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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="<standard input>" /> |
7 | <meta name="inputfile" content="<standard input>" /> |
8 | <meta name="outputfile" content="<standard output>" /> |
8 | <meta name="outputfile" content="<standard output>" /> |
9 | <meta name="created" content="Fri Dec 7 17:49:47 2007" /> |
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12 | <body> |
12 | <body> |
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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917 | this situation even with a relatively standard program structure. Thus |
920 | this situation even with a relatively standard program structure. Thus |
918 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
921 | it 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> |
922 | <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 |
923 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
921 | play around with an Xlib connection), then you have to seperately re-test |
924 | play around with an Xlib connection), then you have to seperately re-test |
922 | wether a file descriptor is really ready with a known-to-be good interface |
925 | whether a file descriptor is really ready with a known-to-be good interface |
923 | such as poll (fortunately in our Xlib example, Xlib already does this on |
926 | such as poll (fortunately in our Xlib example, Xlib already does this on |
924 | its own, so its quite safe to use).</p> |
927 | its own, so its quite safe to use).</p> |
925 | <dl> |
928 | <dl> |
926 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
929 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
927 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
930 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
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1733 | the callback model to a model using method callbacks on objects.</p> |
1736 | the callback model to a model using method callbacks on objects.</p> |
1734 | <p>To use it,</p> |
1737 | <p>To use it,</p> |
1735 | <pre> #include <ev++.h> |
1738 | <pre> #include <ev++.h> |
1736 | |
1739 | |
1737 | </pre> |
1740 | </pre> |
1738 | <p>(it is not installed by default). This automatically includes <cite>ev.h</cite> |
1741 | <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 |
1742 | 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> |
1743 | 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 |
1744 | options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p> |
1742 | <code>EV_MULTIPLICITY</code>.</p> |
1745 | <p>Care has been taken to keep the overhead low. The only data member the C++ |
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1746 | classes add (compared to plain C-style watchers) is the event loop pointer |
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1747 | that the watcher is associated with (or no additional members at all if |
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1748 | you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p> |
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1749 | <p>Currently, functions, and static and non-static member functions can be |
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1750 | used as callbacks. Other types should be easy to add as long as they only |
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1751 | need one additional pointer for context. If you need support for other |
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1752 | types of functors please contact the author (preferably after implementing |
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1753 | it).</p> |
1743 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1754 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1744 | <dl> |
1755 | <dl> |
1745 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1756 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1746 | <dd> |
1757 | <dd> |
1747 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
1758 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
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1758 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1769 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1759 | defines by many implementations.</p> |
1770 | defines by many implementations.</p> |
1760 | <p>All of those classes have these methods:</p> |
1771 | <p>All of those classes have these methods:</p> |
1761 | <p> |
1772 | <p> |
1762 | <dl> |
1773 | <dl> |
1763 | <dt>ev::TYPE::TYPE (object *, object::method *)</dt> |
1774 | <dt>ev::TYPE::TYPE ()</dt> |
1764 | <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> |
1775 | <dt>ev::TYPE::TYPE (struct ev_loop *)</dt> |
1765 | <dt>ev::TYPE::~TYPE</dt> |
1776 | <dt>ev::TYPE::~TYPE</dt> |
1766 | <dd> |
1777 | <dd> |
1767 | <p>The constructor takes a pointer to an object and a method pointer to |
1778 | <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 |
1779 | 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 |
1780 | <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 |
1781 | <code>set</code> method before starting it.</p> |
1771 | automatically associates the default loop with this watcher.</p> |
1782 | <p>It will not set a callback, however: You have to call the templated <code>set</code> |
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1783 | method to set a callback before you can start the watcher.</p> |
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1784 | <p>(The reason why you have to use a method is a limitation in C++ which does |
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1785 | not allow explicit template arguments for constructors).</p> |
1772 | <p>The destructor automatically stops the watcher if it is active.</p> |
1786 | <p>The destructor automatically stops the watcher if it is active.</p> |
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1787 | </dd> |
|
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1788 | <dt>w->set<class, &class::method> (object *)</dt> |
|
|
1789 | <dd> |
|
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1790 | <p>This method sets the callback method to call. The method has to have a |
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1791 | signature of <code>void (*)(ev_TYPE &, int)</code>, it receives the watcher as |
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1792 | first argument and the <code>revents</code> as second. The object must be given as |
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1793 | parameter and is stored in the <code>data</code> member of the watcher.</p> |
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1794 | <p>This method synthesizes efficient thunking code to call your method from |
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1795 | the C callback that libev requires. If your compiler can inline your |
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1796 | callback (i.e. it is visible to it at the place of the <code>set</code> call and |
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1797 | your compiler is good :), then the method will be fully inlined into the |
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1798 | thunking function, making it as fast as a direct C callback.</p> |
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1799 | <p>Example: simple class declaration and watcher initialisation</p> |
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1800 | <pre> struct myclass |
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1801 | { |
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1802 | void io_cb (ev::io &w, int revents) { } |
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1803 | } |
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1804 | |
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1805 | myclass obj; |
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1806 | ev::io iow; |
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1807 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
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1808 | |
|
|
1809 | </pre> |
|
|
1810 | </dd> |
|
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1811 | <dt>w->set (void (*function)(watcher &w, int), void *data = 0)</dt> |
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1812 | <dd> |
|
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1813 | <p>Also sets a callback, but uses a static method or plain function as |
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1814 | callback. The optional <code>data</code> argument will be stored in the watcher's |
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1815 | <code>data</code> member and is free for you to use.</p> |
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1816 | <p>See the method-<code>set</code> above for more details.</p> |
1773 | </dd> |
1817 | </dd> |
1774 | <dt>w->set (struct ev_loop *)</dt> |
1818 | <dt>w->set (struct ev_loop *)</dt> |
1775 | <dd> |
1819 | <dd> |
1776 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1820 | <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> |
1821 | do this when the watcher is inactive (and not pending either).</p> |
1778 | </dd> |
1822 | </dd> |
1779 | <dt>w->set ([args])</dt> |
1823 | <dt>w->set ([args])</dt> |
1780 | <dd> |
1824 | <dd> |
1781 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1825 | <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 |
1826 | called at least once. Unlike the C counterpart, an active watcher gets |
1783 | automatically stopped and restarted.</p> |
1827 | automatically stopped and restarted when reconfiguring it with this |
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1828 | method.</p> |
1784 | </dd> |
1829 | </dd> |
1785 | <dt>w->start ()</dt> |
1830 | <dt>w->start ()</dt> |
1786 | <dd> |
1831 | <dd> |
1787 | <p>Starts the watcher. Note that there is no <code>loop</code> argument as the |
1832 | <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the |
1788 | constructor already takes the loop.</p> |
1833 | constructor already stores the event loop.</p> |
1789 | </dd> |
1834 | </dd> |
1790 | <dt>w->stop ()</dt> |
1835 | <dt>w->stop ()</dt> |
1791 | <dd> |
1836 | <dd> |
1792 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1837 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1793 | </dd> |
1838 | </dd> |
… | |
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1817 | |
1862 | |
1818 | myclass (); |
1863 | myclass (); |
1819 | } |
1864 | } |
1820 | |
1865 | |
1821 | myclass::myclass (int fd) |
1866 | myclass::myclass (int fd) |
1822 | : io (this, &myclass::io_cb), |
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1823 | idle (this, &myclass::idle_cb) |
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1824 | { |
1867 | { |
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1868 | io .set <myclass, &myclass::io_cb > (this); |
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1869 | idle.set <myclass, &myclass::idle_cb> (this); |
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1870 | |
1825 | io.start (fd, ev::READ); |
1871 | io.start (fd, ev::READ); |
1826 | } |
1872 | } |
1827 | |
1873 | |
1828 | |
1874 | |
1829 | |
1875 | |
… | |
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1832 | |
1878 | |
1833 | </div> |
1879 | </div> |
1834 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1880 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1835 | <div id="MACRO_MAGIC_CONTENT"> |
1881 | <div id="MACRO_MAGIC_CONTENT"> |
1836 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
1882 | <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 |
1883 | <code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and |
1838 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1884 | callbacks 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 |
1885 | <p>To make it easier to write programs that cope with either variant, the |
1840 | following macros are defined:</p> |
1886 | following macros are defined:</p> |
1841 | <dl> |
1887 | <dl> |
1842 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
1888 | <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 |
1918 | <p>Similar to the other two macros, this gives you the value of the default |
1873 | loop, if multiple loops are supported ("ev loop default").</p> |
1919 | loop, if multiple loops are supported ("ev loop default").</p> |
1874 | </dd> |
1920 | </dd> |
1875 | </dl> |
1921 | </dl> |
1876 | <p>Example: Declare and initialise a check watcher, utilising the above |
1922 | <p>Example: Declare and initialise a check watcher, utilising the above |
1877 | macros so it will work regardless of wether multiple loops are supported |
1923 | macros so it will work regardless of whether multiple loops are supported |
1878 | or not.</p> |
1924 | or not.</p> |
1879 | <pre> static void |
1925 | <pre> static void |
1880 | check_cb (EV_P_ ev_timer *w, int revents) |
1926 | check_cb (EV_P_ ev_timer *w, int revents) |
1881 | { |
1927 | { |
1882 | ev_check_stop (EV_A_ w); |
1928 | ev_check_stop (EV_A_ w); |
… | |
… | |
2109 | <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions |
2155 | <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 |
2156 | 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 |
2157 | additional independent event loops. Otherwise there will be no support |
2112 | for multiple event loops and there is no first event loop pointer |
2158 | for multiple event loops and there is no first event loop pointer |
2113 | argument. Instead, all functions act on the single default loop.</p> |
2159 | argument. Instead, all functions act on the single default loop.</p> |
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2160 | </dd> |
|
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2161 | <dt>EV_MINPRI</dt> |
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2162 | <dt>EV_MAXPRI</dt> |
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2163 | <dd> |
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2164 | <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to |
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2165 | <code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can |
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2166 | provide for more priorities by overriding those symbols (usually defined |
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2167 | to be <code>-2</code> and <code>2</code>, respectively).</p> |
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2168 | <p>When doing priority-based operations, libev usually has to linearly search |
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2169 | all the priorities, so having many of them (hundreds) uses a lot of space |
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2170 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
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2171 | fine.</p> |
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2172 | <p>If your embedding app does not need any priorities, defining these both to |
|
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2173 | <code>0</code> will save some memory and cpu.</p> |
2114 | </dd> |
2174 | </dd> |
2115 | <dt>EV_PERIODIC_ENABLE</dt> |
2175 | <dt>EV_PERIODIC_ENABLE</dt> |
2116 | <dd> |
2176 | <dd> |
2117 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2177 | <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 |
2178 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
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2222 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2282 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2223 | <div id="COMPLEXITIES_CONTENT"> |
2283 | <div id="COMPLEXITIES_CONTENT"> |
2224 | <p>In this section the complexities of (many of) the algorithms used inside |
2284 | <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 |
2285 | libev will be explained. For complexity discussions about backends see the |
2226 | documentation for <code>ev_default_init</code>.</p> |
2286 | documentation for <code>ev_default_init</code>.</p> |
|
|
2287 | <p>All of the following are about amortised time: If an array needs to be |
|
|
2288 | extended, libev needs to realloc and move the whole array, but this |
|
|
2289 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
2290 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
2291 | it is much faster and asymptotically approaches constant time.</p> |
2227 | <p> |
2292 | <p> |
2228 | <dl> |
2293 | <dl> |
2229 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2294 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
|
|
2295 | <dd> |
|
|
2296 | <p>This means that, when you have a watcher that triggers in one hour and |
|
|
2297 | there are 100 watchers that would trigger before that then inserting will |
|
|
2298 | have to skip those 100 watchers.</p> |
|
|
2299 | </dd> |
2230 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2300 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
|
|
2301 | <dd> |
|
|
2302 | <p>That means that for changing a timer costs less than removing/adding them |
|
|
2303 | as only the relative motion in the event queue has to be paid for.</p> |
|
|
2304 | </dd> |
2231 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2305 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
|
|
2306 | <dd> |
|
|
2307 | <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> |
2308 | =item Stopping check/prepare/idle watchers: O(1)</p> |
|
|
2309 | </dd> |
2233 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2310 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
|
|
2311 | <dd> |
|
|
2312 | <p>These watchers are stored in lists then need to be walked to find the |
|
|
2313 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
2314 | have many watchers waiting for the same fd or signal).</p> |
|
|
2315 | </dd> |
2234 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
2316 | <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> |
2317 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
|
|
2318 | <dd> |
|
|
2319 | <p>A change means an I/O watcher gets started or stopped, which requires |
|
|
2320 | libev to recalculate its status (and possibly tell the kernel).</p> |
|
|
2321 | </dd> |
2236 | <dt>Activating one watcher: O(1)</dt> |
2322 | <dt>Activating one watcher: O(1)</dt> |
|
|
2323 | <dt>Priority handling: O(number_of_priorities)</dt> |
|
|
2324 | <dd> |
|
|
2325 | <p>Priorities are implemented by allocating some space for each |
|
|
2326 | priority. When doing priority-based operations, libev usually has to |
|
|
2327 | linearly search all the priorities.</p> |
|
|
2328 | </dd> |
2237 | </dl> |
2329 | </dl> |
2238 | </p> |
2330 | </p> |
2239 | |
2331 | |
2240 | |
2332 | |
2241 | |
2333 | |