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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="Fri Dec 7 17:49:47 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></li>
31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> 33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></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> 34<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></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> 35<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></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> 38<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>
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> 39<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>
37<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li> 40<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
41<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></li>
38</ul> 42</ul>
39</li> 43</li>
40<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
41<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
42<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 46<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
47<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
48<li><a href="#EMBEDDING">EMBEDDING</a>
49<ul><li><a href="#FILESETS">FILESETS</a>
50<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
51<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
52<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
53</ul>
54</li>
55<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
56<li><a href="#EXAMPLES">EXAMPLES</a></li>
57</ul>
58</li>
59<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
43<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
44</li> 61</li>
45</ul><hr /> 62</ul><hr />
46<!-- INDEX END --> 63<!-- INDEX END -->
47 64
48<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
49<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
50<p>libev - a high performance full-featured event loop written in C</p> 67<p>libev - a high performance full-featured event loop written in C</p>
51 68
52</div> 69</div>
53<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
54<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
55<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
56 73
57</pre> 74</pre>
58 75
59</div> 76</div>
60<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
78<div id="EXAMPLE_PROGRAM_CONTENT">
79<pre> #include &lt;ev.h&gt;
80
81 ev_io stdin_watcher;
82 ev_timer timeout_watcher;
83
84 /* called when data readable on stdin */
85 static void
86 stdin_cb (EV_P_ struct ev_io *w, int revents)
87 {
88 /* puts (&quot;stdin ready&quot;); */
89 ev_io_stop (EV_A_ w); /* just a syntax example */
90 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
91 }
92
93 static void
94 timeout_cb (EV_P_ struct ev_timer *w, int revents)
95 {
96 /* puts (&quot;timeout&quot;); */
97 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
98 }
99
100 int
101 main (void)
102 {
103 struct ev_loop *loop = ev_default_loop (0);
104
105 /* initialise an io watcher, then start it */
106 ev_io_init (&amp;stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
107 ev_io_start (loop, &amp;stdin_watcher);
108
109 /* simple non-repeating 5.5 second timeout */
110 ev_timer_init (&amp;timeout_watcher, timeout_cb, 5.5, 0.);
111 ev_timer_start (loop, &amp;timeout_watcher);
112
113 /* loop till timeout or data ready */
114 ev_loop (loop, 0);
115
116 return 0;
117 }
118
119</pre>
120
121</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1>
61<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
62<p>Libev is an event loop: you register interest in certain events (such as a 124<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 125file descriptor being readable or a timeout occuring), and it will manage
64these event sources and provide your program with events.</p> 126these 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 127<p>To do this, it must take more or less complete control over your process
… …
69watchers</i>, which are relatively small C structures you initialise with the 131watchers</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 132details of the event, and then hand it over to libev by <i>starting</i> the
71watcher.</p> 133watcher.</p>
72 134
73</div> 135</div>
74<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1>
75<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
76<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 138<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 139BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
78timers with customised rescheduling, signal events, process status change 140for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
79events (related to SIGCHLD), and event watchers dealing with the event 141(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 142with customised rescheduling (<code>ev_periodic</code>), synchronous signals
143(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
144watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
145<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
146file watchers (<code>ev_stat</code>) and even limited support for fork events
147(<code>ev_fork</code>).</p>
148<p>It also is quite fast (see this
81fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 149<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
82it to libevent for example).</p> 150for example).</p>
83 151
84</div> 152</div>
85<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 153<h1 id="CONVENTIONS">CONVENTIONS</h1>
86<div id="CONVENTIONS_CONTENT"> 154<div id="CONVENTIONS_CONTENT">
87<p>Libev is very configurable. In this manual the default configuration 155<p>Libev is very configurable. In this manual the default configuration will
88will be described, which supports multiple event loops. For more info 156be described, which supports multiple event loops. For more info about
89about various configuration options please have a look at the file 157various 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 158this manual. If libev was configured without support for multiple event
91support for multiple event loops, then all functions taking an initial 159loops, 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>) 160(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
93will not have this argument.</p>
94 161
95</div> 162</div>
96<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 163<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
97<div id="TIME_REPRESENTATION_CONTENT"> 164<div id="TIME_REPRESENTATION_CONTENT">
98<p>Libev represents time as a single floating point number, representing the 165<p>Libev represents time as a single floating point number, representing the
99(fractional) number of seconds since the (POSIX) epoch (somewhere near 166(fractional) number of seconds since the (POSIX) epoch (somewhere near
100the beginning of 1970, details are complicated, don't ask). This type is 167the 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 168called <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 169to the <code>double</code> type in C, and when you need to do any calculations on
103it, you should treat it as such.</p> 170it, you should treat it as such.</p>
104 171
105
106
107
108
109</div> 172</div>
110<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 173<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
111<div id="GLOBAL_FUNCTIONS_CONTENT"> 174<div id="GLOBAL_FUNCTIONS_CONTENT">
112<p>These functions can be called anytime, even before initialising the 175<p>These functions can be called anytime, even before initialising the
113library in any way.</p> 176library in any way.</p>
114<dl> 177<dl>
115 <dt>ev_tstamp ev_time ()</dt> 178 <dt>ev_tstamp ev_time ()</dt>
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128version of the library your program was compiled against.</p> 191version of the library your program was compiled against.</p>
129 <p>Usually, it's a good idea to terminate if the major versions mismatch, 192 <p>Usually, it's a good idea to terminate if the major versions mismatch,
130as this indicates an incompatible change. Minor versions are usually 193as this indicates an incompatible change. Minor versions are usually
131compatible to older versions, so a larger minor version alone is usually 194compatible to older versions, so a larger minor version alone is usually
132not a problem.</p> 195not a problem.</p>
133 <p>Example: make sure we haven't accidentally been linked against the wrong 196 <p>Example: Make sure we haven't accidentally been linked against the wrong
134version:</p> 197version.</p>
135<pre> assert ((&quot;libev version mismatch&quot;, 198<pre> assert ((&quot;libev version mismatch&quot;,
136 ev_version_major () == EV_VERSION_MAJOR 199 ev_version_major () == EV_VERSION_MAJOR
137 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 200 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
138 201
139</pre> 202</pre>
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169recommended ones.</p> 232recommended ones.</p>
170 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 233 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
171 </dd> 234 </dd>
172 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
173 <dd> 236 <dd>
174 <p>Sets the allocation function to use (the prototype is similar to the 237 <p>Sets the allocation function to use (the prototype is similar - the
175realloc C function, the semantics are identical). It is used to allocate 238semantics is identical - to the realloc C function). It is used to
176and free memory (no surprises here). If it returns zero when memory 239allocate and free memory (no surprises here). If it returns zero when
177needs to be allocated, the library might abort or take some potentially 240memory needs to be allocated, the library might abort or take some
178destructive action. The default is your system realloc function.</p> 241potentially destructive action. The default is your system realloc
242function.</p>
179 <p>You could override this function in high-availability programs to, say, 243 <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, 244free 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> 245or 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 246 <p>Example: Replace the libev allocator with one that waits a bit and then
183retries: better than mine).</p> 247retries).</p>
184<pre> static void * 248<pre> static void *
185 persistent_realloc (void *ptr, long size) 249 persistent_realloc (void *ptr, size_t size)
186 { 250 {
187 for (;;) 251 for (;;)
188 { 252 {
189 void *newptr = realloc (ptr, size); 253 void *newptr = realloc (ptr, size);
190 254
… …
207indicating the system call or subsystem causing the problem. If this 271indicating the system call or subsystem causing the problem. If this
208callback is set, then libev will expect it to remedy the sitution, no 272callback is set, then libev will expect it to remedy the sitution, no
209matter what, when it returns. That is, libev will generally retry the 273matter what, when it returns. That is, libev will generally retry the
210requested operation, or, if the condition doesn't go away, do bad stuff 274requested operation, or, if the condition doesn't go away, do bad stuff
211(such as abort).</p> 275(such as abort).</p>
212 <p>Example: do the same thing as libev does internally:</p> 276 <p>Example: This is basically the same thing that libev does internally, too.</p>
213<pre> static void 277<pre> static void
214 fatal_error (const char *msg) 278 fatal_error (const char *msg)
215 { 279 {
216 perror (msg); 280 perror (msg);
217 abort (); 281 abort ();
… …
223</pre> 287</pre>
224 </dd> 288 </dd>
225</dl> 289</dl>
226 290
227</div> 291</div>
228<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 292<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
229<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 293<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 294<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 295types of such loops, the <i>default</i> loop, which supports signals and child
232events, and dynamically created loops which do not.</p> 296events, and dynamically created loops which do not.</p>
233<p>If you use threads, a common model is to run the default event loop 297<p>If you use threads, a common model is to run the default event loop
… …
261or setgid) then libev will <i>not</i> look at the environment variable 325or setgid) then libev will <i>not</i> look at the environment variable
262<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 326<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
263override the flags completely if it is found in the environment. This is 327override 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 328useful to try out specific backends to test their performance, or to work
265around bugs.</p> 329around bugs.</p>
330 </dd>
331 <dt><code>EVFLAG_FORKCHECK</code></dt>
332 <dd>
333 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
334a fork, you can also make libev check for a fork in each iteration by
335enabling this flag.</p>
336 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
337and thus this might slow down your event loop if you do a lot of loop
338iterations and little real work, but is usually not noticeable (on my
339Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
340without a syscall and thus <i>very</i> fast, but my Linux system also has
341<code>pthread_atfork</code> which is even faster).</p>
342 <p>The big advantage of this flag is that you can forget about fork (and
343forget about forgetting to tell libev about forking) when you use this
344flag.</p>
345 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
346environment variable.</p>
266 </dd> 347 </dd>
267 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 348 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
268 <dd> 349 <dd>
269 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 350 <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, 351libev tries to roll its own fd_set with no limits on the number of fds,
… …
353 <dd> 434 <dd>
354 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 435 <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 436always 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 437handle signal and child watchers, and attempts to do so will be greeted by
357undefined behaviour (or a failed assertion if assertions are enabled).</p> 438undefined 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> 439 <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); 440<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
360 if (!epoller) 441 if (!epoller)
361 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 442 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
362 443
363</pre> 444</pre>
364 </dd> 445 </dd>
365 <dt>ev_default_destroy ()</dt> 446 <dt>ev_default_destroy ()</dt>
366 <dd> 447 <dd>
367 <p>Destroys the default loop again (frees all memory and kernel state 448 <p>Destroys the default loop again (frees all memory and kernel state
368etc.). This stops all registered event watchers (by not touching them in 449etc.). None of the active event watchers will be stopped in the normal
369any way whatsoever, although you cannot rely on this :).</p> 450sense, so e.g. <code>ev_is_active</code> might still return true. It is your
451responsibility to either stop all watchers cleanly yoursef <i>before</i>
452calling this function, or cope with the fact afterwards (which is usually
453the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them
454for example).</p>
370 </dd> 455 </dd>
371 <dt>ev_loop_destroy (loop)</dt> 456 <dt>ev_loop_destroy (loop)</dt>
372 <dd> 457 <dd>
373 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 458 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
374earlier call to <code>ev_loop_new</code>.</p> 459earlier call to <code>ev_loop_new</code>.</p>
… …
395 <dt>ev_loop_fork (loop)</dt> 480 <dt>ev_loop_fork (loop)</dt>
396 <dd> 481 <dd>
397 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 482 <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 483<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> 484after fork, and how you do this is entirely your own problem.</p>
485 </dd>
486 <dt>unsigned int ev_loop_count (loop)</dt>
487 <dd>
488 <p>Returns the count of loop iterations for the loop, which is identical to
489the number of times libev did poll for new events. It starts at <code>0</code> and
490happily wraps around with enough iterations.</p>
491 <p>This value can sometimes be useful as a generation counter of sorts (it
492&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
493<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
400 </dd> 494 </dd>
401 <dt>unsigned int ev_backend (loop)</dt> 495 <dt>unsigned int ev_backend (loop)</dt>
402 <dd> 496 <dd>
403 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 497 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
404use.</p> 498use.</p>
… …
452 be handled here by queueing them when their watcher gets executed. 546 be handled here by queueing them when their watcher gets executed.
453 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 547 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
454 were used, return, otherwise continue with step *. 548 were used, return, otherwise continue with step *.
455 549
456</pre> 550</pre>
457 <p>Example: queue some jobs and then loop until no events are outsanding 551 <p>Example: Queue some jobs and then loop until no events are outsanding
458anymore.</p> 552anymore.</p>
459<pre> ... queue jobs here, make sure they register event watchers as long 553<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..) 554 ... as they still have work to do (even an idle watcher will do..)
461 ev_loop (my_loop, 0); 555 ev_loop (my_loop, 0);
462 ... jobs done. yeah! 556 ... jobs done. yeah!
… …
481example, libev itself uses this for its internal signal pipe: It is not 575example, 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 576visible 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 577no 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 578way 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> 579libraries. 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> 580 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
487running when nothing else is active.</p> 581running when nothing else is active.</p>
488<pre> struct dv_signal exitsig; 582<pre> struct ev_signal exitsig;
489 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 583 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
490 ev_signal_start (myloop, &amp;exitsig); 584 ev_signal_start (loop, &amp;exitsig);
491 evf_unref (myloop); 585 evf_unref (loop);
492 586
493</pre> 587</pre>
494 <p>Example: for some weird reason, unregister the above signal handler again.</p> 588 <p>Example: For some weird reason, unregister the above signal handler again.</p>
495<pre> ev_ref (myloop); 589<pre> ev_ref (loop);
496 ev_signal_stop (myloop, &amp;exitsig); 590 ev_signal_stop (loop, &amp;exitsig);
497 591
498</pre> 592</pre>
499 </dd> 593 </dd>
500</dl> 594</dl>
501 595
596
597
598
599
502</div> 600</div>
503<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 601<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
504<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 602<div id="ANATOMY_OF_A_WATCHER_CONTENT">
505<p>A watcher is a structure that you create and register to record your 603<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 604interest 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> 605become 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) 606<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 633with 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 634*)</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> 635corresponding 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 636<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 637must not touch the values stored in it. Most specifically you must never
540reinitialise it or call its set macro.</p> 638reinitialise 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 639<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 640registered watcher structure as second, and a bitset of received events as
547third argument.</p> 641third argument.</p>
548<p>The received events usually include a single bit per event type received 642<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 643(you can receive multiple events at the same time). The possible bit masks
… …
569 </dd> 663 </dd>
570 <dt><code>EV_CHILD</code></dt> 664 <dt><code>EV_CHILD</code></dt>
571 <dd> 665 <dd>
572 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 666 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
573 </dd> 667 </dd>
668 <dt><code>EV_STAT</code></dt>
669 <dd>
670 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
671 </dd>
574 <dt><code>EV_IDLE</code></dt> 672 <dt><code>EV_IDLE</code></dt>
575 <dd> 673 <dd>
576 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 674 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
577 </dd> 675 </dd>
578 <dt><code>EV_PREPARE</code></dt> 676 <dt><code>EV_PREPARE</code></dt>
… …
583<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 681<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 682received 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 683many 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 684(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
587<code>ev_loop</code> from blocking).</p> 685<code>ev_loop</code> from blocking).</p>
686 </dd>
687 <dt><code>EV_EMBED</code></dt>
688 <dd>
689 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
690 </dd>
691 <dt><code>EV_FORK</code></dt>
692 <dd>
693 <p>The event loop has been resumed in the child process after fork (see
694<code>ev_fork</code>).</p>
588 </dd> 695 </dd>
589 <dt><code>EV_ERROR</code></dt> 696 <dt><code>EV_ERROR</code></dt>
590 <dd> 697 <dd>
591 <p>An unspecified error has occured, the watcher has been stopped. This might 698 <p>An unspecified error has occured, the watcher has been stopped. This might
592happen because the watcher could not be properly started because libev 699happen because the watcher could not be properly started because libev
… …
600programs, though, so beware.</p> 707programs, though, so beware.</p>
601 </dd> 708 </dd>
602</dl> 709</dl>
603 710
604</div> 711</div>
712<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
713<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
714<p>In the following description, <code>TYPE</code> stands for the watcher type,
715e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
716<dl>
717 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
718 <dd>
719 <p>This macro initialises the generic portion of a watcher. The contents
720of the watcher object can be arbitrary (so <code>malloc</code> will do). Only
721the generic parts of the watcher are initialised, you <i>need</i> to call
722the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
723type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
724which rolls both calls into one.</p>
725 <p>You can reinitialise a watcher at any time as long as it has been stopped
726(or never started) and there are no pending events outstanding.</p>
727 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
728int revents)</code>.</p>
729 </dd>
730 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
731 <dd>
732 <p>This macro initialises the type-specific parts of a watcher. You need to
733call <code>ev_init</code> at least once before you call this macro, but you can
734call <code>ev_TYPE_set</code> any number of times. You must not, however, call this
735macro on a watcher that is active (it can be pending, however, which is a
736difference to the <code>ev_init</code> macro).</p>
737 <p>Although some watcher types do not have type-specific arguments
738(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p>
739 </dd>
740 <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt>
741 <dd>
742 <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro
743calls into a single call. This is the most convinient method to initialise
744a watcher. The same limitations apply, of course.</p>
745 </dd>
746 <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt>
747 <dd>
748 <p>Starts (activates) the given watcher. Only active watchers will receive
749events. If the watcher is already active nothing will happen.</p>
750 </dd>
751 <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt>
752 <dd>
753 <p>Stops the given watcher again (if active) and clears the pending
754status. It is possible that stopped watchers are pending (for example,
755non-repeating timers are being stopped when they become pending), but
756<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If
757you want to free or reuse the memory used by the watcher it is therefore a
758good idea to always call its <code>ev_TYPE_stop</code> function.</p>
759 </dd>
760 <dt>bool ev_is_active (ev_TYPE *watcher)</dt>
761 <dd>
762 <p>Returns a true value iff the watcher is active (i.e. it has been started
763and not yet been stopped). As long as a watcher is active you must not modify
764it.</p>
765 </dd>
766 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
767 <dd>
768 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
769events but its callback has not yet been invoked). As long as a watcher
770is pending (but not active) you must not call an init function on it (but
771<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
772libev (e.g. you cnanot <code>free ()</code> it).</p>
773 </dd>
774 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
775 <dd>
776 <p>Returns the callback currently set on the watcher.</p>
777 </dd>
778 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
779 <dd>
780 <p>Change the callback. You can change the callback at virtually any time
781(modulo threads).</p>
782 </dd>
783 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
784 <dt>int ev_priority (ev_TYPE *watcher)</dt>
785 <dd>
786 <p>Set and query the priority of the watcher. The priority is a small
787integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
788(default: <code>-2</code>). Pending watchers with higher priority will be invoked
789before watchers with lower priority, but priority will not keep watchers
790from being executed (except for <code>ev_idle</code> watchers).</p>
791 <p>This means that priorities are <i>only</i> used for ordering callback
792invocation after new events have been received. This is useful, for
793example, to reduce latency after idling, or more often, to bind two
794watchers on the same event and make sure one is called first.</p>
795 <p>If you need to suppress invocation when higher priority events are pending
796you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
797 <p>The default priority used by watchers when no priority has been set is
798always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
799 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
800fine, as long as you do not mind that the priority value you query might
801or might not have been adjusted to be within valid range.</p>
802 </dd>
803</dl>
804
805
806
807
808
809</div>
605<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 810<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"> 811<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 812<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 813and 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 814to associate arbitrary data with your watcher. If you need more data and
… …
626 struct my_io *w = (struct my_io *)w_; 831 struct my_io *w = (struct my_io *)w_;
627 ... 832 ...
628 } 833 }
629 834
630</pre> 835</pre>
631<p>More interesting and less C-conformant ways of catsing your callback type 836<p>More interesting and less C-conformant ways of casting your callback type
632have been omitted....</p> 837instead have been omitted.</p>
838<p>Another common scenario is having some data structure with multiple
839watchers:</p>
840<pre> struct my_biggy
841 {
842 int some_data;
843 ev_timer t1;
844 ev_timer t2;
845 }
633 846
847</pre>
848<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
849you need to use <code>offsetof</code>:</p>
850<pre> #include &lt;stddef.h&gt;
634 851
852 static void
853 t1_cb (EV_P_ struct ev_timer *w, int revents)
854 {
855 struct my_biggy big = (struct my_biggy *
856 (((char *)w) - offsetof (struct my_biggy, t1));
857 }
635 858
859 static void
860 t2_cb (EV_P_ struct ev_timer *w, int revents)
861 {
862 struct my_biggy big = (struct my_biggy *
863 (((char *)w) - offsetof (struct my_biggy, t2));
864 }
636 865
637 866
867
868
869</pre>
870
638</div> 871</div>
639<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 872<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
640<div id="WATCHER_TYPES_CONTENT"> 873<div id="WATCHER_TYPES_CONTENT">
641<p>This section describes each watcher in detail, but will not repeat 874<p>This section describes each watcher in detail, but will not repeat
642information given in the last section.</p> 875information given in the last section. Any initialisation/set macros,
876functions and members specific to the watcher type are explained.</p>
877<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
878while the watcher is active, you can look at the member and expect some
879sensible content, but you must not modify it (you can modify it while the
880watcher is stopped to your hearts content), or <i>[read-write]</i>, which
881means you can expect it to have some sensible content while the watcher
882is active, but you can also modify it. Modifying it may not do something
883sensible or take immediate effect (or do anything at all), but libev will
884not crash or malfunction in any way.</p>
643 885
644 886
645 887
646 888
647 889
648</div> 890</div>
649<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 891<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"> 892<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 893<p>I/O watchers check whether a file descriptor is readable or writable
652in each iteration of the event loop (This behaviour is called 894in each iteration of the event loop, or, more precisely, when reading
653level-triggering because you keep receiving events as long as the 895would 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 896some data. This behaviour is called level-triggering because you keep
655act on the event and neither want to receive future events).</p> 897receiving events as long as the condition persists. Remember you can stop
898the watcher if you don't want to act on the event and neither want to
899receive future events.</p>
656<p>In general you can register as many read and/or write event watchers per 900<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 901fd 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 902descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing).</p> 903required if you know what you are doing).</p>
660<p>You have to be careful with dup'ed file descriptors, though. Some backends 904<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 905(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 906descriptors correctly if you register interest in two or more fds pointing
663to the same underlying file/socket etc. description (that is, they share 907to the same underlying file/socket/etc. description (that is, they share
664the same underlying &quot;file open&quot;).</p> 908the 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 909<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 910(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
667<code>EVBACKEND_POLL</code>).</p> 911<code>EVBACKEND_POLL</code>).</p>
912<p>Another thing you have to watch out for is that it is quite easy to
913receive &quot;spurious&quot; readyness notifications, that is your callback might
914be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
915because there is no data. Not only are some backends known to create a
916lot of those (for example solaris ports), it is very easy to get into
917this situation even with a relatively standard program structure. Thus
918it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
919<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
920<p>If you cannot run the fd in non-blocking mode (for example you should not
921play around with an Xlib connection), then you have to seperately re-test
922wether a file descriptor is really ready with a known-to-be good interface
923such as poll (fortunately in our Xlib example, Xlib already does this on
924its own, so its quite safe to use).</p>
668<dl> 925<dl>
669 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 926 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
670 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 927 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
671 <dd> 928 <dd>
672 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 929 <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 | 930rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
674EV_WRITE</code> to receive the given events.</p> 931<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 932 </dd>
676epoll and solaris ports) can result in spurious readyness notifications 933 <dt>int fd [read-only]</dt>
677for file descriptors, so you practically need to use non-blocking I/O (and 934 <dd>
678treat callback invocation as hint only), or retest separately with a safe 935 <p>The file descriptor being watched.</p>
679interface before doing I/O (XLib can do this), or force the use of either 936 </dd>
680<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 937 <dt>int events [read-only]</dt>
681problem. Also note that it is quite easy to have your callback invoked 938 <dd>
682when the readyness condition is no longer valid even when employing 939 <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> 940 </dd>
686</dl> 941</dl>
687<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 942<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 943readable, but only once. Since it is likely line-buffered, you could
689attempt to read a whole line in the callback:</p> 944attempt to read a whole line in the callback.</p>
690<pre> static void 945<pre> static void
691 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 946 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
692 { 947 {
693 ev_io_stop (loop, w); 948 ev_io_stop (loop, w);
694 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 949 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
705 960
706 961
707</pre> 962</pre>
708 963
709</div> 964</div>
710<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 965<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"> 966<div id="code_ev_timer_code_relative_and_opti-2">
712<p>Timer watchers are simple relative timers that generate an event after a 967<p>Timer watchers are simple relative timers that generate an event after a
713given time, and optionally repeating in regular intervals after that.</p> 968given 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 969<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 970times out after an hour and you reset your system clock to last years
… …
743 </dd> 998 </dd>
744 <dt>ev_timer_again (loop)</dt> 999 <dt>ev_timer_again (loop)</dt>
745 <dd> 1000 <dd>
746 <p>This will act as if the timer timed out and restart it again if it is 1001 <p>This will act as if the timer timed out and restart it again if it is
747repeating. The exact semantics are:</p> 1002repeating. The exact semantics are:</p>
1003 <p>If the timer is pending, its pending status is cleared.</p>
748 <p>If the timer is started but nonrepeating, stop it.</p> 1004 <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 1005 <p>If the timer is repeating, either start it if necessary (with the
750value), or reset the running timer to the repeat value.</p> 1006<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 1007 <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 1008example: 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 1009timeout, 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 1010seconds 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 1011configure 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 1012<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 1013you go into an idle state where you do not expect data to travel on the
1014socket, 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> 1015automatically restart it if need be.</p>
1016 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
1017altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
1018<pre> ev_timer_init (timer, callback, 0., 5.);
1019 ev_timer_again (loop, timer);
1020 ...
1021 timer-&gt;again = 17.;
1022 ev_timer_again (loop, timer);
1023 ...
1024 timer-&gt;again = 10.;
1025 ev_timer_again (loop, timer);
1026
1027</pre>
1028 <p>This is more slightly efficient then stopping/starting the timer each time
1029you want to modify its timeout value.</p>
1030 </dd>
1031 <dt>ev_tstamp repeat [read-write]</dt>
1032 <dd>
1033 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
1034or <code>ev_timer_again</code> is called and determines the next timeout (if any),
1035which is also when any modifications are taken into account.</p>
759 </dd> 1036 </dd>
760</dl> 1037</dl>
761<p>Example: create a timer that fires after 60 seconds.</p> 1038<p>Example: Create a timer that fires after 60 seconds.</p>
762<pre> static void 1039<pre> static void
763 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1040 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
764 { 1041 {
765 .. one minute over, w is actually stopped right here 1042 .. one minute over, w is actually stopped right here
766 } 1043 }
… …
768 struct ev_timer mytimer; 1045 struct ev_timer mytimer;
769 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1046 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
770 ev_timer_start (loop, &amp;mytimer); 1047 ev_timer_start (loop, &amp;mytimer);
771 1048
772</pre> 1049</pre>
773<p>Example: create a timeout timer that times out after 10 seconds of 1050<p>Example: Create a timeout timer that times out after 10 seconds of
774inactivity.</p> 1051inactivity.</p>
775<pre> static void 1052<pre> static void
776 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1053 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
777 { 1054 {
778 .. ten seconds without any activity 1055 .. ten seconds without any activity
… …
791 1068
792 1069
793</pre> 1070</pre>
794 1071
795</div> 1072</div>
796<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 1073<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"> 1074<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 1075<p>Periodic watchers are also timers of a kind, but they are very versatile
799(and unfortunately a bit complex).</p> 1076(and unfortunately a bit complex).</p>
800<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 1077<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 1078but 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 1079to 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 () 1080periodic 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 1081+ 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 1082take 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 1083roughly 10 seconds later and of course not if you reset your system time
807again).</p> 1084again).</p>
808<p>They can also be used to implement vastly more complex timers, such as 1085<p>They can also be used to implement vastly more complex timers, such as
809triggering an event on eahc midnight, local time.</p> 1086triggering an event on eahc midnight, local time.</p>
… …
881 <p>Simply stops and restarts the periodic watcher again. This is only useful 1158 <p>Simply stops and restarts the periodic watcher again. This is only useful
882when you changed some parameters or the reschedule callback would return 1159when 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 1160a different time than the last time it was called (e.g. in a crond like
884program when the crontabs have changed).</p> 1161program when the crontabs have changed).</p>
885 </dd> 1162 </dd>
1163 <dt>ev_tstamp interval [read-write]</dt>
1164 <dd>
1165 <p>The current interval value. Can be modified any time, but changes only
1166take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1167called.</p>
1168 </dd>
1169 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1170 <dd>
1171 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1172switched off. Can be changed any time, but changes only take effect when
1173the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1174 </dd>
886</dl> 1175</dl>
887<p>Example: call a callback every hour, or, more precisely, whenever the 1176<p>Example: Call a callback every hour, or, more precisely, whenever the
888system clock is divisible by 3600. The callback invocation times have 1177system clock is divisible by 3600. The callback invocation times have
889potentially a lot of jittering, but good long-term stability.</p> 1178potentially a lot of jittering, but good long-term stability.</p>
890<pre> static void 1179<pre> static void
891 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1180 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
892 { 1181 {
… …
896 struct ev_periodic hourly_tick; 1185 struct ev_periodic hourly_tick;
897 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1186 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
898 ev_periodic_start (loop, &amp;hourly_tick); 1187 ev_periodic_start (loop, &amp;hourly_tick);
899 1188
900</pre> 1189</pre>
901<p>Example: the same as above, but use a reschedule callback to do it:</p> 1190<p>Example: The same as above, but use a reschedule callback to do it:</p>
902<pre> #include &lt;math.h&gt; 1191<pre> #include &lt;math.h&gt;
903 1192
904 static ev_tstamp 1193 static ev_tstamp
905 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1194 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
906 { 1195 {
… …
908 } 1197 }
909 1198
910 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1199 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
911 1200
912</pre> 1201</pre>
913<p>Example: call a callback every hour, starting now:</p> 1202<p>Example: Call a callback every hour, starting now:</p>
914<pre> struct ev_periodic hourly_tick; 1203<pre> struct ev_periodic hourly_tick;
915 ev_periodic_init (&amp;hourly_tick, clock_cb, 1204 ev_periodic_init (&amp;hourly_tick, clock_cb,
916 fmod (ev_now (loop), 3600.), 3600., 0); 1205 fmod (ev_now (loop), 3600.), 3600., 0);
917 ev_periodic_start (loop, &amp;hourly_tick); 1206 ev_periodic_start (loop, &amp;hourly_tick);
918 1207
… …
920 1209
921 1210
922</pre> 1211</pre>
923 1212
924</div> 1213</div>
925<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1214<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"> 1215<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 1216<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 1217signal 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 1218will try it's best to deliver signals synchronously, i.e. as part of the
930normal event processing, like any other event.</p> 1219normal event processing, like any other event.</p>
… …
939 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1228 <dt>ev_signal_set (ev_signal *, int signum)</dt>
940 <dd> 1229 <dd>
941 <p>Configures the watcher to trigger on the given signal number (usually one 1230 <p>Configures the watcher to trigger on the given signal number (usually one
942of the <code>SIGxxx</code> constants).</p> 1231of the <code>SIGxxx</code> constants).</p>
943 </dd> 1232 </dd>
1233 <dt>int signum [read-only]</dt>
1234 <dd>
1235 <p>The signal the watcher watches out for.</p>
1236 </dd>
944</dl> 1237</dl>
945 1238
946 1239
947 1240
948 1241
949 1242
950</div> 1243</div>
951<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1244<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"> 1245<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 1246<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> 1247some child status changes (most typically when a child of yours dies).</p>
955<dl> 1248<dl>
956 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1249 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
957 <dt>ev_child_set (ev_child *, int pid)</dt> 1250 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
961at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1254at 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 1255the 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 1256<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
964process causing the status change.</p> 1257process causing the status change.</p>
965 </dd> 1258 </dd>
1259 <dt>int pid [read-only]</dt>
1260 <dd>
1261 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1262 </dd>
1263 <dt>int rpid [read-write]</dt>
1264 <dd>
1265 <p>The process id that detected a status change.</p>
1266 </dd>
1267 <dt>int rstatus [read-write]</dt>
1268 <dd>
1269 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1270<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1271 </dd>
966</dl> 1272</dl>
967<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1273<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
968<pre> static void 1274<pre> static void
969 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1275 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
970 { 1276 {
971 ev_unloop (loop, EVUNLOOP_ALL); 1277 ev_unloop (loop, EVUNLOOP_ALL);
972 } 1278 }
… …
979 1285
980 1286
981</pre> 1287</pre>
982 1288
983</div> 1289</div>
1290<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1291<div id="code_ev_stat_code_did_the_file_attri-2">
1292<p>This watches a filesystem path for attribute changes. That is, it calls
1293<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1294compared to the last time, invoking the callback if it did.</p>
1295<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1296not exist&quot; is a status change like any other. The condition &quot;path does
1297not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1298otherwise always forced to be at least one) and all the other fields of
1299the stat buffer having unspecified contents.</p>
1300<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1301relative and your working directory changes, the behaviour is undefined.</p>
1302<p>Since there is no standard to do this, the portable implementation simply
1303calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1304can specify a recommended polling interval for this case. If you specify
1305a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1306unspecified default</i> value will be used (which you can expect to be around
1307five seconds, although this might change dynamically). Libev will also
1308impose a minimum interval which is currently around <code>0.1</code>, but thats
1309usually overkill.</p>
1310<p>This watcher type is not meant for massive numbers of stat watchers,
1311as even with OS-supported change notifications, this can be
1312resource-intensive.</p>
1313<p>At the time of this writing, only the Linux inotify interface is
1314implemented (implementing kqueue support is left as an exercise for the
1315reader). Inotify will be used to give hints only and should not change the
1316semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1317to fall back to regular polling again even with inotify, but changes are
1318usually detected immediately, and if the file exists there will be no
1319polling.</p>
1320<dl>
1321 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1322 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1323 <dd>
1324 <p>Configures the watcher to wait for status changes of the given
1325<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1326be detected and should normally be specified as <code>0</code> to let libev choose
1327a suitable value. The memory pointed to by <code>path</code> must point to the same
1328path for as long as the watcher is active.</p>
1329 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1330relative to the attributes at the time the watcher was started (or the
1331last change was detected).</p>
1332 </dd>
1333 <dt>ev_stat_stat (ev_stat *)</dt>
1334 <dd>
1335 <p>Updates the stat buffer immediately with new values. If you change the
1336watched path in your callback, you could call this fucntion to avoid
1337detecting this change (while introducing a race condition). Can also be
1338useful simply to find out the new values.</p>
1339 </dd>
1340 <dt>ev_statdata attr [read-only]</dt>
1341 <dd>
1342 <p>The most-recently detected attributes of the file. Although the type is of
1343<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1344suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1345was some error while <code>stat</code>ing the file.</p>
1346 </dd>
1347 <dt>ev_statdata prev [read-only]</dt>
1348 <dd>
1349 <p>The previous attributes of the file. The callback gets invoked whenever
1350<code>prev</code> != <code>attr</code>.</p>
1351 </dd>
1352 <dt>ev_tstamp interval [read-only]</dt>
1353 <dd>
1354 <p>The specified interval.</p>
1355 </dd>
1356 <dt>const char *path [read-only]</dt>
1357 <dd>
1358 <p>The filesystem path that is being watched.</p>
1359 </dd>
1360</dl>
1361<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1362<pre> static void
1363 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1364 {
1365 /* /etc/passwd changed in some way */
1366 if (w-&gt;attr.st_nlink)
1367 {
1368 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1369 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1370 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1371 }
1372 else
1373 /* you shalt not abuse printf for puts */
1374 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1375 &quot;if this is windows, they already arrived\n&quot;);
1376 }
1377
1378 ...
1379 ev_stat passwd;
1380
1381 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1382 ev_stat_start (loop, &amp;passwd);
1383
1384
1385
1386
1387</pre>
1388
1389</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> 1390<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"> 1391<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 1392<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 1393priority are pending (prepare, check and other idle watchers do not
988as your process is busy handling sockets or timeouts (or even signals, 1394count).</p>
989imagine) it will not be triggered. But when your process is idle all idle 1395<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 - 1396(or even signals, imagine) of the same or higher priority it will not be
1397triggered. But when your process is idle (or only lower-priority watchers
1398are pending), the idle watchers are being called once per event loop
991until stopped, that is, or your process receives more events and becomes 1399iteration - until stopped, that is, or your process receives more events
992busy.</p> 1400and becomes busy again with higher priority stuff.</p>
993<p>The most noteworthy effect is that as long as any idle watchers are 1401<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> 1402active, the process will not block when waiting for new events.</p>
995<p>Apart from keeping your process non-blocking (which is a useful 1403<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 1404effect 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 1405&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1002 <p>Initialises and configures the idle watcher - it has no parameters of any 1410 <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, 1411kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1004believe me.</p> 1412believe me.</p>
1005 </dd> 1413 </dd>
1006</dl> 1414</dl>
1007<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1415<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> 1416callback, free it. Also, use no error checking, as usual.</p>
1009<pre> static void 1417<pre> static void
1010 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1418 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1011 { 1419 {
1012 free (w); 1420 free (w);
1013 // now do something you wanted to do when the program has 1421 // now do something you wanted to do when the program has
… …
1022 1430
1023 1431
1024</pre> 1432</pre>
1025 1433
1026</div> 1434</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> 1435<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"> 1436<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: 1437<p>Prepare and check watchers are usually (but not always) used in tandem:
1030prepare watchers get invoked before the process blocks and check watchers 1438prepare watchers get invoked before the process blocks and check watchers
1031afterwards.</p> 1439afterwards.</p>
1440<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1441the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1442watchers. Other loops than the current one are fine, however. The
1443rationale behind this is that you do not need to check for recursion in
1444those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1445<code>ev_check</code> so if you have one watcher of each kind they will always be
1446called in pairs bracketing the blocking call.</p>
1032<p>Their main purpose is to integrate other event mechanisms into libev and 1447<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 1448their use is somewhat advanced. This could be used, for example, to track
1034variable changes, implement your own watchers, integrate net-snmp or a 1449variable changes, implement your own watchers, integrate net-snmp or a
1035coroutine library and lots more.</p> 1450coroutine library and lots more. They are also occasionally useful if
1451you cache some data and want to flush it before blocking (for example,
1452in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1453watcher).</p>
1036<p>This is done by examining in each prepare call which file descriptors need 1454<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 1455to 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 1456them 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 1457provide just this functionality). Then, in the check watcher you check for
1040any events that occured (by checking the pending status of all watchers 1458any events that occured (by checking the pending status of all watchers
… …
1056 <p>Initialises and configures the prepare or check watcher - they have no 1474 <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> 1475parameters 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> 1476macros, but using them is utterly, utterly and completely pointless.</p>
1059 </dd> 1477 </dd>
1060</dl> 1478</dl>
1061<p>Example: *TODO*.</p> 1479<p>Example: To include a library such as adns, you would add IO watchers
1480and a timeout watcher in a prepare handler, as required by libadns, and
1481in a check watcher, destroy them and call into libadns. What follows is
1482pseudo-code only of course:</p>
1483<pre> static ev_io iow [nfd];
1484 static ev_timer tw;
1062 1485
1486 static void
1487 io_cb (ev_loop *loop, ev_io *w, int revents)
1488 {
1489 // set the relevant poll flags
1490 // could also call adns_processreadable etc. here
1491 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1492 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1493 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1494 }
1063 1495
1496 // create io watchers for each fd and a timer before blocking
1497 static void
1498 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1499 {
1500 int timeout = 3600000;
1501 struct pollfd fds [nfd];
1502 // actual code will need to loop here and realloc etc.
1503 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1064 1504
1505 /* the callback is illegal, but won't be called as we stop during check */
1506 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1507 ev_timer_start (loop, &amp;tw);
1065 1508
1509 // create on ev_io per pollfd
1510 for (int i = 0; i &lt; nfd; ++i)
1511 {
1512 ev_io_init (iow + i, io_cb, fds [i].fd,
1513 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1514 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1066 1515
1516 fds [i].revents = 0;
1517 iow [i].data = fds + i;
1518 ev_io_start (loop, iow + i);
1519 }
1520 }
1521
1522 // stop all watchers after blocking
1523 static void
1524 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1525 {
1526 ev_timer_stop (loop, &amp;tw);
1527
1528 for (int i = 0; i &lt; nfd; ++i)
1529 ev_io_stop (loop, iow + i);
1530
1531 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1532 }
1533
1534
1535
1536
1537</pre>
1538
1067</div> 1539</div>
1068<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1540<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"> 1541<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 1542<p>This is a rather advanced watcher type that lets you embed one event loop
1071into another.</p> 1543into another (currently only <code>ev_io</code> events are supported in the embedded
1544loop, other types of watchers might be handled in a delayed or incorrect
1545fashion and must not be used).</p>
1072<p>There are primarily two reasons you would want that: work around bugs and 1546<p>There are primarily two reasons you would want that: work around bugs and
1073prioritise I/O.</p> 1547prioritise I/O.</p>
1074<p>As an example for a bug workaround, the kqueue backend might only support 1548<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 1549sockets 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 1550still 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 1555<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 1556to be watched and handled very quickly (with low latency), and even
1083priorities and idle watchers might have too much overhead. In this case 1557priorities 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 1558you 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> 1559a second one, and embed the second one in the first.</p>
1560<p>As long as the watcher is active, the callback will be invoked every time
1561there might be events pending in the embedded loop. The callback must then
1562call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke
1563their callbacks (you could also start an idle watcher to give the embedded
1564loop strictly lower priority for example). You can also set the callback
1565to <code>0</code>, in which case the embed watcher will automatically execute the
1566embedded loop sweep.</p>
1086<p>As long as the watcher is started it will automatically handle events. The 1567<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 1568callback 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 1569set the callback to <code>0</code> to avoid having to specify one if you are not
1089interested in that.</p> 1570interested in that.</p>
1090<p>Also, there have not currently been made special provisions for forking: 1571<p>Also, there have not currently been made special provisions for forking:
… …
1117 else 1598 else
1118 loop_lo = loop_hi; 1599 loop_lo = loop_hi;
1119 1600
1120</pre> 1601</pre>
1121<dl> 1602<dl>
1122 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *loop)</dt> 1603 <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> 1604 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1605 <dd>
1606 <p>Configures the watcher to embed the given loop, which must be
1607embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be
1608invoked automatically, otherwise it is the responsibility of the callback
1609to invoke it (it will continue to be called until the sweep has been done,
1610if you do not want thta, you need to temporarily stop the embed watcher).</p>
1124 <dd> 1611 </dd>
1125 <p>Configures the watcher to embed the given loop, which must be embeddable.</p> 1612 <dt>ev_embed_sweep (loop, ev_embed *)</dt>
1613 <dd>
1614 <p>Make a single, non-blocking sweep over the embedded loop. This works
1615similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1616apropriate way for embedded loops.</p>
1617 </dd>
1618 <dt>struct ev_loop *loop [read-only]</dt>
1619 <dd>
1620 <p>The embedded event loop.</p>
1126 </dd> 1621 </dd>
1127</dl> 1622</dl>
1128 1623
1129 1624
1130 1625
1131 1626
1132 1627
1133</div> 1628</div>
1134<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1629<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>
1630<div id="code_ev_fork_code_the_audacity_to_re-2">
1631<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1632whoever is a good citizen cared to tell libev about it by calling
1633<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1634event loop blocks next and before <code>ev_check</code> watchers are being called,
1635and only in the child after the fork. If whoever good citizen calling
1636<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1637handlers will be invoked, too, of course.</p>
1638<dl>
1639 <dt>ev_fork_init (ev_signal *, callback)</dt>
1640 <dd>
1641 <p>Initialises and configures the fork watcher - it has no parameters of any
1642kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1643believe me.</p>
1644 </dd>
1645</dl>
1646
1647
1648
1649
1650
1651</div>
1652<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1135<div id="OTHER_FUNCTIONS_CONTENT"> 1653<div id="OTHER_FUNCTIONS_CONTENT">
1136<p>There are some other functions of possible interest. Described. Here. Now.</p> 1654<p>There are some other functions of possible interest. Described. Here. Now.</p>
1137<dl> 1655<dl>
1138 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1656 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1139 <dd> 1657 <dd>
… …
1163 1681
1164 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1682 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1165 1683
1166</pre> 1684</pre>
1167 </dd> 1685 </dd>
1168 <dt>ev_feed_event (loop, watcher, int events)</dt> 1686 <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt>
1169 <dd> 1687 <dd>
1170 <p>Feeds the given event set into the event loop, as if the specified event 1688 <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 1689had happened for the specified watcher (which must be a pointer to an
1172initialised but not necessarily started event watcher).</p> 1690initialised but not necessarily started event watcher).</p>
1173 </dd> 1691 </dd>
1174 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 1692 <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt>
1175 <dd> 1693 <dd>
1176 <p>Feed an event on the given fd, as if a file descriptor backend detected 1694 <p>Feed an event on the given fd, as if a file descriptor backend detected
1177the given events it.</p> 1695the given events it.</p>
1178 </dd> 1696 </dd>
1179 <dt>ev_feed_signal_event (loop, int signum)</dt> 1697 <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt>
1180 <dd> 1698 <dd>
1181 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1699 <p>Feed an event as if the given signal occured (<code>loop</code> must be the default
1700loop!).</p>
1182 </dd> 1701 </dd>
1183</dl> 1702</dl>
1184 1703
1185 1704
1186 1705
1187 1706
1188 1707
1189</div> 1708</div>
1190<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1709<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1191<div id="LIBEVENT_EMULATION_CONTENT"> 1710<div id="LIBEVENT_EMULATION_CONTENT">
1192<p>Libev offers a compatibility emulation layer for libevent. It cannot 1711<p>Libev offers a compatibility emulation layer for libevent. It cannot
1193emulate the internals of libevent, so here are some usage hints:</p> 1712emulate the internals of libevent, so here are some usage hints:</p>
1194<dl> 1713<dl>
1195 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1714 <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 1724 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1206to use the libev header file and library.</dt> 1725to use the libev header file and library.</dt>
1207</dl> 1726</dl>
1208 1727
1209</div> 1728</div>
1210<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1729<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1211<div id="C_SUPPORT_CONTENT"> 1730<div id="C_SUPPORT_CONTENT">
1212<p>TBD.</p> 1731<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1732you to use some convinience methods to start/stop watchers and also change
1733the callback model to a model using method callbacks on objects.</p>
1734<p>To use it,</p>
1735<pre> #include &lt;ev++.h&gt;
1213 1736
1737</pre>
1738<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
1739and puts all of its definitions (many of them macros) into the global
1740namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
1741<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
1742<code>EV_MULTIPLICITY</code>.</p>
1743<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1744<dl>
1745 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1746 <dd>
1747 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
1748macros from <cite>ev.h</cite>.</p>
1749 </dd>
1750 <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
1751 <dd>
1752 <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
1753 </dd>
1754 <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
1755 <dd>
1756 <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
1757the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
1758which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1759defines by many implementations.</p>
1760 <p>All of those classes have these methods:</p>
1761 <p>
1762 <dl>
1763 <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
1764 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
1765 <dt>ev::TYPE::~TYPE</dt>
1766 <dd>
1767 <p>The constructor takes a pointer to an object and a method pointer to
1768the event handler callback to call in this class. The constructor calls
1769<code>ev_init</code> for you, which means you have to call the <code>set</code> method
1770before starting it. If you do not specify a loop then the constructor
1771automatically associates the default loop with this watcher.</p>
1772 <p>The destructor automatically stops the watcher if it is active.</p>
1773 </dd>
1774 <dt>w-&gt;set (struct ev_loop *)</dt>
1775 <dd>
1776 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1777do this when the watcher is inactive (and not pending either).</p>
1778 </dd>
1779 <dt>w-&gt;set ([args])</dt>
1780 <dd>
1781 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1782called at least once. Unlike the C counterpart, an active watcher gets
1783automatically stopped and restarted.</p>
1784 </dd>
1785 <dt>w-&gt;start ()</dt>
1786 <dd>
1787 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
1788constructor already takes the loop.</p>
1789 </dd>
1790 <dt>w-&gt;stop ()</dt>
1791 <dd>
1792 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1793 </dd>
1794 <dt>w-&gt;again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
1795 <dd>
1796 <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
1797<code>ev_TYPE_again</code> function.</p>
1798 </dd>
1799 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1800 <dd>
1801 <p>Invokes <code>ev_embed_sweep</code>.</p>
1802 </dd>
1803 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1804 <dd>
1805 <p>Invokes <code>ev_stat_stat</code>.</p>
1806 </dd>
1807 </dl>
1808 </p>
1809 </dd>
1810</dl>
1811<p>Example: Define a class with an IO and idle watcher, start one of them in
1812the constructor.</p>
1813<pre> class myclass
1814 {
1815 ev_io io; void io_cb (ev::io &amp;w, int revents);
1816 ev_idle idle void idle_cb (ev::idle &amp;w, int revents);
1817
1818 myclass ();
1819 }
1820
1821 myclass::myclass (int fd)
1822 : io (this, &amp;myclass::io_cb),
1823 idle (this, &amp;myclass::idle_cb)
1824 {
1825 io.start (fd, ev::READ);
1826 }
1827
1828
1829
1830
1831</pre>
1832
1214</div> 1833</div>
1215<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1834<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1835<div id="MACRO_MAGIC_CONTENT">
1836<p>Libev can be compiled with a variety of options, the most fundemantal is
1837<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1838callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1839<p>To make it easier to write programs that cope with either variant, the
1840following macros are defined:</p>
1841<dl>
1842 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1843 <dd>
1844 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1845loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1846<code>EV_A_</code> is used when other arguments are following. Example:</p>
1847<pre> ev_unref (EV_A);
1848 ev_timer_add (EV_A_ watcher);
1849 ev_loop (EV_A_ 0);
1850
1851</pre>
1852 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1853which is often provided by the following macro.</p>
1854 </dd>
1855 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1856 <dd>
1857 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1858loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1859<code>EV_P_</code> is used when other parameters are following. Example:</p>
1860<pre> // this is how ev_unref is being declared
1861 static void ev_unref (EV_P);
1862
1863 // this is how you can declare your typical callback
1864 static void cb (EV_P_ ev_timer *w, int revents)
1865
1866</pre>
1867 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1868suitable for use with <code>EV_A</code>.</p>
1869 </dd>
1870 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1871 <dd>
1872 <p>Similar to the other two macros, this gives you the value of the default
1873loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1874 </dd>
1875</dl>
1876<p>Example: Declare and initialise a check watcher, utilising the above
1877macros so it will work regardless of wether multiple loops are supported
1878or not.</p>
1879<pre> static void
1880 check_cb (EV_P_ ev_timer *w, int revents)
1881 {
1882 ev_check_stop (EV_A_ w);
1883 }
1884
1885 ev_check check;
1886 ev_check_init (&amp;check, check_cb);
1887 ev_check_start (EV_DEFAULT_ &amp;check);
1888 ev_loop (EV_DEFAULT_ 0);
1889
1890</pre>
1891
1892</div>
1893<h1 id="EMBEDDING">EMBEDDING</h1>
1894<div id="EMBEDDING_CONTENT">
1895<p>Libev can (and often is) directly embedded into host
1896applications. Examples of applications that embed it include the Deliantra
1897Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1898and rxvt-unicode.</p>
1899<p>The goal is to enable you to just copy the neecssary files into your
1900source directory without having to change even a single line in them, so
1901you can easily upgrade by simply copying (or having a checked-out copy of
1902libev somewhere in your source tree).</p>
1903
1904</div>
1905<h2 id="FILESETS">FILESETS</h2>
1906<div id="FILESETS_CONTENT">
1907<p>Depending on what features you need you need to include one or more sets of files
1908in your app.</p>
1909
1910</div>
1911<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1912<div id="CORE_EVENT_LOOP_CONTENT">
1913<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1914configuration (no autoconf):</p>
1915<pre> #define EV_STANDALONE 1
1916 #include &quot;ev.c&quot;
1917
1918</pre>
1919<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1920single C source file only to provide the function implementations. To use
1921it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1922done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1923where you can put other configuration options):</p>
1924<pre> #define EV_STANDALONE 1
1925 #include &quot;ev.h&quot;
1926
1927</pre>
1928<p>Both header files and implementation files can be compiled with a C++
1929compiler (at least, thats a stated goal, and breakage will be treated
1930as a bug).</p>
1931<p>You need the following files in your source tree, or in a directory
1932in your include path (e.g. in libev/ when using -Ilibev):</p>
1933<pre> ev.h
1934 ev.c
1935 ev_vars.h
1936 ev_wrap.h
1937
1938 ev_win32.c required on win32 platforms only
1939
1940 ev_select.c only when select backend is enabled (which is enabled by default)
1941 ev_poll.c only when poll backend is enabled (disabled by default)
1942 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1943 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1944 ev_port.c only when the solaris port backend is enabled (disabled by default)
1945
1946</pre>
1947<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1948to compile this single file.</p>
1949
1950</div>
1951<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1952<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1953<p>To include the libevent compatibility API, also include:</p>
1954<pre> #include &quot;event.c&quot;
1955
1956</pre>
1957<p>in the file including <cite>ev.c</cite>, and:</p>
1958<pre> #include &quot;event.h&quot;
1959
1960</pre>
1961<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1962<p>You need the following additional files for this:</p>
1963<pre> event.h
1964 event.c
1965
1966</pre>
1967
1968</div>
1969<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1970<div id="AUTOCONF_SUPPORT_CONTENT">
1971<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1972whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1973<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1974include <cite>config.h</cite> and configure itself accordingly.</p>
1975<p>For this of course you need the m4 file:</p>
1976<pre> libev.m4
1977
1978</pre>
1979
1980</div>
1981<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1982<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1983<p>Libev can be configured via a variety of preprocessor symbols you have to define
1984before including any of its files. The default is not to build for multiplicity
1985and only include the select backend.</p>
1986<dl>
1987 <dt>EV_STANDALONE</dt>
1988 <dd>
1989 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1990keeps libev from including <cite>config.h</cite>, and it also defines dummy
1991implementations for some libevent functions (such as logging, which is not
1992supported). It will also not define any of the structs usually found in
1993<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1994 </dd>
1995 <dt>EV_USE_MONOTONIC</dt>
1996 <dd>
1997 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1998monotonic clock option at both compiletime and runtime. Otherwise no use
1999of the monotonic clock option will be attempted. If you enable this, you
2000usually have to link against librt or something similar. Enabling it when
2001the functionality isn't available is safe, though, althoguh you have
2002to make sure you link against any libraries where the <code>clock_gettime</code>
2003function is hiding in (often <cite>-lrt</cite>).</p>
2004 </dd>
2005 <dt>EV_USE_REALTIME</dt>
2006 <dd>
2007 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
2008realtime clock option at compiletime (and assume its availability at
2009runtime if successful). Otherwise no use of the realtime clock option will
2010be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
2011(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
2012in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
2013 </dd>
2014 <dt>EV_USE_SELECT</dt>
2015 <dd>
2016 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
2017<code>select</code>(2) backend. No attempt at autodetection will be done: if no
2018other method takes over, select will be it. Otherwise the select backend
2019will not be compiled in.</p>
2020 </dd>
2021 <dt>EV_SELECT_USE_FD_SET</dt>
2022 <dd>
2023 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
2024structure. This is useful if libev doesn't compile due to a missing
2025<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
2026exotic systems. This usually limits the range of file descriptors to some
2027low limit such as 1024 or might have other limitations (winsocket only
2028allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
2029influence the size of the <code>fd_set</code> used.</p>
2030 </dd>
2031 <dt>EV_SELECT_IS_WINSOCKET</dt>
2032 <dd>
2033 <p>When defined to <code>1</code>, the select backend will assume that
2034select/socket/connect etc. don't understand file descriptors but
2035wants osf handles on win32 (this is the case when the select to
2036be used is the winsock select). This means that it will call
2037<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
2038it is assumed that all these functions actually work on fds, even
2039on win32. Should not be defined on non-win32 platforms.</p>
2040 </dd>
2041 <dt>EV_USE_POLL</dt>
2042 <dd>
2043 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
2044backend. Otherwise it will be enabled on non-win32 platforms. It
2045takes precedence over select.</p>
2046 </dd>
2047 <dt>EV_USE_EPOLL</dt>
2048 <dd>
2049 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
2050<code>epoll</code>(7) backend. Its availability will be detected at runtime,
2051otherwise another method will be used as fallback. This is the
2052preferred backend for GNU/Linux systems.</p>
2053 </dd>
2054 <dt>EV_USE_KQUEUE</dt>
2055 <dd>
2056 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
2057<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
2058otherwise another method will be used as fallback. This is the preferred
2059backend for BSD and BSD-like systems, although on most BSDs kqueue only
2060supports some types of fds correctly (the only platform we found that
2061supports ptys for example was NetBSD), so kqueue might be compiled in, but
2062not be used unless explicitly requested. The best way to use it is to find
2063out whether kqueue supports your type of fd properly and use an embedded
2064kqueue loop.</p>
2065 </dd>
2066 <dt>EV_USE_PORT</dt>
2067 <dd>
2068 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
206910 port style backend. Its availability will be detected at runtime,
2070otherwise another method will be used as fallback. This is the preferred
2071backend for Solaris 10 systems.</p>
2072 </dd>
2073 <dt>EV_USE_DEVPOLL</dt>
2074 <dd>
2075 <p>reserved for future expansion, works like the USE symbols above.</p>
2076 </dd>
2077 <dt>EV_USE_INOTIFY</dt>
2078 <dd>
2079 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2080interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2081be detected at runtime.</p>
2082 </dd>
2083 <dt>EV_H</dt>
2084 <dd>
2085 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
2086undefined 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
2087can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
2088 </dd>
2089 <dt>EV_CONFIG_H</dt>
2090 <dd>
2091 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
2092<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
2093<code>EV_H</code>, above.</p>
2094 </dd>
2095 <dt>EV_EVENT_H</dt>
2096 <dd>
2097 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
2098of how the <cite>event.h</cite> header can be found.</p>
2099 </dd>
2100 <dt>EV_PROTOTYPES</dt>
2101 <dd>
2102 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
2103prototypes, but still define all the structs and other symbols. This is
2104occasionally useful if you want to provide your own wrapper functions
2105around libev functions.</p>
2106 </dd>
2107 <dt>EV_MULTIPLICITY</dt>
2108 <dd>
2109 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
2110will have the <code>struct ev_loop *</code> as first argument, and you can create
2111additional independent event loops. Otherwise there will be no support
2112for multiple event loops and there is no first event loop pointer
2113argument. Instead, all functions act on the single default loop.</p>
2114 </dd>
2115 <dt>EV_PERIODIC_ENABLE</dt>
2116 <dd>
2117 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2118defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2119code.</p>
2120 </dd>
2121 <dt>EV_IDLE_ENABLE</dt>
2122 <dd>
2123 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2124defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2125code.</p>
2126 </dd>
2127 <dt>EV_EMBED_ENABLE</dt>
2128 <dd>
2129 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2130defined to be <code>0</code>, then they are not.</p>
2131 </dd>
2132 <dt>EV_STAT_ENABLE</dt>
2133 <dd>
2134 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2135defined to be <code>0</code>, then they are not.</p>
2136 </dd>
2137 <dt>EV_FORK_ENABLE</dt>
2138 <dd>
2139 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2140defined to be <code>0</code>, then they are not.</p>
2141 </dd>
2142 <dt>EV_MINIMAL</dt>
2143 <dd>
2144 <p>If you need to shave off some kilobytes of code at the expense of some
2145speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2146some inlining decisions, saves roughly 30% codesize of amd64.</p>
2147 </dd>
2148 <dt>EV_PID_HASHSIZE</dt>
2149 <dd>
2150 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2151pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2152than enough. If you need to manage thousands of children you might want to
2153increase this value (<i>must</i> be a power of two).</p>
2154 </dd>
2155 <dt>EV_INOTIFY_HASHSIZE</dt>
2156 <dd>
2157 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2158inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2159usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2160watchers you might want to increase this value (<i>must</i> be a power of
2161two).</p>
2162 </dd>
2163 <dt>EV_COMMON</dt>
2164 <dd>
2165 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2166this macro to a something else you can include more and other types of
2167members. You have to define it each time you include one of the files,
2168though, and it must be identical each time.</p>
2169 <p>For example, the perl EV module uses something like this:</p>
2170<pre> #define EV_COMMON \
2171 SV *self; /* contains this struct */ \
2172 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2173
2174</pre>
2175 </dd>
2176 <dt>EV_CB_DECLARE (type)</dt>
2177 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2178 <dt>ev_set_cb (ev, cb)</dt>
2179 <dd>
2180 <p>Can be used to change the callback member declaration in each watcher,
2181and the way callbacks are invoked and set. Must expand to a struct member
2182definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2183their default definitions. One possible use for overriding these is to
2184avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2185method calls instead of plain function calls in C++.</p>
2186
2187</div>
2188<h2 id="EXAMPLES">EXAMPLES</h2>
2189<div id="EXAMPLES_CONTENT">
2190 <p>For a real-world example of a program the includes libev
2191verbatim, you can have a look at the EV perl module
2192(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2193the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2194interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2195will be compiled. It is pretty complex because it provides its own header
2196file.</p>
2197 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2198that everybody includes and which overrides some configure choices:</p>
2199<pre> #define EV_MINIMAL 1
2200 #define EV_USE_POLL 0
2201 #define EV_MULTIPLICITY 0
2202 #define EV_PERIODIC_ENABLE 0
2203 #define EV_STAT_ENABLE 0
2204 #define EV_FORK_ENABLE 0
2205 #define EV_CONFIG_H &lt;config.h&gt;
2206 #define EV_MINPRI 0
2207 #define EV_MAXPRI 0
2208
2209 #include &quot;ev++.h&quot;
2210
2211</pre>
2212 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2213<pre> #include &quot;ev_cpp.h&quot;
2214 #include &quot;ev.c&quot;
2215
2216
2217
2218
2219</pre>
2220
2221</div>
2222<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2223<div id="COMPLEXITIES_CONTENT">
2224 <p>In this section the complexities of (many of) the algorithms used inside
2225libev will be explained. For complexity discussions about backends see the
2226documentation for <code>ev_default_init</code>.</p>
2227 <p>
2228 <dl>
2229 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2230 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2231 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2232 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2233 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2234 <dt>Finding the next timer per loop iteration: O(1)</dt>
2235 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2236 <dt>Activating one watcher: O(1)</dt>
2237 </dl>
2238 </p>
2239
2240
2241
2242
2243
2244</div>
2245<h1 id="AUTHOR">AUTHOR</h1>
1216<div id="AUTHOR_CONTENT"> 2246<div id="AUTHOR_CONTENT">
1217<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2247 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1218 2248
1219</div> 2249</div>
1220</div></body> 2250</div></body>
1221</html> 2251</html>

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