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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" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
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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">
124<p>The newest version of this document is also available as a html-formatted
125web page you might find easier to navigate when reading it for the first
126time: <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
125file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
126these event sources and provide your program with events.</p> 129these 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
… …
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
769events but its callback has not yet been invoked). As long as a watcher 772events but its callback has not yet been invoked). As long as a watcher
770is pending (but not active) you must not call an init function on it (but 773is 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
772libev (e.g. you cnanot <code>free ()</code> it).</p> 775make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
776it).</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>
… …
792invocation after new events have been received. This is useful, for 796invocation after new events have been received. This is useful, for
793example, to reduce latency after idling, or more often, to bind two 797example, to reduce latency after idling, or more often, to bind two
794watchers on the same event and make sure one is called first.</p> 798watchers 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
796you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> 800you 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
802pending.</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
798always <code>0</code>, which is supposed to not be too high and not be too low :).</p> 804always <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
800fine, as long as you do not mind that the priority value you query might 806fine, as long as you do not mind that the priority value you query might
801or might not have been adjusted to be within valid range.</p> 807or might not have been adjusted to be within valid range.</p>
808 </dd>
809 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
810 <dd>
811 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
812<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
813can deal with that fact.</p>
814 </dd>
815 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
816 <dd>
817 <p>If the watcher is pending, this function returns clears its pending status
818and returns its <code>revents</code> bitset (as if its callback was invoked). If the
819watcher 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
… …
917this situation even with a relatively standard program structure. Thus 935this situation even with a relatively standard program structure. Thus
918it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 936it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
919<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 937<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
920<p>If you cannot run the fd in non-blocking mode (for example you should not 938<p>If you cannot run the fd in non-blocking mode (for example you should not
921play around with an Xlib connection), then you have to seperately re-test 939play around with an Xlib connection), then you have to seperately re-test
922wether a file descriptor is really ready with a known-to-be good interface 940whether a file descriptor is really ready with a known-to-be good interface
923such as poll (fortunately in our Xlib example, Xlib already does this on 941such as poll (fortunately in our Xlib example, Xlib already does this on
924its own, so its quite safe to use).</p> 942its own, so its quite safe to use).</p>
925<dl> 943<dl>
926 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 944 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
927 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 945 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
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
1475parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1493parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1476macros, but using them is utterly, utterly and completely pointless.</p> 1494macros, 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
1480and a timeout watcher in a prepare handler, as required by libadns, and 1498into libev. Here are some ideas on how to include libadns into libev
1499(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1500use for an actually working example. Another Perl module named <code>EV::Glib</code>
1501embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1502into the Glib event loop).</p>
1503<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1481in a check watcher, destroy them and call into libadns. What follows is 1504and in a check watcher, destroy them and call into libadns. What follows
1482pseudo-code only of course:</p> 1505is pseudo-code only of course. This requires you to either use a low
1506priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1507the 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
1490 // could also call adns_processreadable etc. here
1491 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1492 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1493 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
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 (&amp;tw, 0, timeout * 1e-3); 1526 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1507 ev_timer_start (loop, &amp;tw); 1527 ev_timer_start (loop, &amp;tw);
1508 1528
1509 // create on ev_io per pollfd 1529 // create one ev_io per pollfd
1510 for (int i = 0; i &lt; nfd; ++i) 1530 for (int i = 0; i &lt; 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 &amp; POLLIN ? EV_READ : 0) 1533 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1514 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1534 | (fds [i].events &amp; 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, &amp;tw); 1545 ev_timer_stop (loop, &amp;tw);
1527 1546
1528 for (int i = 0; i &lt; nfd; ++i) 1547 for (int i = 0; i &lt; 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 &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1554 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
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>
1565in the prepare watcher and would dispose of the check watcher.</p>
1566<p>Method 3: If the module to be embedded supports explicit event
1567notification (adns does), you can also make use of the actual watcher
1568callbacks, 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 {
1572 adns_state ads = (adns_state)w-&gt;data;
1573 update_now (EV_A);
1574
1575 adns_processtimeouts (ads, &amp;tv_now);
1576 }
1577
1578 static void
1579 io_cb (EV_P_ ev_io *w, int revents)
1580 {
1581 adns_state ads = (adns_state)w-&gt;data;
1582 update_now (EV_A);
1583
1584 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1585 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1586 }
1587
1588 // do not ever call adns_afterpoll
1589
1590</pre>
1591<p>Method 4: Do not use a prepare or check watcher because the module you
1592want to embed is too inflexible to support it. Instead, youc na override
1593their poll function. The drawback with this solution is that the main
1594loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1595this.</p>
1596<pre> static gint
1597 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1598 {
1599 int got_events = 0;
1600
1601 for (n = 0; n &lt; nfds; ++n)
1602 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1603
1604 if (timeout &gt;= 0)
1605 // create/start timer
1606
1607 // poll
1608 ev_loop (EV_A_ 0);
1609
1610 // stop timer again
1611 if (timeout &gt;= 0)
1612 ev_timer_stop (EV_A_ &amp;to);
1613
1614 // stop io watchers again - their callbacks should have set
1615 for (n = 0; n &lt; nfds; ++n)
1616 ev_io_stop (EV_A_ iow [n]);
1617
1618 return got_events;
1532 } 1619 }
1533 1620
1534 1621
1535 1622
1536 1623
… …
1733the callback model to a model using method callbacks on objects.</p> 1820the 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 &lt;ev++.h&gt; 1822<pre> #include &lt;ev++.h&gt;
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
1739and puts all of its definitions (many of them macros) into the global 1826of them macros) into the global namespace. All C++ specific things are
1740namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1827put 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 1828options 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++
1830classes add (compared to plain C-style watchers) is the event loop pointer
1831that the watcher is associated with (or no additional members at all if
1832you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1833<p>Currently, functions, and static and non-static member functions can be
1834used as callbacks. Other types should be easy to add as long as they only
1835need one additional pointer for context. If you need support for other
1836types of functors please contact the author (preferably after implementing
1837it).</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.
… …
1758which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1853which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1759defines by many implementations.</p> 1854defines 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
1768the event handler callback to call in this class. The constructor calls 1863with. 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
1770before starting it. If you do not specify a loop then the constructor 1865<code>set</code> method before starting it.</p>
1771automatically 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>
1867method 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
1869not 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-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1873 <dd>
1874 <p>This method sets the callback method to call. The method has to have a
1875signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1876first argument and the <code>revents</code> as second. The object must be given as
1877parameter 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
1879the C callback that libev requires. If your compiler can inline your
1880callback (i.e. it is visible to it at the place of the <code>set</code> call and
1881your compiler is good :), then the method will be fully inlined into the
1882thunking 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 &amp;w, int revents) { }
1887 }
1888
1889 myclass obj;
1890 ev::io iow;
1891 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1892
1893</pre>
1894 </dd>
1895 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1896 <dd>
1897 <p>Also sets a callback, but uses a static method or plain function as
1898callback. 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 &amp;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 &amp;w, int revents) { }
1904 iow.set &lt;io_cb&gt; ();
1905
1906</pre>
1773 </dd> 1907 </dd>
1774 <dt>w-&gt;set (struct ev_loop *)</dt> 1908 <dt>w-&gt;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
1777do this when the watcher is inactive (and not pending either).</p> 1911do this when the watcher is inactive (and not pending either).</p>
1778 </dd> 1912 </dd>
1779 <dt>w-&gt;set ([args])</dt> 1913 <dt>w-&gt;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
1782called at least once. Unlike the C counterpart, an active watcher gets 1916called at least once. Unlike the C counterpart, an active watcher gets
1783automatically stopped and restarted.</p> 1917automatically stopped and restarted when reconfiguring it with this
1918method.</p>
1784 </dd> 1919 </dd>
1785 <dt>w-&gt;start ()</dt> 1920 <dt>w-&gt;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
1788constructor already takes the loop.</p> 1923constructor already stores the event loop.</p>
1789 </dd> 1924 </dd>
1790 <dt>w-&gt;stop ()</dt> 1925 <dt>w-&gt;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, &amp;myclass::io_cb),
1823 idle (this, &amp;myclass::idle_cb)
1824 { 1957 {
1958 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1959 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1960
1825 io.start (fd, ev::READ); 1961 io.start (fd, ev::READ);
1826 } 1962 }
1827 1963
1828 1964
1829 1965
… …
1832 1968
1833</div> 1969</div>
1834<h1 id="MACRO_MAGIC">MACRO MAGIC</h1> 1970<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1835<div id="MACRO_MAGIC_CONTENT"> 1971<div id="MACRO_MAGIC_CONTENT">
1836<p>Libev can be compiled with a variety of options, the most fundemantal is 1972<p>Libev can be compiled with a variety of options, the most fundemantal is
1837<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 1973<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1838callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1974callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1839<p>To make it easier to write programs that cope with either variant, the 1975<p>To make it easier to write programs that cope with either variant, the
1840following macros are defined:</p> 1976following macros are defined:</p>
1841<dl> 1977<dl>
1842 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1978 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1872 <p>Similar to the other two macros, this gives you the value of the default 2008 <p>Similar to the other two macros, this gives you the value of the default
1873loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 2009loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1874 </dd> 2010 </dd>
1875</dl> 2011</dl>
1876<p>Example: Declare and initialise a check watcher, utilising the above 2012<p>Example: Declare and initialise a check watcher, utilising the above
1877macros so it will work regardless of wether multiple loops are supported 2013macros so it will work regardless of whether multiple loops are supported
1878or not.</p> 2014or not.</p>
1879<pre> static void 2015<pre> static void
1880 check_cb (EV_P_ ev_timer *w, int revents) 2016 check_cb (EV_P_ ev_timer *w, int revents)
1881 { 2017 {
1882 ev_check_stop (EV_A_ w); 2018 ev_check_stop (EV_A_ w);
… …
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
2110will have the <code>struct ev_loop *</code> as first argument, and you can create 2246will have the <code>struct ev_loop *</code> as first argument, and you can create
2111additional independent event loops. Otherwise there will be no support 2247additional independent event loops. Otherwise there will be no support
2112for multiple event loops and there is no first event loop pointer 2248for multiple event loops and there is no first event loop pointer
2113argument. Instead, all functions act on the single default loop.</p> 2249argument. 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
2256provide for more priorities by overriding those symbols (usually defined
2257to be <code>-2</code> and <code>2</code>, respectively).</p>
2258 <p>When doing priority-based operations, libev usually has to linearly search
2259all the priorities, so having many of them (hundreds) uses a lot of space
2260and time, so using the defaults of five priorities (-2 .. +2) is usually
2261fine.</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
2118defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2268defined 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
2225libev will be explained. For complexity discussions about backends see the 2375libev will be explained. For complexity discussions about backends see the
2226documentation for <code>ev_default_init</code>.</p> 2376documentation for <code>ev_default_init</code>.</p>
2377 <p>All of the following are about amortised time: If an array needs to be
2378extended, libev needs to realloc and move the whole array, but this
2379happens asymptotically never with higher number of elements, so O(1) might
2380mean it might do a lengthy realloc operation in rare cases, but on average
2381it 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
2387there are 100 watchers that would trigger before that then inserting will
2388have 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
2393as 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
2403correct watcher to remove. The lists are usually short (you don't usually
2404have 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
2410libev 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
2416priority. When doing priority-based operations, libev usually has to
2417linearly search all the priorities.</p>
2418 </dd>
2237 </dl> 2419 </dl>
2238 </p> 2420 </p>
2239 2421
2240 2422
2241 2423

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