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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" /> |
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13 | <div class="pod"> |
13 | <div class="pod"> |
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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766 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
769 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
767 | <dd> |
770 | <dd> |
768 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
771 | <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 |
772 | 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 |
773 | 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 |
774 | <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> |
775 | make sure the watcher is available to libev (e.g. you cannot <code>free ()</code> |
|
|
776 | it).</p> |
773 | </dd> |
777 | </dd> |
774 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
778 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
775 | <dd> |
779 | <dd> |
776 | <p>Returns the callback currently set on the watcher.</p> |
780 | <p>Returns the callback currently set on the watcher.</p> |
777 | </dd> |
781 | </dd> |
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… | |
792 | invocation after new events have been received. This is useful, for |
796 | invocation after new events have been received. This is useful, for |
793 | example, to reduce latency after idling, or more often, to bind two |
797 | 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> |
798 | 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 |
799 | <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> |
800 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
|
|
801 | <p>You <i>must not</i> change the priority of a watcher as long as it is active or |
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802 | pending.</p> |
797 | <p>The default priority used by watchers when no priority has been set is |
803 | <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> |
804 | 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 |
805 | <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 |
806 | 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> |
807 | or might not have been adjusted to be within valid range.</p> |
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|
808 | </dd> |
|
|
809 | <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt> |
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|
810 | <dd> |
|
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811 | <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither |
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812 | <code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback |
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|
813 | can deal with that fact.</p> |
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814 | </dd> |
|
|
815 | <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt> |
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|
816 | <dd> |
|
|
817 | <p>If the watcher is pending, this function returns clears its pending status |
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818 | and returns its <code>revents</code> bitset (as if its callback was invoked). If the |
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819 | watcher isn't pending it does nothing and returns <code>0</code>.</p> |
802 | </dd> |
820 | </dd> |
803 | </dl> |
821 | </dl> |
804 | |
822 | |
805 | |
823 | |
806 | |
824 | |
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1474 | <p>Initialises and configures the prepare or check watcher - they have no |
1492 | <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> |
1493 | 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> |
1494 | macros, but using them is utterly, utterly and completely pointless.</p> |
1477 | </dd> |
1495 | </dd> |
1478 | </dl> |
1496 | </dl> |
1479 | <p>Example: To include a library such as adns, you would add IO watchers |
1497 | <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 |
1498 | into libev. Here are some ideas on how to include libadns into libev |
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1499 | (there is a Perl module named <code>EV::ADNS</code> that does this, which you could |
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1500 | use for an actually working example. Another Perl module named <code>EV::Glib</code> |
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1501 | embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV |
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1502 | into the Glib event loop).</p> |
|
|
1503 | <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 |
1504 | and in a check watcher, destroy them and call into libadns. What follows |
1482 | pseudo-code only of course:</p> |
1505 | is pseudo-code only of course. This requires you to either use a low |
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1506 | priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as |
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1507 | the callbacks for the IO/timeout watchers might not have been called yet.</p> |
1483 | <pre> static ev_io iow [nfd]; |
1508 | <pre> static ev_io iow [nfd]; |
1484 | static ev_timer tw; |
1509 | static ev_timer tw; |
1485 | |
1510 | |
1486 | static void |
1511 | static void |
1487 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1512 | io_cb (ev_loop *loop, ev_io *w, int revents) |
1488 | { |
1513 | { |
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 | } |
1514 | } |
1495 | |
1515 | |
1496 | // create io watchers for each fd and a timer before blocking |
1516 | // create io watchers for each fd and a timer before blocking |
1497 | static void |
1517 | static void |
1498 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1518 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
… | |
… | |
1504 | |
1524 | |
1505 | /* the callback is illegal, but won't be called as we stop during check */ |
1525 | /* the callback is illegal, but won't be called as we stop during check */ |
1506 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1526 | ev_timer_init (&tw, 0, timeout * 1e-3); |
1507 | ev_timer_start (loop, &tw); |
1527 | ev_timer_start (loop, &tw); |
1508 | |
1528 | |
1509 | // create on ev_io per pollfd |
1529 | // create one ev_io per pollfd |
1510 | for (int i = 0; i < nfd; ++i) |
1530 | for (int i = 0; i < nfd; ++i) |
1511 | { |
1531 | { |
1512 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1532 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1513 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1533 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1514 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1534 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1515 | |
1535 | |
1516 | fds [i].revents = 0; |
1536 | fds [i].revents = 0; |
1517 | iow [i].data = fds + i; |
|
|
1518 | ev_io_start (loop, iow + i); |
1537 | ev_io_start (loop, iow + i); |
1519 | } |
1538 | } |
1520 | } |
1539 | } |
1521 | |
1540 | |
1522 | // stop all watchers after blocking |
1541 | // stop all watchers after blocking |
… | |
… | |
1524 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1543 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1525 | { |
1544 | { |
1526 | ev_timer_stop (loop, &tw); |
1545 | ev_timer_stop (loop, &tw); |
1527 | |
1546 | |
1528 | for (int i = 0; i < nfd; ++i) |
1547 | for (int i = 0; i < nfd; ++i) |
|
|
1548 | { |
|
|
1549 | // set the relevant poll flags |
|
|
1550 | // could also call adns_processreadable etc. here |
|
|
1551 | struct pollfd *fd = fds + i; |
|
|
1552 | int revents = ev_clear_pending (iow + i); |
|
|
1553 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1554 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
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1555 | |
|
|
1556 | // now stop the watcher |
1529 | ev_io_stop (loop, iow + i); |
1557 | ev_io_stop (loop, iow + i); |
|
|
1558 | } |
1530 | |
1559 | |
1531 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1560 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
1561 | } |
|
|
1562 | |
|
|
1563 | </pre> |
|
|
1564 | <p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code> |
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1565 | in the prepare watcher and would dispose of the check watcher.</p> |
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1566 | <p>Method 3: If the module to be embedded supports explicit event |
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1567 | notification (adns does), you can also make use of the actual watcher |
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1568 | callbacks, and only destroy/create the watchers in the prepare watcher.</p> |
|
|
1569 | <pre> static void |
|
|
1570 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1571 | { |
|
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1572 | adns_state ads = (adns_state)w->data; |
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1573 | update_now (EV_A); |
|
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1574 | |
|
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1575 | adns_processtimeouts (ads, &tv_now); |
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1576 | } |
|
|
1577 | |
|
|
1578 | static void |
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1579 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1580 | { |
|
|
1581 | adns_state ads = (adns_state)w->data; |
|
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1582 | update_now (EV_A); |
|
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1583 | |
|
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1584 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
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1585 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
1586 | } |
|
|
1587 | |
|
|
1588 | // do not ever call adns_afterpoll |
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1589 | |
|
|
1590 | </pre> |
|
|
1591 | <p>Method 4: Do not use a prepare or check watcher because the module you |
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1592 | want to embed is too inflexible to support it. Instead, youc na override |
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1593 | their poll function. The drawback with this solution is that the main |
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1594 | loop is now no longer controllable by EV. The <code>Glib::EV</code> module does |
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1595 | this.</p> |
|
|
1596 | <pre> static gint |
|
|
1597 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
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1598 | { |
|
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1599 | int got_events = 0; |
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1600 | |
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1601 | for (n = 0; n < nfds; ++n) |
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1602 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
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1603 | |
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1604 | if (timeout >= 0) |
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1605 | // create/start timer |
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1606 | |
|
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1607 | // poll |
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1608 | ev_loop (EV_A_ 0); |
|
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1609 | |
|
|
1610 | // stop timer again |
|
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1611 | if (timeout >= 0) |
|
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1612 | ev_timer_stop (EV_A_ &to); |
|
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1613 | |
|
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1614 | // stop io watchers again - their callbacks should have set |
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1615 | for (n = 0; n < nfds; ++n) |
|
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1616 | ev_io_stop (EV_A_ iow [n]); |
|
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1617 | |
|
|
1618 | return got_events; |
1532 | } |
1619 | } |
1533 | |
1620 | |
1534 | |
1621 | |
1535 | |
1622 | |
1536 | |
1623 | |
… | |
… | |
1733 | the callback model to a model using method callbacks on objects.</p> |
1820 | the callback model to a model using method callbacks on objects.</p> |
1734 | <p>To use it,</p> |
1821 | <p>To use it,</p> |
1735 | <pre> #include <ev++.h> |
1822 | <pre> #include <ev++.h> |
1736 | |
1823 | |
1737 | </pre> |
1824 | </pre> |
1738 | <p>(it is not installed by default). This automatically includes <cite>ev.h</cite> |
1825 | <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 |
1826 | 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> |
1827 | 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 |
1828 | options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p> |
1742 | <code>EV_MULTIPLICITY</code>.</p> |
1829 | <p>Care has been taken to keep the overhead low. The only data member the C++ |
|
|
1830 | classes add (compared to plain C-style watchers) is the event loop pointer |
|
|
1831 | that the watcher is associated with (or no additional members at all if |
|
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1832 | you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p> |
|
|
1833 | <p>Currently, functions, and static and non-static member functions can be |
|
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1834 | used as callbacks. Other types should be easy to add as long as they only |
|
|
1835 | need one additional pointer for context. If you need support for other |
|
|
1836 | types of functors please contact the author (preferably after implementing |
|
|
1837 | it).</p> |
1743 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1838 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1744 | <dl> |
1839 | <dl> |
1745 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1840 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1746 | <dd> |
1841 | <dd> |
1747 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
1842 | <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 |
1853 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1759 | defines by many implementations.</p> |
1854 | defines by many implementations.</p> |
1760 | <p>All of those classes have these methods:</p> |
1855 | <p>All of those classes have these methods:</p> |
1761 | <p> |
1856 | <p> |
1762 | <dl> |
1857 | <dl> |
1763 | <dt>ev::TYPE::TYPE (object *, object::method *)</dt> |
1858 | <dt>ev::TYPE::TYPE ()</dt> |
1764 | <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> |
1859 | <dt>ev::TYPE::TYPE (struct ev_loop *)</dt> |
1765 | <dt>ev::TYPE::~TYPE</dt> |
1860 | <dt>ev::TYPE::~TYPE</dt> |
1766 | <dd> |
1861 | <dd> |
1767 | <p>The constructor takes a pointer to an object and a method pointer to |
1862 | <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 |
1863 | 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 |
1864 | <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 |
1865 | <code>set</code> method before starting it.</p> |
1771 | automatically associates the default loop with this watcher.</p> |
1866 | <p>It will not set a callback, however: You have to call the templated <code>set</code> |
|
|
1867 | method to set a callback before you can start the watcher.</p> |
|
|
1868 | <p>(The reason why you have to use a method is a limitation in C++ which does |
|
|
1869 | not allow explicit template arguments for constructors).</p> |
1772 | <p>The destructor automatically stops the watcher if it is active.</p> |
1870 | <p>The destructor automatically stops the watcher if it is active.</p> |
|
|
1871 | </dd> |
|
|
1872 | <dt>w->set<class, &class::method> (object *)</dt> |
|
|
1873 | <dd> |
|
|
1874 | <p>This method sets the callback method to call. The method has to have a |
|
|
1875 | signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as |
|
|
1876 | first argument and the <code>revents</code> as second. The object must be given as |
|
|
1877 | parameter and is stored in the <code>data</code> member of the watcher.</p> |
|
|
1878 | <p>This method synthesizes efficient thunking code to call your method from |
|
|
1879 | the C callback that libev requires. If your compiler can inline your |
|
|
1880 | callback (i.e. it is visible to it at the place of the <code>set</code> call and |
|
|
1881 | your compiler is good :), then the method will be fully inlined into the |
|
|
1882 | thunking function, making it as fast as a direct C callback.</p> |
|
|
1883 | <p>Example: simple class declaration and watcher initialisation</p> |
|
|
1884 | <pre> struct myclass |
|
|
1885 | { |
|
|
1886 | void io_cb (ev::io &w, int revents) { } |
|
|
1887 | } |
|
|
1888 | |
|
|
1889 | myclass obj; |
|
|
1890 | ev::io iow; |
|
|
1891 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
1892 | |
|
|
1893 | </pre> |
|
|
1894 | </dd> |
|
|
1895 | <dt>w->set<function> (void *data = 0)</dt> |
|
|
1896 | <dd> |
|
|
1897 | <p>Also sets a callback, but uses a static method or plain function as |
|
|
1898 | callback. The optional <code>data</code> argument will be stored in the watcher's |
|
|
1899 | <code>data</code> member and is free for you to use.</p> |
|
|
1900 | <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &w, int)</code>.</p> |
|
|
1901 | <p>See the method-<code>set</code> above for more details.</p> |
|
|
1902 | <p>Example:</p> |
|
|
1903 | <pre> static void io_cb (ev::io &w, int revents) { } |
|
|
1904 | iow.set <io_cb> (); |
|
|
1905 | |
|
|
1906 | </pre> |
1773 | </dd> |
1907 | </dd> |
1774 | <dt>w->set (struct ev_loop *)</dt> |
1908 | <dt>w->set (struct ev_loop *)</dt> |
1775 | <dd> |
1909 | <dd> |
1776 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1910 | <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> |
1911 | do this when the watcher is inactive (and not pending either).</p> |
1778 | </dd> |
1912 | </dd> |
1779 | <dt>w->set ([args])</dt> |
1913 | <dt>w->set ([args])</dt> |
1780 | <dd> |
1914 | <dd> |
1781 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1915 | <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 |
1916 | called at least once. Unlike the C counterpart, an active watcher gets |
1783 | automatically stopped and restarted.</p> |
1917 | automatically stopped and restarted when reconfiguring it with this |
|
|
1918 | method.</p> |
1784 | </dd> |
1919 | </dd> |
1785 | <dt>w->start ()</dt> |
1920 | <dt>w->start ()</dt> |
1786 | <dd> |
1921 | <dd> |
1787 | <p>Starts the watcher. Note that there is no <code>loop</code> argument as the |
1922 | <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the |
1788 | constructor already takes the loop.</p> |
1923 | constructor already stores the event loop.</p> |
1789 | </dd> |
1924 | </dd> |
1790 | <dt>w->stop ()</dt> |
1925 | <dt>w->stop ()</dt> |
1791 | <dd> |
1926 | <dd> |
1792 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1927 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1793 | </dd> |
1928 | </dd> |
… | |
… | |
1817 | |
1952 | |
1818 | myclass (); |
1953 | myclass (); |
1819 | } |
1954 | } |
1820 | |
1955 | |
1821 | myclass::myclass (int fd) |
1956 | myclass::myclass (int fd) |
1822 | : io (this, &myclass::io_cb), |
|
|
1823 | idle (this, &myclass::idle_cb) |
|
|
1824 | { |
1957 | { |
|
|
1958 | io .set <myclass, &myclass::io_cb > (this); |
|
|
1959 | idle.set <myclass, &myclass::idle_cb> (this); |
|
|
1960 | |
1825 | io.start (fd, ev::READ); |
1961 | io.start (fd, ev::READ); |
1826 | } |
1962 | } |
1827 | |
1963 | |
1828 | |
1964 | |
1829 | |
1965 | |
… | |
… | |
2109 | <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions |
2245 | <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 |
2246 | 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 |
2247 | additional independent event loops. Otherwise there will be no support |
2112 | for multiple event loops and there is no first event loop pointer |
2248 | for multiple event loops and there is no first event loop pointer |
2113 | argument. Instead, all functions act on the single default loop.</p> |
2249 | argument. Instead, all functions act on the single default loop.</p> |
|
|
2250 | </dd> |
|
|
2251 | <dt>EV_MINPRI</dt> |
|
|
2252 | <dt>EV_MAXPRI</dt> |
|
|
2253 | <dd> |
|
|
2254 | <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to |
|
|
2255 | <code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can |
|
|
2256 | provide for more priorities by overriding those symbols (usually defined |
|
|
2257 | to be <code>-2</code> and <code>2</code>, respectively).</p> |
|
|
2258 | <p>When doing priority-based operations, libev usually has to linearly search |
|
|
2259 | all the priorities, so having many of them (hundreds) uses a lot of space |
|
|
2260 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
|
|
2261 | fine.</p> |
|
|
2262 | <p>If your embedding app does not need any priorities, defining these both to |
|
|
2263 | <code>0</code> will save some memory and cpu.</p> |
2114 | </dd> |
2264 | </dd> |
2115 | <dt>EV_PERIODIC_ENABLE</dt> |
2265 | <dt>EV_PERIODIC_ENABLE</dt> |
2116 | <dd> |
2266 | <dd> |
2117 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2267 | <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 |
2268 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
… | |
… | |
2222 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2372 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2223 | <div id="COMPLEXITIES_CONTENT"> |
2373 | <div id="COMPLEXITIES_CONTENT"> |
2224 | <p>In this section the complexities of (many of) the algorithms used inside |
2374 | <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 |
2375 | libev will be explained. For complexity discussions about backends see the |
2226 | documentation for <code>ev_default_init</code>.</p> |
2376 | documentation for <code>ev_default_init</code>.</p> |
|
|
2377 | <p>All of the following are about amortised time: If an array needs to be |
|
|
2378 | extended, libev needs to realloc and move the whole array, but this |
|
|
2379 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
2380 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
2381 | it is much faster and asymptotically approaches constant time.</p> |
2227 | <p> |
2382 | <p> |
2228 | <dl> |
2383 | <dl> |
2229 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2384 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
|
|
2385 | <dd> |
|
|
2386 | <p>This means that, when you have a watcher that triggers in one hour and |
|
|
2387 | there are 100 watchers that would trigger before that then inserting will |
|
|
2388 | have to skip those 100 watchers.</p> |
|
|
2389 | </dd> |
2230 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2390 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
|
|
2391 | <dd> |
|
|
2392 | <p>That means that for changing a timer costs less than removing/adding them |
|
|
2393 | as only the relative motion in the event queue has to be paid for.</p> |
|
|
2394 | </dd> |
2231 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2395 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
|
|
2396 | <dd> |
|
|
2397 | <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> |
2398 | =item Stopping check/prepare/idle watchers: O(1)</p> |
|
|
2399 | </dd> |
2233 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2400 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
|
|
2401 | <dd> |
|
|
2402 | <p>These watchers are stored in lists then need to be walked to find the |
|
|
2403 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
2404 | have many watchers waiting for the same fd or signal).</p> |
|
|
2405 | </dd> |
2234 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2406 | <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> |
2407 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
|
|
2408 | <dd> |
|
|
2409 | <p>A change means an I/O watcher gets started or stopped, which requires |
|
|
2410 | libev to recalculate its status (and possibly tell the kernel).</p> |
|
|
2411 | </dd> |
2236 | <dt>Activating one watcher: O(1)</dt> |
2412 | <dt>Activating one watcher: O(1)</dt> |
|
|
2413 | <dt>Priority handling: O(number_of_priorities)</dt> |
|
|
2414 | <dd> |
|
|
2415 | <p>Priorities are implemented by allocating some space for each |
|
|
2416 | priority. When doing priority-based operations, libev usually has to |
|
|
2417 | linearly search all the priorities.</p> |
|
|
2418 | </dd> |
2237 | </dl> |
2419 | </dl> |
2238 | </p> |
2420 | </p> |
2239 | |
2421 | |
2240 | |
2422 | |
2241 | |
2423 | |