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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="Sat Nov 24 05:58:35 2007" /> 9 <meta name="created" content="Wed Dec 12 18:55:28 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 -->
15<h3 id="TOP">Index</h3> 15<h3 id="TOP">Index</h3>
16 16
17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 20<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 21<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 22<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 23<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 24<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 25<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 26<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
26<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 28<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
27</ul> 29</ul>
28</li> 30</li>
29<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
30<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> 32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a>
33<ul><li><a href="#The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</a></li>
34<li><a href="#Watcher_Specific_Functions">Watcher-Specific Functions</a></li>
35</ul>
36</li>
31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> 37<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a>
38<ul><li><a href="#Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</a></li>
39</ul>
40</li>
32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> 41<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a>
42<ul><li><a href="#Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</a></li>
43</ul>
44</li>
33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> 45<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a>
46<ul><li><a href="#Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</a></li>
47</ul>
48</li>
34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 49<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a>
50<ul><li><a href="#Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</a></li>
51</ul>
52</li>
53<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a>
54<ul><li><a href="#Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</a></li>
55</ul>
56</li>
35<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> 57<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a>
58<ul><li><a href="#Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</a></li>
59</ul>
60</li>
36<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> 61<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a>
62<ul><li><a href="#Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</a></li>
63</ul>
64</li>
37<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li> 65<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a>
66<ul><li><a href="#Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</a></li>
67</ul>
68</li>
69<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a>
70<ul><li><a href="#Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</a></li>
71</ul>
72</li>
38</ul> 73</ul>
39</li> 74</li>
40<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 75<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
41<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 76<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
42<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 77<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
78<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
79<li><a href="#EMBEDDING">EMBEDDING</a>
80<ul><li><a href="#FILESETS">FILESETS</a>
81<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
82<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
83<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
84</ul>
85</li>
86<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
87<li><a href="#EXAMPLES">EXAMPLES</a></li>
88</ul>
89</li>
90<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
43<li><a href="#AUTHOR">AUTHOR</a> 91<li><a href="#AUTHOR">AUTHOR</a>
44</li> 92</li>
45</ul><hr /> 93</ul><hr />
46<!-- INDEX END --> 94<!-- INDEX END -->
47 95
48<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 96<h1 id="NAME">NAME</h1>
49<div id="NAME_CONTENT"> 97<div id="NAME_CONTENT">
50<p>libev - a high performance full-featured event loop written in C</p> 98<p>libev - a high performance full-featured event loop written in C</p>
51 99
52</div> 100</div>
53<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 101<h1 id="SYNOPSIS">SYNOPSIS</h1>
54<div id="SYNOPSIS_CONTENT"> 102<div id="SYNOPSIS_CONTENT">
55<pre> #include &lt;ev.h&gt; 103<pre> #include &lt;ev.h&gt;
56 104
57</pre> 105</pre>
58 106
59</div> 107</div>
60<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 108<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
109<div id="EXAMPLE_PROGRAM_CONTENT">
110<pre> #include &lt;ev.h&gt;
111
112 ev_io stdin_watcher;
113 ev_timer timeout_watcher;
114
115 /* called when data readable on stdin */
116 static void
117 stdin_cb (EV_P_ struct ev_io *w, int revents)
118 {
119 /* puts (&quot;stdin ready&quot;); */
120 ev_io_stop (EV_A_ w); /* just a syntax example */
121 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
122 }
123
124 static void
125 timeout_cb (EV_P_ struct ev_timer *w, int revents)
126 {
127 /* puts (&quot;timeout&quot;); */
128 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
129 }
130
131 int
132 main (void)
133 {
134 struct ev_loop *loop = ev_default_loop (0);
135
136 /* initialise an io watcher, then start it */
137 ev_io_init (&amp;stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
138 ev_io_start (loop, &amp;stdin_watcher);
139
140 /* simple non-repeating 5.5 second timeout */
141 ev_timer_init (&amp;timeout_watcher, timeout_cb, 5.5, 0.);
142 ev_timer_start (loop, &amp;timeout_watcher);
143
144 /* loop till timeout or data ready */
145 ev_loop (loop, 0);
146
147 return 0;
148 }
149
150</pre>
151
152</div>
153<h1 id="DESCRIPTION">DESCRIPTION</h1>
61<div id="DESCRIPTION_CONTENT"> 154<div id="DESCRIPTION_CONTENT">
155<p>The newest version of this document is also available as a html-formatted
156web page you might find easier to navigate when reading it for the first
157time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
62<p>Libev is an event loop: you register interest in certain events (such as a 158<p>Libev is an event loop: you register interest in certain events (such as a
63file descriptor being readable or a timeout occuring), and it will manage 159file descriptor being readable or a timeout occuring), and it will manage
64these event sources and provide your program with events.</p> 160these event sources and provide your program with events.</p>
65<p>To do this, it must take more or less complete control over your process 161<p>To do this, it must take more or less complete control over your process
66(or thread) by executing the <i>event loop</i> handler, and will then 162(or thread) by executing the <i>event loop</i> handler, and will then
… …
69watchers</i>, which are relatively small C structures you initialise with the 165watchers</i>, which are relatively small C structures you initialise with the
70details of the event, and then hand it over to libev by <i>starting</i> the 166details of the event, and then hand it over to libev by <i>starting</i> the
71watcher.</p> 167watcher.</p>
72 168
73</div> 169</div>
74<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 170<h1 id="FEATURES">FEATURES</h1>
75<div id="FEATURES_CONTENT"> 171<div id="FEATURES_CONTENT">
76<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 172<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
77kqueue mechanisms for file descriptor events, relative timers, absolute 173BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
78timers with customised rescheduling, signal events, process status change 174for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
79events (related to SIGCHLD), and event watchers dealing with the event 175(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
80loop mechanism itself (idle, prepare and check watchers). It also is quite 176with customised rescheduling (<code>ev_periodic</code>), synchronous signals
177(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
178watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
179<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
180file watchers (<code>ev_stat</code>) and even limited support for fork events
181(<code>ev_fork</code>).</p>
182<p>It also is quite fast (see this
81fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 183<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
82it to libevent for example).</p> 184for example).</p>
83 185
84</div> 186</div>
85<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 187<h1 id="CONVENTIONS">CONVENTIONS</h1>
86<div id="CONVENTIONS_CONTENT"> 188<div id="CONVENTIONS_CONTENT">
87<p>Libev is very configurable. In this manual the default configuration 189<p>Libev is very configurable. In this manual the default configuration will
88will be described, which supports multiple event loops. For more info 190be described, which supports multiple event loops. For more info about
89about various configuration options please have a look at the file 191various configuration options please have a look at <strong>EMBED</strong> section in
90<cite>README.embed</cite> in the libev distribution. If libev was configured without 192this manual. If libev was configured without support for multiple event
91support for multiple event loops, then all functions taking an initial 193loops, then all functions taking an initial argument of name <code>loop</code>
92argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 194(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
93will not have this argument.</p>
94 195
95</div> 196</div>
96<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 197<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
97<div id="TIME_REPRESENTATION_CONTENT"> 198<div id="TIME_REPRESENTATION_CONTENT">
98<p>Libev represents time as a single floating point number, representing the 199<p>Libev represents time as a single floating point number, representing the
99(fractional) number of seconds since the (POSIX) epoch (somewhere near 200(fractional) number of seconds since the (POSIX) epoch (somewhere near
100the beginning of 1970, details are complicated, don't ask). This type is 201the beginning of 1970, details are complicated, don't ask). This type is
101called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 202called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
102to the <code>double</code> type in C, and when you need to do any calculations on 203to the <code>double</code> type in C, and when you need to do any calculations on
103it, you should treat it as such.</p> 204it, you should treat it as such.</p>
104 205
105
106
107
108
109</div> 206</div>
110<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 207<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
111<div id="GLOBAL_FUNCTIONS_CONTENT"> 208<div id="GLOBAL_FUNCTIONS_CONTENT">
112<p>These functions can be called anytime, even before initialising the 209<p>These functions can be called anytime, even before initialising the
113library in any way.</p> 210library in any way.</p>
114<dl> 211<dl>
115 <dt>ev_tstamp ev_time ()</dt> 212 <dt>ev_tstamp ev_time ()</dt>
… …
119you actually want to know.</p> 216you actually want to know.</p>
120 </dd> 217 </dd>
121 <dt>int ev_version_major ()</dt> 218 <dt>int ev_version_major ()</dt>
122 <dt>int ev_version_minor ()</dt> 219 <dt>int ev_version_minor ()</dt>
123 <dd> 220 <dd>
124 <p>You can find out the major and minor version numbers of the library 221 <p>You can find out the major and minor ABI version numbers of the library
125you linked against by calling the functions <code>ev_version_major</code> and 222you linked against by calling the functions <code>ev_version_major</code> and
126<code>ev_version_minor</code>. If you want, you can compare against the global 223<code>ev_version_minor</code>. If you want, you can compare against the global
127symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 224symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
128version of the library your program was compiled against.</p> 225version of the library your program was compiled against.</p>
226 <p>These version numbers refer to the ABI version of the library, not the
227release version.</p>
129 <p>Usually, it's a good idea to terminate if the major versions mismatch, 228 <p>Usually, it's a good idea to terminate if the major versions mismatch,
130as this indicates an incompatible change. Minor versions are usually 229as this indicates an incompatible change. Minor versions are usually
131compatible to older versions, so a larger minor version alone is usually 230compatible to older versions, so a larger minor version alone is usually
132not a problem.</p> 231not a problem.</p>
133 <p>Example: make sure we haven't accidentally been linked against the wrong 232 <p>Example: Make sure we haven't accidentally been linked against the wrong
134version:</p> 233version.</p>
135<pre> assert ((&quot;libev version mismatch&quot;, 234<pre> assert ((&quot;libev version mismatch&quot;,
136 ev_version_major () == EV_VERSION_MAJOR 235 ev_version_major () == EV_VERSION_MAJOR
137 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 236 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
138 237
139</pre> 238</pre>
… …
169recommended ones.</p> 268recommended ones.</p>
170 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 269 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
171 </dd> 270 </dd>
172 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 271 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
173 <dd> 272 <dd>
174 <p>Sets the allocation function to use (the prototype is similar to the 273 <p>Sets the allocation function to use (the prototype is similar - the
175realloc C function, the semantics are identical). It is used to allocate 274semantics is identical - to the realloc C function). It is used to
176and free memory (no surprises here). If it returns zero when memory 275allocate and free memory (no surprises here). If it returns zero when
177needs to be allocated, the library might abort or take some potentially 276memory needs to be allocated, the library might abort or take some
178destructive action. The default is your system realloc function.</p> 277potentially destructive action. The default is your system realloc
278function.</p>
179 <p>You could override this function in high-availability programs to, say, 279 <p>You could override this function in high-availability programs to, say,
180free some memory if it cannot allocate memory, to use a special allocator, 280free some memory if it cannot allocate memory, to use a special allocator,
181or even to sleep a while and retry until some memory is available.</p> 281or even to sleep a while and retry until some memory is available.</p>
182 <p>Example: replace the libev allocator with one that waits a bit and then 282 <p>Example: Replace the libev allocator with one that waits a bit and then
183retries: better than mine).</p> 283retries).</p>
184<pre> static void * 284<pre> static void *
185 persistent_realloc (void *ptr, long size) 285 persistent_realloc (void *ptr, size_t size)
186 { 286 {
187 for (;;) 287 for (;;)
188 { 288 {
189 void *newptr = realloc (ptr, size); 289 void *newptr = realloc (ptr, size);
190 290
… …
207indicating the system call or subsystem causing the problem. If this 307indicating the system call or subsystem causing the problem. If this
208callback is set, then libev will expect it to remedy the sitution, no 308callback is set, then libev will expect it to remedy the sitution, no
209matter what, when it returns. That is, libev will generally retry the 309matter what, when it returns. That is, libev will generally retry the
210requested operation, or, if the condition doesn't go away, do bad stuff 310requested operation, or, if the condition doesn't go away, do bad stuff
211(such as abort).</p> 311(such as abort).</p>
212 <p>Example: do the same thing as libev does internally:</p> 312 <p>Example: This is basically the same thing that libev does internally, too.</p>
213<pre> static void 313<pre> static void
214 fatal_error (const char *msg) 314 fatal_error (const char *msg)
215 { 315 {
216 perror (msg); 316 perror (msg);
217 abort (); 317 abort ();
… …
223</pre> 323</pre>
224 </dd> 324 </dd>
225</dl> 325</dl>
226 326
227</div> 327</div>
228<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 328<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
229<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 329<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
230<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 330<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
231types of such loops, the <i>default</i> loop, which supports signals and child 331types of such loops, the <i>default</i> loop, which supports signals and child
232events, and dynamically created loops which do not.</p> 332events, and dynamically created loops which do not.</p>
233<p>If you use threads, a common model is to run the default event loop 333<p>If you use threads, a common model is to run the default event loop
… …
262<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 362<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
263override the flags completely if it is found in the environment. This is 363override the flags completely if it is found in the environment. This is
264useful to try out specific backends to test their performance, or to work 364useful to try out specific backends to test their performance, or to work
265around bugs.</p> 365around bugs.</p>
266 </dd> 366 </dd>
367 <dt><code>EVFLAG_FORKCHECK</code></dt>
368 <dd>
369 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
370a fork, you can also make libev check for a fork in each iteration by
371enabling this flag.</p>
372 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
373and thus this might slow down your event loop if you do a lot of loop
374iterations and little real work, but is usually not noticeable (on my
375Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
376without a syscall and thus <i>very</i> fast, but my Linux system also has
377<code>pthread_atfork</code> which is even faster).</p>
378 <p>The big advantage of this flag is that you can forget about fork (and
379forget about forgetting to tell libev about forking) when you use this
380flag.</p>
381 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
382environment variable.</p>
383 </dd>
267 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 384 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
268 <dd> 385 <dd>
269 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 386 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
270libev tries to roll its own fd_set with no limits on the number of fds, 387libev tries to roll its own fd_set with no limits on the number of fds,
271but if that fails, expect a fairly low limit on the number of fds when 388but if that fails, expect a fairly low limit on the number of fds when
… …
353 <dd> 470 <dd>
354 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 471 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
355always distinct from the default loop. Unlike the default loop, it cannot 472always distinct from the default loop. Unlike the default loop, it cannot
356handle signal and child watchers, and attempts to do so will be greeted by 473handle signal and child watchers, and attempts to do so will be greeted by
357undefined behaviour (or a failed assertion if assertions are enabled).</p> 474undefined behaviour (or a failed assertion if assertions are enabled).</p>
358 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 475 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
359<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 476<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
360 if (!epoller) 477 if (!epoller)
361 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 478 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
362 479
363</pre> 480</pre>
364 </dd> 481 </dd>
365 <dt>ev_default_destroy ()</dt> 482 <dt>ev_default_destroy ()</dt>
366 <dd> 483 <dd>
367 <p>Destroys the default loop again (frees all memory and kernel state 484 <p>Destroys the default loop again (frees all memory and kernel state
368etc.). This stops all registered event watchers (by not touching them in 485etc.). None of the active event watchers will be stopped in the normal
369any way whatsoever, although you cannot rely on this :).</p> 486sense, so e.g. <code>ev_is_active</code> might still return true. It is your
487responsibility to either stop all watchers cleanly yoursef <i>before</i>
488calling this function, or cope with the fact afterwards (which is usually
489the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
490for example).</p>
370 </dd> 491 </dd>
371 <dt>ev_loop_destroy (loop)</dt> 492 <dt>ev_loop_destroy (loop)</dt>
372 <dd> 493 <dd>
373 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 494 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
374earlier call to <code>ev_loop_new</code>.</p> 495earlier call to <code>ev_loop_new</code>.</p>
… …
395 <dt>ev_loop_fork (loop)</dt> 516 <dt>ev_loop_fork (loop)</dt>
396 <dd> 517 <dd>
397 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 518 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
398<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 519<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
399after fork, and how you do this is entirely your own problem.</p> 520after fork, and how you do this is entirely your own problem.</p>
521 </dd>
522 <dt>unsigned int ev_loop_count (loop)</dt>
523 <dd>
524 <p>Returns the count of loop iterations for the loop, which is identical to
525the number of times libev did poll for new events. It starts at <code>0</code> and
526happily wraps around with enough iterations.</p>
527 <p>This value can sometimes be useful as a generation counter of sorts (it
528&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
529<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
400 </dd> 530 </dd>
401 <dt>unsigned int ev_backend (loop)</dt> 531 <dt>unsigned int ev_backend (loop)</dt>
402 <dd> 532 <dd>
403 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 533 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
404use.</p> 534use.</p>
… …
432one iteration of the loop. This is useful if you are waiting for some 562one iteration of the loop. This is useful if you are waiting for some
433external event in conjunction with something not expressible using other 563external event in conjunction with something not expressible using other
434libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is 564libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
435usually a better approach for this kind of thing.</p> 565usually a better approach for this kind of thing.</p>
436 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 566 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
567<pre> - Before the first iteration, call any pending watchers.
437<pre> * If there are no active watchers (reference count is zero), return. 568 * If there are no active watchers (reference count is zero), return.
438 - Queue prepare watchers and then call all outstanding watchers. 569 - Queue all prepare watchers and then call all outstanding watchers.
439 - If we have been forked, recreate the kernel state. 570 - If we have been forked, recreate the kernel state.
440 - Update the kernel state with all outstanding changes. 571 - Update the kernel state with all outstanding changes.
441 - Update the &quot;event loop time&quot;. 572 - Update the &quot;event loop time&quot;.
442 - Calculate for how long to block. 573 - Calculate for how long to block.
443 - Block the process, waiting for any events. 574 - Block the process, waiting for any events.
… …
452 be handled here by queueing them when their watcher gets executed. 583 be handled here by queueing them when their watcher gets executed.
453 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 584 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
454 were used, return, otherwise continue with step *. 585 were used, return, otherwise continue with step *.
455 586
456</pre> 587</pre>
457 <p>Example: queue some jobs and then loop until no events are outsanding 588 <p>Example: Queue some jobs and then loop until no events are outsanding
458anymore.</p> 589anymore.</p>
459<pre> ... queue jobs here, make sure they register event watchers as long 590<pre> ... queue jobs here, make sure they register event watchers as long
460 ... as they still have work to do (even an idle watcher will do..) 591 ... as they still have work to do (even an idle watcher will do..)
461 ev_loop (my_loop, 0); 592 ev_loop (my_loop, 0);
462 ... jobs done. yeah! 593 ... jobs done. yeah!
… …
481example, libev itself uses this for its internal signal pipe: It is not 612example, libev itself uses this for its internal signal pipe: It is not
482visible to the libev user and should not keep <code>ev_loop</code> from exiting if 613visible to the libev user and should not keep <code>ev_loop</code> from exiting if
483no event watchers registered by it are active. It is also an excellent 614no event watchers registered by it are active. It is also an excellent
484way to do this for generic recurring timers or from within third-party 615way to do this for generic recurring timers or from within third-party
485libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 616libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
486 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 617 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
487running when nothing else is active.</p> 618running when nothing else is active.</p>
488<pre> struct dv_signal exitsig; 619<pre> struct ev_signal exitsig;
489 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 620 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
490 ev_signal_start (myloop, &amp;exitsig); 621 ev_signal_start (loop, &amp;exitsig);
491 evf_unref (myloop); 622 evf_unref (loop);
492 623
493</pre> 624</pre>
494 <p>Example: for some weird reason, unregister the above signal handler again.</p> 625 <p>Example: For some weird reason, unregister the above signal handler again.</p>
495<pre> ev_ref (myloop); 626<pre> ev_ref (loop);
496 ev_signal_stop (myloop, &amp;exitsig); 627 ev_signal_stop (loop, &amp;exitsig);
497 628
498</pre> 629</pre>
499 </dd> 630 </dd>
500</dl> 631</dl>
501 632
633
634
635
636
502</div> 637</div>
503<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 638<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
504<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 639<div id="ANATOMY_OF_A_WATCHER_CONTENT">
505<p>A watcher is a structure that you create and register to record your 640<p>A watcher is a structure that you create and register to record your
506interest in some event. For instance, if you want to wait for STDIN to 641interest in some event. For instance, if you want to wait for STDIN to
507become readable, you would create an <code>ev_io</code> watcher for that:</p> 642become readable, you would create an <code>ev_io</code> watcher for that:</p>
508<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 643<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
535with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 670with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
536*)</code>), and you can stop watching for events at any time by calling the 671*)</code>), and you can stop watching for events at any time by calling the
537corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 672corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
538<p>As long as your watcher is active (has been started but not stopped) you 673<p>As long as your watcher is active (has been started but not stopped) you
539must not touch the values stored in it. Most specifically you must never 674must not touch the values stored in it. Most specifically you must never
540reinitialise it or call its set macro.</p> 675reinitialise it or call its <code>set</code> macro.</p>
541<p>You can check whether an event is active by calling the <code>ev_is_active
542(watcher *)</code> macro. To see whether an event is outstanding (but the
543callback for it has not been called yet) you can use the <code>ev_is_pending
544(watcher *)</code> macro.</p>
545<p>Each and every callback receives the event loop pointer as first, the 676<p>Each and every callback receives the event loop pointer as first, the
546registered watcher structure as second, and a bitset of received events as 677registered watcher structure as second, and a bitset of received events as
547third argument.</p> 678third argument.</p>
548<p>The received events usually include a single bit per event type received 679<p>The received events usually include a single bit per event type received
549(you can receive multiple events at the same time). The possible bit masks 680(you can receive multiple events at the same time). The possible bit masks
… …
569 </dd> 700 </dd>
570 <dt><code>EV_CHILD</code></dt> 701 <dt><code>EV_CHILD</code></dt>
571 <dd> 702 <dd>
572 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 703 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
573 </dd> 704 </dd>
705 <dt><code>EV_STAT</code></dt>
706 <dd>
707 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
708 </dd>
574 <dt><code>EV_IDLE</code></dt> 709 <dt><code>EV_IDLE</code></dt>
575 <dd> 710 <dd>
576 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 711 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
577 </dd> 712 </dd>
578 <dt><code>EV_PREPARE</code></dt> 713 <dt><code>EV_PREPARE</code></dt>
… …
583<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 718<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
584received events. Callbacks of both watcher types can start and stop as 719received events. Callbacks of both watcher types can start and stop as
585many watchers as they want, and all of them will be taken into account 720many watchers as they want, and all of them will be taken into account
586(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 721(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
587<code>ev_loop</code> from blocking).</p> 722<code>ev_loop</code> from blocking).</p>
723 </dd>
724 <dt><code>EV_EMBED</code></dt>
725 <dd>
726 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
727 </dd>
728 <dt><code>EV_FORK</code></dt>
729 <dd>
730 <p>The event loop has been resumed in the child process after fork (see
731<code>ev_fork</code>).</p>
588 </dd> 732 </dd>
589 <dt><code>EV_ERROR</code></dt> 733 <dt><code>EV_ERROR</code></dt>
590 <dd> 734 <dd>
591 <p>An unspecified error has occured, the watcher has been stopped. This might 735 <p>An unspecified error has occured, the watcher has been stopped. This might
592happen because the watcher could not be properly started because libev 736happen because the watcher could not be properly started because libev
… …
600programs, though, so beware.</p> 744programs, though, so beware.</p>
601 </dd> 745 </dd>
602</dl> 746</dl>
603 747
604</div> 748</div>
749<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
750<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
751<p>In the following description, <code>TYPE</code> stands for the watcher type,
752e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
753<dl>
754 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
755 <dd>
756 <p>This macro initialises the generic portion of a watcher. The contents
757of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
758the generic parts of the watcher are initialised, you <i>need</i> to call
759the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
760type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
761which rolls both calls into one.</p>
762 <p>You can reinitialise a watcher at any time as long as it has been stopped
763(or never started) and there are no pending events outstanding.</p>
764 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
765int revents)</code>.</p>
766 </dd>
767 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
768 <dd>
769 <p>This macro initialises the type-specific parts of a watcher. You need to
770call <code>ev_init</code> at least once before you call this macro, but you can
771call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
772macro on a watcher that is active (it can be pending, however, which is a
773difference to the <code>ev_init</code> macro).</p>
774 <p>Although some watcher types do not have type-specific arguments
775(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
776 </dd>
777 <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
778 <dd>
779 <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
780calls into a single call. This is the most convinient method to initialise
781a watcher. The same limitations apply, of course.</p>
782 </dd>
783 <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
784 <dd>
785 <p>Starts (activates) the given watcher. Only active watchers will receive
786events. If the watcher is already active nothing will happen.</p>
787 </dd>
788 <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
789 <dd>
790 <p>Stops the given watcher again (if active) and clears the pending
791status. It is possible that stopped watchers are pending (for example,
792non-repeating timers are being stopped when they become pending), but
793<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
794you want to free or reuse the memory used by the watcher it is therefore a
795good idea to always call its <code>ev_TYPE_stop</code> function.</p>
796 </dd>
797 <dt>bool ev_is_active (ev_TYPE *watcher)</dt>
798 <dd>
799 <p>Returns a true value iff the watcher is active (i.e. it has been started
800and not yet been stopped). As long as a watcher is active you must not modify
801it.</p>
802 </dd>
803 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
804 <dd>
805 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
806events but its callback has not yet been invoked). As long as a watcher
807is pending (but not active) you must not call an init function on it (but
808<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
809make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
810it).</p>
811 </dd>
812 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
813 <dd>
814 <p>Returns the callback currently set on the watcher.</p>
815 </dd>
816 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
817 <dd>
818 <p>Change the callback. You can change the callback at virtually any time
819(modulo threads).</p>
820 </dd>
821 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
822 <dt>int ev_priority (ev_TYPE *watcher)</dt>
823 <dd>
824 <p>Set and query the priority of the watcher. The priority is a small
825integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
826(default: <code>-2</code>). Pending watchers with higher priority will be invoked
827before watchers with lower priority, but priority will not keep watchers
828from being executed (except for <code>ev_idle</code> watchers).</p>
829 <p>This means that priorities are <i>only</i> used for ordering callback
830invocation after new events have been received. This is useful, for
831example, to reduce latency after idling, or more often, to bind two
832watchers on the same event and make sure one is called first.</p>
833 <p>If you need to suppress invocation when higher priority events are pending
834you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
835 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
836pending.</p>
837 <p>The default priority used by watchers when no priority has been set is
838always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
839 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
840fine, as long as you do not mind that the priority value you query might
841or might not have been adjusted to be within valid range.</p>
842 </dd>
843 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
844 <dd>
845 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
846<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
847can deal with that fact.</p>
848 </dd>
849 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
850 <dd>
851 <p>If the watcher is pending, this function returns clears its pending status
852and returns its <code>revents</code> bitset (as if its callback was invoked). If the
853watcher isn't pending it does nothing and returns <code>0</code>.</p>
854 </dd>
855</dl>
856
857
858
859
860
861</div>
605<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 862<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
606<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 863<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
607<p>Each watcher has, by default, a member <code>void *data</code> that you can change 864<p>Each watcher has, by default, a member <code>void *data</code> that you can change
608and read at any time, libev will completely ignore it. This can be used 865and read at any time, libev will completely ignore it. This can be used
609to associate arbitrary data with your watcher. If you need more data and 866to associate arbitrary data with your watcher. If you need more data and
… …
626 struct my_io *w = (struct my_io *)w_; 883 struct my_io *w = (struct my_io *)w_;
627 ... 884 ...
628 } 885 }
629 886
630</pre> 887</pre>
631<p>More interesting and less C-conformant ways of catsing your callback type 888<p>More interesting and less C-conformant ways of casting your callback type
632have been omitted....</p> 889instead have been omitted.</p>
890<p>Another common scenario is having some data structure with multiple
891watchers:</p>
892<pre> struct my_biggy
893 {
894 int some_data;
895 ev_timer t1;
896 ev_timer t2;
897 }
633 898
899</pre>
900<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
901you need to use <code>offsetof</code>:</p>
902<pre> #include &lt;stddef.h&gt;
634 903
904 static void
905 t1_cb (EV_P_ struct ev_timer *w, int revents)
906 {
907 struct my_biggy big = (struct my_biggy *
908 (((char *)w) - offsetof (struct my_biggy, t1));
909 }
635 910
911 static void
912 t2_cb (EV_P_ struct ev_timer *w, int revents)
913 {
914 struct my_biggy big = (struct my_biggy *
915 (((char *)w) - offsetof (struct my_biggy, t2));
916 }
636 917
637 918
919
920
921</pre>
922
638</div> 923</div>
639<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 924<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
640<div id="WATCHER_TYPES_CONTENT"> 925<div id="WATCHER_TYPES_CONTENT">
641<p>This section describes each watcher in detail, but will not repeat 926<p>This section describes each watcher in detail, but will not repeat
642information given in the last section.</p> 927information given in the last section. Any initialisation/set macros,
928functions and members specific to the watcher type are explained.</p>
929<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
930while the watcher is active, you can look at the member and expect some
931sensible content, but you must not modify it (you can modify it while the
932watcher is stopped to your hearts content), or <i>[read-write]</i>, which
933means you can expect it to have some sensible content while the watcher
934is active, but you can also modify it. Modifying it may not do something
935sensible or take immediate effect (or do anything at all), but libev will
936not crash or malfunction in any way.</p>
643 937
644 938
645 939
646 940
647 941
648</div> 942</div>
649<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 943<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
650<div id="code_ev_io_code_is_this_file_descrip-2"> 944<div id="code_ev_io_code_is_this_file_descrip-2">
651<p>I/O watchers check whether a file descriptor is readable or writable 945<p>I/O watchers check whether a file descriptor is readable or writable
652in each iteration of the event loop (This behaviour is called 946in each iteration of the event loop, or, more precisely, when reading
653level-triggering because you keep receiving events as long as the 947would not block the process and writing would at least be able to write
654condition persists. Remember you can stop the watcher if you don't want to 948some data. This behaviour is called level-triggering because you keep
655act on the event and neither want to receive future events).</p> 949receiving events as long as the condition persists. Remember you can stop
950the watcher if you don't want to act on the event and neither want to
951receive future events.</p>
656<p>In general you can register as many read and/or write event watchers per 952<p>In general you can register as many read and/or write event watchers per
657fd as you want (as long as you don't confuse yourself). Setting all file 953fd as you want (as long as you don't confuse yourself). Setting all file
658descriptors to non-blocking mode is also usually a good idea (but not 954descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing).</p> 955required if you know what you are doing).</p>
660<p>You have to be careful with dup'ed file descriptors, though. Some backends 956<p>You have to be careful with dup'ed file descriptors, though. Some backends
661(the linux epoll backend is a notable example) cannot handle dup'ed file 957(the linux epoll backend is a notable example) cannot handle dup'ed file
662descriptors correctly if you register interest in two or more fds pointing 958descriptors correctly if you register interest in two or more fds pointing
663to the same underlying file/socket etc. description (that is, they share 959to the same underlying file/socket/etc. description (that is, they share
664the same underlying &quot;file open&quot;).</p> 960the same underlying &quot;file open&quot;).</p>
665<p>If you must do this, then force the use of a known-to-be-good backend 961<p>If you must do this, then force the use of a known-to-be-good backend
666(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and 962(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
667<code>EVBACKEND_POLL</code>).</p> 963<code>EVBACKEND_POLL</code>).</p>
964<p>Another thing you have to watch out for is that it is quite easy to
965receive &quot;spurious&quot; readyness notifications, that is your callback might
966be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
967because there is no data. Not only are some backends known to create a
968lot of those (for example solaris ports), it is very easy to get into
969this situation even with a relatively standard program structure. Thus
970it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
971<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
972<p>If you cannot run the fd in non-blocking mode (for example you should not
973play around with an Xlib connection), then you have to seperately re-test
974whether a file descriptor is really ready with a known-to-be good interface
975such as poll (fortunately in our Xlib example, Xlib already does this on
976its own, so its quite safe to use).</p>
977
978</div>
979<h3 id="The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</h3>
980<div id="The_special_problem_of_disappearing_-2">
981<p>Some backends (e.g kqueue, epoll) need to be told about closing a file
982descriptor (either by calling <code>close</code> explicitly or by any other means,
983such as <code>dup</code>). The reason is that you register interest in some file
984descriptor, but when it goes away, the operating system will silently drop
985this interest. If another file descriptor with the same number then is
986registered with libev, there is no efficient way to see that this is, in
987fact, a different file descriptor.</p>
988<p>To avoid having to explicitly tell libev about such cases, libev follows
989the following policy: Each time <code>ev_io_set</code> is being called, libev
990will assume that this is potentially a new file descriptor, otherwise
991it is assumed that the file descriptor stays the same. That means that
992you <i>have</i> to call <code>ev_io_set</code> (or <code>ev_io_init</code>) when you change the
993descriptor even if the file descriptor number itself did not change.</p>
994<p>This is how one would do it normally anyway, the important point is that
995the libev application should not optimise around libev but should leave
996optimisations to libev.</p>
997
998
999
1000
1001
1002</div>
1003<h3 id="Watcher_Specific_Functions">Watcher-Specific Functions</h3>
1004<div id="Watcher_Specific_Functions_CONTENT">
668<dl> 1005<dl>
669 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 1006 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
670 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 1007 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
671 <dd> 1008 <dd>
672 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 1009 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
673events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 1010rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
674EV_WRITE</code> to receive the given events.</p> 1011<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
675 <p>Please note that most of the more scalable backend mechanisms (for example 1012 </dd>
676epoll and solaris ports) can result in spurious readyness notifications 1013 <dt>int fd [read-only]</dt>
677for file descriptors, so you practically need to use non-blocking I/O (and 1014 <dd>
678treat callback invocation as hint only), or retest separately with a safe 1015 <p>The file descriptor being watched.</p>
679interface before doing I/O (XLib can do this), or force the use of either 1016 </dd>
680<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 1017 <dt>int events [read-only]</dt>
681problem. Also note that it is quite easy to have your callback invoked 1018 <dd>
682when the readyness condition is no longer valid even when employing 1019 <p>The events being watched.</p>
683typical ways of handling events, so its a good idea to use non-blocking
684I/O unconditionally.</p>
685 </dd> 1020 </dd>
686</dl> 1021</dl>
687<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 1022<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
688readable, but only once. Since it is likely line-buffered, you could 1023readable, but only once. Since it is likely line-buffered, you could
689attempt to read a whole line in the callback:</p> 1024attempt to read a whole line in the callback.</p>
690<pre> static void 1025<pre> static void
691 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1026 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
692 { 1027 {
693 ev_io_stop (loop, w); 1028 ev_io_stop (loop, w);
694 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 1029 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
705 1040
706 1041
707</pre> 1042</pre>
708 1043
709</div> 1044</div>
710<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 1045<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
711<div id="code_ev_timer_code_relative_and_opti-2"> 1046<div id="code_ev_timer_code_relative_and_opti-2">
712<p>Timer watchers are simple relative timers that generate an event after a 1047<p>Timer watchers are simple relative timers that generate an event after a
713given time, and optionally repeating in regular intervals after that.</p> 1048given time, and optionally repeating in regular intervals after that.</p>
714<p>The timers are based on real time, that is, if you register an event that 1049<p>The timers are based on real time, that is, if you register an event that
715times out after an hour and you reset your system clock to last years 1050times out after an hour and you reset your system clock to last years
… …
725 1060
726</pre> 1061</pre>
727<p>The callback is guarenteed to be invoked only when its timeout has passed, 1062<p>The callback is guarenteed to be invoked only when its timeout has passed,
728but if multiple timers become ready during the same loop iteration then 1063but if multiple timers become ready during the same loop iteration then
729order of execution is undefined.</p> 1064order of execution is undefined.</p>
1065
1066</div>
1067<h3 id="Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</h3>
1068<div id="Watcher_Specific_Functions_and_Data_-2">
730<dl> 1069<dl>
731 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 1070 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
732 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 1071 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
733 <dd> 1072 <dd>
734 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 1073 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
743 </dd> 1082 </dd>
744 <dt>ev_timer_again (loop)</dt> 1083 <dt>ev_timer_again (loop)</dt>
745 <dd> 1084 <dd>
746 <p>This will act as if the timer timed out and restart it again if it is 1085 <p>This will act as if the timer timed out and restart it again if it is
747repeating. The exact semantics are:</p> 1086repeating. The exact semantics are:</p>
1087 <p>If the timer is pending, its pending status is cleared.</p>
748 <p>If the timer is started but nonrepeating, stop it.</p> 1088 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
749 <p>If the timer is repeating, either start it if necessary (with the repeat 1089 <p>If the timer is repeating, either start it if necessary (with the
750value), or reset the running timer to the repeat value.</p> 1090<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
751 <p>This sounds a bit complicated, but here is a useful and typical 1091 <p>This sounds a bit complicated, but here is a useful and typical
752example: Imagine you have a tcp connection and you want a so-called idle 1092example: Imagine you have a tcp connection and you want a so-called idle
753timeout, that is, you want to be called when there have been, say, 60 1093timeout, that is, you want to be called when there have been, say, 60
754seconds of inactivity on the socket. The easiest way to do this is to 1094seconds of inactivity on the socket. The easiest way to do this is to
755configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 1095configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
756time you successfully read or write some data. If you go into an idle 1096<code>ev_timer_again</code> each time you successfully read or write some data. If
757state where you do not expect data to travel on the socket, you can stop 1097you go into an idle state where you do not expect data to travel on the
1098socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
758the timer, and again will automatically restart it if need be.</p> 1099automatically restart it if need be.</p>
1100 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
1101altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
1102<pre> ev_timer_init (timer, callback, 0., 5.);
1103 ev_timer_again (loop, timer);
1104 ...
1105 timer-&gt;again = 17.;
1106 ev_timer_again (loop, timer);
1107 ...
1108 timer-&gt;again = 10.;
1109 ev_timer_again (loop, timer);
1110
1111</pre>
1112 <p>This is more slightly efficient then stopping/starting the timer each time
1113you want to modify its timeout value.</p>
1114 </dd>
1115 <dt>ev_tstamp repeat [read-write]</dt>
1116 <dd>
1117 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
1118or <code>ev_timer_again</code> is called and determines the next timeout (if any),
1119which is also when any modifications are taken into account.</p>
759 </dd> 1120 </dd>
760</dl> 1121</dl>
761<p>Example: create a timer that fires after 60 seconds.</p> 1122<p>Example: Create a timer that fires after 60 seconds.</p>
762<pre> static void 1123<pre> static void
763 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1124 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
764 { 1125 {
765 .. one minute over, w is actually stopped right here 1126 .. one minute over, w is actually stopped right here
766 } 1127 }
… …
768 struct ev_timer mytimer; 1129 struct ev_timer mytimer;
769 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1130 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
770 ev_timer_start (loop, &amp;mytimer); 1131 ev_timer_start (loop, &amp;mytimer);
771 1132
772</pre> 1133</pre>
773<p>Example: create a timeout timer that times out after 10 seconds of 1134<p>Example: Create a timeout timer that times out after 10 seconds of
774inactivity.</p> 1135inactivity.</p>
775<pre> static void 1136<pre> static void
776 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1137 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
777 { 1138 {
778 .. ten seconds without any activity 1139 .. ten seconds without any activity
… …
791 1152
792 1153
793</pre> 1154</pre>
794 1155
795</div> 1156</div>
796<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 1157<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
797<div id="code_ev_periodic_code_to_cron_or_not-2"> 1158<div id="code_ev_periodic_code_to_cron_or_not-2">
798<p>Periodic watchers are also timers of a kind, but they are very versatile 1159<p>Periodic watchers are also timers of a kind, but they are very versatile
799(and unfortunately a bit complex).</p> 1160(and unfortunately a bit complex).</p>
800<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 1161<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
801but on wallclock time (absolute time). You can tell a periodic watcher 1162but on wallclock time (absolute time). You can tell a periodic watcher
802to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1163to trigger &quot;at&quot; some specific point in time. For example, if you tell a
803periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 1164periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
804+ 10.&gt;) and then reset your system clock to the last year, then it will 1165+ 10.</code>) and then reset your system clock to the last year, then it will
805take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1166take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
806roughly 10 seconds later and of course not if you reset your system time 1167roughly 10 seconds later).</p>
807again).</p>
808<p>They can also be used to implement vastly more complex timers, such as 1168<p>They can also be used to implement vastly more complex timers, such as
809triggering an event on eahc midnight, local time.</p> 1169triggering an event on each midnight, local time or other, complicated,
1170rules.</p>
810<p>As with timers, the callback is guarenteed to be invoked only when the 1171<p>As with timers, the callback is guarenteed to be invoked only when the
811time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1172time (<code>at</code>) has been passed, but if multiple periodic timers become ready
812during the same loop iteration then order of execution is undefined.</p> 1173during the same loop iteration then order of execution is undefined.</p>
1174
1175</div>
1176<h3 id="Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</h3>
1177<div id="Watcher_Specific_Functions_and_Data_-2">
813<dl> 1178<dl>
814 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1179 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
815 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 1180 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
816 <dd> 1181 <dd>
817 <p>Lots of arguments, lets sort it out... There are basically three modes of 1182 <p>Lots of arguments, lets sort it out... There are basically three modes of
818operation, and we will explain them from simplest to complex:</p> 1183operation, and we will explain them from simplest to complex:</p>
819 <p> 1184 <p>
820 <dl> 1185 <dl>
821 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1186 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
822 <dd> 1187 <dd>
823 <p>In this configuration the watcher triggers an event at the wallclock time 1188 <p>In this configuration the watcher triggers an event at the wallclock time
824<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1189<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
825that is, if it is to be run at January 1st 2011 then it will run when the 1190that is, if it is to be run at January 1st 2011 then it will run when the
826system time reaches or surpasses this time.</p> 1191system time reaches or surpasses this time.</p>
827 </dd> 1192 </dd>
828 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1193 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
829 <dd> 1194 <dd>
830 <p>In this mode the watcher will always be scheduled to time out at the next 1195 <p>In this mode the watcher will always be scheduled to time out at the next
831<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1196<code>at + N * interval</code> time (for some integer N, which can also be negative)
832of any time jumps.</p> 1197and then repeat, regardless of any time jumps.</p>
833 <p>This can be used to create timers that do not drift with respect to system 1198 <p>This can be used to create timers that do not drift with respect to system
834time:</p> 1199time:</p>
835<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1200<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
836 1201
837</pre> 1202</pre>
… …
840full hour (UTC), or more correctly, when the system time is evenly divisible 1205full hour (UTC), or more correctly, when the system time is evenly divisible
841by 3600.</p> 1206by 3600.</p>
842 <p>Another way to think about it (for the mathematically inclined) is that 1207 <p>Another way to think about it (for the mathematically inclined) is that
843<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1208<code>ev_periodic</code> will try to run the callback in this mode at the next possible
844time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1209time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1210 <p>For numerical stability it is preferable that the <code>at</code> value is near
1211<code>ev_now ()</code> (the current time), but there is no range requirement for
1212this value.</p>
845 </dd> 1213 </dd>
846 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1214 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
847 <dd> 1215 <dd>
848 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1216 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
849ignored. Instead, each time the periodic watcher gets scheduled, the 1217ignored. Instead, each time the periodic watcher gets scheduled, the
850reschedule callback will be called with the watcher as first, and the 1218reschedule callback will be called with the watcher as first, and the
851current time as second argument.</p> 1219current time as second argument.</p>
852 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1220 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
853ever, or make any event loop modifications</i>. If you need to stop it, 1221ever, or make any event loop modifications</i>. If you need to stop it,
854return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1222return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
855starting a prepare watcher).</p> 1223starting an <code>ev_prepare</code> watcher, which is legal).</p>
856 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1224 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
857ev_tstamp now)</code>, e.g.:</p> 1225ev_tstamp now)</code>, e.g.:</p>
858<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1226<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
859 { 1227 {
860 return now + 60.; 1228 return now + 60.;
… …
881 <p>Simply stops and restarts the periodic watcher again. This is only useful 1249 <p>Simply stops and restarts the periodic watcher again. This is only useful
882when you changed some parameters or the reschedule callback would return 1250when you changed some parameters or the reschedule callback would return
883a different time than the last time it was called (e.g. in a crond like 1251a different time than the last time it was called (e.g. in a crond like
884program when the crontabs have changed).</p> 1252program when the crontabs have changed).</p>
885 </dd> 1253 </dd>
1254 <dt>ev_tstamp offset [read-write]</dt>
1255 <dd>
1256 <p>When repeating, this contains the offset value, otherwise this is the
1257absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1258 <p>Can be modified any time, but changes only take effect when the periodic
1259timer fires or <code>ev_periodic_again</code> is being called.</p>
1260 </dd>
1261 <dt>ev_tstamp interval [read-write]</dt>
1262 <dd>
1263 <p>The current interval value. Can be modified any time, but changes only
1264take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1265called.</p>
1266 </dd>
1267 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1268 <dd>
1269 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1270switched off. Can be changed any time, but changes only take effect when
1271the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1272 </dd>
886</dl> 1273</dl>
887<p>Example: call a callback every hour, or, more precisely, whenever the 1274<p>Example: Call a callback every hour, or, more precisely, whenever the
888system clock is divisible by 3600. The callback invocation times have 1275system clock is divisible by 3600. The callback invocation times have
889potentially a lot of jittering, but good long-term stability.</p> 1276potentially a lot of jittering, but good long-term stability.</p>
890<pre> static void 1277<pre> static void
891 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1278 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
892 { 1279 {
… …
896 struct ev_periodic hourly_tick; 1283 struct ev_periodic hourly_tick;
897 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1284 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
898 ev_periodic_start (loop, &amp;hourly_tick); 1285 ev_periodic_start (loop, &amp;hourly_tick);
899 1286
900</pre> 1287</pre>
901<p>Example: the same as above, but use a reschedule callback to do it:</p> 1288<p>Example: The same as above, but use a reschedule callback to do it:</p>
902<pre> #include &lt;math.h&gt; 1289<pre> #include &lt;math.h&gt;
903 1290
904 static ev_tstamp 1291 static ev_tstamp
905 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1292 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
906 { 1293 {
… …
908 } 1295 }
909 1296
910 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1297 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
911 1298
912</pre> 1299</pre>
913<p>Example: call a callback every hour, starting now:</p> 1300<p>Example: Call a callback every hour, starting now:</p>
914<pre> struct ev_periodic hourly_tick; 1301<pre> struct ev_periodic hourly_tick;
915 ev_periodic_init (&amp;hourly_tick, clock_cb, 1302 ev_periodic_init (&amp;hourly_tick, clock_cb,
916 fmod (ev_now (loop), 3600.), 3600., 0); 1303 fmod (ev_now (loop), 3600.), 3600., 0);
917 ev_periodic_start (loop, &amp;hourly_tick); 1304 ev_periodic_start (loop, &amp;hourly_tick);
918 1305
… …
920 1307
921 1308
922</pre> 1309</pre>
923 1310
924</div> 1311</div>
925<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1312<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
926<div id="code_ev_signal_code_signal_me_when_a-2"> 1313<div id="code_ev_signal_code_signal_me_when_a-2">
927<p>Signal watchers will trigger an event when the process receives a specific 1314<p>Signal watchers will trigger an event when the process receives a specific
928signal one or more times. Even though signals are very asynchronous, libev 1315signal one or more times. Even though signals are very asynchronous, libev
929will try it's best to deliver signals synchronously, i.e. as part of the 1316will try it's best to deliver signals synchronously, i.e. as part of the
930normal event processing, like any other event.</p> 1317normal event processing, like any other event.</p>
… …
932first watcher gets started will libev actually register a signal watcher 1319first watcher gets started will libev actually register a signal watcher
933with the kernel (thus it coexists with your own signal handlers as long 1320with the kernel (thus it coexists with your own signal handlers as long
934as you don't register any with libev). Similarly, when the last signal 1321as you don't register any with libev). Similarly, when the last signal
935watcher for a signal is stopped libev will reset the signal handler to 1322watcher for a signal is stopped libev will reset the signal handler to
936SIG_DFL (regardless of what it was set to before).</p> 1323SIG_DFL (regardless of what it was set to before).</p>
1324
1325</div>
1326<h3 id="Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</h3>
1327<div id="Watcher_Specific_Functions_and_Data_-2-2">
937<dl> 1328<dl>
938 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt> 1329 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt>
939 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1330 <dt>ev_signal_set (ev_signal *, int signum)</dt>
940 <dd> 1331 <dd>
941 <p>Configures the watcher to trigger on the given signal number (usually one 1332 <p>Configures the watcher to trigger on the given signal number (usually one
942of the <code>SIGxxx</code> constants).</p> 1333of the <code>SIGxxx</code> constants).</p>
943 </dd> 1334 </dd>
1335 <dt>int signum [read-only]</dt>
1336 <dd>
1337 <p>The signal the watcher watches out for.</p>
1338 </dd>
944</dl> 1339</dl>
945 1340
946 1341
947 1342
948 1343
949 1344
950</div> 1345</div>
951<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1346<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
952<div id="code_ev_child_code_wait_for_pid_stat-2"> 1347<div id="code_ev_child_code_watch_out_for_pro-2">
953<p>Child watchers trigger when your process receives a SIGCHLD in response to 1348<p>Child watchers trigger when your process receives a SIGCHLD in response to
954some child status changes (most typically when a child of yours dies).</p> 1349some child status changes (most typically when a child of yours dies).</p>
1350
1351</div>
1352<h3 id="Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</h3>
1353<div id="Watcher_Specific_Functions_and_Data_-2-3">
955<dl> 1354<dl>
956 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1355 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
957 <dt>ev_child_set (ev_child *, int pid)</dt> 1356 <dt>ev_child_set (ev_child *, int pid)</dt>
958 <dd> 1357 <dd>
959 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 1358 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
… …
961at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1360at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
962the status word (use the macros from <code>sys/wait.h</code> and see your systems 1361the status word (use the macros from <code>sys/wait.h</code> and see your systems
963<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1362<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
964process causing the status change.</p> 1363process causing the status change.</p>
965 </dd> 1364 </dd>
1365 <dt>int pid [read-only]</dt>
1366 <dd>
1367 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1368 </dd>
1369 <dt>int rpid [read-write]</dt>
1370 <dd>
1371 <p>The process id that detected a status change.</p>
1372 </dd>
1373 <dt>int rstatus [read-write]</dt>
1374 <dd>
1375 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1376<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1377 </dd>
966</dl> 1378</dl>
967<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1379<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
968<pre> static void 1380<pre> static void
969 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1381 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
970 { 1382 {
971 ev_unloop (loop, EVUNLOOP_ALL); 1383 ev_unloop (loop, EVUNLOOP_ALL);
972 } 1384 }
… …
979 1391
980 1392
981</pre> 1393</pre>
982 1394
983</div> 1395</div>
1396<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1397<div id="code_ev_stat_code_did_the_file_attri-2">
1398<p>This watches a filesystem path for attribute changes. That is, it calls
1399<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1400compared to the last time, invoking the callback if it did.</p>
1401<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1402not exist&quot; is a status change like any other. The condition &quot;path does
1403not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1404otherwise always forced to be at least one) and all the other fields of
1405the stat buffer having unspecified contents.</p>
1406<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1407relative and your working directory changes, the behaviour is undefined.</p>
1408<p>Since there is no standard to do this, the portable implementation simply
1409calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1410can specify a recommended polling interval for this case. If you specify
1411a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1412unspecified default</i> value will be used (which you can expect to be around
1413five seconds, although this might change dynamically). Libev will also
1414impose a minimum interval which is currently around <code>0.1</code>, but thats
1415usually overkill.</p>
1416<p>This watcher type is not meant for massive numbers of stat watchers,
1417as even with OS-supported change notifications, this can be
1418resource-intensive.</p>
1419<p>At the time of this writing, only the Linux inotify interface is
1420implemented (implementing kqueue support is left as an exercise for the
1421reader). Inotify will be used to give hints only and should not change the
1422semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1423to fall back to regular polling again even with inotify, but changes are
1424usually detected immediately, and if the file exists there will be no
1425polling.</p>
1426
1427</div>
1428<h3 id="Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</h3>
1429<div id="Watcher_Specific_Functions_and_Data_-2-4">
1430<dl>
1431 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1432 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1433 <dd>
1434 <p>Configures the watcher to wait for status changes of the given
1435<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1436be detected and should normally be specified as <code>0</code> to let libev choose
1437a suitable value. The memory pointed to by <code>path</code> must point to the same
1438path for as long as the watcher is active.</p>
1439 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1440relative to the attributes at the time the watcher was started (or the
1441last change was detected).</p>
1442 </dd>
1443 <dt>ev_stat_stat (ev_stat *)</dt>
1444 <dd>
1445 <p>Updates the stat buffer immediately with new values. If you change the
1446watched path in your callback, you could call this fucntion to avoid
1447detecting this change (while introducing a race condition). Can also be
1448useful simply to find out the new values.</p>
1449 </dd>
1450 <dt>ev_statdata attr [read-only]</dt>
1451 <dd>
1452 <p>The most-recently detected attributes of the file. Although the type is of
1453<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1454suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1455was some error while <code>stat</code>ing the file.</p>
1456 </dd>
1457 <dt>ev_statdata prev [read-only]</dt>
1458 <dd>
1459 <p>The previous attributes of the file. The callback gets invoked whenever
1460<code>prev</code> != <code>attr</code>.</p>
1461 </dd>
1462 <dt>ev_tstamp interval [read-only]</dt>
1463 <dd>
1464 <p>The specified interval.</p>
1465 </dd>
1466 <dt>const char *path [read-only]</dt>
1467 <dd>
1468 <p>The filesystem path that is being watched.</p>
1469 </dd>
1470</dl>
1471<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1472<pre> static void
1473 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1474 {
1475 /* /etc/passwd changed in some way */
1476 if (w-&gt;attr.st_nlink)
1477 {
1478 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1479 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1480 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1481 }
1482 else
1483 /* you shalt not abuse printf for puts */
1484 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1485 &quot;if this is windows, they already arrived\n&quot;);
1486 }
1487
1488 ...
1489 ev_stat passwd;
1490
1491 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1492 ev_stat_start (loop, &amp;passwd);
1493
1494
1495
1496
1497</pre>
1498
1499</div>
984<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1500<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
985<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1501<div id="code_ev_idle_code_when_you_ve_got_no-2">
986<p>Idle watchers trigger events when there are no other events are pending 1502<p>Idle watchers trigger events when no other events of the same or higher
987(prepare, check and other idle watchers do not count). That is, as long 1503priority are pending (prepare, check and other idle watchers do not
988as your process is busy handling sockets or timeouts (or even signals, 1504count).</p>
989imagine) it will not be triggered. But when your process is idle all idle 1505<p>That is, as long as your process is busy handling sockets or timeouts
990watchers are being called again and again, once per event loop iteration - 1506(or even signals, imagine) of the same or higher priority it will not be
1507triggered. But when your process is idle (or only lower-priority watchers
1508are pending), the idle watchers are being called once per event loop
991until stopped, that is, or your process receives more events and becomes 1509iteration - until stopped, that is, or your process receives more events
992busy.</p> 1510and becomes busy again with higher priority stuff.</p>
993<p>The most noteworthy effect is that as long as any idle watchers are 1511<p>The most noteworthy effect is that as long as any idle watchers are
994active, the process will not block when waiting for new events.</p> 1512active, the process will not block when waiting for new events.</p>
995<p>Apart from keeping your process non-blocking (which is a useful 1513<p>Apart from keeping your process non-blocking (which is a useful
996effect on its own sometimes), idle watchers are a good place to do 1514effect on its own sometimes), idle watchers are a good place to do
997&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1515&quot;pseudo-background processing&quot;, or delay processing stuff to after the
998event loop has handled all outstanding events.</p> 1516event loop has handled all outstanding events.</p>
1517
1518</div>
1519<h3 id="Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</h3>
1520<div id="Watcher_Specific_Functions_and_Data_-2-5">
999<dl> 1521<dl>
1000 <dt>ev_idle_init (ev_signal *, callback)</dt> 1522 <dt>ev_idle_init (ev_signal *, callback)</dt>
1001 <dd> 1523 <dd>
1002 <p>Initialises and configures the idle watcher - it has no parameters of any 1524 <p>Initialises and configures the idle watcher - it has no parameters of any
1003kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1525kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1004believe me.</p> 1526believe me.</p>
1005 </dd> 1527 </dd>
1006</dl> 1528</dl>
1007<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1529<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1008callback, free it. Alos, use no error checking, as usual.</p> 1530callback, free it. Also, use no error checking, as usual.</p>
1009<pre> static void 1531<pre> static void
1010 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1532 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1011 { 1533 {
1012 free (w); 1534 free (w);
1013 // now do something you wanted to do when the program has 1535 // now do something you wanted to do when the program has
… …
1022 1544
1023 1545
1024</pre> 1546</pre>
1025 1547
1026</div> 1548</div>
1027<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1549<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1028<div id="code_ev_prepare_code_and_code_ev_che-2"> 1550<div id="code_ev_prepare_code_and_code_ev_che-2">
1029<p>Prepare and check watchers are usually (but not always) used in tandem: 1551<p>Prepare and check watchers are usually (but not always) used in tandem:
1030prepare watchers get invoked before the process blocks and check watchers 1552prepare watchers get invoked before the process blocks and check watchers
1031afterwards.</p> 1553afterwards.</p>
1554<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1555the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1556watchers. Other loops than the current one are fine, however. The
1557rationale behind this is that you do not need to check for recursion in
1558those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1559<code>ev_check</code> so if you have one watcher of each kind they will always be
1560called in pairs bracketing the blocking call.</p>
1032<p>Their main purpose is to integrate other event mechanisms into libev and 1561<p>Their main purpose is to integrate other event mechanisms into libev and
1033their use is somewhat advanced. This could be used, for example, to track 1562their use is somewhat advanced. This could be used, for example, to track
1034variable changes, implement your own watchers, integrate net-snmp or a 1563variable changes, implement your own watchers, integrate net-snmp or a
1035coroutine library and lots more.</p> 1564coroutine library and lots more. They are also occasionally useful if
1565you cache some data and want to flush it before blocking (for example,
1566in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1567watcher).</p>
1036<p>This is done by examining in each prepare call which file descriptors need 1568<p>This is done by examining in each prepare call which file descriptors need
1037to be watched by the other library, registering <code>ev_io</code> watchers for 1569to be watched by the other library, registering <code>ev_io</code> watchers for
1038them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1570them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1039provide just this functionality). Then, in the check watcher you check for 1571provide just this functionality). Then, in the check watcher you check for
1040any events that occured (by checking the pending status of all watchers 1572any events that occured (by checking the pending status of all watchers
… …
1047are ready to run (it's actually more complicated: it only runs coroutines 1579are ready to run (it's actually more complicated: it only runs coroutines
1048with priority higher than or equal to the event loop and one coroutine 1580with priority higher than or equal to the event loop and one coroutine
1049of lower priority, but only once, using idle watchers to keep the event 1581of lower priority, but only once, using idle watchers to keep the event
1050loop from blocking if lower-priority coroutines are active, thus mapping 1582loop from blocking if lower-priority coroutines are active, thus mapping
1051low-priority coroutines to idle/background tasks).</p> 1583low-priority coroutines to idle/background tasks).</p>
1584<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1585priority, to ensure that they are being run before any other watchers
1586after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1587too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1588supports this, they will be called before other <code>ev_check</code> watchers did
1589their job. As <code>ev_check</code> watchers are often used to embed other event
1590loops those other event loops might be in an unusable state until their
1591<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1592others).</p>
1593
1594</div>
1595<h3 id="Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</h3>
1596<div id="Watcher_Specific_Functions_and_Data_-2-6">
1052<dl> 1597<dl>
1053 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1598 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1054 <dt>ev_check_init (ev_check *, callback)</dt> 1599 <dt>ev_check_init (ev_check *, callback)</dt>
1055 <dd> 1600 <dd>
1056 <p>Initialises and configures the prepare or check watcher - they have no 1601 <p>Initialises and configures the prepare or check watcher - they have no
1057parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1602parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1058macros, but using them is utterly, utterly and completely pointless.</p> 1603macros, but using them is utterly, utterly and completely pointless.</p>
1059 </dd> 1604 </dd>
1060</dl> 1605</dl>
1061<p>Example: *TODO*.</p> 1606<p>There are a number of principal ways to embed other event loops or modules
1607into libev. Here are some ideas on how to include libadns into libev
1608(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1609use for an actually working example. Another Perl module named <code>EV::Glib</code>
1610embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1611into the Glib event loop).</p>
1612<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1613and in a check watcher, destroy them and call into libadns. What follows
1614is pseudo-code only of course. This requires you to either use a low
1615priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1616the callbacks for the IO/timeout watchers might not have been called yet.</p>
1617<pre> static ev_io iow [nfd];
1618 static ev_timer tw;
1062 1619
1620 static void
1621 io_cb (ev_loop *loop, ev_io *w, int revents)
1622 {
1623 }
1063 1624
1625 // create io watchers for each fd and a timer before blocking
1626 static void
1627 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1628 {
1629 int timeout = 3600000;
1630 struct pollfd fds [nfd];
1631 // actual code will need to loop here and realloc etc.
1632 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1064 1633
1634 /* the callback is illegal, but won't be called as we stop during check */
1635 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1636 ev_timer_start (loop, &amp;tw);
1065 1637
1638 // create one ev_io per pollfd
1639 for (int i = 0; i &lt; nfd; ++i)
1640 {
1641 ev_io_init (iow + i, io_cb, fds [i].fd,
1642 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1643 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1066 1644
1645 fds [i].revents = 0;
1646 ev_io_start (loop, iow + i);
1647 }
1648 }
1649
1650 // stop all watchers after blocking
1651 static void
1652 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1653 {
1654 ev_timer_stop (loop, &amp;tw);
1655
1656 for (int i = 0; i &lt; nfd; ++i)
1657 {
1658 // set the relevant poll flags
1659 // could also call adns_processreadable etc. here
1660 struct pollfd *fd = fds + i;
1661 int revents = ev_clear_pending (iow + i);
1662 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1663 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1664
1665 // now stop the watcher
1666 ev_io_stop (loop, iow + i);
1667 }
1668
1669 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1670 }
1671
1672</pre>
1673<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1674in the prepare watcher and would dispose of the check watcher.</p>
1675<p>Method 3: If the module to be embedded supports explicit event
1676notification (adns does), you can also make use of the actual watcher
1677callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1678<pre> static void
1679 timer_cb (EV_P_ ev_timer *w, int revents)
1680 {
1681 adns_state ads = (adns_state)w-&gt;data;
1682 update_now (EV_A);
1683
1684 adns_processtimeouts (ads, &amp;tv_now);
1685 }
1686
1687 static void
1688 io_cb (EV_P_ ev_io *w, int revents)
1689 {
1690 adns_state ads = (adns_state)w-&gt;data;
1691 update_now (EV_A);
1692
1693 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1694 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1695 }
1696
1697 // do not ever call adns_afterpoll
1698
1699</pre>
1700<p>Method 4: Do not use a prepare or check watcher because the module you
1701want to embed is too inflexible to support it. Instead, youc na override
1702their poll function. The drawback with this solution is that the main
1703loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1704this.</p>
1705<pre> static gint
1706 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1707 {
1708 int got_events = 0;
1709
1710 for (n = 0; n &lt; nfds; ++n)
1711 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1712
1713 if (timeout &gt;= 0)
1714 // create/start timer
1715
1716 // poll
1717 ev_loop (EV_A_ 0);
1718
1719 // stop timer again
1720 if (timeout &gt;= 0)
1721 ev_timer_stop (EV_A_ &amp;to);
1722
1723 // stop io watchers again - their callbacks should have set
1724 for (n = 0; n &lt; nfds; ++n)
1725 ev_io_stop (EV_A_ iow [n]);
1726
1727 return got_events;
1728 }
1729
1730
1731
1732
1733</pre>
1734
1067</div> 1735</div>
1068<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1736<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1069<div id="code_ev_embed_code_when_one_backend_-2"> 1737<div id="code_ev_embed_code_when_one_backend_-2">
1070<p>This is a rather advanced watcher type that lets you embed one event loop 1738<p>This is a rather advanced watcher type that lets you embed one event loop
1071into another.</p> 1739into another (currently only <code>ev_io</code> events are supported in the embedded
1740loop, other types of watchers might be handled in a delayed or incorrect
1741fashion and must not be used).</p>
1072<p>There are primarily two reasons you would want that: work around bugs and 1742<p>There are primarily two reasons you would want that: work around bugs and
1073prioritise I/O.</p> 1743prioritise I/O.</p>
1074<p>As an example for a bug workaround, the kqueue backend might only support 1744<p>As an example for a bug workaround, the kqueue backend might only support
1075sockets on some platform, so it is unusable as generic backend, but you 1745sockets on some platform, so it is unusable as generic backend, but you
1076still want to make use of it because you have many sockets and it scales 1746still want to make use of it because you have many sockets and it scales
… …
1081<p>As for prioritising I/O: rarely you have the case where some fds have 1751<p>As for prioritising I/O: rarely you have the case where some fds have
1082to be watched and handled very quickly (with low latency), and even 1752to be watched and handled very quickly (with low latency), and even
1083priorities and idle watchers might have too much overhead. In this case 1753priorities and idle watchers might have too much overhead. In this case
1084you would put all the high priority stuff in one loop and all the rest in 1754you would put all the high priority stuff in one loop and all the rest in
1085a second one, and embed the second one in the first.</p> 1755a second one, and embed the second one in the first.</p>
1756<p>As long as the watcher is active, the callback will be invoked every time
1757there might be events pending in the embedded loop. The callback must then
1758call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1759their callbacks (you could also start an idle watcher to give the embedded
1760loop strictly lower priority for example). You can also set the callback
1761to <code>0</code>, in which case the embed watcher will automatically execute the
1762embedded loop sweep.</p>
1086<p>As long as the watcher is started it will automatically handle events. The 1763<p>As long as the watcher is started it will automatically handle events. The
1087callback will be invoked whenever some events have been handled. You can 1764callback will be invoked whenever some events have been handled. You can
1088set the callback to <code>0</code> to avoid having to specify one if you are not 1765set the callback to <code>0</code> to avoid having to specify one if you are not
1089interested in that.</p> 1766interested in that.</p>
1090<p>Also, there have not currently been made special provisions for forking: 1767<p>Also, there have not currently been made special provisions for forking:
… …
1116 } 1793 }
1117 else 1794 else
1118 loop_lo = loop_hi; 1795 loop_lo = loop_hi;
1119 1796
1120</pre> 1797</pre>
1798
1799</div>
1800<h3 id="Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</h3>
1801<div id="Watcher_Specific_Functions_and_Data_-2-7">
1121<dl> 1802<dl>
1122 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *loop)</dt> 1803 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1123 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *loop)</dt> 1804 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1805 <dd>
1806 <p>Configures the watcher to embed the given loop, which must be
1807embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1808invoked automatically, otherwise it is the responsibility of the callback
1809to invoke it (it will continue to be called until the sweep has been done,
1810if you do not want thta, you need to temporarily stop the embed watcher).</p>
1124 <dd> 1811 </dd>
1125 <p>Configures the watcher to embed the given loop, which must be embeddable.</p> 1812 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1813 <dd>
1814 <p>Make a single, non-blocking sweep over the embedded loop. This works
1815similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1816apropriate way for embedded loops.</p>
1817 </dd>
1818 <dt>struct ev_loop *loop [read-only]</dt>
1819 <dd>
1820 <p>The embedded event loop.</p>
1126 </dd> 1821 </dd>
1127</dl> 1822</dl>
1128 1823
1129 1824
1130 1825
1131 1826
1132 1827
1133</div> 1828</div>
1134<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1829<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
1830<div id="code_ev_fork_code_the_audacity_to_re-2">
1831<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1832whoever is a good citizen cared to tell libev about it by calling
1833<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1834event loop blocks next and before <code>ev_check</code> watchers are being called,
1835and only in the child after the fork. If whoever good citizen calling
1836<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1837handlers will be invoked, too, of course.</p>
1838
1839</div>
1840<h3 id="Watcher_Specific_Functions_and_Data_-10">Watcher-Specific Functions and Data Members</h3>
1841<div id="Watcher_Specific_Functions_and_Data_-2-8">
1842<dl>
1843 <dt>ev_fork_init (ev_signal *, callback)</dt>
1844 <dd>
1845 <p>Initialises and configures the fork watcher - it has no parameters of any
1846kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1847believe me.</p>
1848 </dd>
1849</dl>
1850
1851
1852
1853
1854
1855</div>
1856<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1135<div id="OTHER_FUNCTIONS_CONTENT"> 1857<div id="OTHER_FUNCTIONS_CONTENT">
1136<p>There are some other functions of possible interest. Described. Here. Now.</p> 1858<p>There are some other functions of possible interest. Described. Here. Now.</p>
1137<dl> 1859<dl>
1138 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1860 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1139 <dd> 1861 <dd>
… …
1163 1885
1164 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1886 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1165 1887
1166</pre> 1888</pre>
1167 </dd> 1889 </dd>
1168 <dt>ev_feed_event (loop, watcher, int events)</dt> 1890 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
1169 <dd> 1891 <dd>
1170 <p>Feeds the given event set into the event loop, as if the specified event 1892 <p>Feeds the given event set into the event loop, as if the specified event
1171had happened for the specified watcher (which must be a pointer to an 1893had happened for the specified watcher (which must be a pointer to an
1172initialised but not necessarily started event watcher).</p> 1894initialised but not necessarily started event watcher).</p>
1173 </dd> 1895 </dd>
1174 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1896 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
1175 <dd> 1897 <dd>
1176 <p>Feed an event on the given fd, as if a file descriptor backend detected 1898 <p>Feed an event on the given fd, as if a file descriptor backend detected
1177the given events it.</p> 1899the given events it.</p>
1178 </dd> 1900 </dd>
1179 <dt>ev_feed_signal_event (loop, int signum)</dt> 1901 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
1180 <dd> 1902 <dd>
1181 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1903 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1904loop!).</p>
1182 </dd> 1905 </dd>
1183</dl> 1906</dl>
1184 1907
1185 1908
1186 1909
1187 1910
1188 1911
1189</div> 1912</div>
1190<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1913<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1191<div id="LIBEVENT_EMULATION_CONTENT"> 1914<div id="LIBEVENT_EMULATION_CONTENT">
1192<p>Libev offers a compatibility emulation layer for libevent. It cannot 1915<p>Libev offers a compatibility emulation layer for libevent. It cannot
1193emulate the internals of libevent, so here are some usage hints:</p> 1916emulate the internals of libevent, so here are some usage hints:</p>
1194<dl> 1917<dl>
1195 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1918 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1205 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1928 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1206to use the libev header file and library.</dt> 1929to use the libev header file and library.</dt>
1207</dl> 1930</dl>
1208 1931
1209</div> 1932</div>
1210<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1933<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1211<div id="C_SUPPORT_CONTENT"> 1934<div id="C_SUPPORT_CONTENT">
1212<p>TBD.</p> 1935<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1936you to use some convinience methods to start/stop watchers and also change
1937the callback model to a model using method callbacks on objects.</p>
1938<p>To use it,</p>
1939<pre> #include &lt;ev++.h&gt;
1213 1940
1941</pre>
1942<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1943of them macros) into the global namespace. All C++ specific things are
1944put into the <code>ev</code> namespace. It should support all the same embedding
1945options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1946<p>Care has been taken to keep the overhead low. The only data member the C++
1947classes add (compared to plain C-style watchers) is the event loop pointer
1948that the watcher is associated with (or no additional members at all if
1949you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1950<p>Currently, functions, and static and non-static member functions can be
1951used as callbacks. Other types should be easy to add as long as they only
1952need one additional pointer for context. If you need support for other
1953types of functors please contact the author (preferably after implementing
1954it).</p>
1955<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1956<dl>
1957 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1958 <dd>
1959 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1960macros from <cite>ev.h</cite>.</p>
1961 </dd>
1962 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1963 <dd>
1964 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1965 </dd>
1966 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1967 <dd>
1968 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1969the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1970which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1971defines by many implementations.</p>
1972 <p>All of those classes have these methods:</p>
1973 <p>
1974 <dl>
1975 <dt>ev::TYPE::TYPE ()</dt>
1976 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1977 <dt>ev::TYPE::~TYPE</dt>
1978 <dd>
1979 <p>The constructor (optionally) takes an event loop to associate the watcher
1980with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1981 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1982<code>set</code> method before starting it.</p>
1983 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1984method to set a callback before you can start the watcher.</p>
1985 <p>(The reason why you have to use a method is a limitation in C++ which does
1986not allow explicit template arguments for constructors).</p>
1987 <p>The destructor automatically stops the watcher if it is active.</p>
1988 </dd>
1989 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1990 <dd>
1991 <p>This method sets the callback method to call. The method has to have a
1992signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1993first argument and the <code>revents</code> as second. The object must be given as
1994parameter and is stored in the <code>data</code> member of the watcher.</p>
1995 <p>This method synthesizes efficient thunking code to call your method from
1996the C callback that libev requires. If your compiler can inline your
1997callback (i.e. it is visible to it at the place of the <code>set</code> call and
1998your compiler is good :), then the method will be fully inlined into the
1999thunking function, making it as fast as a direct C callback.</p>
2000 <p>Example: simple class declaration and watcher initialisation</p>
2001<pre> struct myclass
2002 {
2003 void io_cb (ev::io &amp;w, int revents) { }
2004 }
2005
2006 myclass obj;
2007 ev::io iow;
2008 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
2009
2010</pre>
2011 </dd>
2012 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
2013 <dd>
2014 <p>Also sets a callback, but uses a static method or plain function as
2015callback. The optional <code>data</code> argument will be stored in the watcher's
2016<code>data</code> member and is free for you to use.</p>
2017 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
2018 <p>See the method-<code>set</code> above for more details.</p>
2019 <p>Example:</p>
2020<pre> static void io_cb (ev::io &amp;w, int revents) { }
2021 iow.set &lt;io_cb&gt; ();
2022
2023</pre>
2024 </dd>
2025 <dt>w-&gt;set (struct ev_loop *)</dt>
2026 <dd>
2027 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
2028do this when the watcher is inactive (and not pending either).</p>
2029 </dd>
2030 <dt>w-&gt;set ([args])</dt>
2031 <dd>
2032 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
2033called at least once. Unlike the C counterpart, an active watcher gets
2034automatically stopped and restarted when reconfiguring it with this
2035method.</p>
2036 </dd>
2037 <dt>w-&gt;start ()</dt>
2038 <dd>
2039 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
2040constructor already stores the event loop.</p>
2041 </dd>
2042 <dt>w-&gt;stop ()</dt>
2043 <dd>
2044 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
2045 </dd>
2046 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
2047 <dd>
2048 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
2049<code>ev_TYPE_again</code> function.</p>
2050 </dd>
2051 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
2052 <dd>
2053 <p>Invokes <code>ev_embed_sweep</code>.</p>
2054 </dd>
2055 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
2056 <dd>
2057 <p>Invokes <code>ev_stat_stat</code>.</p>
2058 </dd>
2059 </dl>
2060 </p>
2061 </dd>
2062</dl>
2063<p>Example: Define a class with an IO and idle watcher, start one of them in
2064the constructor.</p>
2065<pre> class myclass
2066 {
2067 ev_io io; void io_cb (ev::io &amp;w, int revents);
2068 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
2069
2070 myclass ();
2071 }
2072
2073 myclass::myclass (int fd)
2074 {
2075 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
2076 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
2077
2078 io.start (fd, ev::READ);
2079 }
2080
2081
2082
2083
2084</pre>
2085
1214</div> 2086</div>
1215<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2087<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
2088<div id="MACRO_MAGIC_CONTENT">
2089<p>Libev can be compiled with a variety of options, the most fundemantal is
2090<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
2091callbacks have an initial <code>struct ev_loop *</code> argument.</p>
2092<p>To make it easier to write programs that cope with either variant, the
2093following macros are defined:</p>
2094<dl>
2095 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
2096 <dd>
2097 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
2098loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
2099<code>EV_A_</code> is used when other arguments are following. Example:</p>
2100<pre> ev_unref (EV_A);
2101 ev_timer_add (EV_A_ watcher);
2102 ev_loop (EV_A_ 0);
2103
2104</pre>
2105 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
2106which is often provided by the following macro.</p>
2107 </dd>
2108 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
2109 <dd>
2110 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
2111loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
2112<code>EV_P_</code> is used when other parameters are following. Example:</p>
2113<pre> // this is how ev_unref is being declared
2114 static void ev_unref (EV_P);
2115
2116 // this is how you can declare your typical callback
2117 static void cb (EV_P_ ev_timer *w, int revents)
2118
2119</pre>
2120 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
2121suitable for use with <code>EV_A</code>.</p>
2122 </dd>
2123 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
2124 <dd>
2125 <p>Similar to the other two macros, this gives you the value of the default
2126loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
2127 </dd>
2128</dl>
2129<p>Example: Declare and initialise a check watcher, utilising the above
2130macros so it will work regardless of whether multiple loops are supported
2131or not.</p>
2132<pre> static void
2133 check_cb (EV_P_ ev_timer *w, int revents)
2134 {
2135 ev_check_stop (EV_A_ w);
2136 }
2137
2138 ev_check check;
2139 ev_check_init (&amp;check, check_cb);
2140 ev_check_start (EV_DEFAULT_ &amp;check);
2141 ev_loop (EV_DEFAULT_ 0);
2142
2143</pre>
2144
2145</div>
2146<h1 id="EMBEDDING">EMBEDDING</h1>
2147<div id="EMBEDDING_CONTENT">
2148<p>Libev can (and often is) directly embedded into host
2149applications. Examples of applications that embed it include the Deliantra
2150Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2151and rxvt-unicode.</p>
2152<p>The goal is to enable you to just copy the neecssary files into your
2153source directory without having to change even a single line in them, so
2154you can easily upgrade by simply copying (or having a checked-out copy of
2155libev somewhere in your source tree).</p>
2156
2157</div>
2158<h2 id="FILESETS">FILESETS</h2>
2159<div id="FILESETS_CONTENT">
2160<p>Depending on what features you need you need to include one or more sets of files
2161in your app.</p>
2162
2163</div>
2164<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
2165<div id="CORE_EVENT_LOOP_CONTENT">
2166<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
2167configuration (no autoconf):</p>
2168<pre> #define EV_STANDALONE 1
2169 #include &quot;ev.c&quot;
2170
2171</pre>
2172<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
2173single C source file only to provide the function implementations. To use
2174it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
2175done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
2176where you can put other configuration options):</p>
2177<pre> #define EV_STANDALONE 1
2178 #include &quot;ev.h&quot;
2179
2180</pre>
2181<p>Both header files and implementation files can be compiled with a C++
2182compiler (at least, thats a stated goal, and breakage will be treated
2183as a bug).</p>
2184<p>You need the following files in your source tree, or in a directory
2185in your include path (e.g. in libev/ when using -Ilibev):</p>
2186<pre> ev.h
2187 ev.c
2188 ev_vars.h
2189 ev_wrap.h
2190
2191 ev_win32.c required on win32 platforms only
2192
2193 ev_select.c only when select backend is enabled (which is enabled by default)
2194 ev_poll.c only when poll backend is enabled (disabled by default)
2195 ev_epoll.c only when the epoll backend is enabled (disabled by default)
2196 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2197 ev_port.c only when the solaris port backend is enabled (disabled by default)
2198
2199</pre>
2200<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
2201to compile this single file.</p>
2202
2203</div>
2204<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
2205<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
2206<p>To include the libevent compatibility API, also include:</p>
2207<pre> #include &quot;event.c&quot;
2208
2209</pre>
2210<p>in the file including <cite>ev.c</cite>, and:</p>
2211<pre> #include &quot;event.h&quot;
2212
2213</pre>
2214<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
2215<p>You need the following additional files for this:</p>
2216<pre> event.h
2217 event.c
2218
2219</pre>
2220
2221</div>
2222<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
2223<div id="AUTOCONF_SUPPORT_CONTENT">
2224<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
2225whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
2226<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
2227include <cite>config.h</cite> and configure itself accordingly.</p>
2228<p>For this of course you need the m4 file:</p>
2229<pre> libev.m4
2230
2231</pre>
2232
2233</div>
2234<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
2235<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
2236<p>Libev can be configured via a variety of preprocessor symbols you have to define
2237before including any of its files. The default is not to build for multiplicity
2238and only include the select backend.</p>
2239<dl>
2240 <dt>EV_STANDALONE</dt>
2241 <dd>
2242 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
2243keeps libev from including <cite>config.h</cite>, and it also defines dummy
2244implementations for some libevent functions (such as logging, which is not
2245supported). It will also not define any of the structs usually found in
2246<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
2247 </dd>
2248 <dt>EV_USE_MONOTONIC</dt>
2249 <dd>
2250 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
2251monotonic clock option at both compiletime and runtime. Otherwise no use
2252of the monotonic clock option will be attempted. If you enable this, you
2253usually have to link against librt or something similar. Enabling it when
2254the functionality isn't available is safe, though, althoguh you have
2255to make sure you link against any libraries where the <code>clock_gettime</code>
2256function is hiding in (often <cite>-lrt</cite>).</p>
2257 </dd>
2258 <dt>EV_USE_REALTIME</dt>
2259 <dd>
2260 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
2261realtime clock option at compiletime (and assume its availability at
2262runtime if successful). Otherwise no use of the realtime clock option will
2263be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
2264(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
2265in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
2266 </dd>
2267 <dt>EV_USE_SELECT</dt>
2268 <dd>
2269 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
2270<code>select</code>(2) backend. No attempt at autodetection will be done: if no
2271other method takes over, select will be it. Otherwise the select backend
2272will not be compiled in.</p>
2273 </dd>
2274 <dt>EV_SELECT_USE_FD_SET</dt>
2275 <dd>
2276 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
2277structure. This is useful if libev doesn't compile due to a missing
2278<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
2279exotic systems. This usually limits the range of file descriptors to some
2280low limit such as 1024 or might have other limitations (winsocket only
2281allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
2282influence the size of the <code>fd_set</code> used.</p>
2283 </dd>
2284 <dt>EV_SELECT_IS_WINSOCKET</dt>
2285 <dd>
2286 <p>When defined to <code>1</code>, the select backend will assume that
2287select/socket/connect etc. don't understand file descriptors but
2288wants osf handles on win32 (this is the case when the select to
2289be used is the winsock select). This means that it will call
2290<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
2291it is assumed that all these functions actually work on fds, even
2292on win32. Should not be defined on non-win32 platforms.</p>
2293 </dd>
2294 <dt>EV_USE_POLL</dt>
2295 <dd>
2296 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
2297backend. Otherwise it will be enabled on non-win32 platforms. It
2298takes precedence over select.</p>
2299 </dd>
2300 <dt>EV_USE_EPOLL</dt>
2301 <dd>
2302 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
2303<code>epoll</code>(7) backend. Its availability will be detected at runtime,
2304otherwise another method will be used as fallback. This is the
2305preferred backend for GNU/Linux systems.</p>
2306 </dd>
2307 <dt>EV_USE_KQUEUE</dt>
2308 <dd>
2309 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
2310<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
2311otherwise another method will be used as fallback. This is the preferred
2312backend for BSD and BSD-like systems, although on most BSDs kqueue only
2313supports some types of fds correctly (the only platform we found that
2314supports ptys for example was NetBSD), so kqueue might be compiled in, but
2315not be used unless explicitly requested. The best way to use it is to find
2316out whether kqueue supports your type of fd properly and use an embedded
2317kqueue loop.</p>
2318 </dd>
2319 <dt>EV_USE_PORT</dt>
2320 <dd>
2321 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
232210 port style backend. Its availability will be detected at runtime,
2323otherwise another method will be used as fallback. This is the preferred
2324backend for Solaris 10 systems.</p>
2325 </dd>
2326 <dt>EV_USE_DEVPOLL</dt>
2327 <dd>
2328 <p>reserved for future expansion, works like the USE symbols above.</p>
2329 </dd>
2330 <dt>EV_USE_INOTIFY</dt>
2331 <dd>
2332 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2333interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2334be detected at runtime.</p>
2335 </dd>
2336 <dt>EV_H</dt>
2337 <dd>
2338 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
2339undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This
2340can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
2341 </dd>
2342 <dt>EV_CONFIG_H</dt>
2343 <dd>
2344 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
2345<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
2346<code>EV_H</code>, above.</p>
2347 </dd>
2348 <dt>EV_EVENT_H</dt>
2349 <dd>
2350 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
2351of how the <cite>event.h</cite> header can be found.</p>
2352 </dd>
2353 <dt>EV_PROTOTYPES</dt>
2354 <dd>
2355 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
2356prototypes, but still define all the structs and other symbols. This is
2357occasionally useful if you want to provide your own wrapper functions
2358around libev functions.</p>
2359 </dd>
2360 <dt>EV_MULTIPLICITY</dt>
2361 <dd>
2362 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
2363will have the <code>struct ev_loop *</code> as first argument, and you can create
2364additional independent event loops. Otherwise there will be no support
2365for multiple event loops and there is no first event loop pointer
2366argument. Instead, all functions act on the single default loop.</p>
2367 </dd>
2368 <dt>EV_MINPRI</dt>
2369 <dt>EV_MAXPRI</dt>
2370 <dd>
2371 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2372<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2373provide for more priorities by overriding those symbols (usually defined
2374to be <code>-2</code> and <code>2</code>, respectively).</p>
2375 <p>When doing priority-based operations, libev usually has to linearly search
2376all the priorities, so having many of them (hundreds) uses a lot of space
2377and time, so using the defaults of five priorities (-2 .. +2) is usually
2378fine.</p>
2379 <p>If your embedding app does not need any priorities, defining these both to
2380<code>0</code> will save some memory and cpu.</p>
2381 </dd>
2382 <dt>EV_PERIODIC_ENABLE</dt>
2383 <dd>
2384 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2385defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2386code.</p>
2387 </dd>
2388 <dt>EV_IDLE_ENABLE</dt>
2389 <dd>
2390 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2391defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2392code.</p>
2393 </dd>
2394 <dt>EV_EMBED_ENABLE</dt>
2395 <dd>
2396 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2397defined to be <code>0</code>, then they are not.</p>
2398 </dd>
2399 <dt>EV_STAT_ENABLE</dt>
2400 <dd>
2401 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2402defined to be <code>0</code>, then they are not.</p>
2403 </dd>
2404 <dt>EV_FORK_ENABLE</dt>
2405 <dd>
2406 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2407defined to be <code>0</code>, then they are not.</p>
2408 </dd>
2409 <dt>EV_MINIMAL</dt>
2410 <dd>
2411 <p>If you need to shave off some kilobytes of code at the expense of some
2412speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2413some inlining decisions, saves roughly 30% codesize of amd64.</p>
2414 </dd>
2415 <dt>EV_PID_HASHSIZE</dt>
2416 <dd>
2417 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2418pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2419than enough. If you need to manage thousands of children you might want to
2420increase this value (<i>must</i> be a power of two).</p>
2421 </dd>
2422 <dt>EV_INOTIFY_HASHSIZE</dt>
2423 <dd>
2424 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2425inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2426usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2427watchers you might want to increase this value (<i>must</i> be a power of
2428two).</p>
2429 </dd>
2430 <dt>EV_COMMON</dt>
2431 <dd>
2432 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2433this macro to a something else you can include more and other types of
2434members. You have to define it each time you include one of the files,
2435though, and it must be identical each time.</p>
2436 <p>For example, the perl EV module uses something like this:</p>
2437<pre> #define EV_COMMON \
2438 SV *self; /* contains this struct */ \
2439 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2440
2441</pre>
2442 </dd>
2443 <dt>EV_CB_DECLARE (type)</dt>
2444 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2445 <dt>ev_set_cb (ev, cb)</dt>
2446 <dd>
2447 <p>Can be used to change the callback member declaration in each watcher,
2448and the way callbacks are invoked and set. Must expand to a struct member
2449definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2450their default definitions. One possible use for overriding these is to
2451avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2452method calls instead of plain function calls in C++.</p>
2453
2454</div>
2455<h2 id="EXAMPLES">EXAMPLES</h2>
2456<div id="EXAMPLES_CONTENT">
2457 <p>For a real-world example of a program the includes libev
2458verbatim, you can have a look at the EV perl module
2459(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2460the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2461interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2462will be compiled. It is pretty complex because it provides its own header
2463file.</p>
2464 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2465that everybody includes and which overrides some configure choices:</p>
2466<pre> #define EV_MINIMAL 1
2467 #define EV_USE_POLL 0
2468 #define EV_MULTIPLICITY 0
2469 #define EV_PERIODIC_ENABLE 0
2470 #define EV_STAT_ENABLE 0
2471 #define EV_FORK_ENABLE 0
2472 #define EV_CONFIG_H &lt;config.h&gt;
2473 #define EV_MINPRI 0
2474 #define EV_MAXPRI 0
2475
2476 #include &quot;ev++.h&quot;
2477
2478</pre>
2479 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2480<pre> #include &quot;ev_cpp.h&quot;
2481 #include &quot;ev.c&quot;
2482
2483
2484
2485
2486</pre>
2487
2488</div>
2489<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2490<div id="COMPLEXITIES_CONTENT">
2491 <p>In this section the complexities of (many of) the algorithms used inside
2492libev will be explained. For complexity discussions about backends see the
2493documentation for <code>ev_default_init</code>.</p>
2494 <p>All of the following are about amortised time: If an array needs to be
2495extended, libev needs to realloc and move the whole array, but this
2496happens asymptotically never with higher number of elements, so O(1) might
2497mean it might do a lengthy realloc operation in rare cases, but on average
2498it is much faster and asymptotically approaches constant time.</p>
2499 <p>
2500 <dl>
2501 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2502 <dd>
2503 <p>This means that, when you have a watcher that triggers in one hour and
2504there are 100 watchers that would trigger before that then inserting will
2505have to skip those 100 watchers.</p>
2506 </dd>
2507 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2508 <dd>
2509 <p>That means that for changing a timer costs less than removing/adding them
2510as only the relative motion in the event queue has to be paid for.</p>
2511 </dd>
2512 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2513 <dd>
2514 <p>These just add the watcher into an array or at the head of a list.
2515=item Stopping check/prepare/idle watchers: O(1)</p>
2516 </dd>
2517 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2518 <dd>
2519 <p>These watchers are stored in lists then need to be walked to find the
2520correct watcher to remove. The lists are usually short (you don't usually
2521have many watchers waiting for the same fd or signal).</p>
2522 </dd>
2523 <dt>Finding the next timer per loop iteration: O(1)</dt>
2524 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2525 <dd>
2526 <p>A change means an I/O watcher gets started or stopped, which requires
2527libev to recalculate its status (and possibly tell the kernel).</p>
2528 </dd>
2529 <dt>Activating one watcher: O(1)</dt>
2530 <dt>Priority handling: O(number_of_priorities)</dt>
2531 <dd>
2532 <p>Priorities are implemented by allocating some space for each
2533priority. When doing priority-based operations, libev usually has to
2534linearly search all the priorities.</p>
2535 </dd>
2536 </dl>
2537 </p>
2538
2539
2540
2541
2542
2543</div>
2544<h1 id="AUTHOR">AUTHOR</h1>
1216<div id="AUTHOR_CONTENT"> 2545<div id="AUTHOR_CONTENT">
1217<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2546 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1218 2547
1219</div> 2548</div>
1220</div></body> 2549</div></body>
1221</html> 2550</html>

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