ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/libev/ev.html
(Generate patch)

Comparing libev/ev.html (file contents):
Revision 1.39 by root, Sat Nov 24 09:48:38 2007 UTC vs.
Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC

… …
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 10:48:32 2007" /> 9 <meta name="created" content="Wed Nov 28 12:27:27 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>
26<ul><li><a href="#SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</a></li> 27<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
27<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>
28</ul> 29</ul>
29</li> 30</li>
30<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 31<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
31<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>
32<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>
33<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>
34<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>
35<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>
36<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>
37<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>
38<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>
39</ul> 42</ul>
40</li> 43</li>
41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<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>
44<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
45</li> 61</li>
46</ul><hr /> 62</ul><hr />
47<!-- INDEX END --> 63<!-- INDEX END -->
48 64
49<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
50<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
51<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>
52 68
53</div> 69</div>
54<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
55<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
56<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
57 73
58</pre> 74</pre>
59 75
60</div> 76</div>
61<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>
62<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
63<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
64file descriptor being readable or a timeout occuring), and it will manage 125file descriptor being readable or a timeout occuring), and it will manage
65these event sources and provide your program with events.</p> 126these event sources and provide your program with events.</p>
66<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
… …
70watchers</i>, which are relatively small C structures you initialise with the 131watchers</i>, which are relatively small C structures you initialise with the
71details 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
72watcher.</p> 133watcher.</p>
73 134
74</div> 135</div>
75<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1>
76<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
77<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
78kqueue mechanisms for file descriptor events, relative timers, absolute 139bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms
79timers with customised rescheduling, signal events, process status change 140for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>),
80events (related to SIGCHLD), and event watchers dealing with the event 141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous
81loop mechanism itself (idle, prepare and check watchers). It also is quite 142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and
143event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
144<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
145file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this
82fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
83it to libevent for example).</p> 149for example).</p>
84 150
85</div> 151</div>
86<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 152<h1 id="CONVENTIONS">CONVENTIONS</h1>
87<div id="CONVENTIONS_CONTENT"> 153<div id="CONVENTIONS_CONTENT">
88<p>Libev is very configurable. In this manual the default configuration 154<p>Libev is very configurable. In this manual the default configuration will
89will be described, which supports multiple event loops. For more info 155be described, which supports multiple event loops. For more info about
90about various configuration options please have a look at the file 156various configuration options please have a look at <strong>EMBED</strong> section in
91<cite>README.embed</cite> in the libev distribution. If libev was configured without 157this manual. If libev was configured without support for multiple event
92support for multiple event loops, then all functions taking an initial 158loops, then all functions taking an initial argument of name <code>loop</code>
93argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 159(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
94will not have this argument.</p>
95 160
96</div> 161</div>
97<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 162<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
98<div id="TIME_REPRESENTATION_CONTENT"> 163<div id="TIME_REPRESENTATION_CONTENT">
99<p>Libev represents time as a single floating point number, representing the 164<p>Libev represents time as a single floating point number, representing the
100(fractional) number of seconds since the (POSIX) epoch (somewhere near 165(fractional) number of seconds since the (POSIX) epoch (somewhere near
101the beginning of 1970, details are complicated, don't ask). This type is 166the beginning of 1970, details are complicated, don't ask). This type is
102called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 167called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
103to the <code>double</code> type in C, and when you need to do any calculations on 168to the <code>double</code> type in C, and when you need to do any calculations on
104it, you should treat it as such.</p> 169it, you should treat it as such.</p>
105 170
106
107
108
109
110</div> 171</div>
111<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 172<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
112<div id="GLOBAL_FUNCTIONS_CONTENT"> 173<div id="GLOBAL_FUNCTIONS_CONTENT">
113<p>These functions can be called anytime, even before initialising the 174<p>These functions can be called anytime, even before initialising the
114library in any way.</p> 175library in any way.</p>
115<dl> 176<dl>
116 <dt>ev_tstamp ev_time ()</dt> 177 <dt>ev_tstamp ev_time ()</dt>
… …
129version of the library your program was compiled against.</p> 190version of the library your program was compiled against.</p>
130 <p>Usually, it's a good idea to terminate if the major versions mismatch, 191 <p>Usually, it's a good idea to terminate if the major versions mismatch,
131as this indicates an incompatible change. Minor versions are usually 192as this indicates an incompatible change. Minor versions are usually
132compatible to older versions, so a larger minor version alone is usually 193compatible to older versions, so a larger minor version alone is usually
133not a problem.</p> 194not a problem.</p>
134 <p>Example: make sure we haven't accidentally been linked against the wrong 195 <p>Example: Make sure we haven't accidentally been linked against the wrong
135version:</p> 196version.</p>
136<pre> assert ((&quot;libev version mismatch&quot;, 197<pre> assert ((&quot;libev version mismatch&quot;,
137 ev_version_major () == EV_VERSION_MAJOR 198 ev_version_major () == EV_VERSION_MAJOR
138 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 199 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
139 200
140</pre> 201</pre>
… …
168might be supported on the current system, you would need to look at 229might be supported on the current system, you would need to look at
169<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
170recommended ones.</p> 231recommended ones.</p>
171 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 232 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
172 </dd> 233 </dd>
173 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt>
174 <dd> 235 <dd>
175 <p>Sets the allocation function to use (the prototype is similar to the 236 <p>Sets the allocation function to use (the prototype and semantics are
176realloc C function, the semantics are identical). It is used to allocate 237identical to the realloc C function). It is used to allocate and free
177and free memory (no surprises here). If it returns zero when memory 238memory (no surprises here). If it returns zero when memory needs to be
178needs to be allocated, the library might abort or take some potentially 239allocated, the library might abort or take some potentially destructive
179destructive action. The default is your system realloc function.</p> 240action. The default is your system realloc function.</p>
180 <p>You could override this function in high-availability programs to, say, 241 <p>You could override this function in high-availability programs to, say,
181free some memory if it cannot allocate memory, to use a special allocator, 242free some memory if it cannot allocate memory, to use a special allocator,
182or even to sleep a while and retry until some memory is available.</p> 243or even to sleep a while and retry until some memory is available.</p>
183 <p>Example: replace the libev allocator with one that waits a bit and then 244 <p>Example: Replace the libev allocator with one that waits a bit and then
184retries: better than mine).</p> 245retries).</p>
185<pre> static void * 246<pre> static void *
186 persistent_realloc (void *ptr, long size) 247 persistent_realloc (void *ptr, size_t size)
187 { 248 {
188 for (;;) 249 for (;;)
189 { 250 {
190 void *newptr = realloc (ptr, size); 251 void *newptr = realloc (ptr, size);
191 252
… …
208indicating the system call or subsystem causing the problem. If this 269indicating the system call or subsystem causing the problem. If this
209callback is set, then libev will expect it to remedy the sitution, no 270callback is set, then libev will expect it to remedy the sitution, no
210matter what, when it returns. That is, libev will generally retry the 271matter what, when it returns. That is, libev will generally retry the
211requested operation, or, if the condition doesn't go away, do bad stuff 272requested operation, or, if the condition doesn't go away, do bad stuff
212(such as abort).</p> 273(such as abort).</p>
213 <p>Example: do the same thing as libev does internally:</p> 274 <p>Example: This is basically the same thing that libev does internally, too.</p>
214<pre> static void 275<pre> static void
215 fatal_error (const char *msg) 276 fatal_error (const char *msg)
216 { 277 {
217 perror (msg); 278 perror (msg);
218 abort (); 279 abort ();
… …
224</pre> 285</pre>
225 </dd> 286 </dd>
226</dl> 287</dl>
227 288
228</div> 289</div>
229<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 290<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
230<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 291<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
231<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 292<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
232types of such loops, the <i>default</i> loop, which supports signals and child 293types of such loops, the <i>default</i> loop, which supports signals and child
233events, and dynamically created loops which do not.</p> 294events, and dynamically created loops which do not.</p>
234<p>If you use threads, a common model is to run the default event loop 295<p>If you use threads, a common model is to run the default event loop
… …
354 <dd> 415 <dd>
355 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 416 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
356always distinct from the default loop. Unlike the default loop, it cannot 417always distinct from the default loop. Unlike the default loop, it cannot
357handle signal and child watchers, and attempts to do so will be greeted by 418handle signal and child watchers, and attempts to do so will be greeted by
358undefined behaviour (or a failed assertion if assertions are enabled).</p> 419undefined behaviour (or a failed assertion if assertions are enabled).</p>
359 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 420 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
360<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 421<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
361 if (!epoller) 422 if (!epoller)
362 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 423 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
363 424
364</pre> 425</pre>
… …
457 be handled here by queueing them when their watcher gets executed. 518 be handled here by queueing them when their watcher gets executed.
458 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 519 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
459 were used, return, otherwise continue with step *. 520 were used, return, otherwise continue with step *.
460 521
461</pre> 522</pre>
462 <p>Example: queue some jobs and then loop until no events are outsanding 523 <p>Example: Queue some jobs and then loop until no events are outsanding
463anymore.</p> 524anymore.</p>
464<pre> ... queue jobs here, make sure they register event watchers as long 525<pre> ... queue jobs here, make sure they register event watchers as long
465 ... as they still have work to do (even an idle watcher will do..) 526 ... as they still have work to do (even an idle watcher will do..)
466 ev_loop (my_loop, 0); 527 ev_loop (my_loop, 0);
467 ... jobs done. yeah! 528 ... jobs done. yeah!
… …
486example, libev itself uses this for its internal signal pipe: It is not 547example, libev itself uses this for its internal signal pipe: It is not
487visible to the libev user and should not keep <code>ev_loop</code> from exiting if 548visible to the libev user and should not keep <code>ev_loop</code> from exiting if
488no event watchers registered by it are active. It is also an excellent 549no event watchers registered by it are active. It is also an excellent
489way to do this for generic recurring timers or from within third-party 550way to do this for generic recurring timers or from within third-party
490libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 551libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
491 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 552 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
492running when nothing else is active.</p> 553running when nothing else is active.</p>
493<pre> struct dv_signal exitsig; 554<pre> struct ev_signal exitsig;
494 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 555 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
495 ev_signal_start (myloop, &amp;exitsig); 556 ev_signal_start (loop, &amp;exitsig);
496 evf_unref (myloop); 557 evf_unref (loop);
497 558
498</pre> 559</pre>
499 <p>Example: for some weird reason, unregister the above signal handler again.</p> 560 <p>Example: For some weird reason, unregister the above signal handler again.</p>
500<pre> ev_ref (myloop); 561<pre> ev_ref (loop);
501 ev_signal_stop (myloop, &amp;exitsig); 562 ev_signal_stop (loop, &amp;exitsig);
502 563
503</pre> 564</pre>
504 </dd> 565 </dd>
505</dl> 566</dl>
506 567
568
569
570
571
507</div> 572</div>
508<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 573<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
509<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 574<div id="ANATOMY_OF_A_WATCHER_CONTENT">
510<p>A watcher is a structure that you create and register to record your 575<p>A watcher is a structure that you create and register to record your
511interest in some event. For instance, if you want to wait for STDIN to 576interest in some event. For instance, if you want to wait for STDIN to
512become readable, you would create an <code>ev_io</code> watcher for that:</p> 577become readable, you would create an <code>ev_io</code> watcher for that:</p>
513<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 578<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
570 </dd> 635 </dd>
571 <dt><code>EV_CHILD</code></dt> 636 <dt><code>EV_CHILD</code></dt>
572 <dd> 637 <dd>
573 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 638 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
574 </dd> 639 </dd>
640 <dt><code>EV_STAT</code></dt>
641 <dd>
642 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
643 </dd>
575 <dt><code>EV_IDLE</code></dt> 644 <dt><code>EV_IDLE</code></dt>
576 <dd> 645 <dd>
577 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 646 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
578 </dd> 647 </dd>
579 <dt><code>EV_PREPARE</code></dt> 648 <dt><code>EV_PREPARE</code></dt>
… …
584<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 653<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
585received events. Callbacks of both watcher types can start and stop as 654received events. Callbacks of both watcher types can start and stop as
586many watchers as they want, and all of them will be taken into account 655many watchers as they want, and all of them will be taken into account
587(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 656(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
588<code>ev_loop</code> from blocking).</p> 657<code>ev_loop</code> from blocking).</p>
658 </dd>
659 <dt><code>EV_EMBED</code></dt>
660 <dd>
661 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
662 </dd>
663 <dt><code>EV_FORK</code></dt>
664 <dd>
665 <p>The event loop has been resumed in the child process after fork (see
666<code>ev_fork</code>).</p>
589 </dd> 667 </dd>
590 <dt><code>EV_ERROR</code></dt> 668 <dt><code>EV_ERROR</code></dt>
591 <dd> 669 <dd>
592 <p>An unspecified error has occured, the watcher has been stopped. This might 670 <p>An unspecified error has occured, the watcher has been stopped. This might
593happen because the watcher could not be properly started because libev 671happen because the watcher could not be properly started because libev
… …
601programs, though, so beware.</p> 679programs, though, so beware.</p>
602 </dd> 680 </dd>
603</dl> 681</dl>
604 682
605</div> 683</div>
606<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2> 684<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
607<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2"> 685<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
608<p>In the following description, <code>TYPE</code> stands for the watcher type, 686<p>In the following description, <code>TYPE</code> stands for the watcher type,
609e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p> 687e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
610<dl> 688<dl>
611 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt> 689 <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt>
612 <dd> 690 <dd>
… …
616the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the 694the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the
617type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro 695type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro
618which rolls both calls into one.</p> 696which rolls both calls into one.</p>
619 <p>You can reinitialise a watcher at any time as long as it has been stopped 697 <p>You can reinitialise a watcher at any time as long as it has been stopped
620(or never started) and there are no pending events outstanding.</p> 698(or never started) and there are no pending events outstanding.</p>
621 <p>The callbakc is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher, 699 <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
622int revents)</code>.</p> 700int revents)</code>.</p>
623 </dd> 701 </dd>
624 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt> 702 <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
625 <dd> 703 <dd>
626 <p>This macro initialises the type-specific parts of a watcher. You need to 704 <p>This macro initialises the type-specific parts of a watcher. You need to
… …
663events but its callback has not yet been invoked). As long as a watcher 741events but its callback has not yet been invoked). As long as a watcher
664is pending (but not active) you must not call an init function on it (but 742is pending (but not active) you must not call an init function on it (but
665<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 743<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
666libev (e.g. you cnanot <code>free ()</code> it).</p> 744libev (e.g. you cnanot <code>free ()</code> it).</p>
667 </dd> 745 </dd>
668 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 746 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
669 <dd> 747 <dd>
670 <p>Returns the callback currently set on the watcher.</p> 748 <p>Returns the callback currently set on the watcher.</p>
671 </dd> 749 </dd>
672 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
673 <dd> 751 <dd>
… …
705 struct my_io *w = (struct my_io *)w_; 783 struct my_io *w = (struct my_io *)w_;
706 ... 784 ...
707 } 785 }
708 786
709</pre> 787</pre>
710<p>More interesting and less C-conformant ways of catsing your callback type 788<p>More interesting and less C-conformant ways of casting your callback type
711have been omitted....</p> 789instead have been omitted.</p>
790<p>Another common scenario is having some data structure with multiple
791watchers:</p>
792<pre> struct my_biggy
793 {
794 int some_data;
795 ev_timer t1;
796 ev_timer t2;
797 }
712 798
799</pre>
800<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
801you need to use <code>offsetof</code>:</p>
802<pre> #include &lt;stddef.h&gt;
713 803
804 static void
805 t1_cb (EV_P_ struct ev_timer *w, int revents)
806 {
807 struct my_biggy big = (struct my_biggy *
808 (((char *)w) - offsetof (struct my_biggy, t1));
809 }
714 810
811 static void
812 t2_cb (EV_P_ struct ev_timer *w, int revents)
813 {
814 struct my_biggy big = (struct my_biggy *
815 (((char *)w) - offsetof (struct my_biggy, t2));
816 }
715 817
716 818
819
820
821</pre>
822
717</div> 823</div>
718<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 824<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
719<div id="WATCHER_TYPES_CONTENT"> 825<div id="WATCHER_TYPES_CONTENT">
720<p>This section describes each watcher in detail, but will not repeat 826<p>This section describes each watcher in detail, but will not repeat
721information given in the last section.</p> 827information given in the last section. Any initialisation/set macros,
828functions and members specific to the watcher type are explained.</p>
829<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
830while the watcher is active, you can look at the member and expect some
831sensible content, but you must not modify it (you can modify it while the
832watcher is stopped to your hearts content), or <i>[read-write]</i>, which
833means you can expect it to have some sensible content while the watcher
834is active, but you can also modify it. Modifying it may not do something
835sensible or take immediate effect (or do anything at all), but libev will
836not crash or malfunction in any way.</p>
722 837
723 838
724 839
725 840
726 841
727</div> 842</div>
728<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 843<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
729<div id="code_ev_io_code_is_this_file_descrip-2"> 844<div id="code_ev_io_code_is_this_file_descrip-2">
730<p>I/O watchers check whether a file descriptor is readable or writable 845<p>I/O watchers check whether a file descriptor is readable or writable
731in each iteration of the event loop (This behaviour is called 846in each iteration of the event loop, or, more precisely, when reading
732level-triggering because you keep receiving events as long as the 847would not block the process and writing would at least be able to write
733condition persists. Remember you can stop the watcher if you don't want to 848some data. This behaviour is called level-triggering because you keep
734act on the event and neither want to receive future events).</p> 849receiving events as long as the condition persists. Remember you can stop
850the watcher if you don't want to act on the event and neither want to
851receive future events.</p>
735<p>In general you can register as many read and/or write event watchers per 852<p>In general you can register as many read and/or write event watchers per
736fd as you want (as long as you don't confuse yourself). Setting all file 853fd as you want (as long as you don't confuse yourself). Setting all file
737descriptors to non-blocking mode is also usually a good idea (but not 854descriptors to non-blocking mode is also usually a good idea (but not
738required if you know what you are doing).</p> 855required if you know what you are doing).</p>
739<p>You have to be careful with dup'ed file descriptors, though. Some backends 856<p>You have to be careful with dup'ed file descriptors, though. Some backends
740(the linux epoll backend is a notable example) cannot handle dup'ed file 857(the linux epoll backend is a notable example) cannot handle dup'ed file
741descriptors correctly if you register interest in two or more fds pointing 858descriptors correctly if you register interest in two or more fds pointing
742to the same underlying file/socket etc. description (that is, they share 859to the same underlying file/socket/etc. description (that is, they share
743the same underlying &quot;file open&quot;).</p> 860the same underlying &quot;file open&quot;).</p>
744<p>If you must do this, then force the use of a known-to-be-good backend 861<p>If you must do this, then force the use of a known-to-be-good backend
745(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and 862(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
746<code>EVBACKEND_POLL</code>).</p> 863<code>EVBACKEND_POLL</code>).</p>
864<p>Another thing you have to watch out for is that it is quite easy to
865receive &quot;spurious&quot; readyness notifications, that is your callback might
866be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
867because there is no data. Not only are some backends known to create a
868lot of those (for example solaris ports), it is very easy to get into
869this situation even with a relatively standard program structure. Thus
870it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
871<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
872<p>If you cannot run the fd in non-blocking mode (for example you should not
873play around with an Xlib connection), then you have to seperately re-test
874wether a file descriptor is really ready with a known-to-be good interface
875such as poll (fortunately in our Xlib example, Xlib already does this on
876its own, so its quite safe to use).</p>
747<dl> 877<dl>
748 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 878 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
749 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 879 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
750 <dd> 880 <dd>
751 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 881 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
752events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 882rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
753EV_WRITE</code> to receive the given events.</p> 883<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
754 <p>Please note that most of the more scalable backend mechanisms (for example 884 </dd>
755epoll and solaris ports) can result in spurious readyness notifications 885 <dt>int fd [read-only]</dt>
756for file descriptors, so you practically need to use non-blocking I/O (and 886 <dd>
757treat callback invocation as hint only), or retest separately with a safe 887 <p>The file descriptor being watched.</p>
758interface before doing I/O (XLib can do this), or force the use of either 888 </dd>
759<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this 889 <dt>int events [read-only]</dt>
760problem. Also note that it is quite easy to have your callback invoked 890 <dd>
761when the readyness condition is no longer valid even when employing 891 <p>The events being watched.</p>
762typical ways of handling events, so its a good idea to use non-blocking
763I/O unconditionally.</p>
764 </dd> 892 </dd>
765</dl> 893</dl>
766<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 894<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
767readable, but only once. Since it is likely line-buffered, you could 895readable, but only once. Since it is likely line-buffered, you could
768attempt to read a whole line in the callback:</p> 896attempt to read a whole line in the callback.</p>
769<pre> static void 897<pre> static void
770 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 898 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
771 { 899 {
772 ev_io_stop (loop, w); 900 ev_io_stop (loop, w);
773 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 901 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
784 912
785 913
786</pre> 914</pre>
787 915
788</div> 916</div>
789<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 917<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
790<div id="code_ev_timer_code_relative_and_opti-2"> 918<div id="code_ev_timer_code_relative_and_opti-2">
791<p>Timer watchers are simple relative timers that generate an event after a 919<p>Timer watchers are simple relative timers that generate an event after a
792given time, and optionally repeating in regular intervals after that.</p> 920given time, and optionally repeating in regular intervals after that.</p>
793<p>The timers are based on real time, that is, if you register an event that 921<p>The timers are based on real time, that is, if you register an event that
794times out after an hour and you reset your system clock to last years 922times out after an hour and you reset your system clock to last years
… …
826repeating. The exact semantics are:</p> 954repeating. The exact semantics are:</p>
827 <p>If the timer is started but nonrepeating, stop it.</p> 955 <p>If the timer is started but nonrepeating, stop it.</p>
828 <p>If the timer is repeating, either start it if necessary (with the repeat 956 <p>If the timer is repeating, either start it if necessary (with the repeat
829value), or reset the running timer to the repeat value.</p> 957value), or reset the running timer to the repeat value.</p>
830 <p>This sounds a bit complicated, but here is a useful and typical 958 <p>This sounds a bit complicated, but here is a useful and typical
831example: Imagine you have a tcp connection and you want a so-called idle 959example: Imagine you have a tcp connection and you want a so-called
832timeout, that is, you want to be called when there have been, say, 60 960idle timeout, that is, you want to be called when there have been,
833seconds of inactivity on the socket. The easiest way to do this is to 961say, 60 seconds of inactivity on the socket. The easiest way to do
834configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 962this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
835time you successfully read or write some data. If you go into an idle 963<code>ev_timer_again</code> each time you successfully read or write some data. If
836state where you do not expect data to travel on the socket, you can stop 964you go into an idle state where you do not expect data to travel on the
837the timer, and again will automatically restart it if need be.</p> 965socket, you can stop the timer, and again will automatically restart it if
966need be.</p>
967 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
968and only ever use the <code>repeat</code> value:</p>
969<pre> ev_timer_init (timer, callback, 0., 5.);
970 ev_timer_again (loop, timer);
971 ...
972 timer-&gt;again = 17.;
973 ev_timer_again (loop, timer);
974 ...
975 timer-&gt;again = 10.;
976 ev_timer_again (loop, timer);
977
978</pre>
979 <p>This is more efficient then stopping/starting the timer eahc time you want
980to modify its timeout value.</p>
981 </dd>
982 <dt>ev_tstamp repeat [read-write]</dt>
983 <dd>
984 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
985or <code>ev_timer_again</code> is called and determines the next timeout (if any),
986which is also when any modifications are taken into account.</p>
838 </dd> 987 </dd>
839</dl> 988</dl>
840<p>Example: create a timer that fires after 60 seconds.</p> 989<p>Example: Create a timer that fires after 60 seconds.</p>
841<pre> static void 990<pre> static void
842 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 991 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
843 { 992 {
844 .. one minute over, w is actually stopped right here 993 .. one minute over, w is actually stopped right here
845 } 994 }
… …
847 struct ev_timer mytimer; 996 struct ev_timer mytimer;
848 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 997 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
849 ev_timer_start (loop, &amp;mytimer); 998 ev_timer_start (loop, &amp;mytimer);
850 999
851</pre> 1000</pre>
852<p>Example: create a timeout timer that times out after 10 seconds of 1001<p>Example: Create a timeout timer that times out after 10 seconds of
853inactivity.</p> 1002inactivity.</p>
854<pre> static void 1003<pre> static void
855 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1004 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
856 { 1005 {
857 .. ten seconds without any activity 1006 .. ten seconds without any activity
… …
870 1019
871 1020
872</pre> 1021</pre>
873 1022
874</div> 1023</div>
875<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 1024<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
876<div id="code_ev_periodic_code_to_cron_or_not-2"> 1025<div id="code_ev_periodic_code_to_cron_or_not-2">
877<p>Periodic watchers are also timers of a kind, but they are very versatile 1026<p>Periodic watchers are also timers of a kind, but they are very versatile
878(and unfortunately a bit complex).</p> 1027(and unfortunately a bit complex).</p>
879<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 1028<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
880but on wallclock time (absolute time). You can tell a periodic watcher 1029but on wallclock time (absolute time). You can tell a periodic watcher
… …
960 <p>Simply stops and restarts the periodic watcher again. This is only useful 1109 <p>Simply stops and restarts the periodic watcher again. This is only useful
961when you changed some parameters or the reschedule callback would return 1110when you changed some parameters or the reschedule callback would return
962a different time than the last time it was called (e.g. in a crond like 1111a different time than the last time it was called (e.g. in a crond like
963program when the crontabs have changed).</p> 1112program when the crontabs have changed).</p>
964 </dd> 1113 </dd>
1114 <dt>ev_tstamp interval [read-write]</dt>
1115 <dd>
1116 <p>The current interval value. Can be modified any time, but changes only
1117take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1118called.</p>
1119 </dd>
1120 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1121 <dd>
1122 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1123switched off. Can be changed any time, but changes only take effect when
1124the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1125 </dd>
965</dl> 1126</dl>
966<p>Example: call a callback every hour, or, more precisely, whenever the 1127<p>Example: Call a callback every hour, or, more precisely, whenever the
967system clock is divisible by 3600. The callback invocation times have 1128system clock is divisible by 3600. The callback invocation times have
968potentially a lot of jittering, but good long-term stability.</p> 1129potentially a lot of jittering, but good long-term stability.</p>
969<pre> static void 1130<pre> static void
970 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1131 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
971 { 1132 {
… …
975 struct ev_periodic hourly_tick; 1136 struct ev_periodic hourly_tick;
976 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1137 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
977 ev_periodic_start (loop, &amp;hourly_tick); 1138 ev_periodic_start (loop, &amp;hourly_tick);
978 1139
979</pre> 1140</pre>
980<p>Example: the same as above, but use a reschedule callback to do it:</p> 1141<p>Example: The same as above, but use a reschedule callback to do it:</p>
981<pre> #include &lt;math.h&gt; 1142<pre> #include &lt;math.h&gt;
982 1143
983 static ev_tstamp 1144 static ev_tstamp
984 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1145 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
985 { 1146 {
… …
987 } 1148 }
988 1149
989 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1150 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
990 1151
991</pre> 1152</pre>
992<p>Example: call a callback every hour, starting now:</p> 1153<p>Example: Call a callback every hour, starting now:</p>
993<pre> struct ev_periodic hourly_tick; 1154<pre> struct ev_periodic hourly_tick;
994 ev_periodic_init (&amp;hourly_tick, clock_cb, 1155 ev_periodic_init (&amp;hourly_tick, clock_cb,
995 fmod (ev_now (loop), 3600.), 3600., 0); 1156 fmod (ev_now (loop), 3600.), 3600., 0);
996 ev_periodic_start (loop, &amp;hourly_tick); 1157 ev_periodic_start (loop, &amp;hourly_tick);
997 1158
… …
999 1160
1000 1161
1001</pre> 1162</pre>
1002 1163
1003</div> 1164</div>
1004<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 1165<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
1005<div id="code_ev_signal_code_signal_me_when_a-2"> 1166<div id="code_ev_signal_code_signal_me_when_a-2">
1006<p>Signal watchers will trigger an event when the process receives a specific 1167<p>Signal watchers will trigger an event when the process receives a specific
1007signal one or more times. Even though signals are very asynchronous, libev 1168signal one or more times. Even though signals are very asynchronous, libev
1008will try it's best to deliver signals synchronously, i.e. as part of the 1169will try it's best to deliver signals synchronously, i.e. as part of the
1009normal event processing, like any other event.</p> 1170normal event processing, like any other event.</p>
… …
1018 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1179 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1019 <dd> 1180 <dd>
1020 <p>Configures the watcher to trigger on the given signal number (usually one 1181 <p>Configures the watcher to trigger on the given signal number (usually one
1021of the <code>SIGxxx</code> constants).</p> 1182of the <code>SIGxxx</code> constants).</p>
1022 </dd> 1183 </dd>
1184 <dt>int signum [read-only]</dt>
1185 <dd>
1186 <p>The signal the watcher watches out for.</p>
1187 </dd>
1023</dl> 1188</dl>
1024 1189
1025 1190
1026 1191
1027 1192
1028 1193
1029</div> 1194</div>
1030<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> 1195<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
1031<div id="code_ev_child_code_wait_for_pid_stat-2"> 1196<div id="code_ev_child_code_watch_out_for_pro-2">
1032<p>Child watchers trigger when your process receives a SIGCHLD in response to 1197<p>Child watchers trigger when your process receives a SIGCHLD in response to
1033some child status changes (most typically when a child of yours dies).</p> 1198some child status changes (most typically when a child of yours dies).</p>
1034<dl> 1199<dl>
1035 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1200 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1036 <dt>ev_child_set (ev_child *, int pid)</dt> 1201 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
1040at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1205at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1041the status word (use the macros from <code>sys/wait.h</code> and see your systems 1206the status word (use the macros from <code>sys/wait.h</code> and see your systems
1042<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1207<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1043process causing the status change.</p> 1208process causing the status change.</p>
1044 </dd> 1209 </dd>
1210 <dt>int pid [read-only]</dt>
1211 <dd>
1212 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1213 </dd>
1214 <dt>int rpid [read-write]</dt>
1215 <dd>
1216 <p>The process id that detected a status change.</p>
1217 </dd>
1218 <dt>int rstatus [read-write]</dt>
1219 <dd>
1220 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1221<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1222 </dd>
1045</dl> 1223</dl>
1046<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1224<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1047<pre> static void 1225<pre> static void
1048 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1226 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1049 { 1227 {
1050 ev_unloop (loop, EVUNLOOP_ALL); 1228 ev_unloop (loop, EVUNLOOP_ALL);
1051 } 1229 }
… …
1058 1236
1059 1237
1060</pre> 1238</pre>
1061 1239
1062</div> 1240</div>
1241<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1242<div id="code_ev_stat_code_did_the_file_attri-2">
1243<p>This watches a filesystem path for attribute changes. That is, it calls
1244<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1245compared to the last time, invoking the callback if it did.</p>
1246<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1247not exist&quot; is a status change like any other. The condition &quot;path does
1248not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1249otherwise always forced to be at least one) and all the other fields of
1250the stat buffer having unspecified contents.</p>
1251<p>Since there is no standard to do this, the portable implementation simply
1252calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1253can specify a recommended polling interval for this case. If you specify
1254a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1255unspecified default</i> value will be used (which you can expect to be around
1256five seconds, although this might change dynamically). Libev will also
1257impose a minimum interval which is currently around <code>0.1</code>, but thats
1258usually overkill.</p>
1259<p>This watcher type is not meant for massive numbers of stat watchers,
1260as even with OS-supported change notifications, this can be
1261resource-intensive.</p>
1262<p>At the time of this writing, only the Linux inotify interface is
1263implemented (implementing kqueue support is left as an exercise for the
1264reader). Inotify will be used to give hints only and should not change the
1265semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1266to fall back to regular polling again even with inotify, but changes are
1267usually detected immediately, and if the file exists there will be no
1268polling.</p>
1269<dl>
1270 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1271 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1272 <dd>
1273 <p>Configures the watcher to wait for status changes of the given
1274<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1275be detected and should normally be specified as <code>0</code> to let libev choose
1276a suitable value. The memory pointed to by <code>path</code> must point to the same
1277path for as long as the watcher is active.</p>
1278 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1279relative to the attributes at the time the watcher was started (or the
1280last change was detected).</p>
1281 </dd>
1282 <dt>ev_stat_stat (ev_stat *)</dt>
1283 <dd>
1284 <p>Updates the stat buffer immediately with new values. If you change the
1285watched path in your callback, you could call this fucntion to avoid
1286detecting this change (while introducing a race condition). Can also be
1287useful simply to find out the new values.</p>
1288 </dd>
1289 <dt>ev_statdata attr [read-only]</dt>
1290 <dd>
1291 <p>The most-recently detected attributes of the file. Although the type is of
1292<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1293suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1294was some error while <code>stat</code>ing the file.</p>
1295 </dd>
1296 <dt>ev_statdata prev [read-only]</dt>
1297 <dd>
1298 <p>The previous attributes of the file. The callback gets invoked whenever
1299<code>prev</code> != <code>attr</code>.</p>
1300 </dd>
1301 <dt>ev_tstamp interval [read-only]</dt>
1302 <dd>
1303 <p>The specified interval.</p>
1304 </dd>
1305 <dt>const char *path [read-only]</dt>
1306 <dd>
1307 <p>The filesystem path that is being watched.</p>
1308 </dd>
1309</dl>
1310<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1311<pre> static void
1312 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1313 {
1314 /* /etc/passwd changed in some way */
1315 if (w-&gt;attr.st_nlink)
1316 {
1317 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1318 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1319 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1320 }
1321 else
1322 /* you shalt not abuse printf for puts */
1323 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1324 &quot;if this is windows, they already arrived\n&quot;);
1325 }
1326
1327 ...
1328 ev_stat passwd;
1329
1330 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1331 ev_stat_start (loop, &amp;passwd);
1332
1333
1334
1335
1336</pre>
1337
1338</div>
1063<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 1339<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1064<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1340<div id="code_ev_idle_code_when_you_ve_got_no-2">
1065<p>Idle watchers trigger events when there are no other events are pending 1341<p>Idle watchers trigger events when there are no other events are pending
1066(prepare, check and other idle watchers do not count). That is, as long 1342(prepare, check and other idle watchers do not count). That is, as long
1067as your process is busy handling sockets or timeouts (or even signals, 1343as your process is busy handling sockets or timeouts (or even signals,
1068imagine) it will not be triggered. But when your process is idle all idle 1344imagine) it will not be triggered. But when your process is idle all idle
… …
1081 <p>Initialises and configures the idle watcher - it has no parameters of any 1357 <p>Initialises and configures the idle watcher - it has no parameters of any
1082kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1358kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1083believe me.</p> 1359believe me.</p>
1084 </dd> 1360 </dd>
1085</dl> 1361</dl>
1086<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1362<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1087callback, free it. Alos, use no error checking, as usual.</p> 1363callback, free it. Also, use no error checking, as usual.</p>
1088<pre> static void 1364<pre> static void
1089 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1365 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1090 { 1366 {
1091 free (w); 1367 free (w);
1092 // now do something you wanted to do when the program has 1368 // now do something you wanted to do when the program has
… …
1101 1377
1102 1378
1103</pre> 1379</pre>
1104 1380
1105</div> 1381</div>
1106<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1382<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1107<div id="code_ev_prepare_code_and_code_ev_che-2"> 1383<div id="code_ev_prepare_code_and_code_ev_che-2">
1108<p>Prepare and check watchers are usually (but not always) used in tandem: 1384<p>Prepare and check watchers are usually (but not always) used in tandem:
1109prepare watchers get invoked before the process blocks and check watchers 1385prepare watchers get invoked before the process blocks and check watchers
1110afterwards.</p> 1386afterwards.</p>
1387<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1388the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1389watchers. Other loops than the current one are fine, however. The
1390rationale behind this is that you do not need to check for recursion in
1391those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1392<code>ev_check</code> so if you have one watcher of each kind they will always be
1393called in pairs bracketing the blocking call.</p>
1111<p>Their main purpose is to integrate other event mechanisms into libev and 1394<p>Their main purpose is to integrate other event mechanisms into libev and
1112their use is somewhat advanced. This could be used, for example, to track 1395their use is somewhat advanced. This could be used, for example, to track
1113variable changes, implement your own watchers, integrate net-snmp or a 1396variable changes, implement your own watchers, integrate net-snmp or a
1114coroutine library and lots more.</p> 1397coroutine library and lots more. They are also occasionally useful if
1398you cache some data and want to flush it before blocking (for example,
1399in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1400watcher).</p>
1115<p>This is done by examining in each prepare call which file descriptors need 1401<p>This is done by examining in each prepare call which file descriptors need
1116to be watched by the other library, registering <code>ev_io</code> watchers for 1402to be watched by the other library, registering <code>ev_io</code> watchers for
1117them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1403them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1118provide just this functionality). Then, in the check watcher you check for 1404provide just this functionality). Then, in the check watcher you check for
1119any events that occured (by checking the pending status of all watchers 1405any events that occured (by checking the pending status of all watchers
… …
1135 <p>Initialises and configures the prepare or check watcher - they have no 1421 <p>Initialises and configures the prepare or check watcher - they have no
1136parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1422parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1137macros, but using them is utterly, utterly and completely pointless.</p> 1423macros, but using them is utterly, utterly and completely pointless.</p>
1138 </dd> 1424 </dd>
1139</dl> 1425</dl>
1140<p>Example: *TODO*.</p> 1426<p>Example: To include a library such as adns, you would add IO watchers
1427and a timeout watcher in a prepare handler, as required by libadns, and
1428in a check watcher, destroy them and call into libadns. What follows is
1429pseudo-code only of course:</p>
1430<pre> static ev_io iow [nfd];
1431 static ev_timer tw;
1141 1432
1433 static void
1434 io_cb (ev_loop *loop, ev_io *w, int revents)
1435 {
1436 // set the relevant poll flags
1437 // could also call adns_processreadable etc. here
1438 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1439 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1440 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1441 }
1142 1442
1443 // create io watchers for each fd and a timer before blocking
1444 static void
1445 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1446 {
1447 int timeout = 3600000;truct pollfd fds [nfd];
1448 // actual code will need to loop here and realloc etc.
1449 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1143 1450
1451 /* the callback is illegal, but won't be called as we stop during check */
1452 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1453 ev_timer_start (loop, &amp;tw);
1144 1454
1455 // create on ev_io per pollfd
1456 for (int i = 0; i &lt; nfd; ++i)
1457 {
1458 ev_io_init (iow + i, io_cb, fds [i].fd,
1459 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1460 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1145 1461
1462 fds [i].revents = 0;
1463 iow [i].data = fds + i;
1464 ev_io_start (loop, iow + i);
1465 }
1466 }
1467
1468 // stop all watchers after blocking
1469 static void
1470 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1471 {
1472 ev_timer_stop (loop, &amp;tw);
1473
1474 for (int i = 0; i &lt; nfd; ++i)
1475 ev_io_stop (loop, iow + i);
1476
1477 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1478 }
1479
1480
1481
1482
1483</pre>
1484
1146</div> 1485</div>
1147<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> 1486<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1148<div id="code_ev_embed_code_when_one_backend_-2"> 1487<div id="code_ev_embed_code_when_one_backend_-2">
1149<p>This is a rather advanced watcher type that lets you embed one event loop 1488<p>This is a rather advanced watcher type that lets you embed one event loop
1150into another (currently only <code>ev_io</code> events are supported in the embedded 1489into another (currently only <code>ev_io</code> events are supported in the embedded
1151loop, other types of watchers might be handled in a delayed or incorrect 1490loop, other types of watchers might be handled in a delayed or incorrect
1152fashion and must not be used).</p> 1491fashion and must not be used).</p>
… …
1220 <dd> 1559 <dd>
1221 <p>Make a single, non-blocking sweep over the embedded loop. This works 1560 <p>Make a single, non-blocking sweep over the embedded loop. This works
1222similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1561similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1223apropriate way for embedded loops.</p> 1562apropriate way for embedded loops.</p>
1224 </dd> 1563 </dd>
1564 <dt>struct ev_loop *loop [read-only]</dt>
1565 <dd>
1566 <p>The embedded event loop.</p>
1567 </dd>
1225</dl> 1568</dl>
1226 1569
1227 1570
1228 1571
1229 1572
1230 1573
1231</div> 1574</div>
1232<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1575<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>
1576<div id="code_ev_fork_code_the_audacity_to_re-2">
1577<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1578whoever is a good citizen cared to tell libev about it by calling
1579<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1580event loop blocks next and before <code>ev_check</code> watchers are being called,
1581and only in the child after the fork. If whoever good citizen calling
1582<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1583handlers will be invoked, too, of course.</p>
1584<dl>
1585 <dt>ev_fork_init (ev_signal *, callback)</dt>
1586 <dd>
1587 <p>Initialises and configures the fork watcher - it has no parameters of any
1588kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1589believe me.</p>
1590 </dd>
1591</dl>
1592
1593
1594
1595
1596
1597</div>
1598<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1233<div id="OTHER_FUNCTIONS_CONTENT"> 1599<div id="OTHER_FUNCTIONS_CONTENT">
1234<p>There are some other functions of possible interest. Described. Here. Now.</p> 1600<p>There are some other functions of possible interest. Described. Here. Now.</p>
1235<dl> 1601<dl>
1236 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1602 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1237 <dd> 1603 <dd>
… …
1284 1650
1285 1651
1286 1652
1287 1653
1288</div> 1654</div>
1289<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1655<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1290<div id="LIBEVENT_EMULATION_CONTENT"> 1656<div id="LIBEVENT_EMULATION_CONTENT">
1291<p>Libev offers a compatibility emulation layer for libevent. It cannot 1657<p>Libev offers a compatibility emulation layer for libevent. It cannot
1292emulate the internals of libevent, so here are some usage hints:</p> 1658emulate the internals of libevent, so here are some usage hints:</p>
1293<dl> 1659<dl>
1294 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1660 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1304 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1670 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1305to use the libev header file and library.</dt> 1671to use the libev header file and library.</dt>
1306</dl> 1672</dl>
1307 1673
1308</div> 1674</div>
1309<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1675<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1310<div id="C_SUPPORT_CONTENT"> 1676<div id="C_SUPPORT_CONTENT">
1311<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1677<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1312you to use some convinience methods to start/stop watchers and also change 1678you to use some convinience methods to start/stop watchers and also change
1313the callback model to a model using method callbacks on objects.</p> 1679the callback model to a model using method callbacks on objects.</p>
1314<p>To use it,</p> 1680<p>To use it,</p>
… …
1378 </dd> 1744 </dd>
1379 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1745 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1380 <dd> 1746 <dd>
1381 <p>Invokes <code>ev_embed_sweep</code>.</p> 1747 <p>Invokes <code>ev_embed_sweep</code>.</p>
1382 </dd> 1748 </dd>
1749 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1750 <dd>
1751 <p>Invokes <code>ev_stat_stat</code>.</p>
1752 </dd>
1383 </dl> 1753 </dl>
1384 </p> 1754 </p>
1385 </dd> 1755 </dd>
1386</dl> 1756</dl>
1387<p>Example: Define a class with an IO and idle watcher, start one of them in 1757<p>Example: Define a class with an IO and idle watcher, start one of them in
… …
1399 idle (this, &amp;myclass::idle_cb) 1769 idle (this, &amp;myclass::idle_cb)
1400 { 1770 {
1401 io.start (fd, ev::READ); 1771 io.start (fd, ev::READ);
1402 } 1772 }
1403 1773
1404</pre>
1405 1774
1775
1776
1777</pre>
1778
1406</div> 1779</div>
1407<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1780<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1781<div id="MACRO_MAGIC_CONTENT">
1782<p>Libev can be compiled with a variety of options, the most fundemantal is
1783<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1784callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1785<p>To make it easier to write programs that cope with either variant, the
1786following macros are defined:</p>
1787<dl>
1788 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1789 <dd>
1790 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1791loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1792<code>EV_A_</code> is used when other arguments are following. Example:</p>
1793<pre> ev_unref (EV_A);
1794 ev_timer_add (EV_A_ watcher);
1795 ev_loop (EV_A_ 0);
1796
1797</pre>
1798 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1799which is often provided by the following macro.</p>
1800 </dd>
1801 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1802 <dd>
1803 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1804loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1805<code>EV_P_</code> is used when other parameters are following. Example:</p>
1806<pre> // this is how ev_unref is being declared
1807 static void ev_unref (EV_P);
1808
1809 // this is how you can declare your typical callback
1810 static void cb (EV_P_ ev_timer *w, int revents)
1811
1812</pre>
1813 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1814suitable for use with <code>EV_A</code>.</p>
1815 </dd>
1816 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1817 <dd>
1818 <p>Similar to the other two macros, this gives you the value of the default
1819loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1820 </dd>
1821</dl>
1822<p>Example: Declare and initialise a check watcher, working regardless of
1823wether multiple loops are supported or not.</p>
1824<pre> static void
1825 check_cb (EV_P_ ev_timer *w, int revents)
1826 {
1827 ev_check_stop (EV_A_ w);
1828 }
1829
1830 ev_check check;
1831 ev_check_init (&amp;check, check_cb);
1832 ev_check_start (EV_DEFAULT_ &amp;check);
1833 ev_loop (EV_DEFAULT_ 0);
1834
1835
1836
1837
1838</pre>
1839
1840</div>
1841<h1 id="EMBEDDING">EMBEDDING</h1>
1842<div id="EMBEDDING_CONTENT">
1843<p>Libev can (and often is) directly embedded into host
1844applications. Examples of applications that embed it include the Deliantra
1845Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1846and rxvt-unicode.</p>
1847<p>The goal is to enable you to just copy the neecssary files into your
1848source directory without having to change even a single line in them, so
1849you can easily upgrade by simply copying (or having a checked-out copy of
1850libev somewhere in your source tree).</p>
1851
1852</div>
1853<h2 id="FILESETS">FILESETS</h2>
1854<div id="FILESETS_CONTENT">
1855<p>Depending on what features you need you need to include one or more sets of files
1856in your app.</p>
1857
1858</div>
1859<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
1860<div id="CORE_EVENT_LOOP_CONTENT">
1861<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
1862configuration (no autoconf):</p>
1863<pre> #define EV_STANDALONE 1
1864 #include &quot;ev.c&quot;
1865
1866</pre>
1867<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
1868single C source file only to provide the function implementations. To use
1869it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
1870done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
1871where you can put other configuration options):</p>
1872<pre> #define EV_STANDALONE 1
1873 #include &quot;ev.h&quot;
1874
1875</pre>
1876<p>Both header files and implementation files can be compiled with a C++
1877compiler (at least, thats a stated goal, and breakage will be treated
1878as a bug).</p>
1879<p>You need the following files in your source tree, or in a directory
1880in your include path (e.g. in libev/ when using -Ilibev):</p>
1881<pre> ev.h
1882 ev.c
1883 ev_vars.h
1884 ev_wrap.h
1885
1886 ev_win32.c required on win32 platforms only
1887
1888 ev_select.c only when select backend is enabled (which is by default)
1889 ev_poll.c only when poll backend is enabled (disabled by default)
1890 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1891 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1892 ev_port.c only when the solaris port backend is enabled (disabled by default)
1893
1894</pre>
1895<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
1896to compile this single file.</p>
1897
1898</div>
1899<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
1900<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
1901<p>To include the libevent compatibility API, also include:</p>
1902<pre> #include &quot;event.c&quot;
1903
1904</pre>
1905<p>in the file including <cite>ev.c</cite>, and:</p>
1906<pre> #include &quot;event.h&quot;
1907
1908</pre>
1909<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
1910<p>You need the following additional files for this:</p>
1911<pre> event.h
1912 event.c
1913
1914</pre>
1915
1916</div>
1917<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
1918<div id="AUTOCONF_SUPPORT_CONTENT">
1919<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
1920whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
1921<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
1922include <cite>config.h</cite> and configure itself accordingly.</p>
1923<p>For this of course you need the m4 file:</p>
1924<pre> libev.m4
1925
1926</pre>
1927
1928</div>
1929<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
1930<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
1931<p>Libev can be configured via a variety of preprocessor symbols you have to define
1932before including any of its files. The default is not to build for multiplicity
1933and only include the select backend.</p>
1934<dl>
1935 <dt>EV_STANDALONE</dt>
1936 <dd>
1937 <p>Must always be <code>1</code> if you do not use autoconf configuration, which
1938keeps libev from including <cite>config.h</cite>, and it also defines dummy
1939implementations for some libevent functions (such as logging, which is not
1940supported). It will also not define any of the structs usually found in
1941<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
1942 </dd>
1943 <dt>EV_USE_MONOTONIC</dt>
1944 <dd>
1945 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1946monotonic clock option at both compiletime and runtime. Otherwise no use
1947of the monotonic clock option will be attempted. If you enable this, you
1948usually have to link against librt or something similar. Enabling it when
1949the functionality isn't available is safe, though, althoguh you have
1950to make sure you link against any libraries where the <code>clock_gettime</code>
1951function is hiding in (often <cite>-lrt</cite>).</p>
1952 </dd>
1953 <dt>EV_USE_REALTIME</dt>
1954 <dd>
1955 <p>If defined to be <code>1</code>, libev will try to detect the availability of the
1956realtime clock option at compiletime (and assume its availability at
1957runtime if successful). Otherwise no use of the realtime clock option will
1958be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get
1959(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
1960in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
1961 </dd>
1962 <dt>EV_USE_SELECT</dt>
1963 <dd>
1964 <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
1965<code>select</code>(2) backend. No attempt at autodetection will be done: if no
1966other method takes over, select will be it. Otherwise the select backend
1967will not be compiled in.</p>
1968 </dd>
1969 <dt>EV_SELECT_USE_FD_SET</dt>
1970 <dd>
1971 <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
1972structure. This is useful if libev doesn't compile due to a missing
1973<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on
1974exotic systems. This usually limits the range of file descriptors to some
1975low limit such as 1024 or might have other limitations (winsocket only
1976allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might
1977influence the size of the <code>fd_set</code> used.</p>
1978 </dd>
1979 <dt>EV_SELECT_IS_WINSOCKET</dt>
1980 <dd>
1981 <p>When defined to <code>1</code>, the select backend will assume that
1982select/socket/connect etc. don't understand file descriptors but
1983wants osf handles on win32 (this is the case when the select to
1984be used is the winsock select). This means that it will call
1985<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise,
1986it is assumed that all these functions actually work on fds, even
1987on win32. Should not be defined on non-win32 platforms.</p>
1988 </dd>
1989 <dt>EV_USE_POLL</dt>
1990 <dd>
1991 <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
1992backend. Otherwise it will be enabled on non-win32 platforms. It
1993takes precedence over select.</p>
1994 </dd>
1995 <dt>EV_USE_EPOLL</dt>
1996 <dd>
1997 <p>If defined to be <code>1</code>, libev will compile in support for the Linux
1998<code>epoll</code>(7) backend. Its availability will be detected at runtime,
1999otherwise another method will be used as fallback. This is the
2000preferred backend for GNU/Linux systems.</p>
2001 </dd>
2002 <dt>EV_USE_KQUEUE</dt>
2003 <dd>
2004 <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
2005<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime,
2006otherwise another method will be used as fallback. This is the preferred
2007backend for BSD and BSD-like systems, although on most BSDs kqueue only
2008supports some types of fds correctly (the only platform we found that
2009supports ptys for example was NetBSD), so kqueue might be compiled in, but
2010not be used unless explicitly requested. The best way to use it is to find
2011out whether kqueue supports your type of fd properly and use an embedded
2012kqueue loop.</p>
2013 </dd>
2014 <dt>EV_USE_PORT</dt>
2015 <dd>
2016 <p>If defined to be <code>1</code>, libev will compile in support for the Solaris
201710 port style backend. Its availability will be detected at runtime,
2018otherwise another method will be used as fallback. This is the preferred
2019backend for Solaris 10 systems.</p>
2020 </dd>
2021 <dt>EV_USE_DEVPOLL</dt>
2022 <dd>
2023 <p>reserved for future expansion, works like the USE symbols above.</p>
2024 </dd>
2025 <dt>EV_USE_INOTIFY</dt>
2026 <dd>
2027 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2028interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2029be detected at runtime.</p>
2030 </dd>
2031 <dt>EV_H</dt>
2032 <dd>
2033 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
2034undefined 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
2035can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
2036 </dd>
2037 <dt>EV_CONFIG_H</dt>
2038 <dd>
2039 <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
2040<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
2041<code>EV_H</code>, above.</p>
2042 </dd>
2043 <dt>EV_EVENT_H</dt>
2044 <dd>
2045 <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
2046of how the <cite>event.h</cite> header can be found.</p>
2047 </dd>
2048 <dt>EV_PROTOTYPES</dt>
2049 <dd>
2050 <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function
2051prototypes, but still define all the structs and other symbols. This is
2052occasionally useful if you want to provide your own wrapper functions
2053around libev functions.</p>
2054 </dd>
2055 <dt>EV_MULTIPLICITY</dt>
2056 <dd>
2057 <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
2058will have the <code>struct ev_loop *</code> as first argument, and you can create
2059additional independent event loops. Otherwise there will be no support
2060for multiple event loops and there is no first event loop pointer
2061argument. Instead, all functions act on the single default loop.</p>
2062 </dd>
2063 <dt>EV_PERIODIC_ENABLE</dt>
2064 <dd>
2065 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2066defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2067code.</p>
2068 </dd>
2069 <dt>EV_EMBED_ENABLE</dt>
2070 <dd>
2071 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2072defined to be <code>0</code>, then they are not.</p>
2073 </dd>
2074 <dt>EV_STAT_ENABLE</dt>
2075 <dd>
2076 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2077defined to be <code>0</code>, then they are not.</p>
2078 </dd>
2079 <dt>EV_FORK_ENABLE</dt>
2080 <dd>
2081 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2082defined to be <code>0</code>, then they are not.</p>
2083 </dd>
2084 <dt>EV_MINIMAL</dt>
2085 <dd>
2086 <p>If you need to shave off some kilobytes of code at the expense of some
2087speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2088some inlining decisions, saves roughly 30% codesize of amd64.</p>
2089 </dd>
2090 <dt>EV_PID_HASHSIZE</dt>
2091 <dd>
2092 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2093pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2094than enough. If you need to manage thousands of children you might want to
2095increase this value (<i>must</i> be a power of two).</p>
2096 </dd>
2097 <dt>EV_INOTIFY_HASHSIZE</dt>
2098 <dd>
2099 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2100inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2101usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2102watchers you might want to increase this value (<i>must</i> be a power of
2103two).</p>
2104 </dd>
2105 <dt>EV_COMMON</dt>
2106 <dd>
2107 <p>By default, all watchers have a <code>void *data</code> member. By redefining
2108this macro to a something else you can include more and other types of
2109members. You have to define it each time you include one of the files,
2110though, and it must be identical each time.</p>
2111 <p>For example, the perl EV module uses something like this:</p>
2112<pre> #define EV_COMMON \
2113 SV *self; /* contains this struct */ \
2114 SV *cb_sv, *fh /* note no trailing &quot;;&quot; */
2115
2116</pre>
2117 </dd>
2118 <dt>EV_CB_DECLARE (type)</dt>
2119 <dt>EV_CB_INVOKE (watcher, revents)</dt>
2120 <dt>ev_set_cb (ev, cb)</dt>
2121 <dd>
2122 <p>Can be used to change the callback member declaration in each watcher,
2123and the way callbacks are invoked and set. Must expand to a struct member
2124definition and a statement, respectively. See the <cite>ev.v</cite> header file for
2125their default definitions. One possible use for overriding these is to
2126avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
2127method calls instead of plain function calls in C++.</p>
2128
2129</div>
2130<h2 id="EXAMPLES">EXAMPLES</h2>
2131<div id="EXAMPLES_CONTENT">
2132 <p>For a real-world example of a program the includes libev
2133verbatim, you can have a look at the EV perl module
2134(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
2135the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2136interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2137will be compiled. It is pretty complex because it provides its own header
2138file.</p>
2139 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2140that everybody includes and which overrides some autoconf choices:</p>
2141<pre> #define EV_USE_POLL 0
2142 #define EV_MULTIPLICITY 0
2143 #define EV_PERIODICS 0
2144 #define EV_CONFIG_H &lt;config.h&gt;
2145
2146 #include &quot;ev++.h&quot;
2147
2148</pre>
2149 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
2150<pre> #include &quot;ev_cpp.h&quot;
2151 #include &quot;ev.c&quot;
2152
2153
2154
2155
2156</pre>
2157
2158</div>
2159<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2160<div id="COMPLEXITIES_CONTENT">
2161 <p>In this section the complexities of (many of) the algorithms used inside
2162libev will be explained. For complexity discussions about backends see the
2163documentation for <code>ev_default_init</code>.</p>
2164 <p>
2165 <dl>
2166 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2167 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2168 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2169 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2170 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2171 <dt>Finding the next timer per loop iteration: O(1)</dt>
2172 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2173 <dt>Activating one watcher: O(1)</dt>
2174 </dl>
2175 </p>
2176
2177
2178
2179
2180
2181</div>
2182<h1 id="AUTHOR">AUTHOR</h1>
1408<div id="AUTHOR_CONTENT"> 2183<div id="AUTHOR_CONTENT">
1409<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2184 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1410 2185
1411</div> 2186</div>
1412</div></body> 2187</div></body>
1413</html> 2188</html>

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines