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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="Mon Nov 26 11:20:35 2007" /> 9 <meta name="created" content="Wed Dec 12 18:55:04 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>
… …
26<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">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>
33<ul><li><a href="#The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</a></li>
34<li><a href="#Watcher_Specific_Functions">Watcher-Specific Functions</a></li>
35</ul>
36</li>
32<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> 37<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a>
38<ul><li><a href="#Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</a></li>
39</ul>
40</li>
33<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li> 41<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a>
42<ul><li><a href="#Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</a></li>
43</ul>
44</li>
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> 45<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a>
46<ul><li><a href="#Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</a></li>
47</ul>
48</li>
35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> 49<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a>
50<ul><li><a href="#Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</a></li>
51</ul>
52</li>
53<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a>
54<ul><li><a href="#Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</a></li>
55</ul>
56</li>
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> 57<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a>
58<ul><li><a href="#Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</a></li>
59</ul>
60</li>
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> 61<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a>
62<ul><li><a href="#Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</a></li>
63</ul>
64</li>
38<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> 65<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a>
66<ul><li><a href="#Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</a></li>
67</ul>
68</li>
69<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
39</ul> 70</ul>
40</li> 71</li>
41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 72<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 73<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 74<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
75<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
44<li><a href="#EMBEDDING">EMBEDDING</a> 76<li><a href="#EMBEDDING">EMBEDDING</a>
45<ul><li><a href="#FILESETS">FILESETS</a> 77<ul><li><a href="#FILESETS">FILESETS</a>
46<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> 78<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
47<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> 79<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
48<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> 80<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
… …
56<li><a href="#AUTHOR">AUTHOR</a> 88<li><a href="#AUTHOR">AUTHOR</a>
57</li> 89</li>
58</ul><hr /> 90</ul><hr />
59<!-- INDEX END --> 91<!-- INDEX END -->
60 92
61<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 93<h1 id="NAME">NAME</h1>
62<div id="NAME_CONTENT"> 94<div id="NAME_CONTENT">
63<p>libev - a high performance full-featured event loop written in C</p> 95<p>libev - a high performance full-featured event loop written in C</p>
64 96
65</div> 97</div>
66<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 98<h1 id="SYNOPSIS">SYNOPSIS</h1>
67<div id="SYNOPSIS_CONTENT"> 99<div id="SYNOPSIS_CONTENT">
68<pre> #include &lt;ev.h&gt; 100<pre> #include &lt;ev.h&gt;
69 101
70</pre> 102</pre>
71 103
72</div> 104</div>
73<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 105<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
106<div id="EXAMPLE_PROGRAM_CONTENT">
107<pre> #include &lt;ev.h&gt;
108
109 ev_io stdin_watcher;
110 ev_timer timeout_watcher;
111
112 /* called when data readable on stdin */
113 static void
114 stdin_cb (EV_P_ struct ev_io *w, int revents)
115 {
116 /* puts (&quot;stdin ready&quot;); */
117 ev_io_stop (EV_A_ w); /* just a syntax example */
118 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
119 }
120
121 static void
122 timeout_cb (EV_P_ struct ev_timer *w, int revents)
123 {
124 /* puts (&quot;timeout&quot;); */
125 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
126 }
127
128 int
129 main (void)
130 {
131 struct ev_loop *loop = ev_default_loop (0);
132
133 /* initialise an io watcher, then start it */
134 ev_io_init (&amp;stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
135 ev_io_start (loop, &amp;stdin_watcher);
136
137 /* simple non-repeating 5.5 second timeout */
138 ev_timer_init (&amp;timeout_watcher, timeout_cb, 5.5, 0.);
139 ev_timer_start (loop, &amp;timeout_watcher);
140
141 /* loop till timeout or data ready */
142 ev_loop (loop, 0);
143
144 return 0;
145 }
146
147</pre>
148
149</div>
150<h1 id="DESCRIPTION">DESCRIPTION</h1>
74<div id="DESCRIPTION_CONTENT"> 151<div id="DESCRIPTION_CONTENT">
152<p>The newest version of this document is also available as a html-formatted
153web page you might find easier to navigate when reading it for the first
154time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
75<p>Libev is an event loop: you register interest in certain events (such as a 155<p>Libev is an event loop: you register interest in certain events (such as a
76file descriptor being readable or a timeout occuring), and it will manage 156file descriptor being readable or a timeout occuring), and it will manage
77these event sources and provide your program with events.</p> 157these event sources and provide your program with events.</p>
78<p>To do this, it must take more or less complete control over your process 158<p>To do this, it must take more or less complete control over your process
79(or thread) by executing the <i>event loop</i> handler, and will then 159(or thread) by executing the <i>event loop</i> handler, and will then
… …
82watchers</i>, which are relatively small C structures you initialise with the 162watchers</i>, which are relatively small C structures you initialise with the
83details of the event, and then hand it over to libev by <i>starting</i> the 163details of the event, and then hand it over to libev by <i>starting</i> the
84watcher.</p> 164watcher.</p>
85 165
86</div> 166</div>
87<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 167<h1 id="FEATURES">FEATURES</h1>
88<div id="FEATURES_CONTENT"> 168<div id="FEATURES_CONTENT">
89<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 169<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
90kqueue mechanisms for file descriptor events, relative timers, absolute 170BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
91timers with customised rescheduling, signal events, process status change 171for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
92events (related to SIGCHLD), and event watchers dealing with the event 172(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
93loop mechanism itself (idle, prepare and check watchers). It also is quite 173with customised rescheduling (<code>ev_periodic</code>), synchronous signals
174(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
175watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
176<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
177file watchers (<code>ev_stat</code>) and even limited support for fork events
178(<code>ev_fork</code>).</p>
179<p>It also is quite fast (see this
94fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 180<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
95it to libevent for example).</p> 181for example).</p>
96 182
97</div> 183</div>
98<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 184<h1 id="CONVENTIONS">CONVENTIONS</h1>
99<div id="CONVENTIONS_CONTENT"> 185<div id="CONVENTIONS_CONTENT">
100<p>Libev is very configurable. In this manual the default configuration 186<p>Libev is very configurable. In this manual the default configuration will
101will be described, which supports multiple event loops. For more info 187be described, which supports multiple event loops. For more info about
102about various configuration options please have a look at the file 188various configuration options please have a look at <strong>EMBED</strong> section in
103<cite>README.embed</cite> in the libev distribution. If libev was configured without 189this manual. If libev was configured without support for multiple event
104support for multiple event loops, then all functions taking an initial 190loops, then all functions taking an initial argument of name <code>loop</code>
105argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 191(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
106will not have this argument.</p>
107 192
108</div> 193</div>
109<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 194<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
110<div id="TIME_REPRESENTATION_CONTENT"> 195<div id="TIME_REPRESENTATION_CONTENT">
111<p>Libev represents time as a single floating point number, representing the 196<p>Libev represents time as a single floating point number, representing the
112(fractional) number of seconds since the (POSIX) epoch (somewhere near 197(fractional) number of seconds since the (POSIX) epoch (somewhere near
113the beginning of 1970, details are complicated, don't ask). This type is 198the beginning of 1970, details are complicated, don't ask). This type is
114called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 199called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
115to the <code>double</code> type in C, and when you need to do any calculations on 200to the <code>double</code> type in C, and when you need to do any calculations on
116it, you should treat it as such.</p> 201it, you should treat it as such.</p>
117 202
118
119
120
121
122</div> 203</div>
123<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 204<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
124<div id="GLOBAL_FUNCTIONS_CONTENT"> 205<div id="GLOBAL_FUNCTIONS_CONTENT">
125<p>These functions can be called anytime, even before initialising the 206<p>These functions can be called anytime, even before initialising the
126library in any way.</p> 207library in any way.</p>
127<dl> 208<dl>
128 <dt>ev_tstamp ev_time ()</dt> 209 <dt>ev_tstamp ev_time ()</dt>
… …
132you actually want to know.</p> 213you actually want to know.</p>
133 </dd> 214 </dd>
134 <dt>int ev_version_major ()</dt> 215 <dt>int ev_version_major ()</dt>
135 <dt>int ev_version_minor ()</dt> 216 <dt>int ev_version_minor ()</dt>
136 <dd> 217 <dd>
137 <p>You can find out the major and minor version numbers of the library 218 <p>You can find out the major and minor ABI version numbers of the library
138you linked against by calling the functions <code>ev_version_major</code> and 219you linked against by calling the functions <code>ev_version_major</code> and
139<code>ev_version_minor</code>. If you want, you can compare against the global 220<code>ev_version_minor</code>. If you want, you can compare against the global
140symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 221symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
141version of the library your program was compiled against.</p> 222version of the library your program was compiled against.</p>
223 <p>These version numbers refer to the ABI version of the library, not the
224release version.</p>
142 <p>Usually, it's a good idea to terminate if the major versions mismatch, 225 <p>Usually, it's a good idea to terminate if the major versions mismatch,
143as this indicates an incompatible change. Minor versions are usually 226as this indicates an incompatible change. Minor versions are usually
144compatible to older versions, so a larger minor version alone is usually 227compatible to older versions, so a larger minor version alone is usually
145not a problem.</p> 228not a problem.</p>
146 <p>Example: make sure we haven't accidentally been linked against the wrong 229 <p>Example: Make sure we haven't accidentally been linked against the wrong
147version:</p> 230version.</p>
148<pre> assert ((&quot;libev version mismatch&quot;, 231<pre> assert ((&quot;libev version mismatch&quot;,
149 ev_version_major () == EV_VERSION_MAJOR 232 ev_version_major () == EV_VERSION_MAJOR
150 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 233 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
151 234
152</pre> 235</pre>
… …
182recommended ones.</p> 265recommended ones.</p>
183 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 266 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
184 </dd> 267 </dd>
185 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 268 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
186 <dd> 269 <dd>
187 <p>Sets the allocation function to use (the prototype is similar to the 270 <p>Sets the allocation function to use (the prototype is similar - the
188realloc C function, the semantics are identical). It is used to allocate 271semantics is identical - to the realloc C function). It is used to
189and free memory (no surprises here). If it returns zero when memory 272allocate and free memory (no surprises here). If it returns zero when
190needs to be allocated, the library might abort or take some potentially 273memory needs to be allocated, the library might abort or take some
191destructive action. The default is your system realloc function.</p> 274potentially destructive action. The default is your system realloc
275function.</p>
192 <p>You could override this function in high-availability programs to, say, 276 <p>You could override this function in high-availability programs to, say,
193free some memory if it cannot allocate memory, to use a special allocator, 277free some memory if it cannot allocate memory, to use a special allocator,
194or even to sleep a while and retry until some memory is available.</p> 278or even to sleep a while and retry until some memory is available.</p>
195 <p>Example: replace the libev allocator with one that waits a bit and then 279 <p>Example: Replace the libev allocator with one that waits a bit and then
196retries: better than mine).</p> 280retries).</p>
197<pre> static void * 281<pre> static void *
198 persistent_realloc (void *ptr, long size) 282 persistent_realloc (void *ptr, size_t size)
199 { 283 {
200 for (;;) 284 for (;;)
201 { 285 {
202 void *newptr = realloc (ptr, size); 286 void *newptr = realloc (ptr, size);
203 287
… …
220indicating the system call or subsystem causing the problem. If this 304indicating the system call or subsystem causing the problem. If this
221callback is set, then libev will expect it to remedy the sitution, no 305callback is set, then libev will expect it to remedy the sitution, no
222matter what, when it returns. That is, libev will generally retry the 306matter what, when it returns. That is, libev will generally retry the
223requested operation, or, if the condition doesn't go away, do bad stuff 307requested operation, or, if the condition doesn't go away, do bad stuff
224(such as abort).</p> 308(such as abort).</p>
225 <p>Example: do the same thing as libev does internally:</p> 309 <p>Example: This is basically the same thing that libev does internally, too.</p>
226<pre> static void 310<pre> static void
227 fatal_error (const char *msg) 311 fatal_error (const char *msg)
228 { 312 {
229 perror (msg); 313 perror (msg);
230 abort (); 314 abort ();
… …
236</pre> 320</pre>
237 </dd> 321 </dd>
238</dl> 322</dl>
239 323
240</div> 324</div>
241<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 325<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
242<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 326<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
243<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 327<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
244types of such loops, the <i>default</i> loop, which supports signals and child 328types of such loops, the <i>default</i> loop, which supports signals and child
245events, and dynamically created loops which do not.</p> 329events, and dynamically created loops which do not.</p>
246<p>If you use threads, a common model is to run the default event loop 330<p>If you use threads, a common model is to run the default event loop
… …
275<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 359<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
276override the flags completely if it is found in the environment. This is 360override the flags completely if it is found in the environment. This is
277useful to try out specific backends to test their performance, or to work 361useful to try out specific backends to test their performance, or to work
278around bugs.</p> 362around bugs.</p>
279 </dd> 363 </dd>
364 <dt><code>EVFLAG_FORKCHECK</code></dt>
365 <dd>
366 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
367a fork, you can also make libev check for a fork in each iteration by
368enabling this flag.</p>
369 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
370and thus this might slow down your event loop if you do a lot of loop
371iterations and little real work, but is usually not noticeable (on my
372Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
373without a syscall and thus <i>very</i> fast, but my Linux system also has
374<code>pthread_atfork</code> which is even faster).</p>
375 <p>The big advantage of this flag is that you can forget about fork (and
376forget about forgetting to tell libev about forking) when you use this
377flag.</p>
378 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
379environment variable.</p>
380 </dd>
280 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 381 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
281 <dd> 382 <dd>
282 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 383 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
283libev tries to roll its own fd_set with no limits on the number of fds, 384libev tries to roll its own fd_set with no limits on the number of fds,
284but if that fails, expect a fairly low limit on the number of fds when 385but if that fails, expect a fairly low limit on the number of fds when
… …
366 <dd> 467 <dd>
367 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 468 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
368always distinct from the default loop. Unlike the default loop, it cannot 469always distinct from the default loop. Unlike the default loop, it cannot
369handle signal and child watchers, and attempts to do so will be greeted by 470handle signal and child watchers, and attempts to do so will be greeted by
370undefined behaviour (or a failed assertion if assertions are enabled).</p> 471undefined behaviour (or a failed assertion if assertions are enabled).</p>
371 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 472 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
372<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 473<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
373 if (!epoller) 474 if (!epoller)
374 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 475 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
375 476
376</pre> 477</pre>
… …
412 <dt>ev_loop_fork (loop)</dt> 513 <dt>ev_loop_fork (loop)</dt>
413 <dd> 514 <dd>
414 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 515 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
415<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 516<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
416after fork, and how you do this is entirely your own problem.</p> 517after fork, and how you do this is entirely your own problem.</p>
518 </dd>
519 <dt>unsigned int ev_loop_count (loop)</dt>
520 <dd>
521 <p>Returns the count of loop iterations for the loop, which is identical to
522the number of times libev did poll for new events. It starts at <code>0</code> and
523happily wraps around with enough iterations.</p>
524 <p>This value can sometimes be useful as a generation counter of sorts (it
525&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
526<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
417 </dd> 527 </dd>
418 <dt>unsigned int ev_backend (loop)</dt> 528 <dt>unsigned int ev_backend (loop)</dt>
419 <dd> 529 <dd>
420 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 530 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
421use.</p> 531use.</p>
… …
449one iteration of the loop. This is useful if you are waiting for some 559one iteration of the loop. This is useful if you are waiting for some
450external event in conjunction with something not expressible using other 560external event in conjunction with something not expressible using other
451libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is 561libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
452usually a better approach for this kind of thing.</p> 562usually a better approach for this kind of thing.</p>
453 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 563 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
564<pre> - Before the first iteration, call any pending watchers.
454<pre> * If there are no active watchers (reference count is zero), return. 565 * If there are no active watchers (reference count is zero), return.
455 - Queue prepare watchers and then call all outstanding watchers. 566 - Queue all prepare watchers and then call all outstanding watchers.
456 - If we have been forked, recreate the kernel state. 567 - If we have been forked, recreate the kernel state.
457 - Update the kernel state with all outstanding changes. 568 - Update the kernel state with all outstanding changes.
458 - Update the &quot;event loop time&quot;. 569 - Update the &quot;event loop time&quot;.
459 - Calculate for how long to block. 570 - Calculate for how long to block.
460 - Block the process, waiting for any events. 571 - Block the process, waiting for any events.
… …
469 be handled here by queueing them when their watcher gets executed. 580 be handled here by queueing them when their watcher gets executed.
470 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 581 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
471 were used, return, otherwise continue with step *. 582 were used, return, otherwise continue with step *.
472 583
473</pre> 584</pre>
474 <p>Example: queue some jobs and then loop until no events are outsanding 585 <p>Example: Queue some jobs and then loop until no events are outsanding
475anymore.</p> 586anymore.</p>
476<pre> ... queue jobs here, make sure they register event watchers as long 587<pre> ... queue jobs here, make sure they register event watchers as long
477 ... as they still have work to do (even an idle watcher will do..) 588 ... as they still have work to do (even an idle watcher will do..)
478 ev_loop (my_loop, 0); 589 ev_loop (my_loop, 0);
479 ... jobs done. yeah! 590 ... jobs done. yeah!
… …
498example, libev itself uses this for its internal signal pipe: It is not 609example, libev itself uses this for its internal signal pipe: It is not
499visible to the libev user and should not keep <code>ev_loop</code> from exiting if 610visible to the libev user and should not keep <code>ev_loop</code> from exiting if
500no event watchers registered by it are active. It is also an excellent 611no event watchers registered by it are active. It is also an excellent
501way to do this for generic recurring timers or from within third-party 612way to do this for generic recurring timers or from within third-party
502libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 613libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
503 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 614 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
504running when nothing else is active.</p> 615running when nothing else is active.</p>
505<pre> struct dv_signal exitsig; 616<pre> struct ev_signal exitsig;
506 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 617 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
507 ev_signal_start (myloop, &amp;exitsig); 618 ev_signal_start (loop, &amp;exitsig);
508 evf_unref (myloop); 619 evf_unref (loop);
509 620
510</pre> 621</pre>
511 <p>Example: for some weird reason, unregister the above signal handler again.</p> 622 <p>Example: For some weird reason, unregister the above signal handler again.</p>
512<pre> ev_ref (myloop); 623<pre> ev_ref (loop);
513 ev_signal_stop (myloop, &amp;exitsig); 624 ev_signal_stop (loop, &amp;exitsig);
514 625
515</pre> 626</pre>
516 </dd> 627 </dd>
517</dl> 628</dl>
518 629
519 630
520 631
521 632
522 633
523</div> 634</div>
524<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 635<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
525<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 636<div id="ANATOMY_OF_A_WATCHER_CONTENT">
526<p>A watcher is a structure that you create and register to record your 637<p>A watcher is a structure that you create and register to record your
527interest in some event. For instance, if you want to wait for STDIN to 638interest in some event. For instance, if you want to wait for STDIN to
528become readable, you would create an <code>ev_io</code> watcher for that:</p> 639become readable, you would create an <code>ev_io</code> watcher for that:</p>
529<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 640<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
586 </dd> 697 </dd>
587 <dt><code>EV_CHILD</code></dt> 698 <dt><code>EV_CHILD</code></dt>
588 <dd> 699 <dd>
589 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 700 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
590 </dd> 701 </dd>
702 <dt><code>EV_STAT</code></dt>
703 <dd>
704 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
705 </dd>
591 <dt><code>EV_IDLE</code></dt> 706 <dt><code>EV_IDLE</code></dt>
592 <dd> 707 <dd>
593 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 708 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
594 </dd> 709 </dd>
595 <dt><code>EV_PREPARE</code></dt> 710 <dt><code>EV_PREPARE</code></dt>
… …
600<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 715<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
601received events. Callbacks of both watcher types can start and stop as 716received events. Callbacks of both watcher types can start and stop as
602many watchers as they want, and all of them will be taken into account 717many watchers as they want, and all of them will be taken into account
603(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 718(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
604<code>ev_loop</code> from blocking).</p> 719<code>ev_loop</code> from blocking).</p>
720 </dd>
721 <dt><code>EV_EMBED</code></dt>
722 <dd>
723 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
724 </dd>
725 <dt><code>EV_FORK</code></dt>
726 <dd>
727 <p>The event loop has been resumed in the child process after fork (see
728<code>ev_fork</code>).</p>
605 </dd> 729 </dd>
606 <dt><code>EV_ERROR</code></dt> 730 <dt><code>EV_ERROR</code></dt>
607 <dd> 731 <dd>
608 <p>An unspecified error has occured, the watcher has been stopped. This might 732 <p>An unspecified error has occured, the watcher has been stopped. This might
609happen because the watcher could not be properly started because libev 733happen because the watcher could not be properly started because libev
… …
676 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 800 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
677 <dd> 801 <dd>
678 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 802 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
679events but its callback has not yet been invoked). As long as a watcher 803events but its callback has not yet been invoked). As long as a watcher
680is pending (but not active) you must not call an init function on it (but 804is pending (but not active) you must not call an init function on it (but
681<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 805<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
682libev (e.g. you cnanot <code>free ()</code> it).</p> 806make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
807it).</p>
683 </dd> 808 </dd>
684 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 809 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
685 <dd> 810 <dd>
686 <p>Returns the callback currently set on the watcher.</p> 811 <p>Returns the callback currently set on the watcher.</p>
687 </dd> 812 </dd>
688 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 813 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
689 <dd> 814 <dd>
690 <p>Change the callback. You can change the callback at virtually any time 815 <p>Change the callback. You can change the callback at virtually any time
691(modulo threads).</p> 816(modulo threads).</p>
817 </dd>
818 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
819 <dt>int ev_priority (ev_TYPE *watcher)</dt>
820 <dd>
821 <p>Set and query the priority of the watcher. The priority is a small
822integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
823(default: <code>-2</code>). Pending watchers with higher priority will be invoked
824before watchers with lower priority, but priority will not keep watchers
825from being executed (except for <code>ev_idle</code> watchers).</p>
826 <p>This means that priorities are <i>only</i> used for ordering callback
827invocation after new events have been received. This is useful, for
828example, to reduce latency after idling, or more often, to bind two
829watchers on the same event and make sure one is called first.</p>
830 <p>If you need to suppress invocation when higher priority events are pending
831you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
832 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
833pending.</p>
834 <p>The default priority used by watchers when no priority has been set is
835always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
836 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
837fine, as long as you do not mind that the priority value you query might
838or might not have been adjusted to be within valid range.</p>
839 </dd>
840 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
841 <dd>
842 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
843<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
844can deal with that fact.</p>
845 </dd>
846 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
847 <dd>
848 <p>If the watcher is pending, this function returns clears its pending status
849and returns its <code>revents</code> bitset (as if its callback was invoked). If the
850watcher isn't pending it does nothing and returns <code>0</code>.</p>
692 </dd> 851 </dd>
693</dl> 852</dl>
694 853
695 854
696 855
… …
721 struct my_io *w = (struct my_io *)w_; 880 struct my_io *w = (struct my_io *)w_;
722 ... 881 ...
723 } 882 }
724 883
725</pre> 884</pre>
726<p>More interesting and less C-conformant ways of catsing your callback type 885<p>More interesting and less C-conformant ways of casting your callback type
727have been omitted....</p> 886instead have been omitted.</p>
887<p>Another common scenario is having some data structure with multiple
888watchers:</p>
889<pre> struct my_biggy
890 {
891 int some_data;
892 ev_timer t1;
893 ev_timer t2;
894 }
728 895
896</pre>
897<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
898you need to use <code>offsetof</code>:</p>
899<pre> #include &lt;stddef.h&gt;
729 900
901 static void
902 t1_cb (EV_P_ struct ev_timer *w, int revents)
903 {
904 struct my_biggy big = (struct my_biggy *
905 (((char *)w) - offsetof (struct my_biggy, t1));
906 }
730 907
908 static void
909 t2_cb (EV_P_ struct ev_timer *w, int revents)
910 {
911 struct my_biggy big = (struct my_biggy *
912 (((char *)w) - offsetof (struct my_biggy, t2));
913 }
731 914
732 915
916
917
918</pre>
919
733</div> 920</div>
734<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 921<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
735<div id="WATCHER_TYPES_CONTENT"> 922<div id="WATCHER_TYPES_CONTENT">
736<p>This section describes each watcher in detail, but will not repeat 923<p>This section describes each watcher in detail, but will not repeat
737information given in the last section.</p> 924information given in the last section. Any initialisation/set macros,
925functions and members specific to the watcher type are explained.</p>
926<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
927while the watcher is active, you can look at the member and expect some
928sensible content, but you must not modify it (you can modify it while the
929watcher is stopped to your hearts content), or <i>[read-write]</i>, which
930means you can expect it to have some sensible content while the watcher
931is active, but you can also modify it. Modifying it may not do something
932sensible or take immediate effect (or do anything at all), but libev will
933not crash or malfunction in any way.</p>
738 934
739 935
740 936
741 937
742 938
… …
770this situation even with a relatively standard program structure. Thus 966this situation even with a relatively standard program structure. Thus
771it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 967it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
772<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 968<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
773<p>If you cannot run the fd in non-blocking mode (for example you should not 969<p>If you cannot run the fd in non-blocking mode (for example you should not
774play around with an Xlib connection), then you have to seperately re-test 970play around with an Xlib connection), then you have to seperately re-test
775wether a file descriptor is really ready with a known-to-be good interface 971whether a file descriptor is really ready with a known-to-be good interface
776such as poll (fortunately in our Xlib example, Xlib already does this on 972such as poll (fortunately in our Xlib example, Xlib already does this on
777its own, so its quite safe to use).</p> 973its own, so its quite safe to use).</p>
974
975</div>
976<h3 id="The_special_problem_of_disappearing_">The special problem of disappearing file descriptors</h3>
977<div id="The_special_problem_of_disappearing_-2">
978<p>Some backends (e.g kqueue, epoll) need to be told about closing a file
979descriptor (either by calling <code>close</code> explicitly or by any other means,
980such as <code>dup</code>). The reason is that you register interest in some file
981descriptor, but when it goes away, the operating system will silently drop
982this interest. If another file descriptor with the same number then is
983registered with libev, there is no efficient way to see that this is, in
984fact, a different file descriptor.</p>
985<p>To avoid having to explicitly tell libev about such cases, libev follows
986the following policy: Each time <code>ev_io_set</code> is being called, libev
987will assume that this is potentially a new file descriptor, otherwise
988it is assumed that the file descriptor stays the same. That means that
989you <i>have</i> to call <code>ev_io_set</code> (or <code>ev_io_init</code>) when you change the
990descriptor even if the file descriptor number itself did not change.</p>
991<p>This is how one would do it normally anyway, the important point is that
992the libev application should not optimise around libev but should leave
993optimisations to libev.</p>
994
995
996
997
998
999</div>
1000<h3 id="Watcher_Specific_Functions">Watcher-Specific Functions</h3>
1001<div id="Watcher_Specific_Functions_CONTENT">
778<dl> 1002<dl>
779 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 1003 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
780 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 1004 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
781 <dd> 1005 <dd>
782 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 1006 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
783rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or 1007rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
784<code>EV_READ | EV_WRITE</code> to receive the given events.</p> 1008<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
785 </dd> 1009 </dd>
1010 <dt>int fd [read-only]</dt>
1011 <dd>
1012 <p>The file descriptor being watched.</p>
1013 </dd>
1014 <dt>int events [read-only]</dt>
1015 <dd>
1016 <p>The events being watched.</p>
1017 </dd>
786</dl> 1018</dl>
787<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 1019<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
788readable, but only once. Since it is likely line-buffered, you could 1020readable, but only once. Since it is likely line-buffered, you could
789attempt to read a whole line in the callback:</p> 1021attempt to read a whole line in the callback.</p>
790<pre> static void 1022<pre> static void
791 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1023 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
792 { 1024 {
793 ev_io_stop (loop, w); 1025 ev_io_stop (loop, w);
794 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 1026 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
825 1057
826</pre> 1058</pre>
827<p>The callback is guarenteed to be invoked only when its timeout has passed, 1059<p>The callback is guarenteed to be invoked only when its timeout has passed,
828but if multiple timers become ready during the same loop iteration then 1060but if multiple timers become ready during the same loop iteration then
829order of execution is undefined.</p> 1061order of execution is undefined.</p>
1062
1063</div>
1064<h3 id="Watcher_Specific_Functions_and_Data_">Watcher-Specific Functions and Data Members</h3>
1065<div id="Watcher_Specific_Functions_and_Data_-2">
830<dl> 1066<dl>
831 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 1067 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
832 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 1068 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
833 <dd> 1069 <dd>
834 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 1070 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
843 </dd> 1079 </dd>
844 <dt>ev_timer_again (loop)</dt> 1080 <dt>ev_timer_again (loop)</dt>
845 <dd> 1081 <dd>
846 <p>This will act as if the timer timed out and restart it again if it is 1082 <p>This will act as if the timer timed out and restart it again if it is
847repeating. The exact semantics are:</p> 1083repeating. The exact semantics are:</p>
1084 <p>If the timer is pending, its pending status is cleared.</p>
848 <p>If the timer is started but nonrepeating, stop it.</p> 1085 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
849 <p>If the timer is repeating, either start it if necessary (with the repeat 1086 <p>If the timer is repeating, either start it if necessary (with the
850value), or reset the running timer to the repeat value.</p> 1087<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
851 <p>This sounds a bit complicated, but here is a useful and typical 1088 <p>This sounds a bit complicated, but here is a useful and typical
852example: Imagine you have a tcp connection and you want a so-called idle 1089example: Imagine you have a tcp connection and you want a so-called idle
853timeout, that is, you want to be called when there have been, say, 60 1090timeout, that is, you want to be called when there have been, say, 60
854seconds of inactivity on the socket. The easiest way to do this is to 1091seconds of inactivity on the socket. The easiest way to do this is to
855configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 1092configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
856time you successfully read or write some data. If you go into an idle 1093<code>ev_timer_again</code> each time you successfully read or write some data. If
857state where you do not expect data to travel on the socket, you can stop 1094you go into an idle state where you do not expect data to travel on the
1095socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
858the timer, and again will automatically restart it if need be.</p> 1096automatically restart it if need be.</p>
1097 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
1098altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
1099<pre> ev_timer_init (timer, callback, 0., 5.);
1100 ev_timer_again (loop, timer);
1101 ...
1102 timer-&gt;again = 17.;
1103 ev_timer_again (loop, timer);
1104 ...
1105 timer-&gt;again = 10.;
1106 ev_timer_again (loop, timer);
1107
1108</pre>
1109 <p>This is more slightly efficient then stopping/starting the timer each time
1110you want to modify its timeout value.</p>
1111 </dd>
1112 <dt>ev_tstamp repeat [read-write]</dt>
1113 <dd>
1114 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
1115or <code>ev_timer_again</code> is called and determines the next timeout (if any),
1116which is also when any modifications are taken into account.</p>
859 </dd> 1117 </dd>
860</dl> 1118</dl>
861<p>Example: create a timer that fires after 60 seconds.</p> 1119<p>Example: Create a timer that fires after 60 seconds.</p>
862<pre> static void 1120<pre> static void
863 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1121 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
864 { 1122 {
865 .. one minute over, w is actually stopped right here 1123 .. one minute over, w is actually stopped right here
866 } 1124 }
… …
868 struct ev_timer mytimer; 1126 struct ev_timer mytimer;
869 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 1127 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
870 ev_timer_start (loop, &amp;mytimer); 1128 ev_timer_start (loop, &amp;mytimer);
871 1129
872</pre> 1130</pre>
873<p>Example: create a timeout timer that times out after 10 seconds of 1131<p>Example: Create a timeout timer that times out after 10 seconds of
874inactivity.</p> 1132inactivity.</p>
875<pre> static void 1133<pre> static void
876 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1134 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
877 { 1135 {
878 .. ten seconds without any activity 1136 .. ten seconds without any activity
… …
901but on wallclock time (absolute time). You can tell a periodic watcher 1159but on wallclock time (absolute time). You can tell a periodic watcher
902to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1160to trigger &quot;at&quot; some specific point in time. For example, if you tell a
903periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () 1161periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
904+ 10.</code>) and then reset your system clock to the last year, then it will 1162+ 10.</code>) and then reset your system clock to the last year, then it will
905take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1163take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
906roughly 10 seconds later and of course not if you reset your system time 1164roughly 10 seconds later).</p>
907again).</p>
908<p>They can also be used to implement vastly more complex timers, such as 1165<p>They can also be used to implement vastly more complex timers, such as
909triggering an event on eahc midnight, local time.</p> 1166triggering an event on each midnight, local time or other, complicated,
1167rules.</p>
910<p>As with timers, the callback is guarenteed to be invoked only when the 1168<p>As with timers, the callback is guarenteed to be invoked only when the
911time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1169time (<code>at</code>) has been passed, but if multiple periodic timers become ready
912during the same loop iteration then order of execution is undefined.</p> 1170during the same loop iteration then order of execution is undefined.</p>
1171
1172</div>
1173<h3 id="Watcher_Specific_Functions_and_Data_-3">Watcher-Specific Functions and Data Members</h3>
1174<div id="Watcher_Specific_Functions_and_Data_-2">
913<dl> 1175<dl>
914 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1176 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
915 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 1177 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
916 <dd> 1178 <dd>
917 <p>Lots of arguments, lets sort it out... There are basically three modes of 1179 <p>Lots of arguments, lets sort it out... There are basically three modes of
918operation, and we will explain them from simplest to complex:</p> 1180operation, and we will explain them from simplest to complex:</p>
919 <p> 1181 <p>
920 <dl> 1182 <dl>
921 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1183 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
922 <dd> 1184 <dd>
923 <p>In this configuration the watcher triggers an event at the wallclock time 1185 <p>In this configuration the watcher triggers an event at the wallclock time
924<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1186<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
925that is, if it is to be run at January 1st 2011 then it will run when the 1187that is, if it is to be run at January 1st 2011 then it will run when the
926system time reaches or surpasses this time.</p> 1188system time reaches or surpasses this time.</p>
927 </dd> 1189 </dd>
928 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1190 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
929 <dd> 1191 <dd>
930 <p>In this mode the watcher will always be scheduled to time out at the next 1192 <p>In this mode the watcher will always be scheduled to time out at the next
931<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1193<code>at + N * interval</code> time (for some integer N, which can also be negative)
932of any time jumps.</p> 1194and then repeat, regardless of any time jumps.</p>
933 <p>This can be used to create timers that do not drift with respect to system 1195 <p>This can be used to create timers that do not drift with respect to system
934time:</p> 1196time:</p>
935<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1197<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
936 1198
937</pre> 1199</pre>
… …
940full hour (UTC), or more correctly, when the system time is evenly divisible 1202full hour (UTC), or more correctly, when the system time is evenly divisible
941by 3600.</p> 1203by 3600.</p>
942 <p>Another way to think about it (for the mathematically inclined) is that 1204 <p>Another way to think about it (for the mathematically inclined) is that
943<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1205<code>ev_periodic</code> will try to run the callback in this mode at the next possible
944time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1206time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1207 <p>For numerical stability it is preferable that the <code>at</code> value is near
1208<code>ev_now ()</code> (the current time), but there is no range requirement for
1209this value.</p>
945 </dd> 1210 </dd>
946 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1211 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
947 <dd> 1212 <dd>
948 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1213 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
949ignored. Instead, each time the periodic watcher gets scheduled, the 1214ignored. Instead, each time the periodic watcher gets scheduled, the
950reschedule callback will be called with the watcher as first, and the 1215reschedule callback will be called with the watcher as first, and the
951current time as second argument.</p> 1216current time as second argument.</p>
952 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1217 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
953ever, or make any event loop modifications</i>. If you need to stop it, 1218ever, or make any event loop modifications</i>. If you need to stop it,
954return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1219return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
955starting a prepare watcher).</p> 1220starting an <code>ev_prepare</code> watcher, which is legal).</p>
956 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1221 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
957ev_tstamp now)</code>, e.g.:</p> 1222ev_tstamp now)</code>, e.g.:</p>
958<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1223<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
959 { 1224 {
960 return now + 60.; 1225 return now + 60.;
… …
981 <p>Simply stops and restarts the periodic watcher again. This is only useful 1246 <p>Simply stops and restarts the periodic watcher again. This is only useful
982when you changed some parameters or the reschedule callback would return 1247when you changed some parameters or the reschedule callback would return
983a different time than the last time it was called (e.g. in a crond like 1248a different time than the last time it was called (e.g. in a crond like
984program when the crontabs have changed).</p> 1249program when the crontabs have changed).</p>
985 </dd> 1250 </dd>
1251 <dt>ev_tstamp offset [read-write]</dt>
1252 <dd>
1253 <p>When repeating, this contains the offset value, otherwise this is the
1254absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1255 <p>Can be modified any time, but changes only take effect when the periodic
1256timer fires or <code>ev_periodic_again</code> is being called.</p>
1257 </dd>
1258 <dt>ev_tstamp interval [read-write]</dt>
1259 <dd>
1260 <p>The current interval value. Can be modified any time, but changes only
1261take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1262called.</p>
1263 </dd>
1264 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1265 <dd>
1266 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1267switched off. Can be changed any time, but changes only take effect when
1268the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1269 </dd>
986</dl> 1270</dl>
987<p>Example: call a callback every hour, or, more precisely, whenever the 1271<p>Example: Call a callback every hour, or, more precisely, whenever the
988system clock is divisible by 3600. The callback invocation times have 1272system clock is divisible by 3600. The callback invocation times have
989potentially a lot of jittering, but good long-term stability.</p> 1273potentially a lot of jittering, but good long-term stability.</p>
990<pre> static void 1274<pre> static void
991 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1275 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
992 { 1276 {
… …
996 struct ev_periodic hourly_tick; 1280 struct ev_periodic hourly_tick;
997 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1281 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
998 ev_periodic_start (loop, &amp;hourly_tick); 1282 ev_periodic_start (loop, &amp;hourly_tick);
999 1283
1000</pre> 1284</pre>
1001<p>Example: the same as above, but use a reschedule callback to do it:</p> 1285<p>Example: The same as above, but use a reschedule callback to do it:</p>
1002<pre> #include &lt;math.h&gt; 1286<pre> #include &lt;math.h&gt;
1003 1287
1004 static ev_tstamp 1288 static ev_tstamp
1005 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1289 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1006 { 1290 {
… …
1008 } 1292 }
1009 1293
1010 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1294 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1011 1295
1012</pre> 1296</pre>
1013<p>Example: call a callback every hour, starting now:</p> 1297<p>Example: Call a callback every hour, starting now:</p>
1014<pre> struct ev_periodic hourly_tick; 1298<pre> struct ev_periodic hourly_tick;
1015 ev_periodic_init (&amp;hourly_tick, clock_cb, 1299 ev_periodic_init (&amp;hourly_tick, clock_cb,
1016 fmod (ev_now (loop), 3600.), 3600., 0); 1300 fmod (ev_now (loop), 3600.), 3600., 0);
1017 ev_periodic_start (loop, &amp;hourly_tick); 1301 ev_periodic_start (loop, &amp;hourly_tick);
1018 1302
… …
1032first watcher gets started will libev actually register a signal watcher 1316first watcher gets started will libev actually register a signal watcher
1033with the kernel (thus it coexists with your own signal handlers as long 1317with the kernel (thus it coexists with your own signal handlers as long
1034as you don't register any with libev). Similarly, when the last signal 1318as you don't register any with libev). Similarly, when the last signal
1035watcher for a signal is stopped libev will reset the signal handler to 1319watcher for a signal is stopped libev will reset the signal handler to
1036SIG_DFL (regardless of what it was set to before).</p> 1320SIG_DFL (regardless of what it was set to before).</p>
1321
1322</div>
1323<h3 id="Watcher_Specific_Functions_and_Data_-4">Watcher-Specific Functions and Data Members</h3>
1324<div id="Watcher_Specific_Functions_and_Data_-2-2">
1037<dl> 1325<dl>
1038 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt> 1326 <dt>ev_signal_init (ev_signal *, callback, int signum)</dt>
1039 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1327 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1040 <dd> 1328 <dd>
1041 <p>Configures the watcher to trigger on the given signal number (usually one 1329 <p>Configures the watcher to trigger on the given signal number (usually one
1042of the <code>SIGxxx</code> constants).</p> 1330of the <code>SIGxxx</code> constants).</p>
1331 </dd>
1332 <dt>int signum [read-only]</dt>
1333 <dd>
1334 <p>The signal the watcher watches out for.</p>
1043 </dd> 1335 </dd>
1044</dl> 1336</dl>
1045 1337
1046 1338
1047 1339
… …
1050</div> 1342</div>
1051<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2> 1343<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
1052<div id="code_ev_child_code_watch_out_for_pro-2"> 1344<div id="code_ev_child_code_watch_out_for_pro-2">
1053<p>Child watchers trigger when your process receives a SIGCHLD in response to 1345<p>Child watchers trigger when your process receives a SIGCHLD in response to
1054some child status changes (most typically when a child of yours dies).</p> 1346some child status changes (most typically when a child of yours dies).</p>
1347
1348</div>
1349<h3 id="Watcher_Specific_Functions_and_Data_-5">Watcher-Specific Functions and Data Members</h3>
1350<div id="Watcher_Specific_Functions_and_Data_-2-3">
1055<dl> 1351<dl>
1056 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 1352 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
1057 <dt>ev_child_set (ev_child *, int pid)</dt> 1353 <dt>ev_child_set (ev_child *, int pid)</dt>
1058 <dd> 1354 <dd>
1059 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 1355 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
… …
1061at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1357at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1062the status word (use the macros from <code>sys/wait.h</code> and see your systems 1358the status word (use the macros from <code>sys/wait.h</code> and see your systems
1063<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1359<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1064process causing the status change.</p> 1360process causing the status change.</p>
1065 </dd> 1361 </dd>
1362 <dt>int pid [read-only]</dt>
1363 <dd>
1364 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1365 </dd>
1366 <dt>int rpid [read-write]</dt>
1367 <dd>
1368 <p>The process id that detected a status change.</p>
1369 </dd>
1370 <dt>int rstatus [read-write]</dt>
1371 <dd>
1372 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1373<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1374 </dd>
1066</dl> 1375</dl>
1067<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1376<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1068<pre> static void 1377<pre> static void
1069 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1378 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1070 { 1379 {
1071 ev_unloop (loop, EVUNLOOP_ALL); 1380 ev_unloop (loop, EVUNLOOP_ALL);
1072 } 1381 }
… …
1079 1388
1080 1389
1081</pre> 1390</pre>
1082 1391
1083</div> 1392</div>
1393<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1394<div id="code_ev_stat_code_did_the_file_attri-2">
1395<p>This watches a filesystem path for attribute changes. That is, it calls
1396<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1397compared to the last time, invoking the callback if it did.</p>
1398<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1399not exist&quot; is a status change like any other. The condition &quot;path does
1400not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1401otherwise always forced to be at least one) and all the other fields of
1402the stat buffer having unspecified contents.</p>
1403<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1404relative and your working directory changes, the behaviour is undefined.</p>
1405<p>Since there is no standard to do this, the portable implementation simply
1406calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1407can specify a recommended polling interval for this case. If you specify
1408a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1409unspecified default</i> value will be used (which you can expect to be around
1410five seconds, although this might change dynamically). Libev will also
1411impose a minimum interval which is currently around <code>0.1</code>, but thats
1412usually overkill.</p>
1413<p>This watcher type is not meant for massive numbers of stat watchers,
1414as even with OS-supported change notifications, this can be
1415resource-intensive.</p>
1416<p>At the time of this writing, only the Linux inotify interface is
1417implemented (implementing kqueue support is left as an exercise for the
1418reader). Inotify will be used to give hints only and should not change the
1419semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1420to fall back to regular polling again even with inotify, but changes are
1421usually detected immediately, and if the file exists there will be no
1422polling.</p>
1423
1424</div>
1425<h3 id="Watcher_Specific_Functions_and_Data_-6">Watcher-Specific Functions and Data Members</h3>
1426<div id="Watcher_Specific_Functions_and_Data_-2-4">
1427<dl>
1428 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1429 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1430 <dd>
1431 <p>Configures the watcher to wait for status changes of the given
1432<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1433be detected and should normally be specified as <code>0</code> to let libev choose
1434a suitable value. The memory pointed to by <code>path</code> must point to the same
1435path for as long as the watcher is active.</p>
1436 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1437relative to the attributes at the time the watcher was started (or the
1438last change was detected).</p>
1439 </dd>
1440 <dt>ev_stat_stat (ev_stat *)</dt>
1441 <dd>
1442 <p>Updates the stat buffer immediately with new values. If you change the
1443watched path in your callback, you could call this fucntion to avoid
1444detecting this change (while introducing a race condition). Can also be
1445useful simply to find out the new values.</p>
1446 </dd>
1447 <dt>ev_statdata attr [read-only]</dt>
1448 <dd>
1449 <p>The most-recently detected attributes of the file. Although the type is of
1450<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1451suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1452was some error while <code>stat</code>ing the file.</p>
1453 </dd>
1454 <dt>ev_statdata prev [read-only]</dt>
1455 <dd>
1456 <p>The previous attributes of the file. The callback gets invoked whenever
1457<code>prev</code> != <code>attr</code>.</p>
1458 </dd>
1459 <dt>ev_tstamp interval [read-only]</dt>
1460 <dd>
1461 <p>The specified interval.</p>
1462 </dd>
1463 <dt>const char *path [read-only]</dt>
1464 <dd>
1465 <p>The filesystem path that is being watched.</p>
1466 </dd>
1467</dl>
1468<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1469<pre> static void
1470 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1471 {
1472 /* /etc/passwd changed in some way */
1473 if (w-&gt;attr.st_nlink)
1474 {
1475 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1476 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1477 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1478 }
1479 else
1480 /* you shalt not abuse printf for puts */
1481 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1482 &quot;if this is windows, they already arrived\n&quot;);
1483 }
1484
1485 ...
1486 ev_stat passwd;
1487
1488 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1489 ev_stat_start (loop, &amp;passwd);
1490
1491
1492
1493
1494</pre>
1495
1496</div>
1084<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1497<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1085<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1498<div id="code_ev_idle_code_when_you_ve_got_no-2">
1086<p>Idle watchers trigger events when there are no other events are pending 1499<p>Idle watchers trigger events when no other events of the same or higher
1087(prepare, check and other idle watchers do not count). That is, as long 1500priority are pending (prepare, check and other idle watchers do not
1088as your process is busy handling sockets or timeouts (or even signals, 1501count).</p>
1089imagine) it will not be triggered. But when your process is idle all idle 1502<p>That is, as long as your process is busy handling sockets or timeouts
1090watchers are being called again and again, once per event loop iteration - 1503(or even signals, imagine) of the same or higher priority it will not be
1504triggered. But when your process is idle (or only lower-priority watchers
1505are pending), the idle watchers are being called once per event loop
1091until stopped, that is, or your process receives more events and becomes 1506iteration - until stopped, that is, or your process receives more events
1092busy.</p> 1507and becomes busy again with higher priority stuff.</p>
1093<p>The most noteworthy effect is that as long as any idle watchers are 1508<p>The most noteworthy effect is that as long as any idle watchers are
1094active, the process will not block when waiting for new events.</p> 1509active, the process will not block when waiting for new events.</p>
1095<p>Apart from keeping your process non-blocking (which is a useful 1510<p>Apart from keeping your process non-blocking (which is a useful
1096effect on its own sometimes), idle watchers are a good place to do 1511effect on its own sometimes), idle watchers are a good place to do
1097&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1512&quot;pseudo-background processing&quot;, or delay processing stuff to after the
1098event loop has handled all outstanding events.</p> 1513event loop has handled all outstanding events.</p>
1514
1515</div>
1516<h3 id="Watcher_Specific_Functions_and_Data_-7">Watcher-Specific Functions and Data Members</h3>
1517<div id="Watcher_Specific_Functions_and_Data_-2-5">
1099<dl> 1518<dl>
1100 <dt>ev_idle_init (ev_signal *, callback)</dt> 1519 <dt>ev_idle_init (ev_signal *, callback)</dt>
1101 <dd> 1520 <dd>
1102 <p>Initialises and configures the idle watcher - it has no parameters of any 1521 <p>Initialises and configures the idle watcher - it has no parameters of any
1103kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1522kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1104believe me.</p> 1523believe me.</p>
1105 </dd> 1524 </dd>
1106</dl> 1525</dl>
1107<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1526<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1108callback, free it. Alos, use no error checking, as usual.</p> 1527callback, free it. Also, use no error checking, as usual.</p>
1109<pre> static void 1528<pre> static void
1110 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1529 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1111 { 1530 {
1112 free (w); 1531 free (w);
1113 // now do something you wanted to do when the program has 1532 // now do something you wanted to do when the program has
… …
1157are ready to run (it's actually more complicated: it only runs coroutines 1576are ready to run (it's actually more complicated: it only runs coroutines
1158with priority higher than or equal to the event loop and one coroutine 1577with priority higher than or equal to the event loop and one coroutine
1159of lower priority, but only once, using idle watchers to keep the event 1578of lower priority, but only once, using idle watchers to keep the event
1160loop from blocking if lower-priority coroutines are active, thus mapping 1579loop from blocking if lower-priority coroutines are active, thus mapping
1161low-priority coroutines to idle/background tasks).</p> 1580low-priority coroutines to idle/background tasks).</p>
1581<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1582priority, to ensure that they are being run before any other watchers
1583after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1584too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1585supports this, they will be called before other <code>ev_check</code> watchers did
1586their job. As <code>ev_check</code> watchers are often used to embed other event
1587loops those other event loops might be in an unusable state until their
1588<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1589others).</p>
1590
1591</div>
1592<h3 id="Watcher_Specific_Functions_and_Data_-8">Watcher-Specific Functions and Data Members</h3>
1593<div id="Watcher_Specific_Functions_and_Data_-2-6">
1162<dl> 1594<dl>
1163 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1595 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1164 <dt>ev_check_init (ev_check *, callback)</dt> 1596 <dt>ev_check_init (ev_check *, callback)</dt>
1165 <dd> 1597 <dd>
1166 <p>Initialises and configures the prepare or check watcher - they have no 1598 <p>Initialises and configures the prepare or check watcher - they have no
1167parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1599parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1168macros, but using them is utterly, utterly and completely pointless.</p> 1600macros, but using them is utterly, utterly and completely pointless.</p>
1169 </dd> 1601 </dd>
1170</dl> 1602</dl>
1171<p>Example: To include a library such as adns, you would add IO watchers 1603<p>There are a number of principal ways to embed other event loops or modules
1172and a timeout watcher in a prepare handler, as required by libadns, and 1604into libev. Here are some ideas on how to include libadns into libev
1605(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1606use for an actually working example. Another Perl module named <code>EV::Glib</code>
1607embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1608into the Glib event loop).</p>
1609<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1173in a check watcher, destroy them and call into libadns. What follows is 1610and in a check watcher, destroy them and call into libadns. What follows
1174pseudo-code only of course:</p> 1611is pseudo-code only of course. This requires you to either use a low
1612priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1613the callbacks for the IO/timeout watchers might not have been called yet.</p>
1175<pre> static ev_io iow [nfd]; 1614<pre> static ev_io iow [nfd];
1176 static ev_timer tw; 1615 static ev_timer tw;
1177 1616
1178 static void 1617 static void
1179 io_cb (ev_loop *loop, ev_io *w, int revents) 1618 io_cb (ev_loop *loop, ev_io *w, int revents)
1180 { 1619 {
1181 // set the relevant poll flags
1182 // could also call adns_processreadable etc. here
1183 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1184 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1185 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1186 } 1620 }
1187 1621
1188 // create io watchers for each fd and a timer before blocking 1622 // create io watchers for each fd and a timer before blocking
1189 static void 1623 static void
1190 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1624 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1191 { 1625 {
1192 int timeout = 3600000;truct pollfd fds [nfd]; 1626 int timeout = 3600000;
1627 struct pollfd fds [nfd];
1193 // actual code will need to loop here and realloc etc. 1628 // actual code will need to loop here and realloc etc.
1194 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1629 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1195 1630
1196 /* the callback is illegal, but won't be called as we stop during check */ 1631 /* the callback is illegal, but won't be called as we stop during check */
1197 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1632 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1198 ev_timer_start (loop, &amp;tw); 1633 ev_timer_start (loop, &amp;tw);
1199 1634
1200 // create on ev_io per pollfd 1635 // create one ev_io per pollfd
1201 for (int i = 0; i &lt; nfd; ++i) 1636 for (int i = 0; i &lt; nfd; ++i)
1202 { 1637 {
1203 ev_io_init (iow + i, io_cb, fds [i].fd, 1638 ev_io_init (iow + i, io_cb, fds [i].fd,
1204 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1639 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1205 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1640 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1206 1641
1207 fds [i].revents = 0; 1642 fds [i].revents = 0;
1208 iow [i].data = fds + i;
1209 ev_io_start (loop, iow + i); 1643 ev_io_start (loop, iow + i);
1210 } 1644 }
1211 } 1645 }
1212 1646
1213 // stop all watchers after blocking 1647 // stop all watchers after blocking
… …
1215 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1649 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1216 { 1650 {
1217 ev_timer_stop (loop, &amp;tw); 1651 ev_timer_stop (loop, &amp;tw);
1218 1652
1219 for (int i = 0; i &lt; nfd; ++i) 1653 for (int i = 0; i &lt; nfd; ++i)
1654 {
1655 // set the relevant poll flags
1656 // could also call adns_processreadable etc. here
1657 struct pollfd *fd = fds + i;
1658 int revents = ev_clear_pending (iow + i);
1659 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1660 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1661
1662 // now stop the watcher
1220 ev_io_stop (loop, iow + i); 1663 ev_io_stop (loop, iow + i);
1664 }
1221 1665
1222 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1666 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1667 }
1668
1669</pre>
1670<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1671in the prepare watcher and would dispose of the check watcher.</p>
1672<p>Method 3: If the module to be embedded supports explicit event
1673notification (adns does), you can also make use of the actual watcher
1674callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1675<pre> static void
1676 timer_cb (EV_P_ ev_timer *w, int revents)
1677 {
1678 adns_state ads = (adns_state)w-&gt;data;
1679 update_now (EV_A);
1680
1681 adns_processtimeouts (ads, &amp;tv_now);
1682 }
1683
1684 static void
1685 io_cb (EV_P_ ev_io *w, int revents)
1686 {
1687 adns_state ads = (adns_state)w-&gt;data;
1688 update_now (EV_A);
1689
1690 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1691 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1692 }
1693
1694 // do not ever call adns_afterpoll
1695
1696</pre>
1697<p>Method 4: Do not use a prepare or check watcher because the module you
1698want to embed is too inflexible to support it. Instead, youc na override
1699their poll function. The drawback with this solution is that the main
1700loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1701this.</p>
1702<pre> static gint
1703 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1704 {
1705 int got_events = 0;
1706
1707 for (n = 0; n &lt; nfds; ++n)
1708 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1709
1710 if (timeout &gt;= 0)
1711 // create/start timer
1712
1713 // poll
1714 ev_loop (EV_A_ 0);
1715
1716 // stop timer again
1717 if (timeout &gt;= 0)
1718 ev_timer_stop (EV_A_ &amp;to);
1719
1720 // stop io watchers again - their callbacks should have set
1721 for (n = 0; n &lt; nfds; ++n)
1722 ev_io_stop (EV_A_ iow [n]);
1723
1724 return got_events;
1223 } 1725 }
1224 1726
1225 1727
1226 1728
1227 1729
… …
1288 } 1790 }
1289 else 1791 else
1290 loop_lo = loop_hi; 1792 loop_lo = loop_hi;
1291 1793
1292</pre> 1794</pre>
1795
1796</div>
1797<h3 id="Watcher_Specific_Functions_and_Data_-9">Watcher-Specific Functions and Data Members</h3>
1798<div id="Watcher_Specific_Functions_and_Data_-2-7">
1293<dl> 1799<dl>
1294 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> 1800 <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1295 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> 1801 <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt>
1296 <dd> 1802 <dd>
1297 <p>Configures the watcher to embed the given loop, which must be 1803 <p>Configures the watcher to embed the given loop, which must be
… …
1304 <dd> 1810 <dd>
1305 <p>Make a single, non-blocking sweep over the embedded loop. This works 1811 <p>Make a single, non-blocking sweep over the embedded loop. This works
1306similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1812similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1307apropriate way for embedded loops.</p> 1813apropriate way for embedded loops.</p>
1308 </dd> 1814 </dd>
1815 <dt>struct ev_loop *loop [read-only]</dt>
1816 <dd>
1817 <p>The embedded event loop.</p>
1818 </dd>
1309</dl> 1819</dl>
1310 1820
1311 1821
1312 1822
1313 1823
1314 1824
1315</div> 1825</div>
1316<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1826<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>
1827<div id="code_ev_fork_code_the_audacity_to_re-2">
1828<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1829whoever is a good citizen cared to tell libev about it by calling
1830<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1831event loop blocks next and before <code>ev_check</code> watchers are being called,
1832and only in the child after the fork. If whoever good citizen calling
1833<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1834handlers will be invoked, too, of course.</p>
1835<dl>
1836 <dt>ev_fork_init (ev_signal *, callback)</dt>
1837 <dd>
1838 <p>Initialises and configures the fork watcher - it has no parameters of any
1839kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1840believe me.</p>
1841 </dd>
1842</dl>
1843
1844
1845
1846
1847
1848</div>
1849<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1317<div id="OTHER_FUNCTIONS_CONTENT"> 1850<div id="OTHER_FUNCTIONS_CONTENT">
1318<p>There are some other functions of possible interest. Described. Here. Now.</p> 1851<p>There are some other functions of possible interest. Described. Here. Now.</p>
1319<dl> 1852<dl>
1320 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1853 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1321 <dd> 1854 <dd>
… …
1368 1901
1369 1902
1370 1903
1371 1904
1372</div> 1905</div>
1373<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1906<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1374<div id="LIBEVENT_EMULATION_CONTENT"> 1907<div id="LIBEVENT_EMULATION_CONTENT">
1375<p>Libev offers a compatibility emulation layer for libevent. It cannot 1908<p>Libev offers a compatibility emulation layer for libevent. It cannot
1376emulate the internals of libevent, so here are some usage hints:</p> 1909emulate the internals of libevent, so here are some usage hints:</p>
1377<dl> 1910<dl>
1378 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1911 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1388 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1921 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1389to use the libev header file and library.</dt> 1922to use the libev header file and library.</dt>
1390</dl> 1923</dl>
1391 1924
1392</div> 1925</div>
1393<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1926<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1394<div id="C_SUPPORT_CONTENT"> 1927<div id="C_SUPPORT_CONTENT">
1395<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1928<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1396you to use some convinience methods to start/stop watchers and also change 1929you to use some convinience methods to start/stop watchers and also change
1397the callback model to a model using method callbacks on objects.</p> 1930the callback model to a model using method callbacks on objects.</p>
1398<p>To use it,</p> 1931<p>To use it,</p>
1399<pre> #include &lt;ev++.h&gt; 1932<pre> #include &lt;ev++.h&gt;
1400 1933
1401</pre> 1934</pre>
1402<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1935<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1403and puts all of its definitions (many of them macros) into the global 1936of them macros) into the global namespace. All C++ specific things are
1404namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1937put into the <code>ev</code> namespace. It should support all the same embedding
1405<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1938options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1406<code>EV_MULTIPLICITY</code>.</p> 1939<p>Care has been taken to keep the overhead low. The only data member the C++
1940classes add (compared to plain C-style watchers) is the event loop pointer
1941that the watcher is associated with (or no additional members at all if
1942you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1943<p>Currently, functions, and static and non-static member functions can be
1944used as callbacks. Other types should be easy to add as long as they only
1945need one additional pointer for context. If you need support for other
1946types of functors please contact the author (preferably after implementing
1947it).</p>
1407<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1948<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1408<dl> 1949<dl>
1409 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1950 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1410 <dd> 1951 <dd>
1411 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1952 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1422which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1963which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1423defines by many implementations.</p> 1964defines by many implementations.</p>
1424 <p>All of those classes have these methods:</p> 1965 <p>All of those classes have these methods:</p>
1425 <p> 1966 <p>
1426 <dl> 1967 <dl>
1427 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1968 <dt>ev::TYPE::TYPE ()</dt>
1428 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1969 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1429 <dt>ev::TYPE::~TYPE</dt> 1970 <dt>ev::TYPE::~TYPE</dt>
1430 <dd> 1971 <dd>
1431 <p>The constructor takes a pointer to an object and a method pointer to 1972 <p>The constructor (optionally) takes an event loop to associate the watcher
1432the event handler callback to call in this class. The constructor calls 1973with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1433<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1974 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1434before starting it. If you do not specify a loop then the constructor 1975<code>set</code> method before starting it.</p>
1435automatically associates the default loop with this watcher.</p> 1976 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1977method to set a callback before you can start the watcher.</p>
1978 <p>(The reason why you have to use a method is a limitation in C++ which does
1979not allow explicit template arguments for constructors).</p>
1436 <p>The destructor automatically stops the watcher if it is active.</p> 1980 <p>The destructor automatically stops the watcher if it is active.</p>
1981 </dd>
1982 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1983 <dd>
1984 <p>This method sets the callback method to call. The method has to have a
1985signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1986first argument and the <code>revents</code> as second. The object must be given as
1987parameter and is stored in the <code>data</code> member of the watcher.</p>
1988 <p>This method synthesizes efficient thunking code to call your method from
1989the C callback that libev requires. If your compiler can inline your
1990callback (i.e. it is visible to it at the place of the <code>set</code> call and
1991your compiler is good :), then the method will be fully inlined into the
1992thunking function, making it as fast as a direct C callback.</p>
1993 <p>Example: simple class declaration and watcher initialisation</p>
1994<pre> struct myclass
1995 {
1996 void io_cb (ev::io &amp;w, int revents) { }
1997 }
1998
1999 myclass obj;
2000 ev::io iow;
2001 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
2002
2003</pre>
2004 </dd>
2005 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
2006 <dd>
2007 <p>Also sets a callback, but uses a static method or plain function as
2008callback. The optional <code>data</code> argument will be stored in the watcher's
2009<code>data</code> member and is free for you to use.</p>
2010 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
2011 <p>See the method-<code>set</code> above for more details.</p>
2012 <p>Example:</p>
2013<pre> static void io_cb (ev::io &amp;w, int revents) { }
2014 iow.set &lt;io_cb&gt; ();
2015
2016</pre>
1437 </dd> 2017 </dd>
1438 <dt>w-&gt;set (struct ev_loop *)</dt> 2018 <dt>w-&gt;set (struct ev_loop *)</dt>
1439 <dd> 2019 <dd>
1440 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 2020 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1441do this when the watcher is inactive (and not pending either).</p> 2021do this when the watcher is inactive (and not pending either).</p>
1442 </dd> 2022 </dd>
1443 <dt>w-&gt;set ([args])</dt> 2023 <dt>w-&gt;set ([args])</dt>
1444 <dd> 2024 <dd>
1445 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 2025 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1446called at least once. Unlike the C counterpart, an active watcher gets 2026called at least once. Unlike the C counterpart, an active watcher gets
1447automatically stopped and restarted.</p> 2027automatically stopped and restarted when reconfiguring it with this
2028method.</p>
1448 </dd> 2029 </dd>
1449 <dt>w-&gt;start ()</dt> 2030 <dt>w-&gt;start ()</dt>
1450 <dd> 2031 <dd>
1451 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 2032 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1452constructor already takes the loop.</p> 2033constructor already stores the event loop.</p>
1453 </dd> 2034 </dd>
1454 <dt>w-&gt;stop ()</dt> 2035 <dt>w-&gt;stop ()</dt>
1455 <dd> 2036 <dd>
1456 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 2037 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1457 </dd> 2038 </dd>
… …
1461<code>ev_TYPE_again</code> function.</p> 2042<code>ev_TYPE_again</code> function.</p>
1462 </dd> 2043 </dd>
1463 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 2044 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1464 <dd> 2045 <dd>
1465 <p>Invokes <code>ev_embed_sweep</code>.</p> 2046 <p>Invokes <code>ev_embed_sweep</code>.</p>
2047 </dd>
2048 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
2049 <dd>
2050 <p>Invokes <code>ev_stat_stat</code>.</p>
1466 </dd> 2051 </dd>
1467 </dl> 2052 </dl>
1468 </p> 2053 </p>
1469 </dd> 2054 </dd>
1470</dl> 2055</dl>
… …
1477 2062
1478 myclass (); 2063 myclass ();
1479 } 2064 }
1480 2065
1481 myclass::myclass (int fd) 2066 myclass::myclass (int fd)
1482 : io (this, &amp;myclass::io_cb),
1483 idle (this, &amp;myclass::idle_cb)
1484 { 2067 {
2068 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
2069 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
2070
1485 io.start (fd, ev::READ); 2071 io.start (fd, ev::READ);
1486 } 2072 }
1487 2073
1488</pre>
1489 2074
2075
2076
2077</pre>
2078
1490</div> 2079</div>
1491<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 2080<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
2081<div id="MACRO_MAGIC_CONTENT">
2082<p>Libev can be compiled with a variety of options, the most fundemantal is
2083<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
2084callbacks have an initial <code>struct ev_loop *</code> argument.</p>
2085<p>To make it easier to write programs that cope with either variant, the
2086following macros are defined:</p>
2087<dl>
2088 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
2089 <dd>
2090 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
2091loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
2092<code>EV_A_</code> is used when other arguments are following. Example:</p>
2093<pre> ev_unref (EV_A);
2094 ev_timer_add (EV_A_ watcher);
2095 ev_loop (EV_A_ 0);
2096
2097</pre>
2098 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
2099which is often provided by the following macro.</p>
2100 </dd>
2101 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
2102 <dd>
2103 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
2104loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
2105<code>EV_P_</code> is used when other parameters are following. Example:</p>
2106<pre> // this is how ev_unref is being declared
2107 static void ev_unref (EV_P);
2108
2109 // this is how you can declare your typical callback
2110 static void cb (EV_P_ ev_timer *w, int revents)
2111
2112</pre>
2113 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
2114suitable for use with <code>EV_A</code>.</p>
2115 </dd>
2116 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
2117 <dd>
2118 <p>Similar to the other two macros, this gives you the value of the default
2119loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
2120 </dd>
2121</dl>
2122<p>Example: Declare and initialise a check watcher, utilising the above
2123macros so it will work regardless of whether multiple loops are supported
2124or not.</p>
2125<pre> static void
2126 check_cb (EV_P_ ev_timer *w, int revents)
2127 {
2128 ev_check_stop (EV_A_ w);
2129 }
2130
2131 ev_check check;
2132 ev_check_init (&amp;check, check_cb);
2133 ev_check_start (EV_DEFAULT_ &amp;check);
2134 ev_loop (EV_DEFAULT_ 0);
2135
2136</pre>
2137
2138</div>
2139<h1 id="EMBEDDING">EMBEDDING</h1>
1492<div id="EMBEDDING_CONTENT"> 2140<div id="EMBEDDING_CONTENT">
1493<p>Libev can (and often is) directly embedded into host 2141<p>Libev can (and often is) directly embedded into host
1494applications. Examples of applications that embed it include the Deliantra 2142applications. Examples of applications that embed it include the Deliantra
1495Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2143Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1496and rxvt-unicode.</p> 2144and rxvt-unicode.</p>
… …
1533 ev_vars.h 2181 ev_vars.h
1534 ev_wrap.h 2182 ev_wrap.h
1535 2183
1536 ev_win32.c required on win32 platforms only 2184 ev_win32.c required on win32 platforms only
1537 2185
1538 ev_select.c only when select backend is enabled (which is by default) 2186 ev_select.c only when select backend is enabled (which is enabled by default)
1539 ev_poll.c only when poll backend is enabled (disabled by default) 2187 ev_poll.c only when poll backend is enabled (disabled by default)
1540 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2188 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1541 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2189 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1542 ev_port.c only when the solaris port backend is enabled (disabled by default) 2190 ev_port.c only when the solaris port backend is enabled (disabled by default)
1543 2191
… …
1670 </dd> 2318 </dd>
1671 <dt>EV_USE_DEVPOLL</dt> 2319 <dt>EV_USE_DEVPOLL</dt>
1672 <dd> 2320 <dd>
1673 <p>reserved for future expansion, works like the USE symbols above.</p> 2321 <p>reserved for future expansion, works like the USE symbols above.</p>
1674 </dd> 2322 </dd>
2323 <dt>EV_USE_INOTIFY</dt>
2324 <dd>
2325 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2326interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2327be detected at runtime.</p>
2328 </dd>
1675 <dt>EV_H</dt> 2329 <dt>EV_H</dt>
1676 <dd> 2330 <dd>
1677 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2331 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1678undefined 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 2332undefined 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
1679can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2333can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1702will have the <code>struct ev_loop *</code> as first argument, and you can create 2356will have the <code>struct ev_loop *</code> as first argument, and you can create
1703additional independent event loops. Otherwise there will be no support 2357additional independent event loops. Otherwise there will be no support
1704for multiple event loops and there is no first event loop pointer 2358for multiple event loops and there is no first event loop pointer
1705argument. Instead, all functions act on the single default loop.</p> 2359argument. Instead, all functions act on the single default loop.</p>
1706 </dd> 2360 </dd>
1707 <dt>EV_PERIODICS</dt> 2361 <dt>EV_MINPRI</dt>
2362 <dt>EV_MAXPRI</dt>
2363 <dd>
2364 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2365<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2366provide for more priorities by overriding those symbols (usually defined
2367to be <code>-2</code> and <code>2</code>, respectively).</p>
2368 <p>When doing priority-based operations, libev usually has to linearly search
2369all the priorities, so having many of them (hundreds) uses a lot of space
2370and time, so using the defaults of five priorities (-2 .. +2) is usually
2371fine.</p>
2372 <p>If your embedding app does not need any priorities, defining these both to
2373<code>0</code> will save some memory and cpu.</p>
1708 <dd> 2374 </dd>
2375 <dt>EV_PERIODIC_ENABLE</dt>
2376 <dd>
1709 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported, 2377 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1710otherwise not. This saves a few kb of code.</p> 2378defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2379code.</p>
2380 </dd>
2381 <dt>EV_IDLE_ENABLE</dt>
2382 <dd>
2383 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2384defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2385code.</p>
2386 </dd>
2387 <dt>EV_EMBED_ENABLE</dt>
2388 <dd>
2389 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2390defined to be <code>0</code>, then they are not.</p>
2391 </dd>
2392 <dt>EV_STAT_ENABLE</dt>
2393 <dd>
2394 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2395defined to be <code>0</code>, then they are not.</p>
2396 </dd>
2397 <dt>EV_FORK_ENABLE</dt>
2398 <dd>
2399 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2400defined to be <code>0</code>, then they are not.</p>
2401 </dd>
2402 <dt>EV_MINIMAL</dt>
2403 <dd>
2404 <p>If you need to shave off some kilobytes of code at the expense of some
2405speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2406some inlining decisions, saves roughly 30% codesize of amd64.</p>
2407 </dd>
2408 <dt>EV_PID_HASHSIZE</dt>
2409 <dd>
2410 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2411pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2412than enough. If you need to manage thousands of children you might want to
2413increase this value (<i>must</i> be a power of two).</p>
2414 </dd>
2415 <dt>EV_INOTIFY_HASHSIZE</dt>
2416 <dd>
2417 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2418inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2419usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2420watchers you might want to increase this value (<i>must</i> be a power of
2421two).</p>
1711 </dd> 2422 </dd>
1712 <dt>EV_COMMON</dt> 2423 <dt>EV_COMMON</dt>
1713 <dd> 2424 <dd>
1714 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2425 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1715this macro to a something else you can include more and other types of 2426this macro to a something else you can include more and other types of
… …
1742the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2453the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
1743interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2454interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
1744will be compiled. It is pretty complex because it provides its own header 2455will be compiled. It is pretty complex because it provides its own header
1745file.</p> 2456file.</p>
1746 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2457 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
1747that everybody includes and which overrides some autoconf choices:</p> 2458that everybody includes and which overrides some configure choices:</p>
2459<pre> #define EV_MINIMAL 1
1748<pre> #define EV_USE_POLL 0 2460 #define EV_USE_POLL 0
1749 #define EV_MULTIPLICITY 0 2461 #define EV_MULTIPLICITY 0
1750 #define EV_PERIODICS 0 2462 #define EV_PERIODIC_ENABLE 0
2463 #define EV_STAT_ENABLE 0
2464 #define EV_FORK_ENABLE 0
1751 #define EV_CONFIG_H &lt;config.h&gt; 2465 #define EV_CONFIG_H &lt;config.h&gt;
2466 #define EV_MINPRI 0
2467 #define EV_MAXPRI 0
1752 2468
1753 #include &quot;ev++.h&quot; 2469 #include &quot;ev++.h&quot;
1754 2470
1755</pre> 2471</pre>
1756 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2472 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
1761 2477
1762 2478
1763</pre> 2479</pre>
1764 2480
1765</div> 2481</div>
1766<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p> 2482<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
1767<div id="COMPLEXITIES_CONTENT"> 2483<div id="COMPLEXITIES_CONTENT">
1768 <p>In this section the complexities of (many of) the algorithms used inside 2484 <p>In this section the complexities of (many of) the algorithms used inside
1769libev will be explained. For complexity discussions about backends see the 2485libev will be explained. For complexity discussions about backends see the
1770documentation for <code>ev_default_init</code>.</p> 2486documentation for <code>ev_default_init</code>.</p>
2487 <p>All of the following are about amortised time: If an array needs to be
2488extended, libev needs to realloc and move the whole array, but this
2489happens asymptotically never with higher number of elements, so O(1) might
2490mean it might do a lengthy realloc operation in rare cases, but on average
2491it is much faster and asymptotically approaches constant time.</p>
1771 <p> 2492 <p>
1772 <dl> 2493 <dl>
1773 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2494 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2495 <dd>
2496 <p>This means that, when you have a watcher that triggers in one hour and
2497there are 100 watchers that would trigger before that then inserting will
2498have to skip those 100 watchers.</p>
2499 </dd>
1774 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2500 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2501 <dd>
2502 <p>That means that for changing a timer costs less than removing/adding them
2503as only the relative motion in the event queue has to be paid for.</p>
2504 </dd>
1775 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2505 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2506 <dd>
2507 <p>These just add the watcher into an array or at the head of a list.
1776 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2508=item Stopping check/prepare/idle watchers: O(1)</p>
2509 </dd>
1777 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt> 2510 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2511 <dd>
2512 <p>These watchers are stored in lists then need to be walked to find the
2513correct watcher to remove. The lists are usually short (you don't usually
2514have many watchers waiting for the same fd or signal).</p>
2515 </dd>
1778 <dt>Finding the next timer per loop iteration: O(1)</dt> 2516 <dt>Finding the next timer per loop iteration: O(1)</dt>
1779 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2517 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2518 <dd>
2519 <p>A change means an I/O watcher gets started or stopped, which requires
2520libev to recalculate its status (and possibly tell the kernel).</p>
2521 </dd>
1780 <dt>Activating one watcher: O(1)</dt> 2522 <dt>Activating one watcher: O(1)</dt>
2523 <dt>Priority handling: O(number_of_priorities)</dt>
2524 <dd>
2525 <p>Priorities are implemented by allocating some space for each
2526priority. When doing priority-based operations, libev usually has to
2527linearly search all the priorities.</p>
2528 </dd>
1781 </dl> 2529 </dl>
1782 </p> 2530 </p>
1783 2531
1784 2532
1785 2533
1786 2534
1787 2535
1788</div> 2536</div>
1789<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2537<h1 id="AUTHOR">AUTHOR</h1>
1790<div id="AUTHOR_CONTENT"> 2538<div id="AUTHOR_CONTENT">
1791 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2539 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1792 2540
1793</div> 2541</div>
1794</div></body> 2542</div></body>

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