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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="Tue Nov 27 09:20:40 2007" /> 9 <meta name="created" content="Thu Nov 29 18:28:02 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>
… …
35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process 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>
36<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</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>
37<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>
38<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>
39<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>
40</ul> 42</ul>
41</li> 43</li>
42<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
43<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
44<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>
45<li><a href="#EMBEDDING">EMBEDDING</a> 48<li><a href="#EMBEDDING">EMBEDDING</a>
46<ul><li><a href="#FILESETS">FILESETS</a> 49<ul><li><a href="#FILESETS">FILESETS</a>
47<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> 50<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
48<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> 51<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
49<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> 52<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
… …
57<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
58</li> 61</li>
59</ul><hr /> 62</ul><hr />
60<!-- INDEX END --> 63<!-- INDEX END -->
61 64
62<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
63<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
64<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>
65 68
66</div> 69</div>
67<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
68<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
69<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
70 73
71</pre> 74</pre>
72 75
73</div> 76</div>
74<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>
75<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
76<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
77file descriptor being readable or a timeout occuring), and it will manage 125file descriptor being readable or a timeout occuring), and it will manage
78these event sources and provide your program with events.</p> 126these event sources and provide your program with events.</p>
79<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
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83watchers</i>, which are relatively small C structures you initialise with the 131watchers</i>, which are relatively small C structures you initialise with the
84details 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
85watcher.</p> 133watcher.</p>
86 134
87</div> 135</div>
88<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1>
89<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
90<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
91kqueue mechanisms for file descriptor events, relative timers, absolute 139BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
92timers with customised rescheduling, signal events, process status change 140for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
93events (related to SIGCHLD), and event watchers dealing with the event 141(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
94loop 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
95fast (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
96it to libevent for example).</p> 150for example).</p>
97 151
98</div> 152</div>
99<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 153<h1 id="CONVENTIONS">CONVENTIONS</h1>
100<div id="CONVENTIONS_CONTENT"> 154<div id="CONVENTIONS_CONTENT">
101<p>Libev is very configurable. In this manual the default configuration 155<p>Libev is very configurable. In this manual the default configuration will
102will be described, which supports multiple event loops. For more info 156be described, which supports multiple event loops. For more info about
103about various configuration options please have a look at the file 157various configuration options please have a look at <strong>EMBED</strong> section in
104<cite>README.embed</cite> in the libev distribution. If libev was configured without 158this manual. If libev was configured without support for multiple event
105support for multiple event loops, then all functions taking an initial 159loops, then all functions taking an initial argument of name <code>loop</code>
106argument 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>
107will not have this argument.</p>
108 161
109</div> 162</div>
110<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 163<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
111<div id="TIME_REPRESENTATION_CONTENT"> 164<div id="TIME_REPRESENTATION_CONTENT">
112<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
113(fractional) number of seconds since the (POSIX) epoch (somewhere near 166(fractional) number of seconds since the (POSIX) epoch (somewhere near
114the 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
115called <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
116to 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
117it, you should treat it as such.</p> 170it, you should treat it as such.</p>
118 171
119
120
121
122
123</div> 172</div>
124<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 173<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
125<div id="GLOBAL_FUNCTIONS_CONTENT"> 174<div id="GLOBAL_FUNCTIONS_CONTENT">
126<p>These functions can be called anytime, even before initialising the 175<p>These functions can be called anytime, even before initialising the
127library in any way.</p> 176library in any way.</p>
128<dl> 177<dl>
129 <dt>ev_tstamp ev_time ()</dt> 178 <dt>ev_tstamp ev_time ()</dt>
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142version of the library your program was compiled against.</p> 191version of the library your program was compiled against.</p>
143 <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,
144as this indicates an incompatible change. Minor versions are usually 193as this indicates an incompatible change. Minor versions are usually
145compatible to older versions, so a larger minor version alone is usually 194compatible to older versions, so a larger minor version alone is usually
146not a problem.</p> 195not a problem.</p>
147 <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
148version:</p> 197version.</p>
149<pre> assert ((&quot;libev version mismatch&quot;, 198<pre> assert ((&quot;libev version mismatch&quot;,
150 ev_version_major () == EV_VERSION_MAJOR 199 ev_version_major () == EV_VERSION_MAJOR
151 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 200 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
152 201
153</pre> 202</pre>
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183recommended ones.</p> 232recommended ones.</p>
184 <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>
185 </dd> 234 </dd>
186 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
187 <dd> 236 <dd>
188 <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
189realloc C function, the semantics are identical). It is used to allocate 238semantics is identical - to the realloc C function). It is used to
190and free memory (no surprises here). If it returns zero when memory 239allocate and free memory (no surprises here). If it returns zero when
191needs to be allocated, the library might abort or take some potentially 240memory needs to be allocated, the library might abort or take some
192destructive action. The default is your system realloc function.</p> 241potentially destructive action. The default is your system realloc
242function.</p>
193 <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,
194free 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,
195or 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>
196 <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
197retries: better than mine).</p> 247retries).</p>
198<pre> static void * 248<pre> static void *
199 persistent_realloc (void *ptr, long size) 249 persistent_realloc (void *ptr, size_t size)
200 { 250 {
201 for (;;) 251 for (;;)
202 { 252 {
203 void *newptr = realloc (ptr, size); 253 void *newptr = realloc (ptr, size);
204 254
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221indicating the system call or subsystem causing the problem. If this 271indicating the system call or subsystem causing the problem. If this
222callback 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
223matter what, when it returns. That is, libev will generally retry the 273matter what, when it returns. That is, libev will generally retry the
224requested 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
225(such as abort).</p> 275(such as abort).</p>
226 <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>
227<pre> static void 277<pre> static void
228 fatal_error (const char *msg) 278 fatal_error (const char *msg)
229 { 279 {
230 perror (msg); 280 perror (msg);
231 abort (); 281 abort ();
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237</pre> 287</pre>
238 </dd> 288 </dd>
239</dl> 289</dl>
240 290
241</div> 291</div>
242<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>
243<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 293<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
244<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
245types 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
246events, and dynamically created loops which do not.</p> 296events, and dynamically created loops which do not.</p>
247<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
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275or 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
276<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 326<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
277override 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
278useful 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
279around 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 noticable (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>
280 </dd> 347 </dd>
281 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 348 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
282 <dd> 349 <dd>
283 <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
284libev 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,
… …
367 <dd> 434 <dd>
368 <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
369always distinct from the default loop. Unlike the default loop, it cannot 436always distinct from the default loop. Unlike the default loop, it cannot
370handle 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
371undefined behaviour (or a failed assertion if assertions are enabled).</p> 438undefined behaviour (or a failed assertion if assertions are enabled).</p>
372 <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>
373<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);
374 if (!epoller) 441 if (!epoller)
375 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;);
376 443
377</pre> 444</pre>
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470 be handled here by queueing them when their watcher gets executed. 537 be handled here by queueing them when their watcher gets executed.
471 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 538 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
472 were used, return, otherwise continue with step *. 539 were used, return, otherwise continue with step *.
473 540
474</pre> 541</pre>
475 <p>Example: queue some jobs and then loop until no events are outsanding 542 <p>Example: Queue some jobs and then loop until no events are outsanding
476anymore.</p> 543anymore.</p>
477<pre> ... queue jobs here, make sure they register event watchers as long 544<pre> ... queue jobs here, make sure they register event watchers as long
478 ... as they still have work to do (even an idle watcher will do..) 545 ... as they still have work to do (even an idle watcher will do..)
479 ev_loop (my_loop, 0); 546 ev_loop (my_loop, 0);
480 ... jobs done. yeah! 547 ... jobs done. yeah!
… …
499example, libev itself uses this for its internal signal pipe: It is not 566example, libev itself uses this for its internal signal pipe: It is not
500visible to the libev user and should not keep <code>ev_loop</code> from exiting if 567visible to the libev user and should not keep <code>ev_loop</code> from exiting if
501no event watchers registered by it are active. It is also an excellent 568no event watchers registered by it are active. It is also an excellent
502way to do this for generic recurring timers or from within third-party 569way to do this for generic recurring timers or from within third-party
503libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 570libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
504 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 571 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
505running when nothing else is active.</p> 572running when nothing else is active.</p>
506<pre> struct dv_signal exitsig; 573<pre> struct ev_signal exitsig;
507 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 574 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
508 ev_signal_start (myloop, &amp;exitsig); 575 ev_signal_start (loop, &amp;exitsig);
509 evf_unref (myloop); 576 evf_unref (loop);
510 577
511</pre> 578</pre>
512 <p>Example: for some weird reason, unregister the above signal handler again.</p> 579 <p>Example: For some weird reason, unregister the above signal handler again.</p>
513<pre> ev_ref (myloop); 580<pre> ev_ref (loop);
514 ev_signal_stop (myloop, &amp;exitsig); 581 ev_signal_stop (loop, &amp;exitsig);
515 582
516</pre> 583</pre>
517 </dd> 584 </dd>
518</dl> 585</dl>
519 586
520 587
521 588
522 589
523 590
524</div> 591</div>
525<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 592<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
526<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 593<div id="ANATOMY_OF_A_WATCHER_CONTENT">
527<p>A watcher is a structure that you create and register to record your 594<p>A watcher is a structure that you create and register to record your
528interest in some event. For instance, if you want to wait for STDIN to 595interest in some event. For instance, if you want to wait for STDIN to
529become readable, you would create an <code>ev_io</code> watcher for that:</p> 596become readable, you would create an <code>ev_io</code> watcher for that:</p>
530<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 597<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
606received events. Callbacks of both watcher types can start and stop as 673received events. Callbacks of both watcher types can start and stop as
607many watchers as they want, and all of them will be taken into account 674many watchers as they want, and all of them will be taken into account
608(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 675(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
609<code>ev_loop</code> from blocking).</p> 676<code>ev_loop</code> from blocking).</p>
610 </dd> 677 </dd>
678 <dt><code>EV_EMBED</code></dt>
679 <dd>
680 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
681 </dd>
682 <dt><code>EV_FORK</code></dt>
683 <dd>
684 <p>The event loop has been resumed in the child process after fork (see
685<code>ev_fork</code>).</p>
686 </dd>
611 <dt><code>EV_ERROR</code></dt> 687 <dt><code>EV_ERROR</code></dt>
612 <dd> 688 <dd>
613 <p>An unspecified error has occured, the watcher has been stopped. This might 689 <p>An unspecified error has occured, the watcher has been stopped. This might
614happen because the watcher could not be properly started because libev 690happen because the watcher could not be properly started because libev
615ran out of memory, a file descriptor was found to be closed or any other 691ran out of memory, a file descriptor was found to be closed or any other
… …
684events but its callback has not yet been invoked). As long as a watcher 760events but its callback has not yet been invoked). As long as a watcher
685is pending (but not active) you must not call an init function on it (but 761is pending (but not active) you must not call an init function on it (but
686<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 762<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
687libev (e.g. you cnanot <code>free ()</code> it).</p> 763libev (e.g. you cnanot <code>free ()</code> it).</p>
688 </dd> 764 </dd>
689 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 765 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
690 <dd> 766 <dd>
691 <p>Returns the callback currently set on the watcher.</p> 767 <p>Returns the callback currently set on the watcher.</p>
692 </dd> 768 </dd>
693 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 769 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
694 <dd> 770 <dd>
… …
726 struct my_io *w = (struct my_io *)w_; 802 struct my_io *w = (struct my_io *)w_;
727 ... 803 ...
728 } 804 }
729 805
730</pre> 806</pre>
731<p>More interesting and less C-conformant ways of catsing your callback type 807<p>More interesting and less C-conformant ways of casting your callback type
732have been omitted....</p> 808instead have been omitted.</p>
809<p>Another common scenario is having some data structure with multiple
810watchers:</p>
811<pre> struct my_biggy
812 {
813 int some_data;
814 ev_timer t1;
815 ev_timer t2;
816 }
733 817
818</pre>
819<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
820you need to use <code>offsetof</code>:</p>
821<pre> #include &lt;stddef.h&gt;
734 822
823 static void
824 t1_cb (EV_P_ struct ev_timer *w, int revents)
825 {
826 struct my_biggy big = (struct my_biggy *
827 (((char *)w) - offsetof (struct my_biggy, t1));
828 }
735 829
830 static void
831 t2_cb (EV_P_ struct ev_timer *w, int revents)
832 {
833 struct my_biggy big = (struct my_biggy *
834 (((char *)w) - offsetof (struct my_biggy, t2));
835 }
736 836
737 837
838
839
840</pre>
841
738</div> 842</div>
739<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 843<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
740<div id="WATCHER_TYPES_CONTENT"> 844<div id="WATCHER_TYPES_CONTENT">
741<p>This section describes each watcher in detail, but will not repeat 845<p>This section describes each watcher in detail, but will not repeat
742information given in the last section. Any initialisation/set macros, 846information given in the last section. Any initialisation/set macros,
743functions and members specific to the watcher type are explained.</p> 847functions and members specific to the watcher type are explained.</p>
744<p>Members are additionally marked with either <i>[read-only]</i>, meaning that, 848<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
… …
804 <dt>int events [read-only]</dt> 908 <dt>int events [read-only]</dt>
805 <dd> 909 <dd>
806 <p>The events being watched.</p> 910 <p>The events being watched.</p>
807 </dd> 911 </dd>
808</dl> 912</dl>
809<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 913<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
810readable, but only once. Since it is likely line-buffered, you could 914readable, but only once. Since it is likely line-buffered, you could
811attempt to read a whole line in the callback:</p> 915attempt to read a whole line in the callback.</p>
812<pre> static void 916<pre> static void
813 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 917 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
814 { 918 {
815 ev_io_stop (loop, w); 919 ev_io_stop (loop, w);
816 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 920 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
865 </dd> 969 </dd>
866 <dt>ev_timer_again (loop)</dt> 970 <dt>ev_timer_again (loop)</dt>
867 <dd> 971 <dd>
868 <p>This will act as if the timer timed out and restart it again if it is 972 <p>This will act as if the timer timed out and restart it again if it is
869repeating. The exact semantics are:</p> 973repeating. The exact semantics are:</p>
974 <p>If the timer is pending, its pending status is cleared.</p>
870 <p>If the timer is started but nonrepeating, stop it.</p> 975 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
871 <p>If the timer is repeating, either start it if necessary (with the repeat 976 <p>If the timer is repeating, either start it if necessary (with the
872value), or reset the running timer to the repeat value.</p> 977<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
873 <p>This sounds a bit complicated, but here is a useful and typical 978 <p>This sounds a bit complicated, but here is a useful and typical
874example: Imagine you have a tcp connection and you want a so-called 979example: Imagine you have a tcp connection and you want a so-called idle
875idle timeout, that is, you want to be called when there have been, 980timeout, that is, you want to be called when there have been, say, 60
876say, 60 seconds of inactivity on the socket. The easiest way to do 981seconds of inactivity on the socket. The easiest way to do this is to
877this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling 982configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
878<code>ev_timer_again</code> each time you successfully read or write some data. If 983<code>ev_timer_again</code> each time you successfully read or write some data. If
879you go into an idle state where you do not expect data to travel on the 984you go into an idle state where you do not expect data to travel on the
880socket, you can stop the timer, and again will automatically restart it if 985socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
881need be.</p> 986automatically restart it if need be.</p>
882 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 987 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
883and only ever use the <code>repeat</code> value:</p> 988altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
884<pre> ev_timer_init (timer, callback, 0., 5.); 989<pre> ev_timer_init (timer, callback, 0., 5.);
885 ev_timer_again (loop, timer); 990 ev_timer_again (loop, timer);
886 ... 991 ...
887 timer-&gt;again = 17.; 992 timer-&gt;again = 17.;
888 ev_timer_again (loop, timer); 993 ev_timer_again (loop, timer);
889 ... 994 ...
890 timer-&gt;again = 10.; 995 timer-&gt;again = 10.;
891 ev_timer_again (loop, timer); 996 ev_timer_again (loop, timer);
892 997
893</pre> 998</pre>
894 <p>This is more efficient then stopping/starting the timer eahc time you want 999 <p>This is more slightly efficient then stopping/starting the timer each time
895to modify its timeout value.</p> 1000you want to modify its timeout value.</p>
896 </dd> 1001 </dd>
897 <dt>ev_tstamp repeat [read-write]</dt> 1002 <dt>ev_tstamp repeat [read-write]</dt>
898 <dd> 1003 <dd>
899 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1004 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
900or <code>ev_timer_again</code> is called and determines the next timeout (if any), 1005or <code>ev_timer_again</code> is called and determines the next timeout (if any),
901which is also when any modifications are taken into account.</p> 1006which is also when any modifications are taken into account.</p>
902 </dd> 1007 </dd>
903</dl> 1008</dl>
904<p>Example: create a timer that fires after 60 seconds.</p> 1009<p>Example: Create a timer that fires after 60 seconds.</p>
905<pre> static void 1010<pre> static void
906 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1011 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
907 { 1012 {
908 .. one minute over, w is actually stopped right here 1013 .. one minute over, w is actually stopped right here
909 } 1014 }
… …
911 struct ev_timer mytimer; 1016 struct ev_timer mytimer;
912 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1017 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
913 ev_timer_start (loop, &amp;mytimer); 1018 ev_timer_start (loop, &amp;mytimer);
914 1019
915</pre> 1020</pre>
916<p>Example: create a timeout timer that times out after 10 seconds of 1021<p>Example: Create a timeout timer that times out after 10 seconds of
917inactivity.</p> 1022inactivity.</p>
918<pre> static void 1023<pre> static void
919 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1024 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
920 { 1025 {
921 .. ten seconds without any activity 1026 .. ten seconds without any activity
… …
1037 <p>The current reschedule callback, or <code>0</code>, if this functionality is 1142 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1038switched off. Can be changed any time, but changes only take effect when 1143switched off. Can be changed any time, but changes only take effect when
1039the periodic timer fires or <code>ev_periodic_again</code> is being called.</p> 1144the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1040 </dd> 1145 </dd>
1041</dl> 1146</dl>
1042<p>Example: call a callback every hour, or, more precisely, whenever the 1147<p>Example: Call a callback every hour, or, more precisely, whenever the
1043system clock is divisible by 3600. The callback invocation times have 1148system clock is divisible by 3600. The callback invocation times have
1044potentially a lot of jittering, but good long-term stability.</p> 1149potentially a lot of jittering, but good long-term stability.</p>
1045<pre> static void 1150<pre> static void
1046 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1151 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1047 { 1152 {
… …
1051 struct ev_periodic hourly_tick; 1156 struct ev_periodic hourly_tick;
1052 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1157 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
1053 ev_periodic_start (loop, &amp;hourly_tick); 1158 ev_periodic_start (loop, &amp;hourly_tick);
1054 1159
1055</pre> 1160</pre>
1056<p>Example: the same as above, but use a reschedule callback to do it:</p> 1161<p>Example: The same as above, but use a reschedule callback to do it:</p>
1057<pre> #include &lt;math.h&gt; 1162<pre> #include &lt;math.h&gt;
1058 1163
1059 static ev_tstamp 1164 static ev_tstamp
1060 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1165 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1061 { 1166 {
… …
1063 } 1168 }
1064 1169
1065 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1170 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1066 1171
1067</pre> 1172</pre>
1068<p>Example: call a callback every hour, starting now:</p> 1173<p>Example: Call a callback every hour, starting now:</p>
1069<pre> struct ev_periodic hourly_tick; 1174<pre> struct ev_periodic hourly_tick;
1070 ev_periodic_init (&amp;hourly_tick, clock_cb, 1175 ev_periodic_init (&amp;hourly_tick, clock_cb,
1071 fmod (ev_now (loop), 3600.), 3600., 0); 1176 fmod (ev_now (loop), 3600.), 3600., 0);
1072 ev_periodic_start (loop, &amp;hourly_tick); 1177 ev_periodic_start (loop, &amp;hourly_tick);
1073 1178
… …
1134 <dd> 1239 <dd>
1135 <p>The process exit/trace status caused by <code>rpid</code> (see your systems 1240 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1136<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p> 1241<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1137 </dd> 1242 </dd>
1138</dl> 1243</dl>
1139<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1244<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1140<pre> static void 1245<pre> static void
1141 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1246 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1142 { 1247 {
1143 ev_unloop (loop, EVUNLOOP_ALL); 1248 ev_unloop (loop, EVUNLOOP_ALL);
1144 } 1249 }
… …
1161<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1266<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1162not exist&quot; is a status change like any other. The condition &quot;path does 1267not exist&quot; is a status change like any other. The condition &quot;path does
1163not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is 1268not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1164otherwise always forced to be at least one) and all the other fields of 1269otherwise always forced to be at least one) and all the other fields of
1165the stat buffer having unspecified contents.</p> 1270the stat buffer having unspecified contents.</p>
1271<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1272relative and your working directory changes, the behaviour is undefined.</p>
1166<p>Since there is no standard to do this, the portable implementation simply 1273<p>Since there is no standard to do this, the portable implementation simply
1167calls <code>stat (2)</code> regulalry on the path to see if it changed somehow. You 1274calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1168can specify a recommended polling interval for this case. If you specify 1275can specify a recommended polling interval for this case. If you specify
1169a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1276a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1170unspecified default</i> value will be used (which you can expect to be around 1277unspecified default</i> value will be used (which you can expect to be around
1171five seconds, although this might change dynamically). Libev will also 1278five seconds, although this might change dynamically). Libev will also
1172impose a minimum interval which is currently around <code>0.1</code>, but thats 1279impose a minimum interval which is currently around <code>0.1</code>, but thats
1173usually overkill.</p> 1280usually overkill.</p>
1174<p>This watcher type is not meant for massive numbers of stat watchers, 1281<p>This watcher type is not meant for massive numbers of stat watchers,
1175as even with OS-supported change notifications, this can be 1282as even with OS-supported change notifications, this can be
1176resource-intensive.</p> 1283resource-intensive.</p>
1177<p>At the time of this writing, no specific OS backends are implemented, but 1284<p>At the time of this writing, only the Linux inotify interface is
1178if demand increases, at least a kqueue and inotify backend will be added.</p> 1285implemented (implementing kqueue support is left as an exercise for the
1286reader). Inotify will be used to give hints only and should not change the
1287semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1288to fall back to regular polling again even with inotify, but changes are
1289usually detected immediately, and if the file exists there will be no
1290polling.</p>
1179<dl> 1291<dl>
1180 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> 1292 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1181 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> 1293 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1182 <dd> 1294 <dd>
1183 <p>Configures the watcher to wait for status changes of the given 1295 <p>Configures the watcher to wait for status changes of the given
… …
1267 <p>Initialises and configures the idle watcher - it has no parameters of any 1379 <p>Initialises and configures the idle watcher - it has no parameters of any
1268kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1380kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1269believe me.</p> 1381believe me.</p>
1270 </dd> 1382 </dd>
1271</dl> 1383</dl>
1272<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1384<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1273callback, free it. Alos, use no error checking, as usual.</p> 1385callback, free it. Also, use no error checking, as usual.</p>
1274<pre> static void 1386<pre> static void
1275 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1387 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1276 { 1388 {
1277 free (w); 1389 free (w);
1278 // now do something you wanted to do when the program has 1390 // now do something you wanted to do when the program has
… …
1480 1592
1481 1593
1482 1594
1483 1595
1484</div> 1596</div>
1485<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1597<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>
1598<div id="code_ev_fork_code_the_audacity_to_re-2">
1599<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1600whoever is a good citizen cared to tell libev about it by calling
1601<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1602event loop blocks next and before <code>ev_check</code> watchers are being called,
1603and only in the child after the fork. If whoever good citizen calling
1604<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1605handlers will be invoked, too, of course.</p>
1606<dl>
1607 <dt>ev_fork_init (ev_signal *, callback)</dt>
1608 <dd>
1609 <p>Initialises and configures the fork watcher - it has no parameters of any
1610kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1611believe me.</p>
1612 </dd>
1613</dl>
1614
1615
1616
1617
1618
1619</div>
1620<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1486<div id="OTHER_FUNCTIONS_CONTENT"> 1621<div id="OTHER_FUNCTIONS_CONTENT">
1487<p>There are some other functions of possible interest. Described. Here. Now.</p> 1622<p>There are some other functions of possible interest. Described. Here. Now.</p>
1488<dl> 1623<dl>
1489 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1624 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1490 <dd> 1625 <dd>
… …
1537 1672
1538 1673
1539 1674
1540 1675
1541</div> 1676</div>
1542<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1677<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1543<div id="LIBEVENT_EMULATION_CONTENT"> 1678<div id="LIBEVENT_EMULATION_CONTENT">
1544<p>Libev offers a compatibility emulation layer for libevent. It cannot 1679<p>Libev offers a compatibility emulation layer for libevent. It cannot
1545emulate the internals of libevent, so here are some usage hints:</p> 1680emulate the internals of libevent, so here are some usage hints:</p>
1546<dl> 1681<dl>
1547 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1682 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1557 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1692 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1558to use the libev header file and library.</dt> 1693to use the libev header file and library.</dt>
1559</dl> 1694</dl>
1560 1695
1561</div> 1696</div>
1562<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1697<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1563<div id="C_SUPPORT_CONTENT"> 1698<div id="C_SUPPORT_CONTENT">
1564<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1699<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1565you to use some convinience methods to start/stop watchers and also change 1700you to use some convinience methods to start/stop watchers and also change
1566the callback model to a model using method callbacks on objects.</p> 1701the callback model to a model using method callbacks on objects.</p>
1567<p>To use it,</p> 1702<p>To use it,</p>
… …
1656 idle (this, &amp;myclass::idle_cb) 1791 idle (this, &amp;myclass::idle_cb)
1657 { 1792 {
1658 io.start (fd, ev::READ); 1793 io.start (fd, ev::READ);
1659 } 1794 }
1660 1795
1661</pre>
1662 1796
1797
1798
1799</pre>
1800
1663</div> 1801</div>
1664<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1802<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1803<div id="MACRO_MAGIC_CONTENT">
1804<p>Libev can be compiled with a variety of options, the most fundemantal is
1805<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1806callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1807<p>To make it easier to write programs that cope with either variant, the
1808following macros are defined:</p>
1809<dl>
1810 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1811 <dd>
1812 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1813loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1814<code>EV_A_</code> is used when other arguments are following. Example:</p>
1815<pre> ev_unref (EV_A);
1816 ev_timer_add (EV_A_ watcher);
1817 ev_loop (EV_A_ 0);
1818
1819</pre>
1820 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1821which is often provided by the following macro.</p>
1822 </dd>
1823 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1824 <dd>
1825 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1826loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1827<code>EV_P_</code> is used when other parameters are following. Example:</p>
1828<pre> // this is how ev_unref is being declared
1829 static void ev_unref (EV_P);
1830
1831 // this is how you can declare your typical callback
1832 static void cb (EV_P_ ev_timer *w, int revents)
1833
1834</pre>
1835 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1836suitable for use with <code>EV_A</code>.</p>
1837 </dd>
1838 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1839 <dd>
1840 <p>Similar to the other two macros, this gives you the value of the default
1841loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1842 </dd>
1843</dl>
1844<p>Example: Declare and initialise a check watcher, working regardless of
1845wether multiple loops are supported or not.</p>
1846<pre> static void
1847 check_cb (EV_P_ ev_timer *w, int revents)
1848 {
1849 ev_check_stop (EV_A_ w);
1850 }
1851
1852 ev_check check;
1853 ev_check_init (&amp;check, check_cb);
1854 ev_check_start (EV_DEFAULT_ &amp;check);
1855 ev_loop (EV_DEFAULT_ 0);
1856
1857
1858
1859
1860</pre>
1861
1862</div>
1863<h1 id="EMBEDDING">EMBEDDING</h1>
1665<div id="EMBEDDING_CONTENT"> 1864<div id="EMBEDDING_CONTENT">
1666<p>Libev can (and often is) directly embedded into host 1865<p>Libev can (and often is) directly embedded into host
1667applications. Examples of applications that embed it include the Deliantra 1866applications. Examples of applications that embed it include the Deliantra
1668Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 1867Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1669and rxvt-unicode.</p> 1868and rxvt-unicode.</p>
… …
1843 </dd> 2042 </dd>
1844 <dt>EV_USE_DEVPOLL</dt> 2043 <dt>EV_USE_DEVPOLL</dt>
1845 <dd> 2044 <dd>
1846 <p>reserved for future expansion, works like the USE symbols above.</p> 2045 <p>reserved for future expansion, works like the USE symbols above.</p>
1847 </dd> 2046 </dd>
2047 <dt>EV_USE_INOTIFY</dt>
2048 <dd>
2049 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2050interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2051be detected at runtime.</p>
2052 </dd>
1848 <dt>EV_H</dt> 2053 <dt>EV_H</dt>
1849 <dd> 2054 <dd>
1850 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2055 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1851undefined 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 2056undefined 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
1852can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2057can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1891 <dt>EV_STAT_ENABLE</dt> 2096 <dt>EV_STAT_ENABLE</dt>
1892 <dd> 2097 <dd>
1893 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If 2098 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
1894defined to be <code>0</code>, then they are not.</p> 2099defined to be <code>0</code>, then they are not.</p>
1895 </dd> 2100 </dd>
2101 <dt>EV_FORK_ENABLE</dt>
2102 <dd>
2103 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2104defined to be <code>0</code>, then they are not.</p>
2105 </dd>
1896 <dt>EV_MINIMAL</dt> 2106 <dt>EV_MINIMAL</dt>
1897 <dd> 2107 <dd>
1898 <p>If you need to shave off some kilobytes of code at the expense of some 2108 <p>If you need to shave off some kilobytes of code at the expense of some
1899speed, define this symbol to <code>1</code>. Currently only used for gcc to override 2109speed, define this symbol to <code>1</code>. Currently only used for gcc to override
1900some inlining decisions, saves roughly 30% codesize of amd64.</p> 2110some inlining decisions, saves roughly 30% codesize of amd64.</p>
2111 </dd>
2112 <dt>EV_PID_HASHSIZE</dt>
2113 <dd>
2114 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2115pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2116than enough. If you need to manage thousands of children you might want to
2117increase this value (<i>must</i> be a power of two).</p>
2118 </dd>
2119 <dt>EV_INOTIFY_HASHSIZE</dt>
2120 <dd>
2121 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2122inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2123usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2124watchers you might want to increase this value (<i>must</i> be a power of
2125two).</p>
1901 </dd> 2126 </dd>
1902 <dt>EV_COMMON</dt> 2127 <dt>EV_COMMON</dt>
1903 <dd> 2128 <dd>
1904 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2129 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1905this macro to a something else you can include more and other types of 2130this macro to a something else you can include more and other types of
… …
1951 2176
1952 2177
1953</pre> 2178</pre>
1954 2179
1955</div> 2180</div>
1956<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2181<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
1957<div id="COMPLEXITIES_CONTENT"> 2182<div id="COMPLEXITIES_CONTENT">
1958 <p>In this section the complexities of (many of) the algorithms used inside 2183 <p>In this section the complexities of (many of) the algorithms used inside
1959libev will be explained. For complexity discussions about backends see the 2184libev will be explained. For complexity discussions about backends see the
1960documentation for <code>ev_default_init</code>.</p> 2185documentation for <code>ev_default_init</code>.</p>
1961 <p> 2186 <p>
1962 <dl> 2187 <dl>
1963 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2188 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
1964 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2189 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
1965 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2190 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
1966 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2191 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
1967 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2192 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
1968 <dt>Finding the next timer per loop iteration: O(1)</dt> 2193 <dt>Finding the next timer per loop iteration: O(1)</dt>
1969 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2194 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
1970 <dt>Activating one watcher: O(1)</dt> 2195 <dt>Activating one watcher: O(1)</dt>
1971 </dl> 2196 </dl>
1972 </p> 2197 </p>
… …
1974 2199
1975 2200
1976 2201
1977 2202
1978</div> 2203</div>
1979<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2204<h1 id="AUTHOR">AUTHOR</h1>
1980<div id="AUTHOR_CONTENT"> 2205<div id="AUTHOR_CONTENT">
1981 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2206 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1982 2207
1983</div> 2208</div>
1984</div></body> 2209</div></body>

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