… | |
… | |
486 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
486 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
487 | usually a better approach for this kind of thing. |
487 | usually a better approach for this kind of thing. |
488 | |
488 | |
489 | Here are the gory details of what C<ev_loop> does: |
489 | Here are the gory details of what C<ev_loop> does: |
490 | |
490 | |
|
|
491 | - Before the first iteration, call any pending watchers. |
491 | * If there are no active watchers (reference count is zero), return. |
492 | * If there are no active watchers (reference count is zero), return. |
492 | - Queue prepare watchers and then call all outstanding watchers. |
493 | - Queue all prepare watchers and then call all outstanding watchers. |
493 | - If we have been forked, recreate the kernel state. |
494 | - If we have been forked, recreate the kernel state. |
494 | - Update the kernel state with all outstanding changes. |
495 | - Update the kernel state with all outstanding changes. |
495 | - Update the "event loop time". |
496 | - Update the "event loop time". |
496 | - Calculate for how long to block. |
497 | - Calculate for how long to block. |
497 | - Block the process, waiting for any events. |
498 | - Block the process, waiting for any events. |
… | |
… | |
1073 | but on wallclock time (absolute time). You can tell a periodic watcher |
1074 | but on wallclock time (absolute time). You can tell a periodic watcher |
1074 | to trigger "at" some specific point in time. For example, if you tell a |
1075 | to trigger "at" some specific point in time. For example, if you tell a |
1075 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1076 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1076 | + 10.>) and then reset your system clock to the last year, then it will |
1077 | + 10.>) and then reset your system clock to the last year, then it will |
1077 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1078 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1078 | roughly 10 seconds later and of course not if you reset your system time |
1079 | roughly 10 seconds later). |
1079 | again). |
|
|
1080 | |
1080 | |
1081 | They can also be used to implement vastly more complex timers, such as |
1081 | They can also be used to implement vastly more complex timers, such as |
1082 | triggering an event on eahc midnight, local time. |
1082 | triggering an event on each midnight, local time or other, complicated, |
|
|
1083 | rules. |
1083 | |
1084 | |
1084 | As with timers, the callback is guarenteed to be invoked only when the |
1085 | As with timers, the callback is guarenteed to be invoked only when the |
1085 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1086 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1086 | during the same loop iteration then order of execution is undefined. |
1087 | during the same loop iteration then order of execution is undefined. |
1087 | |
1088 | |
… | |
… | |
1094 | Lots of arguments, lets sort it out... There are basically three modes of |
1095 | Lots of arguments, lets sort it out... There are basically three modes of |
1095 | operation, and we will explain them from simplest to complex: |
1096 | operation, and we will explain them from simplest to complex: |
1096 | |
1097 | |
1097 | =over 4 |
1098 | =over 4 |
1098 | |
1099 | |
1099 | =item * absolute timer (interval = reschedule_cb = 0) |
1100 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1100 | |
1101 | |
1101 | In this configuration the watcher triggers an event at the wallclock time |
1102 | In this configuration the watcher triggers an event at the wallclock time |
1102 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1103 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1103 | that is, if it is to be run at January 1st 2011 then it will run when the |
1104 | that is, if it is to be run at January 1st 2011 then it will run when the |
1104 | system time reaches or surpasses this time. |
1105 | system time reaches or surpasses this time. |
1105 | |
1106 | |
1106 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1107 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1107 | |
1108 | |
1108 | In this mode the watcher will always be scheduled to time out at the next |
1109 | In this mode the watcher will always be scheduled to time out at the next |
1109 | C<at + N * interval> time (for some integer N) and then repeat, regardless |
1110 | C<at + N * interval> time (for some integer N, which can also be negative) |
1110 | of any time jumps. |
1111 | and then repeat, regardless of any time jumps. |
1111 | |
1112 | |
1112 | This can be used to create timers that do not drift with respect to system |
1113 | This can be used to create timers that do not drift with respect to system |
1113 | time: |
1114 | time: |
1114 | |
1115 | |
1115 | ev_periodic_set (&periodic, 0., 3600., 0); |
1116 | ev_periodic_set (&periodic, 0., 3600., 0); |
… | |
… | |
1121 | |
1122 | |
1122 | Another way to think about it (for the mathematically inclined) is that |
1123 | Another way to think about it (for the mathematically inclined) is that |
1123 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1124 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1124 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1125 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1125 | |
1126 | |
|
|
1127 | For numerical stability it is preferable that the C<at> value is near |
|
|
1128 | C<ev_now ()> (the current time), but there is no range requirement for |
|
|
1129 | this value. |
|
|
1130 | |
1126 | =item * manual reschedule mode (reschedule_cb = callback) |
1131 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1127 | |
1132 | |
1128 | In this mode the values for C<interval> and C<at> are both being |
1133 | In this mode the values for C<interval> and C<at> are both being |
1129 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1134 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1130 | reschedule callback will be called with the watcher as first, and the |
1135 | reschedule callback will be called with the watcher as first, and the |
1131 | current time as second argument. |
1136 | current time as second argument. |
1132 | |
1137 | |
1133 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1138 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1134 | ever, or make any event loop modifications>. If you need to stop it, |
1139 | ever, or make any event loop modifications>. If you need to stop it, |
1135 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
1140 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
1136 | starting a prepare watcher). |
1141 | starting an C<ev_prepare> watcher, which is legal). |
1137 | |
1142 | |
1138 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1143 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1139 | ev_tstamp now)>, e.g.: |
1144 | ev_tstamp now)>, e.g.: |
1140 | |
1145 | |
1141 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1146 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
… | |
… | |
1163 | |
1168 | |
1164 | Simply stops and restarts the periodic watcher again. This is only useful |
1169 | Simply stops and restarts the periodic watcher again. This is only useful |
1165 | when you changed some parameters or the reschedule callback would return |
1170 | when you changed some parameters or the reschedule callback would return |
1166 | a different time than the last time it was called (e.g. in a crond like |
1171 | a different time than the last time it was called (e.g. in a crond like |
1167 | program when the crontabs have changed). |
1172 | program when the crontabs have changed). |
|
|
1173 | |
|
|
1174 | =item ev_tstamp offset [read-write] |
|
|
1175 | |
|
|
1176 | When repeating, this contains the offset value, otherwise this is the |
|
|
1177 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
|
|
1178 | |
|
|
1179 | Can be modified any time, but changes only take effect when the periodic |
|
|
1180 | timer fires or C<ev_periodic_again> is being called. |
1168 | |
1181 | |
1169 | =item ev_tstamp interval [read-write] |
1182 | =item ev_tstamp interval [read-write] |
1170 | |
1183 | |
1171 | The current interval value. Can be modified any time, but changes only |
1184 | The current interval value. Can be modified any time, but changes only |
1172 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1185 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
… | |
… | |
1481 | with priority higher than or equal to the event loop and one coroutine |
1494 | with priority higher than or equal to the event loop and one coroutine |
1482 | of lower priority, but only once, using idle watchers to keep the event |
1495 | of lower priority, but only once, using idle watchers to keep the event |
1483 | loop from blocking if lower-priority coroutines are active, thus mapping |
1496 | loop from blocking if lower-priority coroutines are active, thus mapping |
1484 | low-priority coroutines to idle/background tasks). |
1497 | low-priority coroutines to idle/background tasks). |
1485 | |
1498 | |
|
|
1499 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
|
|
1500 | priority, to ensure that they are being run before any other watchers |
|
|
1501 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
|
|
1502 | too) should not activate ("feed") events into libev. While libev fully |
|
|
1503 | supports this, they will be called before other C<ev_check> watchers did |
|
|
1504 | their job. As C<ev_check> watchers are often used to embed other event |
|
|
1505 | loops those other event loops might be in an unusable state until their |
|
|
1506 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
|
|
1507 | others). |
|
|
1508 | |
1486 | =over 4 |
1509 | =over 4 |
1487 | |
1510 | |
1488 | =item ev_prepare_init (ev_prepare *, callback) |
1511 | =item ev_prepare_init (ev_prepare *, callback) |
1489 | |
1512 | |
1490 | =item ev_check_init (ev_check *, callback) |
1513 | =item ev_check_init (ev_check *, callback) |
… | |
… | |
1493 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1516 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1494 | macros, but using them is utterly, utterly and completely pointless. |
1517 | macros, but using them is utterly, utterly and completely pointless. |
1495 | |
1518 | |
1496 | =back |
1519 | =back |
1497 | |
1520 | |
1498 | Example: To include a library such as adns, you would add IO watchers |
1521 | There are a number of principal ways to embed other event loops or modules |
1499 | and a timeout watcher in a prepare handler, as required by libadns, and |
1522 | into libev. Here are some ideas on how to include libadns into libev |
|
|
1523 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
|
|
1524 | use for an actually working example. Another Perl module named C<EV::Glib> |
|
|
1525 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
|
|
1526 | into the Glib event loop). |
|
|
1527 | |
|
|
1528 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1500 | in a check watcher, destroy them and call into libadns. What follows is |
1529 | and in a check watcher, destroy them and call into libadns. What follows |
1501 | pseudo-code only of course: |
1530 | is pseudo-code only of course. This requires you to either use a low |
|
|
1531 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
|
|
1532 | the callbacks for the IO/timeout watchers might not have been called yet. |
1502 | |
1533 | |
1503 | static ev_io iow [nfd]; |
1534 | static ev_io iow [nfd]; |
1504 | static ev_timer tw; |
1535 | static ev_timer tw; |
1505 | |
1536 | |
1506 | static void |
1537 | static void |
1507 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1538 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1508 | { |
1539 | { |
1509 | // set the relevant poll flags |
|
|
1510 | // could also call adns_processreadable etc. here |
|
|
1511 | struct pollfd *fd = (struct pollfd *)w->data; |
|
|
1512 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1513 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1514 | } |
1540 | } |
1515 | |
1541 | |
1516 | // create io watchers for each fd and a timer before blocking |
1542 | // create io watchers for each fd and a timer before blocking |
1517 | static void |
1543 | static void |
1518 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1544 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
… | |
… | |
1524 | |
1550 | |
1525 | /* the callback is illegal, but won't be called as we stop during check */ |
1551 | /* the callback is illegal, but won't be called as we stop during check */ |
1526 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1552 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1527 | ev_timer_start (loop, &tw); |
1553 | ev_timer_start (loop, &tw); |
1528 | |
1554 | |
1529 | // create on ev_io per pollfd |
1555 | // create one ev_io per pollfd |
1530 | for (int i = 0; i < nfd; ++i) |
1556 | for (int i = 0; i < nfd; ++i) |
1531 | { |
1557 | { |
1532 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1558 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1533 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1559 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1534 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1560 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1535 | |
1561 | |
1536 | fds [i].revents = 0; |
1562 | fds [i].revents = 0; |
1537 | iow [i].data = fds + i; |
|
|
1538 | ev_io_start (loop, iow + i); |
1563 | ev_io_start (loop, iow + i); |
1539 | } |
1564 | } |
1540 | } |
1565 | } |
1541 | |
1566 | |
1542 | // stop all watchers after blocking |
1567 | // stop all watchers after blocking |
… | |
… | |
1544 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1569 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1545 | { |
1570 | { |
1546 | ev_timer_stop (loop, &tw); |
1571 | ev_timer_stop (loop, &tw); |
1547 | |
1572 | |
1548 | for (int i = 0; i < nfd; ++i) |
1573 | for (int i = 0; i < nfd; ++i) |
|
|
1574 | { |
|
|
1575 | // set the relevant poll flags |
|
|
1576 | // could also call adns_processreadable etc. here |
|
|
1577 | struct pollfd *fd = fds + i; |
|
|
1578 | int revents = ev_clear_pending (iow + i); |
|
|
1579 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1580 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1581 | |
|
|
1582 | // now stop the watcher |
1549 | ev_io_stop (loop, iow + i); |
1583 | ev_io_stop (loop, iow + i); |
|
|
1584 | } |
1550 | |
1585 | |
1551 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1586 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
1587 | } |
|
|
1588 | |
|
|
1589 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
|
|
1590 | in the prepare watcher and would dispose of the check watcher. |
|
|
1591 | |
|
|
1592 | Method 3: If the module to be embedded supports explicit event |
|
|
1593 | notification (adns does), you can also make use of the actual watcher |
|
|
1594 | callbacks, and only destroy/create the watchers in the prepare watcher. |
|
|
1595 | |
|
|
1596 | static void |
|
|
1597 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1598 | { |
|
|
1599 | adns_state ads = (adns_state)w->data; |
|
|
1600 | update_now (EV_A); |
|
|
1601 | |
|
|
1602 | adns_processtimeouts (ads, &tv_now); |
|
|
1603 | } |
|
|
1604 | |
|
|
1605 | static void |
|
|
1606 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1607 | { |
|
|
1608 | adns_state ads = (adns_state)w->data; |
|
|
1609 | update_now (EV_A); |
|
|
1610 | |
|
|
1611 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
1612 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
1613 | } |
|
|
1614 | |
|
|
1615 | // do not ever call adns_afterpoll |
|
|
1616 | |
|
|
1617 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
1618 | want to embed is too inflexible to support it. Instead, youc na override |
|
|
1619 | their poll function. The drawback with this solution is that the main |
|
|
1620 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
|
|
1621 | this. |
|
|
1622 | |
|
|
1623 | static gint |
|
|
1624 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
1625 | { |
|
|
1626 | int got_events = 0; |
|
|
1627 | |
|
|
1628 | for (n = 0; n < nfds; ++n) |
|
|
1629 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
1630 | |
|
|
1631 | if (timeout >= 0) |
|
|
1632 | // create/start timer |
|
|
1633 | |
|
|
1634 | // poll |
|
|
1635 | ev_loop (EV_A_ 0); |
|
|
1636 | |
|
|
1637 | // stop timer again |
|
|
1638 | if (timeout >= 0) |
|
|
1639 | ev_timer_stop (EV_A_ &to); |
|
|
1640 | |
|
|
1641 | // stop io watchers again - their callbacks should have set |
|
|
1642 | for (n = 0; n < nfds; ++n) |
|
|
1643 | ev_io_stop (EV_A_ iow [n]); |
|
|
1644 | |
|
|
1645 | return got_events; |
1552 | } |
1646 | } |
1553 | |
1647 | |
1554 | |
1648 | |
1555 | =head2 C<ev_embed> - when one backend isn't enough... |
1649 | =head2 C<ev_embed> - when one backend isn't enough... |
1556 | |
1650 | |