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5 | <title>libev</title> |
5 | <title>libev</title> |
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14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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119 | </pre> |
119 | </pre> |
120 | |
120 | |
121 | </div> |
121 | </div> |
122 | <h1 id="DESCRIPTION">DESCRIPTION</h1> |
122 | <h1 id="DESCRIPTION">DESCRIPTION</h1> |
123 | <div id="DESCRIPTION_CONTENT"> |
123 | <div id="DESCRIPTION_CONTENT"> |
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124 | <p>The newest version of this document is also available as a html-formatted |
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125 | web page you might find easier to navigate when reading it for the first |
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126 | time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p> |
124 | <p>Libev is an event loop: you register interest in certain events (such as a |
127 | <p>Libev is an event loop: you register interest in certain events (such as a |
125 | file descriptor being readable or a timeout occuring), and it will manage |
128 | file descriptor being readable or a timeout occuring), and it will manage |
126 | these event sources and provide your program with events.</p> |
129 | these event sources and provide your program with events.</p> |
127 | <p>To do this, it must take more or less complete control over your process |
130 | <p>To do this, it must take more or less complete control over your process |
128 | (or thread) by executing the <i>event loop</i> handler, and will then |
131 | (or thread) by executing the <i>event loop</i> handler, and will then |
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526 | 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 |
527 | external event in conjunction with something not expressible using other |
530 | external event in conjunction with something not expressible using other |
528 | 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 |
529 | usually a better approach for this kind of thing.</p> |
532 | usually a better approach for this kind of thing.</p> |
530 | <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. |
531 | <pre> * If there are no active watchers (reference count is zero), return. |
535 | * If there are no active watchers (reference count is zero), return. |
532 | - Queue prepare watchers and then call all outstanding watchers. |
536 | - Queue all prepare watchers and then call all outstanding watchers. |
533 | - If we have been forked, recreate the kernel state. |
537 | - If we have been forked, recreate the kernel state. |
534 | - Update the kernel state with all outstanding changes. |
538 | - Update the kernel state with all outstanding changes. |
535 | - Update the "event loop time". |
539 | - Update the "event loop time". |
536 | - Calculate for how long to block. |
540 | - Calculate for how long to block. |
537 | - Block the process, waiting for any events. |
541 | - Block the process, waiting for any events. |
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766 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
770 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
767 | <dd> |
771 | <dd> |
768 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
772 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
769 | events but its callback has not yet been invoked). As long as a watcher |
773 | events but its callback has not yet been invoked). As long as a watcher |
770 | is pending (but not active) you must not call an init function on it (but |
774 | is pending (but not active) you must not call an init function on it (but |
771 | <code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to |
775 | <code>ev_TYPE_set</code> is safe), you must not change its priority, and you must |
772 | libev (e.g. you cnanot <code>free ()</code> it).</p> |
776 | make sure the watcher is available to libev (e.g. you cannot <code>free ()</code> |
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777 | it).</p> |
773 | </dd> |
778 | </dd> |
774 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
779 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
775 | <dd> |
780 | <dd> |
776 | <p>Returns the callback currently set on the watcher.</p> |
781 | <p>Returns the callback currently set on the watcher.</p> |
777 | </dd> |
782 | </dd> |
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792 | invocation after new events have been received. This is useful, for |
797 | invocation after new events have been received. This is useful, for |
793 | example, to reduce latency after idling, or more often, to bind two |
798 | example, to reduce latency after idling, or more often, to bind two |
794 | watchers on the same event and make sure one is called first.</p> |
799 | watchers on the same event and make sure one is called first.</p> |
795 | <p>If you need to suppress invocation when higher priority events are pending |
800 | <p>If you need to suppress invocation when higher priority events are pending |
796 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
801 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
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802 | <p>You <i>must not</i> change the priority of a watcher as long as it is active or |
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803 | pending.</p> |
797 | <p>The default priority used by watchers when no priority has been set is |
804 | <p>The default priority used by watchers when no priority has been set is |
798 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
805 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
799 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
806 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
800 | fine, as long as you do not mind that the priority value you query might |
807 | fine, as long as you do not mind that the priority value you query might |
801 | or might not have been adjusted to be within valid range.</p> |
808 | or might not have been adjusted to be within valid range.</p> |
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809 | </dd> |
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810 | <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt> |
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811 | <dd> |
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812 | <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither |
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813 | <code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback |
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814 | can deal with that fact.</p> |
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815 | </dd> |
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816 | <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt> |
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817 | <dd> |
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818 | <p>If the watcher is pending, this function returns clears its pending status |
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819 | and returns its <code>revents</code> bitset (as if its callback was invoked). If the |
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820 | watcher isn't pending it does nothing and returns <code>0</code>.</p> |
802 | </dd> |
821 | </dd> |
803 | </dl> |
822 | </dl> |
804 | |
823 | |
805 | |
824 | |
806 | |
825 | |
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1465 | are ready to run (it's actually more complicated: it only runs coroutines |
1484 | are ready to run (it's actually more complicated: it only runs coroutines |
1466 | with priority higher than or equal to the event loop and one coroutine |
1485 | with priority higher than or equal to the event loop and one coroutine |
1467 | of lower priority, but only once, using idle watchers to keep the event |
1486 | of lower priority, but only once, using idle watchers to keep the event |
1468 | loop from blocking if lower-priority coroutines are active, thus mapping |
1487 | loop from blocking if lower-priority coroutines are active, thus mapping |
1469 | low-priority coroutines to idle/background tasks).</p> |
1488 | low-priority coroutines to idle/background tasks).</p> |
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1489 | <p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>) |
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1490 | priority, to ensure that they are being run before any other watchers |
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1491 | after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers, |
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1492 | too) should not activate ("feed") events into libev. While libev fully |
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1493 | supports this, they will be called before other <code>ev_check</code> watchers did |
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1494 | their job. As <code>ev_check</code> watchers are often used to embed other event |
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1495 | loops those other event loops might be in an unusable state until their |
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1496 | <code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with |
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1497 | others).</p> |
1470 | <dl> |
1498 | <dl> |
1471 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1499 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1472 | <dt>ev_check_init (ev_check *, callback)</dt> |
1500 | <dt>ev_check_init (ev_check *, callback)</dt> |
1473 | <dd> |
1501 | <dd> |
1474 | <p>Initialises and configures the prepare or check watcher - they have no |
1502 | <p>Initialises and configures the prepare or check watcher - they have no |
1475 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1503 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1476 | macros, but using them is utterly, utterly and completely pointless.</p> |
1504 | macros, but using them is utterly, utterly and completely pointless.</p> |
1477 | </dd> |
1505 | </dd> |
1478 | </dl> |
1506 | </dl> |
1479 | <p>Example: To include a library such as adns, you would add IO watchers |
1507 | <p>There are a number of principal ways to embed other event loops or modules |
1480 | and a timeout watcher in a prepare handler, as required by libadns, and |
1508 | into libev. Here are some ideas on how to include libadns into libev |
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1509 | (there is a Perl module named <code>EV::ADNS</code> that does this, which you could |
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1510 | use for an actually working example. Another Perl module named <code>EV::Glib</code> |
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1511 | embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV |
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1512 | into the Glib event loop).</p> |
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1513 | <p>Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1481 | in a check watcher, destroy them and call into libadns. What follows is |
1514 | and in a check watcher, destroy them and call into libadns. What follows |
1482 | pseudo-code only of course:</p> |
1515 | is pseudo-code only of course. This requires you to either use a low |
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1516 | priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as |
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1517 | the callbacks for the IO/timeout watchers might not have been called yet.</p> |
1483 | <pre> static ev_io iow [nfd]; |
1518 | <pre> static ev_io iow [nfd]; |
1484 | static ev_timer tw; |
1519 | static ev_timer tw; |
1485 | |
1520 | |
1486 | static void |
1521 | static void |
1487 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1522 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1488 | { |
1523 | { |
1489 | // set the relevant poll flags |
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1490 | // could also call adns_processreadable etc. here |
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1491 | struct pollfd *fd = (struct pollfd *)w->data; |
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1492 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
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1493 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
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1494 | } |
1524 | } |
1495 | |
1525 | |
1496 | // create io watchers for each fd and a timer before blocking |
1526 | // create io watchers for each fd and a timer before blocking |
1497 | static void |
1527 | static void |
1498 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1528 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
… | |
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1504 | |
1534 | |
1505 | /* the callback is illegal, but won't be called as we stop during check */ |
1535 | /* the callback is illegal, but won't be called as we stop during check */ |
1506 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1536 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1507 | ev_timer_start (loop, &tw); |
1537 | ev_timer_start (loop, &tw); |
1508 | |
1538 | |
1509 | // create on ev_io per pollfd |
1539 | // create one ev_io per pollfd |
1510 | for (int i = 0; i < nfd; ++i) |
1540 | for (int i = 0; i < nfd; ++i) |
1511 | { |
1541 | { |
1512 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1542 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1513 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1543 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1514 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1544 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1515 | |
1545 | |
1516 | fds [i].revents = 0; |
1546 | fds [i].revents = 0; |
1517 | iow [i].data = fds + i; |
|
|
1518 | ev_io_start (loop, iow + i); |
1547 | ev_io_start (loop, iow + i); |
1519 | } |
1548 | } |
1520 | } |
1549 | } |
1521 | |
1550 | |
1522 | // stop all watchers after blocking |
1551 | // stop all watchers after blocking |
… | |
… | |
1524 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1553 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1525 | { |
1554 | { |
1526 | ev_timer_stop (loop, &tw); |
1555 | ev_timer_stop (loop, &tw); |
1527 | |
1556 | |
1528 | for (int i = 0; i < nfd; ++i) |
1557 | for (int i = 0; i < nfd; ++i) |
|
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1558 | { |
|
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1559 | // set the relevant poll flags |
|
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1560 | // could also call adns_processreadable etc. here |
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1561 | struct pollfd *fd = fds + i; |
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1562 | int revents = ev_clear_pending (iow + i); |
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1563 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
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1564 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
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1565 | |
|
|
1566 | // now stop the watcher |
1529 | ev_io_stop (loop, iow + i); |
1567 | ev_io_stop (loop, iow + i); |
|
|
1568 | } |
1530 | |
1569 | |
1531 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1570 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
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1571 | } |
|
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1572 | |
|
|
1573 | </pre> |
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1574 | <p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code> |
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1575 | in the prepare watcher and would dispose of the check watcher.</p> |
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1576 | <p>Method 3: If the module to be embedded supports explicit event |
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1577 | notification (adns does), you can also make use of the actual watcher |
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1578 | callbacks, and only destroy/create the watchers in the prepare watcher.</p> |
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1579 | <pre> static void |
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1580 | timer_cb (EV_P_ ev_timer *w, int revents) |
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1581 | { |
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1582 | adns_state ads = (adns_state)w->data; |
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1583 | update_now (EV_A); |
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1584 | |
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1585 | adns_processtimeouts (ads, &tv_now); |
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1586 | } |
|
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1587 | |
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1588 | static void |
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1589 | io_cb (EV_P_ ev_io *w, int revents) |
|
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1590 | { |
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1591 | adns_state ads = (adns_state)w->data; |
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1592 | update_now (EV_A); |
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1593 | |
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1594 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
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1595 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
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1596 | } |
|
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1597 | |
|
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1598 | // do not ever call adns_afterpoll |
|
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1599 | |
|
|
1600 | </pre> |
|
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1601 | <p>Method 4: Do not use a prepare or check watcher because the module you |
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1602 | want to embed is too inflexible to support it. Instead, youc na override |
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1603 | their poll function. The drawback with this solution is that the main |
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1604 | loop is now no longer controllable by EV. The <code>Glib::EV</code> module does |
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1605 | this.</p> |
|
|
1606 | <pre> static gint |
|
|
1607 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
1608 | { |
|
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1609 | int got_events = 0; |
|
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1610 | |
|
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1611 | for (n = 0; n < nfds; ++n) |
|
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1612 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
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1613 | |
|
|
1614 | if (timeout >= 0) |
|
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1615 | // create/start timer |
|
|
1616 | |
|
|
1617 | // poll |
|
|
1618 | ev_loop (EV_A_ 0); |
|
|
1619 | |
|
|
1620 | // stop timer again |
|
|
1621 | if (timeout >= 0) |
|
|
1622 | ev_timer_stop (EV_A_ &to); |
|
|
1623 | |
|
|
1624 | // stop io watchers again - their callbacks should have set |
|
|
1625 | for (n = 0; n < nfds; ++n) |
|
|
1626 | ev_io_stop (EV_A_ iow [n]); |
|
|
1627 | |
|
|
1628 | return got_events; |
1532 | } |
1629 | } |
1533 | |
1630 | |
1534 | |
1631 | |
1535 | |
1632 | |
1536 | |
1633 | |
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1733 | the callback model to a model using method callbacks on objects.</p> |
1830 | the callback model to a model using method callbacks on objects.</p> |
1734 | <p>To use it,</p> |
1831 | <p>To use it,</p> |
1735 | <pre> #include <ev++.h> |
1832 | <pre> #include <ev++.h> |
1736 | |
1833 | |
1737 | </pre> |
1834 | </pre> |
1738 | <p>(it is not installed by default). This automatically includes <cite>ev.h</cite> |
1835 | <p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many |
1739 | and puts all of its definitions (many of them macros) into the global |
1836 | of them macros) into the global namespace. All C++ specific things are |
1740 | namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> |
1837 | put into the <code>ev</code> namespace. It should support all the same embedding |
1741 | <p>It should support all the same embedding options as <cite>ev.h</cite>, most notably |
1838 | options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p> |
1742 | <code>EV_MULTIPLICITY</code>.</p> |
1839 | <p>Care has been taken to keep the overhead low. The only data member the C++ |
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|
1840 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
1841 | that the watcher is associated with (or no additional members at all if |
|
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1842 | you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p> |
|
|
1843 | <p>Currently, functions, and static and non-static member functions can be |
|
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1844 | used as callbacks. Other types should be easy to add as long as they only |
|
|
1845 | need one additional pointer for context. If you need support for other |
|
|
1846 | types of functors please contact the author (preferably after implementing |
|
|
1847 | it).</p> |
1743 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1848 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1744 | <dl> |
1849 | <dl> |
1745 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1850 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1746 | <dd> |
1851 | <dd> |
1747 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
1852 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
… | |
… | |
1758 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1863 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1759 | defines by many implementations.</p> |
1864 | defines by many implementations.</p> |
1760 | <p>All of those classes have these methods:</p> |
1865 | <p>All of those classes have these methods:</p> |
1761 | <p> |
1866 | <p> |
1762 | <dl> |
1867 | <dl> |
1763 | <dt>ev::TYPE::TYPE (object *, object::method *)</dt> |
1868 | <dt>ev::TYPE::TYPE ()</dt> |
1764 | <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> |
1869 | <dt>ev::TYPE::TYPE (struct ev_loop *)</dt> |
1765 | <dt>ev::TYPE::~TYPE</dt> |
1870 | <dt>ev::TYPE::~TYPE</dt> |
1766 | <dd> |
1871 | <dd> |
1767 | <p>The constructor takes a pointer to an object and a method pointer to |
1872 | <p>The constructor (optionally) takes an event loop to associate the watcher |
1768 | the event handler callback to call in this class. The constructor calls |
1873 | with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p> |
1769 | <code>ev_init</code> for you, which means you have to call the <code>set</code> method |
1874 | <p>The constructor calls <code>ev_init</code> for you, which means you have to call the |
1770 | before starting it. If you do not specify a loop then the constructor |
1875 | <code>set</code> method before starting it.</p> |
1771 | automatically associates the default loop with this watcher.</p> |
1876 | <p>It will not set a callback, however: You have to call the templated <code>set</code> |
|
|
1877 | method to set a callback before you can start the watcher.</p> |
|
|
1878 | <p>(The reason why you have to use a method is a limitation in C++ which does |
|
|
1879 | not allow explicit template arguments for constructors).</p> |
1772 | <p>The destructor automatically stops the watcher if it is active.</p> |
1880 | <p>The destructor automatically stops the watcher if it is active.</p> |
|
|
1881 | </dd> |
|
|
1882 | <dt>w->set<class, &class::method> (object *)</dt> |
|
|
1883 | <dd> |
|
|
1884 | <p>This method sets the callback method to call. The method has to have a |
|
|
1885 | signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as |
|
|
1886 | first argument and the <code>revents</code> as second. The object must be given as |
|
|
1887 | parameter and is stored in the <code>data</code> member of the watcher.</p> |
|
|
1888 | <p>This method synthesizes efficient thunking code to call your method from |
|
|
1889 | the C callback that libev requires. If your compiler can inline your |
|
|
1890 | callback (i.e. it is visible to it at the place of the <code>set</code> call and |
|
|
1891 | your compiler is good :), then the method will be fully inlined into the |
|
|
1892 | thunking function, making it as fast as a direct C callback.</p> |
|
|
1893 | <p>Example: simple class declaration and watcher initialisation</p> |
|
|
1894 | <pre> struct myclass |
|
|
1895 | { |
|
|
1896 | void io_cb (ev::io &w, int revents) { } |
|
|
1897 | } |
|
|
1898 | |
|
|
1899 | myclass obj; |
|
|
1900 | ev::io iow; |
|
|
1901 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
1902 | |
|
|
1903 | </pre> |
|
|
1904 | </dd> |
|
|
1905 | <dt>w->set<function> (void *data = 0)</dt> |
|
|
1906 | <dd> |
|
|
1907 | <p>Also sets a callback, but uses a static method or plain function as |
|
|
1908 | callback. The optional <code>data</code> argument will be stored in the watcher's |
|
|
1909 | <code>data</code> member and is free for you to use.</p> |
|
|
1910 | <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &w, int)</code>.</p> |
|
|
1911 | <p>See the method-<code>set</code> above for more details.</p> |
|
|
1912 | <p>Example:</p> |
|
|
1913 | <pre> static void io_cb (ev::io &w, int revents) { } |
|
|
1914 | iow.set <io_cb> (); |
|
|
1915 | |
|
|
1916 | </pre> |
1773 | </dd> |
1917 | </dd> |
1774 | <dt>w->set (struct ev_loop *)</dt> |
1918 | <dt>w->set (struct ev_loop *)</dt> |
1775 | <dd> |
1919 | <dd> |
1776 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1920 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1777 | do this when the watcher is inactive (and not pending either).</p> |
1921 | do this when the watcher is inactive (and not pending either).</p> |
1778 | </dd> |
1922 | </dd> |
1779 | <dt>w->set ([args])</dt> |
1923 | <dt>w->set ([args])</dt> |
1780 | <dd> |
1924 | <dd> |
1781 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1925 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1782 | called at least once. Unlike the C counterpart, an active watcher gets |
1926 | called at least once. Unlike the C counterpart, an active watcher gets |
1783 | automatically stopped and restarted.</p> |
1927 | automatically stopped and restarted when reconfiguring it with this |
|
|
1928 | method.</p> |
1784 | </dd> |
1929 | </dd> |
1785 | <dt>w->start ()</dt> |
1930 | <dt>w->start ()</dt> |
1786 | <dd> |
1931 | <dd> |
1787 | <p>Starts the watcher. Note that there is no <code>loop</code> argument as the |
1932 | <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the |
1788 | constructor already takes the loop.</p> |
1933 | constructor already stores the event loop.</p> |
1789 | </dd> |
1934 | </dd> |
1790 | <dt>w->stop ()</dt> |
1935 | <dt>w->stop ()</dt> |
1791 | <dd> |
1936 | <dd> |
1792 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1937 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1793 | </dd> |
1938 | </dd> |
… | |
… | |
1817 | |
1962 | |
1818 | myclass (); |
1963 | myclass (); |
1819 | } |
1964 | } |
1820 | |
1965 | |
1821 | myclass::myclass (int fd) |
1966 | myclass::myclass (int fd) |
1822 | : io (this, &myclass::io_cb), |
|
|
1823 | idle (this, &myclass::idle_cb) |
|
|
1824 | { |
1967 | { |
|
|
1968 | io .set <myclass, &myclass::io_cb > (this); |
|
|
1969 | idle.set <myclass, &myclass::idle_cb> (this); |
|
|
1970 | |
1825 | io.start (fd, ev::READ); |
1971 | io.start (fd, ev::READ); |
1826 | } |
1972 | } |
1827 | |
1973 | |
1828 | |
1974 | |
1829 | |
1975 | |
… | |
… | |
2109 | <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions |
2255 | <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions |
2110 | will have the <code>struct ev_loop *</code> as first argument, and you can create |
2256 | will have the <code>struct ev_loop *</code> as first argument, and you can create |
2111 | additional independent event loops. Otherwise there will be no support |
2257 | additional independent event loops. Otherwise there will be no support |
2112 | for multiple event loops and there is no first event loop pointer |
2258 | for multiple event loops and there is no first event loop pointer |
2113 | argument. Instead, all functions act on the single default loop.</p> |
2259 | argument. Instead, all functions act on the single default loop.</p> |
|
|
2260 | </dd> |
|
|
2261 | <dt>EV_MINPRI</dt> |
|
|
2262 | <dt>EV_MAXPRI</dt> |
|
|
2263 | <dd> |
|
|
2264 | <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to |
|
|
2265 | <code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can |
|
|
2266 | provide for more priorities by overriding those symbols (usually defined |
|
|
2267 | to be <code>-2</code> and <code>2</code>, respectively).</p> |
|
|
2268 | <p>When doing priority-based operations, libev usually has to linearly search |
|
|
2269 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
2270 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
2271 | fine.</p> |
|
|
2272 | <p>If your embedding app does not need any priorities, defining these both to |
|
|
2273 | <code>0</code> will save some memory and cpu.</p> |
2114 | </dd> |
2274 | </dd> |
2115 | <dt>EV_PERIODIC_ENABLE</dt> |
2275 | <dt>EV_PERIODIC_ENABLE</dt> |
2116 | <dd> |
2276 | <dd> |
2117 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2277 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2118 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
2278 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
… | |
… | |
2222 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2382 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2223 | <div id="COMPLEXITIES_CONTENT"> |
2383 | <div id="COMPLEXITIES_CONTENT"> |
2224 | <p>In this section the complexities of (many of) the algorithms used inside |
2384 | <p>In this section the complexities of (many of) the algorithms used inside |
2225 | libev will be explained. For complexity discussions about backends see the |
2385 | libev will be explained. For complexity discussions about backends see the |
2226 | documentation for <code>ev_default_init</code>.</p> |
2386 | documentation for <code>ev_default_init</code>.</p> |
|
|
2387 | <p>All of the following are about amortised time: If an array needs to be |
|
|
2388 | extended, libev needs to realloc and move the whole array, but this |
|
|
2389 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
2390 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
2391 | it is much faster and asymptotically approaches constant time.</p> |
2227 | <p> |
2392 | <p> |
2228 | <dl> |
2393 | <dl> |
2229 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2394 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
|
|
2395 | <dd> |
|
|
2396 | <p>This means that, when you have a watcher that triggers in one hour and |
|
|
2397 | there are 100 watchers that would trigger before that then inserting will |
|
|
2398 | have to skip those 100 watchers.</p> |
|
|
2399 | </dd> |
2230 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2400 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
|
|
2401 | <dd> |
|
|
2402 | <p>That means that for changing a timer costs less than removing/adding them |
|
|
2403 | as only the relative motion in the event queue has to be paid for.</p> |
|
|
2404 | </dd> |
2231 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2405 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
|
|
2406 | <dd> |
|
|
2407 | <p>These just add the watcher into an array or at the head of a list. |
2232 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2408 | =item Stopping check/prepare/idle watchers: O(1)</p> |
|
|
2409 | </dd> |
2233 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2410 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
|
|
2411 | <dd> |
|
|
2412 | <p>These watchers are stored in lists then need to be walked to find the |
|
|
2413 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
2414 | have many watchers waiting for the same fd or signal).</p> |
|
|
2415 | </dd> |
2234 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2416 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2235 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
2417 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
|
|
2418 | <dd> |
|
|
2419 | <p>A change means an I/O watcher gets started or stopped, which requires |
|
|
2420 | libev to recalculate its status (and possibly tell the kernel).</p> |
|
|
2421 | </dd> |
2236 | <dt>Activating one watcher: O(1)</dt> |
2422 | <dt>Activating one watcher: O(1)</dt> |
|
|
2423 | <dt>Priority handling: O(number_of_priorities)</dt> |
|
|
2424 | <dd> |
|
|
2425 | <p>Priorities are implemented by allocating some space for each |
|
|
2426 | priority. When doing priority-based operations, libev usually has to |
|
|
2427 | linearly search all the priorities.</p> |
|
|
2428 | </dd> |
2237 | </dl> |
2429 | </dl> |
2238 | </p> |
2430 | </p> |
2239 | |
2431 | |
2240 | |
2432 | |
2241 | |
2433 | |