code>) and then reset your system clock to the last year, then it will |
1100 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
1101 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
1101 | roughly 10 seconds later and of course not if you reset your system time |
1102 | roughly 10 seconds later).</p> |
1102 | again).</p> |
|
|
1103 | <p>They can also be used to implement vastly more complex timers, such as |
1103 | <p>They can also be used to implement vastly more complex timers, such as |
1104 | triggering an event on eahc midnight, local time.</p> |
1104 | triggering an event on each midnight, local time or other, complicated, |
|
|
1105 | rules.</p> |
1105 | <p>As with timers, the callback is guarenteed to be invoked only when the |
1106 | <p>As with timers, the callback is guarenteed to be invoked only when the |
1106 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
1107 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
1107 | during the same loop iteration then order of execution is undefined.</p> |
1108 | during the same loop iteration then order of execution is undefined.</p> |
1108 | <dl> |
1109 | <dl> |
1109 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
1110 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
… | |
… | |
1111 | <dd> |
1112 | <dd> |
1112 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
1113 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
1113 | operation, and we will explain them from simplest to complex:</p> |
1114 | operation, and we will explain them from simplest to complex:</p> |
1114 | <p> |
1115 | <p> |
1115 | <dl> |
1116 | <dl> |
1116 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
1117 | <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt> |
1117 | <dd> |
1118 | <dd> |
1118 | <p>In this configuration the watcher triggers an event at the wallclock time |
1119 | <p>In this configuration the watcher triggers an event at the wallclock time |
1119 | <code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, |
1120 | <code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, |
1120 | that is, if it is to be run at January 1st 2011 then it will run when the |
1121 | that is, if it is to be run at January 1st 2011 then it will run when the |
1121 | system time reaches or surpasses this time.</p> |
1122 | system time reaches or surpasses this time.</p> |
1122 | </dd> |
1123 | </dd> |
1123 | <dt>* non-repeating interval timer (interval > 0, reschedule_cb = 0)</dt> |
1124 | <dt>* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)</dt> |
1124 | <dd> |
1125 | <dd> |
1125 | <p>In this mode the watcher will always be scheduled to time out at the next |
1126 | <p>In this mode the watcher will always be scheduled to time out at the next |
1126 | <code>at + N * interval</code> time (for some integer N) and then repeat, regardless |
1127 | <code>at + N * interval</code> time (for some integer N, which can also be negative) |
1127 | of any time jumps.</p> |
1128 | and then repeat, regardless of any time jumps.</p> |
1128 | <p>This can be used to create timers that do not drift with respect to system |
1129 | <p>This can be used to create timers that do not drift with respect to system |
1129 | time:</p> |
1130 | time:</p> |
1130 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
1131 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
1131 | |
1132 | |
1132 | </pre> |
1133 | </pre> |
… | |
… | |
1135 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1136 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1136 | by 3600.</p> |
1137 | by 3600.</p> |
1137 | <p>Another way to think about it (for the mathematically inclined) is that |
1138 | <p>Another way to think about it (for the mathematically inclined) is that |
1138 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
1139 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
1139 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
1140 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
|
|
1141 | <p>For numerical stability it is preferable that the <code>at</code> value is near |
|
|
1142 | <code>ev_now ()</code> (the current time), but there is no range requirement for |
|
|
1143 | this value.</p> |
1140 | </dd> |
1144 | </dd> |
1141 | <dt>* manual reschedule mode (reschedule_cb = callback)</dt> |
1145 | <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt> |
1142 | <dd> |
1146 | <dd> |
1143 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
1147 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
1144 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1148 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1145 | reschedule callback will be called with the watcher as first, and the |
1149 | reschedule callback will be called with the watcher as first, and the |
1146 | current time as second argument.</p> |
1150 | current time as second argument.</p> |
1147 | <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
1151 | <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
1148 | ever, or make any event loop modifications</i>. If you need to stop it, |
1152 | ever, or make any event loop modifications</i>. If you need to stop it, |
1149 | return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
1153 | return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
1150 | starting a prepare watcher).</p> |
1154 | starting an <code>ev_prepare</code> watcher, which is legal).</p> |
1151 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1155 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1152 | ev_tstamp now)</code>, e.g.:</p> |
1156 | ev_tstamp now)</code>, e.g.:</p> |
1153 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1157 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1154 | { |
1158 | { |
1155 | return now + 60.; |
1159 | return now + 60.; |
… | |
… | |
1175 | <dd> |
1179 | <dd> |
1176 | <p>Simply stops and restarts the periodic watcher again. This is only useful |
1180 | <p>Simply stops and restarts the periodic watcher again. This is only useful |
1177 | when you changed some parameters or the reschedule callback would return |
1181 | when you changed some parameters or the reschedule callback would return |
1178 | a different time than the last time it was called (e.g. in a crond like |
1182 | a different time than the last time it was called (e.g. in a crond like |
1179 | program when the crontabs have changed).</p> |
1183 | program when the crontabs have changed).</p> |
|
|
1184 | </dd> |
|
|
1185 | <dt>ev_tstamp offset [read-write]</dt> |
|
|
1186 | <dd> |
|
|
1187 | <p>When repeating, this contains the offset value, otherwise this is the |
|
|
1188 | absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p> |
|
|
1189 | <p>Can be modified any time, but changes only take effect when the periodic |
|
|
1190 | timer fires or <code>ev_periodic_again</code> is being called.</p> |
1180 | </dd> |
1191 | </dd> |
1181 | <dt>ev_tstamp interval [read-write]</dt> |
1192 | <dt>ev_tstamp interval [read-write]</dt> |
1182 | <dd> |
1193 | <dd> |
1183 | <p>The current interval value. Can be modified any time, but changes only |
1194 | <p>The current interval value. Can be modified any time, but changes only |
1184 | take effect when the periodic timer fires or <code>ev_periodic_again</code> is being |
1195 | take effect when the periodic timer fires or <code>ev_periodic_again</code> is being |
… | |
… | |
1483 | are ready to run (it's actually more complicated: it only runs coroutines |
1494 | are ready to run (it's actually more complicated: it only runs coroutines |
1484 | with priority higher than or equal to the event loop and one coroutine |
1495 | with priority higher than or equal to the event loop and one coroutine |
1485 | of lower priority, but only once, using idle watchers to keep the event |
1496 | of lower priority, but only once, using idle watchers to keep the event |
1486 | loop from blocking if lower-priority coroutines are active, thus mapping |
1497 | loop from blocking if lower-priority coroutines are active, thus mapping |
1487 | low-priority coroutines to idle/background tasks).</p> |
1498 | low-priority coroutines to idle/background tasks).</p> |
|
|
1499 | <p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>) |
|
|
1500 | priority, to ensure that they are being run before any other watchers |
|
|
1501 | after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers, |
|
|
1502 | too) should not activate ("feed") events into libev. While libev fully |
|
|
1503 | supports this, they will be called before other <code>ev_check</code> watchers did |
|
|
1504 | their job. As <code>ev_check</code> watchers are often used to embed other event |
|
|
1505 | loops those other event loops might be in an unusable state until their |
|
|
1506 | <code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with |
|
|
1507 | others).</p> |
1488 | <dl> |
1508 | <dl> |
1489 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1509 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1490 | <dt>ev_check_init (ev_check *, callback)</dt> |
1510 | <dt>ev_check_init (ev_check *, callback)</dt> |
1491 | <dd> |
1511 | <dd> |
1492 | <p>Initialises and configures the prepare or check watcher - they have no |
1512 | <p>Initialises and configures the prepare or check watcher - they have no |
1493 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1513 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1494 | macros, but using them is utterly, utterly and completely pointless.</p> |
1514 | macros, but using them is utterly, utterly and completely pointless.</p> |
1495 | </dd> |
1515 | </dd> |
1496 | </dl> |
1516 | </dl> |
1497 | <p>Example: To include a library such as adns, you would add IO watchers |
1517 | <p>There are a number of principal ways to embed other event loops or modules |
1498 | and a timeout watcher in a prepare handler, as required by libadns, and |
1518 | into libev. Here are some ideas on how to include libadns into libev |
|
|
1519 | (there is a Perl module named <code>EV::ADNS</code> that does this, which you could |
|
|
1520 | use for an actually working example. Another Perl module named <code>EV::Glib</code> |
|
|
1521 | embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV |
|
|
1522 | into the Glib event loop).</p> |
|
|
1523 | <p>Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1499 | in a check watcher, destroy them and call into libadns. What follows is |
1524 | and in a check watcher, destroy them and call into libadns. What follows |
1500 | pseudo-code only of course:</p> |
1525 | is pseudo-code only of course. This requires you to either use a low |
|
|
1526 | priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as |
|
|
1527 | the callbacks for the IO/timeout watchers might not have been called yet.</p> |
1501 | <pre> static ev_io iow [nfd]; |
1528 | <pre> static ev_io iow [nfd]; |
1502 | static ev_timer tw; |
1529 | static ev_timer tw; |
1503 | |
1530 | |
1504 | static void |
1531 | static void |
1505 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1532 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1506 | { |
1533 | { |
1507 | // set the relevant poll flags |
|
|
1508 | // could also call adns_processreadable etc. here |
|
|
1509 | struct pollfd *fd = (struct pollfd *)w->data; |
|
|
1510 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1511 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1512 | } |
1534 | } |
1513 | |
1535 | |
1514 | // create io watchers for each fd and a timer before blocking |
1536 | // create io watchers for each fd and a timer before blocking |
1515 | static void |
1537 | static void |
1516 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1538 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
… | |
… | |
1522 | |
1544 | |
1523 | /* the callback is illegal, but won't be called as we stop during check */ |
1545 | /* the callback is illegal, but won't be called as we stop during check */ |
1524 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1546 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1525 | ev_timer_start (loop, &tw); |
1547 | ev_timer_start (loop, &tw); |
1526 | |
1548 | |
1527 | // create on ev_io per pollfd |
1549 | // create one ev_io per pollfd |
1528 | for (int i = 0; i < nfd; ++i) |
1550 | for (int i = 0; i < nfd; ++i) |
1529 | { |
1551 | { |
1530 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1552 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1531 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1553 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1532 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1554 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1533 | |
1555 | |
1534 | fds [i].revents = 0; |
1556 | fds [i].revents = 0; |
1535 | iow [i].data = fds + i; |
|
|
1536 | ev_io_start (loop, iow + i); |
1557 | ev_io_start (loop, iow + i); |
1537 | } |
1558 | } |
1538 | } |
1559 | } |
1539 | |
1560 | |
1540 | // stop all watchers after blocking |
1561 | // stop all watchers after blocking |
… | |
… | |
1542 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1563 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1543 | { |
1564 | { |
1544 | ev_timer_stop (loop, &tw); |
1565 | ev_timer_stop (loop, &tw); |
1545 | |
1566 | |
1546 | for (int i = 0; i < nfd; ++i) |
1567 | for (int i = 0; i < nfd; ++i) |
|
|
1568 | { |
|
|
1569 | // set the relevant poll flags |
|
|
1570 | // could also call adns_processreadable etc. here |
|
|
1571 | struct pollfd *fd = fds + i; |
|
|
1572 | int revents = ev_clear_pending (iow + i); |
|
|
1573 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1574 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1575 | |
|
|
1576 | // now stop the watcher |
1547 | ev_io_stop (loop, iow + i); |
1577 | ev_io_stop (loop, iow + i); |
|
|
1578 | } |
1548 | |
1579 | |
1549 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1580 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
1581 | } |
|
|
1582 | |
|
|
1583 | </pre> |
|
|
1584 | <p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code> |
|
|
1585 | in the prepare watcher and would dispose of the check watcher.</p> |
|
|
1586 | <p>Method 3: If the module to be embedded supports explicit event |
|
|
1587 | notification (adns does), you can also make use of the actual watcher |
|
|
1588 | callbacks, and only destroy/create the watchers in the prepare watcher.</p> |
|
|
1589 | <pre> static void |
|
|
1590 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1591 | { |
|
|
1592 | adns_state ads = (adns_state)w->data; |
|
|
1593 | update_now (EV_A); |
|
|
1594 | |
|
|
1595 | adns_processtimeouts (ads, &tv_now); |
|
|
1596 | } |
|
|
1597 | |
|
|
1598 | static void |
|
|
1599 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1600 | { |
|
|
1601 | adns_state ads = (adns_state)w->data; |
|
|
1602 | update_now (EV_A); |
|
|
1603 | |
|
|
1604 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
1605 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
1606 | } |
|
|
1607 | |
|
|
1608 | // do not ever call adns_afterpoll |
|
|
1609 | |
|
|
1610 | </pre> |
|
|
1611 | <p>Method 4: Do not use a prepare or check watcher because the module you |
|
|
1612 | want to embed is too inflexible to support it. Instead, youc na override |
|
|
1613 | their poll function. The drawback with this solution is that the main |
|
|
1614 | loop is now no longer controllable by EV. The <code>Glib::EV</code> module does |
|
|
1615 | this.</p> |
|
|
1616 | <pre> static gint |
|
|
1617 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
1618 | { |
|
|
1619 | int got_events = 0; |
|
|
1620 | |
|
|
1621 | for (n = 0; n < nfds; ++n) |
|
|
1622 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
1623 | |
|
|
1624 | if (timeout >= 0) |
|
|
1625 | // create/start timer |
|
|
1626 | |
|
|
1627 | // poll |
|
|
1628 | ev_loop (EV_A_ 0); |
|
|
1629 | |
|
|
1630 | // stop timer again |
|
|
1631 | if (timeout >= 0) |
|
|
1632 | ev_timer_stop (EV_A_ &to); |
|
|
1633 | |
|
|
1634 | // stop io watchers again - their callbacks should have set |
|
|
1635 | for (n = 0; n < nfds; ++n) |
|
|
1636 | ev_io_stop (EV_A_ iow [n]); |
|
|
1637 | |
|
|
1638 | return got_events; |
1550 | } |
1639 | } |
1551 | |
1640 | |
1552 | |
1641 | |
1553 | |
1642 | |
1554 | |
1643 | |