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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;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Fri Dec 7 20:07:44 2007" /> 9 <meta name="created" content="Sat Dec 8 15:27:35 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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769 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 769 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
770 <dd> 770 <dd>
771 <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
772events 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
773is 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
774<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
775libev (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>
776 </dd> 777 </dd>
777 <dt>callback ev_cb (ev_TYPE *watcher)</dt> 778 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
778 <dd> 779 <dd>
779 <p>Returns the callback currently set on the watcher.</p> 780 <p>Returns the callback currently set on the watcher.</p>
780 </dd> 781 </dd>
… …
795invocation after new events have been received. This is useful, for 796invocation after new events have been received. This is useful, for
796example, to reduce latency after idling, or more often, to bind two 797example, to reduce latency after idling, or more often, to bind two
797watchers 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>
798 <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
799you 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>
800 <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
801always <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>
802 <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
803fine, 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
804or 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>
805 </dd> 820 </dd>
806</dl> 821</dl>
807 822
808 823
809 824
… …
1736the callback model to a model using method callbacks on objects.</p> 1751the callback model to a model using method callbacks on objects.</p>
1737<p>To use it,</p> 1752<p>To use it,</p>
1738<pre> #include &lt;ev++.h&gt; 1753<pre> #include &lt;ev++.h&gt;
1739 1754
1740</pre> 1755</pre>
1741<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1756<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1742and puts all of its definitions (many of them macros) into the global 1757of them macros) into the global namespace. All C++ specific things are
1743namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1758put into the <code>ev</code> namespace. It should support all the same embedding
1744<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1759options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1745<code>EV_MULTIPLICITY</code>.</p> 1760<p>Care has been taken to keep the overhead low. The only data member the C++
1761classes add (compared to plain C-style watchers) is the event loop pointer
1762that the watcher is associated with (or no additional members at all if
1763you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1764<p>Currently, functions, and static and non-static member functions can be
1765used as callbacks. Other types should be easy to add as long as they only
1766need one additional pointer for context. If you need support for other
1767types of functors please contact the author (preferably after implementing
1768it).</p>
1746<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1769<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1747<dl> 1770<dl>
1748 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1771 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1749 <dd> 1772 <dd>
1750 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1773 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1761which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1784which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1762defines by many implementations.</p> 1785defines by many implementations.</p>
1763 <p>All of those classes have these methods:</p> 1786 <p>All of those classes have these methods:</p>
1764 <p> 1787 <p>
1765 <dl> 1788 <dl>
1766 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1789 <dt>ev::TYPE::TYPE ()</dt>
1767 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1790 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1768 <dt>ev::TYPE::~TYPE</dt> 1791 <dt>ev::TYPE::~TYPE</dt>
1769 <dd> 1792 <dd>
1770 <p>The constructor takes a pointer to an object and a method pointer to 1793 <p>The constructor (optionally) takes an event loop to associate the watcher
1771the event handler callback to call in this class. The constructor calls 1794with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1772<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1795 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1773before starting it. If you do not specify a loop then the constructor 1796<code>set</code> method before starting it.</p>
1774automatically associates the default loop with this watcher.</p> 1797 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1798method to set a callback before you can start the watcher.</p>
1799 <p>(The reason why you have to use a method is a limitation in C++ which does
1800not allow explicit template arguments for constructors).</p>
1775 <p>The destructor automatically stops the watcher if it is active.</p> 1801 <p>The destructor automatically stops the watcher if it is active.</p>
1802 </dd>
1803 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1804 <dd>
1805 <p>This method sets the callback method to call. The method has to have a
1806signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1807first argument and the <code>revents</code> as second. The object must be given as
1808parameter and is stored in the <code>data</code> member of the watcher.</p>
1809 <p>This method synthesizes efficient thunking code to call your method from
1810the C callback that libev requires. If your compiler can inline your
1811callback (i.e. it is visible to it at the place of the <code>set</code> call and
1812your compiler is good :), then the method will be fully inlined into the
1813thunking function, making it as fast as a direct C callback.</p>
1814 <p>Example: simple class declaration and watcher initialisation</p>
1815<pre> struct myclass
1816 {
1817 void io_cb (ev::io &amp;w, int revents) { }
1818 }
1819
1820 myclass obj;
1821 ev::io iow;
1822 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1823
1824</pre>
1825 </dd>
1826 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1827 <dd>
1828 <p>Also sets a callback, but uses a static method or plain function as
1829callback. The optional <code>data</code> argument will be stored in the watcher's
1830<code>data</code> member and is free for you to use.</p>
1831 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1832 <p>See the method-<code>set</code> above for more details.</p>
1833 <p>Example:</p>
1834<pre> static void io_cb (ev::io &amp;w, int revents) { }
1835 iow.set &lt;io_cb&gt; ();
1836
1837</pre>
1776 </dd> 1838 </dd>
1777 <dt>w-&gt;set (struct ev_loop *)</dt> 1839 <dt>w-&gt;set (struct ev_loop *)</dt>
1778 <dd> 1840 <dd>
1779 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1841 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1780do this when the watcher is inactive (and not pending either).</p> 1842do this when the watcher is inactive (and not pending either).</p>
1781 </dd> 1843 </dd>
1782 <dt>w-&gt;set ([args])</dt> 1844 <dt>w-&gt;set ([args])</dt>
1783 <dd> 1845 <dd>
1784 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1846 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1785called at least once. Unlike the C counterpart, an active watcher gets 1847called at least once. Unlike the C counterpart, an active watcher gets
1786automatically stopped and restarted.</p> 1848automatically stopped and restarted when reconfiguring it with this
1849method.</p>
1787 </dd> 1850 </dd>
1788 <dt>w-&gt;start ()</dt> 1851 <dt>w-&gt;start ()</dt>
1789 <dd> 1852 <dd>
1790 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1853 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1791constructor already takes the loop.</p> 1854constructor already stores the event loop.</p>
1792 </dd> 1855 </dd>
1793 <dt>w-&gt;stop ()</dt> 1856 <dt>w-&gt;stop ()</dt>
1794 <dd> 1857 <dd>
1795 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1858 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1796 </dd> 1859 </dd>
… …
1820 1883
1821 myclass (); 1884 myclass ();
1822 } 1885 }
1823 1886
1824 myclass::myclass (int fd) 1887 myclass::myclass (int fd)
1825 : io (this, &amp;myclass::io_cb),
1826 idle (this, &amp;myclass::idle_cb)
1827 { 1888 {
1889 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1890 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1891
1828 io.start (fd, ev::READ); 1892 io.start (fd, ev::READ);
1829 } 1893 }
1830 1894
1831 1895
1832 1896
… …
2239<h1 id="COMPLEXITIES">COMPLEXITIES</h1> 2303<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2240<div id="COMPLEXITIES_CONTENT"> 2304<div id="COMPLEXITIES_CONTENT">
2241 <p>In this section the complexities of (many of) the algorithms used inside 2305 <p>In this section the complexities of (many of) the algorithms used inside
2242libev will be explained. For complexity discussions about backends see the 2306libev will be explained. For complexity discussions about backends see the
2243documentation for <code>ev_default_init</code>.</p> 2307documentation for <code>ev_default_init</code>.</p>
2308 <p>All of the following are about amortised time: If an array needs to be
2309extended, libev needs to realloc and move the whole array, but this
2310happens asymptotically never with higher number of elements, so O(1) might
2311mean it might do a lengthy realloc operation in rare cases, but on average
2312it is much faster and asymptotically approaches constant time.</p>
2244 <p> 2313 <p>
2245 <dl> 2314 <dl>
2246 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2315 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2247 <dd> 2316 <dd>
2248 <p>This means that, when you have a watcher that triggers in one hour and 2317 <p>This means that, when you have a watcher that triggers in one hour and
… …
2254 <p>That means that for changing a timer costs less than removing/adding them 2323 <p>That means that for changing a timer costs less than removing/adding them
2255as only the relative motion in the event queue has to be paid for.</p> 2324as only the relative motion in the event queue has to be paid for.</p>
2256 </dd> 2325 </dd>
2257 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2326 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2258 <dd> 2327 <dd>
2259 <p>These just add the watcher into an array or at the head of a list. If 2328 <p>These just add the watcher into an array or at the head of a list.
2260the array needs to be extended libev needs to realloc and move the whole
2261array, but this happen asymptotically less and less with more watchers,
2262thus amortised O(1).</p>
2263 </dd>
2264 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2329=item Stopping check/prepare/idle watchers: O(1)</p>
2330 </dd>
2265 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> 2331 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2266 <dd> 2332 <dd>
2267 <p>These watchers are stored in lists then need to be walked to find the 2333 <p>These watchers are stored in lists then need to be walked to find the
2268correct watcher to remove. The lists are usually short (you don't usually 2334correct watcher to remove. The lists are usually short (you don't usually
2269have many watchers waiting for the same fd or signal).</p> 2335have many watchers waiting for the same fd or signal).</p>

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