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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 12 08:58:02 2007" /> 9 <meta name="created" content="Mon Nov 12 10:07:10 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 -->
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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="#DESCRIPTION">DESCRIPTION</a></li> 19<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 20<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 21<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
22<li><a href="#TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li> 23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
23<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
24<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 26<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
26</ul> 27</ul>
27</li> 28</li>
28<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 29<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
29<ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li> 30<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>
30<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li> 31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
31<li><a href="#ev_periodic">ev_periodic</a></li> 32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
32<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li> 33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
33<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li> 34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>
34<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li> 35<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>
35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> 36<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>
36</ul> 37</ul>
37</li> 38</li>
38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
39<li><a href="#AUTHOR">AUTHOR</a> 42<li><a href="#AUTHOR">AUTHOR</a>
40</li> 43</li>
41</ul><hr /> 44</ul><hr />
42<!-- INDEX END --> 45<!-- INDEX END -->
43 46
… …
55</div> 58</div>
56<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 59<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>
57<div id="DESCRIPTION_CONTENT"> 60<div id="DESCRIPTION_CONTENT">
58<p>Libev is an event loop: you register interest in certain events (such as a 61<p>Libev is an event loop: you register interest in certain events (such as a
59file descriptor being readable or a timeout occuring), and it will manage 62file descriptor being readable or a timeout occuring), and it will manage
60these event sources and provide your program events.</p> 63these event sources and provide your program with events.</p>
61<p>To do this, it must take more or less complete control over your process 64<p>To do this, it must take more or less complete control over your process
62(or thread) by executing the <i>event loop</i> handler, and will then 65(or thread) by executing the <i>event loop</i> handler, and will then
63communicate events via a callback mechanism.</p> 66communicate events via a callback mechanism.</p>
64<p>You register interest in certain events by registering so-called <i>event 67<p>You register interest in certain events by registering so-called <i>event
65watchers</i>, which are relatively small C structures you initialise with the 68watchers</i>, which are relatively small C structures you initialise with the
… …
71<div id="FEATURES_CONTENT"> 74<div id="FEATURES_CONTENT">
72<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 75<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific
73kqueue mechanisms for file descriptor events, relative timers, absolute 76kqueue mechanisms for file descriptor events, relative timers, absolute
74timers with customised rescheduling, signal events, process status change 77timers with customised rescheduling, signal events, process status change
75events (related to SIGCHLD), and event watchers dealing with the event 78events (related to SIGCHLD), and event watchers dealing with the event
76loop mechanism itself (idle, prepare and check watchers).</p> 79loop mechanism itself (idle, prepare and check watchers). It also is quite
80fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing
81it to libevent for example).</p>
77 82
78</div> 83</div>
79<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 84<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
80<div id="CONVENTIONS_CONTENT"> 85<div id="CONVENTIONS_CONTENT">
81<p>Libev is very configurable. In this manual the default configuration 86<p>Libev is very configurable. In this manual the default configuration
82will be described, which supports multiple event loops. For more info 87will be described, which supports multiple event loops. For more info
83about various configuraiton options please have a look at the file 88about various configuration options please have a look at the file
84<cite>README.embed</cite> in the libev distribution. If libev was configured without 89<cite>README.embed</cite> in the libev distribution. If libev was configured without
85support for multiple event loops, then all functions taking an initial 90support for multiple event loops, then all functions taking an initial
86argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 91argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
87will not have this argument.</p> 92will not have this argument.</p>
88 93
89</div> 94</div>
90<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 95<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
91<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> 96<div id="TIME_REPRESENTATION_CONTENT">
92<p>Libev represents time as a single floating point number. This type is 97<p>Libev represents time as a single floating point number, representing the
98(fractional) number of seconds since the (POSIX) epoch (somewhere near
99the beginning of 1970, details are complicated, don't ask). This type is
93called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 100called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
94to the double type in C.</p> 101to the double type in C.</p>
102
103</div>
104<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105<div id="GLOBAL_FUNCTIONS_CONTENT">
106<p>These functions can be called anytime, even before initialising the
107library in any way.</p>
95<dl> 108<dl>
96 <dt>ev_tstamp ev_time ()</dt> 109 <dt>ev_tstamp ev_time ()</dt>
97 <dd> 110 <dd>
98 <p>Returns the current time as libev would use it.</p> 111 <p>Returns the current time as libev would use it.</p>
99 </dd> 112 </dd>
… …
103 <p>You can find out the major and minor version numbers of the library 116 <p>You can find out the major and minor version numbers of the library
104you linked against by calling the functions <code>ev_version_major</code> and 117you linked against by calling the functions <code>ev_version_major</code> and
105<code>ev_version_minor</code>. If you want, you can compare against the global 118<code>ev_version_minor</code>. If you want, you can compare against the global
106symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 119symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
107version of the library your program was compiled against.</p> 120version of the library your program was compiled against.</p>
108 <p>Usually, its a good idea to terminate if the major versions mismatch, 121 <p>Usually, it's a good idea to terminate if the major versions mismatch,
109as this indicates an incompatible change. Minor versions are usually 122as this indicates an incompatible change. Minor versions are usually
110compatible to older versions, so a larger minor version alone is usually 123compatible to older versions, so a larger minor version alone is usually
111not a problem.</p> 124not a problem.</p>
112 </dd> 125 </dd>
113 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 126 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
114 <dd> 127 <dd>
115 <p>Sets the allocation function to use (the prototype is similar to the 128 <p>Sets the allocation function to use (the prototype is similar to the
116realloc function). It is used to allocate and free memory (no surprises 129realloc C function, the semantics are identical). It is used to allocate
117here). If it returns zero when memory needs to be allocated, the library 130and free memory (no surprises here). If it returns zero when memory
118might abort or take some potentially destructive action. The default is 131needs to be allocated, the library might abort or take some potentially
119your system realloc function.</p> 132destructive action. The default is your system realloc function.</p>
120 <p>You could override this function in high-availability programs to, say, 133 <p>You could override this function in high-availability programs to, say,
121free some memory if it cannot allocate memory, to use a special allocator, 134free some memory if it cannot allocate memory, to use a special allocator,
122or even to sleep a while and retry until some memory is available.</p> 135or even to sleep a while and retry until some memory is available.</p>
123 </dd> 136 </dd>
124 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 137 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
125 <dd> 138 <dd>
126 <p>Set the callback function to call on a retryable syscall error (such 139 <p>Set the callback function to call on a retryable syscall error (such
127as failed select, poll, epoll_wait). The message is a printable string 140as failed select, poll, epoll_wait). The message is a printable string
128indicating the system call or subsystem causing the problem. If this 141indicating the system call or subsystem causing the problem. If this
129callback is set, then libev will expect it to remedy the sitution, no 142callback is set, then libev will expect it to remedy the sitution, no
130matter what, when it returns. That is, libev will geenrally retry the 143matter what, when it returns. That is, libev will generally retry the
131requested operation, or, if the condition doesn't go away, do bad stuff 144requested operation, or, if the condition doesn't go away, do bad stuff
132(such as abort).</p> 145(such as abort).</p>
133 </dd> 146 </dd>
134</dl> 147</dl>
135 148
… …
138<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 151<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
139<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 152<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
140types of such loops, the <i>default</i> loop, which supports signals and child 153types of such loops, the <i>default</i> loop, which supports signals and child
141events, and dynamically created loops which do not.</p> 154events, and dynamically created loops which do not.</p>
142<p>If you use threads, a common model is to run the default event loop 155<p>If you use threads, a common model is to run the default event loop
143in your main thread (or in a separate thrad) and for each thread you 156in your main thread (or in a separate thread) and for each thread you
144create, you also create another event loop. Libev itself does no lockign 157create, you also create another event loop. Libev itself does no locking
145whatsoever, so if you mix calls to different event loops, make sure you 158whatsoever, so if you mix calls to the same event loop in different
146lock (this is usually a bad idea, though, even if done right).</p> 159threads, make sure you lock (this is usually a bad idea, though, even if
160done correctly, because it's hideous and inefficient).</p>
147<dl> 161<dl>
148 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 162 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
149 <dd> 163 <dd>
150 <p>This will initialise the default event loop if it hasn't been initialised 164 <p>This will initialise the default event loop if it hasn't been initialised
151yet and return it. If the default loop could not be initialised, returns 165yet and return it. If the default loop could not be initialised, returns
152false. If it already was initialised it simply returns it (and ignores the 166false. If it already was initialised it simply returns it (and ignores the
153flags).</p> 167flags).</p>
154 <p>If you don't know what event loop to use, use the one returned from this 168 <p>If you don't know what event loop to use, use the one returned from this
155function.</p> 169function.</p>
156 <p>The flags argument can be used to specify special behaviour or specific 170 <p>The flags argument can be used to specify special behaviour or specific
157backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p> 171backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>
158 <p>It supports the following flags:</p> 172 <p>It supports the following flags:</p>
159 <p> 173 <p>
160 <dl> 174 <dl>
161 <dt>EVFLAG_AUTO</dt> 175 <dt><code>EVFLAG_AUTO</code></dt>
162 <dd> 176 <dd>
163 <p>The default flags value. Use this if you have no clue (its the right 177 <p>The default flags value. Use this if you have no clue (it's the right
164thing, believe me).</p> 178thing, believe me).</p>
165 </dd> 179 </dd>
166 <dt>EVFLAG_NOENV</dt> 180 <dt><code>EVFLAG_NOENV</code></dt>
167 <dd> 181 <dd>
168 <p>If this flag bit is ored into the flag value then libev will <i>not</i> look 182 <p>If this flag bit is ored into the flag value (or the program runs setuid
169at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this 183or setgid) then libev will <i>not</i> look at the environment variable
170environment variable will override the flags completely. This is useful 184<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
185override the flags completely if it is found in the environment. This is
171to try out specific backends to tets their performance, or to work around 186useful to try out specific backends to test their performance, or to work
172bugs.</p> 187around bugs.</p>
173 </dd> 188 </dd>
174 <dt>EVMETHOD_SELECT portable select backend</dt> 189 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>
175 <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> 190 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
176 <dt>EVMETHOD_EPOLL linux only</dt> 191 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
177 <dt>EVMETHOD_KQUEUE some bsds only</dt> 192 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
178 <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> 193 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
179 <dt>EVMETHOD_PORT solaris 10 only</dt> 194 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
180 <dd> 195 <dd>
181 <p>If one or more of these are ored into the flags value, then only these 196 <p>If one or more of these are ored into the flags value, then only these
182backends will be tried (in the reverse order as given here). If one are 197backends will be tried (in the reverse order as given here). If one are
183specified, any backend will do.</p> 198specified, any backend will do.</p>
184 </dd> 199 </dd>
… …
194 </dd> 209 </dd>
195 <dt>ev_default_destroy ()</dt> 210 <dt>ev_default_destroy ()</dt>
196 <dd> 211 <dd>
197 <p>Destroys the default loop again (frees all memory and kernel state 212 <p>Destroys the default loop again (frees all memory and kernel state
198etc.). This stops all registered event watchers (by not touching them in 213etc.). This stops all registered event watchers (by not touching them in
199any way whatsoever, although you cnanot rely on this :).</p> 214any way whatsoever, although you cannot rely on this :).</p>
200 </dd> 215 </dd>
201 <dt>ev_loop_destroy (loop)</dt> 216 <dt>ev_loop_destroy (loop)</dt>
202 <dd> 217 <dd>
203 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 218 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
204earlier call to <code>ev_loop_new</code>.</p> 219earlier call to <code>ev_loop_new</code>.</p>
… …
210after forking, in either the parent or child process (or both, but that 225after forking, in either the parent or child process (or both, but that
211again makes little sense).</p> 226again makes little sense).</p>
212 <p>You <i>must</i> call this function after forking if and only if you want to 227 <p>You <i>must</i> call this function after forking if and only if you want to
213use the event library in both processes. If you just fork+exec, you don't 228use the event library in both processes. If you just fork+exec, you don't
214have to call it.</p> 229have to call it.</p>
215 <p>The function itself is quite fast and its usually not a problem to call 230 <p>The function itself is quite fast and it's usually not a problem to call
216it just in case after a fork. To make this easy, the function will fit in 231it just in case after a fork. To make this easy, the function will fit in
217quite nicely into a call to <code>pthread_atfork</code>:</p> 232quite nicely into a call to <code>pthread_atfork</code>:</p>
218<pre> pthread_atfork (0, 0, ev_default_fork); 233<pre> pthread_atfork (0, 0, ev_default_fork);
219 234
220</pre> 235</pre>
… …
228 <dt>unsigned int ev_method (loop)</dt> 243 <dt>unsigned int ev_method (loop)</dt>
229 <dd> 244 <dd>
230 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 245 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in
231use.</p> 246use.</p>
232 </dd> 247 </dd>
233 <dt>ev_tstamp = ev_now (loop)</dt> 248 <dt>ev_tstamp ev_now (loop)</dt>
234 <dd> 249 <dd>
235 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 250 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
236got events and started processing them. This timestamp does not change 251got events and started processing them. This timestamp does not change
237as long as callbacks are being processed, and this is also the base time 252as long as callbacks are being processed, and this is also the base time
238used for relative timers. You can treat it as the timestamp of the event 253used for relative timers. You can treat it as the timestamp of the event
… …
245events.</p> 260events.</p>
246 <p>If the flags argument is specified as 0, it will not return until either 261 <p>If the flags argument is specified as 0, it will not return until either
247no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 262no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
248 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 263 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
249those events and any outstanding ones, but will not block your process in 264those events and any outstanding ones, but will not block your process in
250case there are no events.</p> 265case there are no events and will return after one iteration of the loop.</p>
251 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 266 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
252neccessary) and will handle those and any outstanding ones. It will block 267neccessary) and will handle those and any outstanding ones. It will block
253your process until at least one new event arrives.</p> 268your process until at least one new event arrives, and will return after
269one iteration of the loop.</p>
254 <p>This flags value could be used to implement alternative looping 270 <p>This flags value could be used to implement alternative looping
255constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 271constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
256more generic mechanism.</p> 272more generic mechanism.</p>
257 </dd> 273 </dd>
258 <dt>ev_unloop (loop, how)</dt> 274 <dt>ev_unloop (loop, how)</dt>
259 <dd> 275 <dd>
260 <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument 276 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
277has processed all outstanding events). The <code>how</code> argument must be either
261must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> 278<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or
262call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> 279<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
263calls return.</p>
264 </dd> 280 </dd>
265 <dt>ev_ref (loop)</dt> 281 <dt>ev_ref (loop)</dt>
266 <dt>ev_unref (loop)</dt> 282 <dt>ev_unref (loop)</dt>
267 <dd> 283 <dd>
268 <p>Ref/unref can be used to add or remove a refcount on the event loop: Every 284 <p>Ref/unref can be used to add or remove a reference count on the event
269watcher keeps one reference. If you have a long-runing watcher you never 285loop: Every watcher keeps one reference, and as long as the reference
270unregister that should not keep ev_loop from running, ev_unref() after 286count is nonzero, <code>ev_loop</code> will not return on its own. If you have
271starting, and ev_ref() before stopping it. Libev itself uses this for 287a watcher you never unregister that should not keep <code>ev_loop</code> from
272example for its internal signal pipe: It is not visible to you as a user 288returning, ev_unref() after starting, and ev_ref() before stopping it. For
273and should not keep <code>ev_loop</code> from exiting if the work is done. It is 289example, libev itself uses this for its internal signal pipe: It is not
274also an excellent way to do this for generic recurring timers or from 290visible to the libev user and should not keep <code>ev_loop</code> from exiting if
275within third-party libraries. Just remember to unref after start and ref 291no event watchers registered by it are active. It is also an excellent
276before stop.</p> 292way to do this for generic recurring timers or from within third-party
293libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
277 </dd> 294 </dd>
278</dl> 295</dl>
279 296
280</div> 297</div>
281<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 298<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
282<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 299<div id="ANATOMY_OF_A_WATCHER_CONTENT">
283<p>A watcher is a structure that you create and register to record your 300<p>A watcher is a structure that you create and register to record your
284interest in some event. For instance, if you want to wait for STDIN to 301interest in some event. For instance, if you want to wait for STDIN to
285become readable, you would create an ev_io watcher for that:</p> 302become readable, you would create an <code>ev_io</code> watcher for that:</p>
286<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 303<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
287 { 304 {
288 ev_io_stop (w); 305 ev_io_stop (w);
289 ev_unloop (loop, EVUNLOOP_ALL); 306 ev_unloop (loop, EVUNLOOP_ALL);
290 } 307 }
… …
314*)</code>), and you can stop watching for events at any time by calling the 331*)</code>), and you can stop watching for events at any time by calling the
315corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 332corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
316<p>As long as your watcher is active (has been started but not stopped) you 333<p>As long as your watcher is active (has been started but not stopped) you
317must not touch the values stored in it. Most specifically you must never 334must not touch the values stored in it. Most specifically you must never
318reinitialise it or call its set method.</p> 335reinitialise it or call its set method.</p>
319<p>You cna check wether an event is active by calling the <code>ev_is_active 336<p>You can check whether an event is active by calling the <code>ev_is_active
320(watcher *)</code> macro. To see wether an event is outstanding (but the 337(watcher *)</code> macro. To see whether an event is outstanding (but the
321callback for it has not been called yet) you cna use the <code>ev_is_pending 338callback for it has not been called yet) you can use the <code>ev_is_pending
322(watcher *)</code> macro.</p> 339(watcher *)</code> macro.</p>
323<p>Each and every callback receives the event loop pointer as first, the 340<p>Each and every callback receives the event loop pointer as first, the
324registered watcher structure as second, and a bitset of received events as 341registered watcher structure as second, and a bitset of received events as
325third argument.</p> 342third argument.</p>
326<p>The rceeived events usually include a single bit per event type received 343<p>The received events usually include a single bit per event type received
327(you can receive multiple events at the same time). The possible bit masks 344(you can receive multiple events at the same time). The possible bit masks
328are:</p> 345are:</p>
329<dl> 346<dl>
330 <dt>EV_READ</dt> 347 <dt><code>EV_READ</code></dt>
331 <dt>EV_WRITE</dt> 348 <dt><code>EV_WRITE</code></dt>
332 <dd> 349 <dd>
333 <p>The file descriptor in the ev_io watcher has become readable and/or 350 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
334writable.</p> 351writable.</p>
335 </dd> 352 </dd>
336 <dt>EV_TIMEOUT</dt> 353 <dt><code>EV_TIMEOUT</code></dt>
337 <dd>
338 <p>The ev_timer watcher has timed out.</p>
339 </dd> 354 <dd>
340 <dt>EV_PERIODIC</dt> 355 <p>The <code>ev_timer</code> watcher has timed out.</p>
341 <dd> 356 </dd>
342 <p>The ev_periodic watcher has timed out.</p> 357 <dt><code>EV_PERIODIC</code></dt>
343 </dd> 358 <dd>
344 <dt>EV_SIGNAL</dt> 359 <p>The <code>ev_periodic</code> watcher has timed out.</p>
345 <dd> 360 </dd>
361 <dt><code>EV_SIGNAL</code></dt>
362 <dd>
346 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 363 <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
347 </dd>
348 <dt>EV_CHILD</dt>
349 <dd> 364 </dd>
365 <dt><code>EV_CHILD</code></dt>
366 <dd>
350 <p>The pid specified in the ev_child watcher has received a status change.</p> 367 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
351 </dd>
352 <dt>EV_IDLE</dt>
353 <dd> 368 </dd>
369 <dt><code>EV_IDLE</code></dt>
370 <dd>
354 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 371 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
355 </dd>
356 <dt>EV_PREPARE</dt>
357 <dt>EV_CHECK</dt>
358 <dd> 372 </dd>
373 <dt><code>EV_PREPARE</code></dt>
374 <dt><code>EV_CHECK</code></dt>
375 <dd>
359 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 376 <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
360to gather new events, and all ev_check watchers are invoked just after 377to gather new events, and all <code>ev_check</code> watchers are invoked just after
361<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 378<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
362received events. Callbacks of both watcher types can start and stop as 379received events. Callbacks of both watcher types can start and stop as
363many watchers as they want, and all of them will be taken into account 380many watchers as they want, and all of them will be taken into account
364(for example, a ev_prepare watcher might start an idle watcher to keep 381(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
365<code>ev_loop</code> from blocking).</p> 382<code>ev_loop</code> from blocking).</p>
366 </dd> 383 </dd>
367 <dt>EV_ERROR</dt> 384 <dt><code>EV_ERROR</code></dt>
368 <dd> 385 <dd>
369 <p>An unspecified error has occured, the watcher has been stopped. This might 386 <p>An unspecified error has occured, the watcher has been stopped. This might
370happen because the watcher could not be properly started because libev 387happen because the watcher could not be properly started because libev
371ran out of memory, a file descriptor was found to be closed or any other 388ran out of memory, a file descriptor was found to be closed or any other
372problem. You best act on it by reporting the problem and somehow coping 389problem. You best act on it by reporting the problem and somehow coping
… …
381 398
382</div> 399</div>
383<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 400<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
384<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 401<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
385<p>Each watcher has, by default, a member <code>void *data</code> that you can change 402<p>Each watcher has, by default, a member <code>void *data</code> that you can change
386and read at any time, libev will completely ignore it. This cna be used 403and read at any time, libev will completely ignore it. This can be used
387to associate arbitrary data with your watcher. If you need more data and 404to associate arbitrary data with your watcher. If you need more data and
388don't want to allocate memory and store a pointer to it in that data 405don't want to allocate memory and store a pointer to it in that data
389member, you can also &quot;subclass&quot; the watcher type and provide your own 406member, you can also &quot;subclass&quot; the watcher type and provide your own
390data:</p> 407data:</p>
391<pre> struct my_io 408<pre> struct my_io
… …
418<div id="WATCHER_TYPES_CONTENT"> 435<div id="WATCHER_TYPES_CONTENT">
419<p>This section describes each watcher in detail, but will not repeat 436<p>This section describes each watcher in detail, but will not repeat
420information given in the last section.</p> 437information given in the last section.</p>
421 438
422</div> 439</div>
423<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 440<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
424<div id="struct_ev_io_is_my_file_descriptor_r-2"> 441<div id="code_ev_io_code_is_this_file_descrip-2">
425<p>I/O watchers check wether a file descriptor is readable or writable 442<p>I/O watchers check whether a file descriptor is readable or writable
426in each iteration of the event loop (This behaviour is called 443in each iteration of the event loop (This behaviour is called
427level-triggering because you keep receiving events as long as the 444level-triggering because you keep receiving events as long as the
428condition persists. Remember you cna stop the watcher if you don't want to 445condition persists. Remember you can stop the watcher if you don't want to
429act on the event and neither want to receive future events).</p> 446act on the event and neither want to receive future events).</p>
447<p>In general you can register as many read and/or write event watchers oer
448fd as you want (as long as you don't confuse yourself). Setting all file
449descriptors to non-blocking mode is also usually a good idea (but not
450required if you know what you are doing).</p>
451<p>You have to be careful with dup'ed file descriptors, though. Some backends
452(the linux epoll backend is a notable example) cannot handle dup'ed file
453descriptors correctly if you register interest in two or more fds pointing
454to the same file/socket etc. description.</p>
455<p>If you must do this, then force the use of a known-to-be-good backend
456(at the time of this writing, this includes only EVMETHOD_SELECT and
457EVMETHOD_POLL).</p>
430<dl> 458<dl>
431 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 459 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
432 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 460 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
433 <dd> 461 <dd>
434 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 462 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
435events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 463events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
436EV_WRITE</code> to receive the given events.</p> 464EV_WRITE</code> to receive the given events.</p>
437 </dd> 465 </dd>
438</dl> 466</dl>
439 467
440</div> 468</div>
441<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 469<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
442<div id="struct_ev_timer_relative_and_optiona-2"> 470<div id="code_ev_timer_code_relative_and_opti-2">
443<p>Timer watchers are simple relative timers that generate an event after a 471<p>Timer watchers are simple relative timers that generate an event after a
444given time, and optionally repeating in regular intervals after that.</p> 472given time, and optionally repeating in regular intervals after that.</p>
445<p>The timers are based on real time, that is, if you register an event that 473<p>The timers are based on real time, that is, if you register an event that
446times out after an hour and youreset your system clock to last years 474times out after an hour and youreset your system clock to last years
447time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 475time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
448detecting time jumps is hard, and soem inaccuracies are unavoidable (the 476detecting time jumps is hard, and soem inaccuracies are unavoidable (the
449monotonic clock option helps a lot here).</p> 477monotonic clock option helps a lot here).</p>
478<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
479time. This is usually the right thing as this timestamp refers to the time
480of the event triggering whatever timeout you are modifying/starting. If
481you suspect event processing to be delayed and you *need* to base the timeout
482ion the current time, use something like this to adjust for this:</p>
483<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
484
485</pre>
450<dl> 486<dl>
451 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 487 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
452 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 488 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
453 <dd> 489 <dd>
454 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 490 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
470value), or reset the running timer to the repeat value.</p> 506value), or reset the running timer to the repeat value.</p>
471 <p>This sounds a bit complicated, but here is a useful and typical 507 <p>This sounds a bit complicated, but here is a useful and typical
472example: Imagine you have a tcp connection and you want a so-called idle 508example: Imagine you have a tcp connection and you want a so-called idle
473timeout, that is, you want to be called when there have been, say, 60 509timeout, that is, you want to be called when there have been, say, 60
474seconds of inactivity on the socket. The easiest way to do this is to 510seconds of inactivity on the socket. The easiest way to do this is to
475configure an ev_timer with after=repeat=60 and calling ev_timer_again each 511configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
476time you successfully read or write some data. If you go into an idle 512time you successfully read or write some data. If you go into an idle
477state where you do not expect data to travel on the socket, you can stop 513state where you do not expect data to travel on the socket, you can stop
478the timer, and again will automatically restart it if need be.</p> 514the timer, and again will automatically restart it if need be.</p>
479 </dd> 515 </dd>
480</dl> 516</dl>
481 517
482</div> 518</div>
483<h2 id="ev_periodic">ev_periodic</h2> 519<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
484<div id="ev_periodic_CONTENT"> 520<div id="code_ev_periodic_code_to_cron_or_not-2">
485<p>Periodic watchers are also timers of a kind, but they are very versatile 521<p>Periodic watchers are also timers of a kind, but they are very versatile
486(and unfortunately a bit complex).</p> 522(and unfortunately a bit complex).</p>
487<p>Unlike ev_timer's, they are not based on real time (or relative time) 523<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
488but on wallclock time (absolute time). You can tell a periodic watcher 524but on wallclock time (absolute time). You can tell a periodic watcher
489to trigger &quot;at&quot; some specific point in time. For example, if you tell a 525to trigger &quot;at&quot; some specific point in time. For example, if you tell a
490periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 526periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now ()
491+ 10.&gt;) and then reset your system clock to the last year, then it will 527+ 10.&gt;) and then reset your system clock to the last year, then it will
492take a year to trigger the event (unlike an ev_timer, which would trigger 528take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
493roughly 10 seconds later and of course not if you reset your system time 529roughly 10 seconds later and of course not if you reset your system time
494again).</p> 530again).</p>
495<p>They can also be used to implement vastly more complex timers, such as 531<p>They can also be used to implement vastly more complex timers, such as
496triggering an event on eahc midnight, local time.</p> 532triggering an event on eahc midnight, local time.</p>
497<dl> 533<dl>
… …
523<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 559<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
524 560
525</pre> 561</pre>
526 <p>This doesn't mean there will always be 3600 seconds in between triggers, 562 <p>This doesn't mean there will always be 3600 seconds in between triggers,
527but only that the the callback will be called when the system time shows a 563but only that the the callback will be called when the system time shows a
528full hour (UTC), or more correct, when the system time is evenly divisible 564full hour (UTC), or more correctly, when the system time is evenly divisible
529by 3600.</p> 565by 3600.</p>
530 <p>Another way to think about it (for the mathematically inclined) is that 566 <p>Another way to think about it (for the mathematically inclined) is that
531ev_periodic will try to run the callback in this mode at the next possible 567<code>ev_periodic</code> will try to run the callback in this mode at the next possible
532time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 568time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
533 </dd> 569 </dd>
534 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 570 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
535 <dd> 571 <dd>
536 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 572 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
537ignored. Instead, each time the periodic watcher gets scheduled, the 573ignored. Instead, each time the periodic watcher gets scheduled, the
538reschedule callback will be called with the watcher as first, and the 574reschedule callback will be called with the watcher as first, and the
539current time as second argument.</p> 575current time as second argument.</p>
540 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 576 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
541periodic watcher, ever, or make any event loop modificstions</i>. If you need 577ever, or make any event loop modifications</i>. If you need to stop it,
542to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 578return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
579starting a prepare watcher).</p>
543 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 580 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
544ev_tstamp now)&gt;, e.g.:</p> 581ev_tstamp now)</code>, e.g.:</p>
545<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 582<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
546 { 583 {
547 return now + 60.; 584 return now + 60.;
548 } 585 }
549 586
550</pre> 587</pre>
551 <p>It must return the next time to trigger, based on the passed time value 588 <p>It must return the next time to trigger, based on the passed time value
552(that is, the lowest time value larger than to the second argument). It 589(that is, the lowest time value larger than to the second argument). It
553will usually be called just before the callback will be triggered, but 590will usually be called just before the callback will be triggered, but
554might be called at other times, too.</p> 591might be called at other times, too.</p>
592 <p>NOTE: <i>This callback must always return a time that is later than the
593passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
555 <p>This can be used to create very complex timers, such as a timer that 594 <p>This can be used to create very complex timers, such as a timer that
556triggers on each midnight, local time. To do this, you would calculate the 595triggers on each midnight, local time. To do this, you would calculate the
557next midnight after <code>now</code> and return the timestamp value for this. How you do this 596next midnight after <code>now</code> and return the timestamp value for this. How
558is, again, up to you (but it is not trivial).</p> 597you do this is, again, up to you (but it is not trivial, which is the main
598reason I omitted it as an example).</p>
559 </dd> 599 </dd>
560 </dl> 600 </dl>
561 </p> 601 </p>
562 </dd> 602 </dd>
563 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 603 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
568program when the crontabs have changed).</p> 608program when the crontabs have changed).</p>
569 </dd> 609 </dd>
570</dl> 610</dl>
571 611
572</div> 612</div>
573<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 613<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
574<div id="ev_signal_signal_me_when_a_signal_ge-2"> 614<div id="code_ev_signal_code_signal_me_when_a-2">
575<p>Signal watchers will trigger an event when the process receives a specific 615<p>Signal watchers will trigger an event when the process receives a specific
576signal one or more times. Even though signals are very asynchronous, libev 616signal one or more times. Even though signals are very asynchronous, libev
577will try its best to deliver signals synchronously, i.e. as part of the 617will try it's best to deliver signals synchronously, i.e. as part of the
578normal event processing, like any other event.</p> 618normal event processing, like any other event.</p>
579<p>You cna configure as many watchers as you like per signal. Only when the 619<p>You can configure as many watchers as you like per signal. Only when the
580first watcher gets started will libev actually register a signal watcher 620first watcher gets started will libev actually register a signal watcher
581with the kernel (thus it coexists with your own signal handlers as long 621with the kernel (thus it coexists with your own signal handlers as long
582as you don't register any with libev). Similarly, when the last signal 622as you don't register any with libev). Similarly, when the last signal
583watcher for a signal is stopped libev will reset the signal handler to 623watcher for a signal is stopped libev will reset the signal handler to
584SIG_DFL (regardless of what it was set to before).</p> 624SIG_DFL (regardless of what it was set to before).</p>
… …
590of the <code>SIGxxx</code> constants).</p> 630of the <code>SIGxxx</code> constants).</p>
591 </dd> 631 </dd>
592</dl> 632</dl>
593 633
594</div> 634</div>
595<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 635<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
596<div id="ev_child_wait_for_pid_status_changes-2"> 636<div id="code_ev_child_code_wait_for_pid_stat-2">
597<p>Child watchers trigger when your process receives a SIGCHLD in response to 637<p>Child watchers trigger when your process receives a SIGCHLD in response to
598some child status changes (most typically when a child of yours dies).</p> 638some child status changes (most typically when a child of yours dies).</p>
599<dl> 639<dl>
600 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 640 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
601 <dt>ev_child_set (ev_child *, int pid)</dt> 641 <dt>ev_child_set (ev_child *, int pid)</dt>
602 <dd> 642 <dd>
603 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 643 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
604<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 644<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
605at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 645at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
606the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 646the status word (use the macros from <code>sys/wait.h</code> and see your systems
647<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
607contains the pid of the process causing the status change.</p> 648process causing the status change.</p>
608 </dd> 649 </dd>
609</dl> 650</dl>
610 651
611</div> 652</div>
612<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 653<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
613<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 654<div id="code_ev_idle_code_when_you_ve_got_no-2">
614<p>Idle watchers trigger events when there are no other I/O or timer (or 655<p>Idle watchers trigger events when there are no other events are pending
615periodic) events pending. That is, as long as your process is busy 656(prepare, check and other idle watchers do not count). That is, as long
616handling sockets or timeouts it will not be called. But when your process 657as your process is busy handling sockets or timeouts (or even signals,
617is idle all idle watchers are being called again and again - until 658imagine) it will not be triggered. But when your process is idle all idle
659watchers are being called again and again, once per event loop iteration -
618stopped, that is, or your process receives more events.</p> 660until stopped, that is, or your process receives more events and becomes
661busy.</p>
619<p>The most noteworthy effect is that as long as any idle watchers are 662<p>The most noteworthy effect is that as long as any idle watchers are
620active, the process will not block when waiting for new events.</p> 663active, the process will not block when waiting for new events.</p>
621<p>Apart from keeping your process non-blocking (which is a useful 664<p>Apart from keeping your process non-blocking (which is a useful
622effect on its own sometimes), idle watchers are a good place to do 665effect on its own sometimes), idle watchers are a good place to do
623&quot;pseudo-background processing&quot;, or delay processing stuff to after the 666&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
630believe me.</p> 673believe me.</p>
631 </dd> 674 </dd>
632</dl> 675</dl>
633 676
634</div> 677</div>
635<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 678<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
636<div id="prepare_and_check_your_hooks_into_th-2"> 679<div id="code_ev_prepare_code_and_code_ev_che-2">
637<p>Prepare and check watchers usually (but not always) are used in 680<p>Prepare and check watchers are usually (but not always) used in tandem:
638tandom. Prepare watchers get invoked before the process blocks and check 681prepare watchers get invoked before the process blocks and check watchers
639watchers afterwards.</p> 682afterwards.</p>
640<p>Their main purpose is to integrate other event mechanisms into libev. This 683<p>Their main purpose is to integrate other event mechanisms into libev. This
641could be used, for example, to track variable changes, implement your own 684could be used, for example, to track variable changes, implement your own
642watchers, integrate net-snmp or a coroutine library and lots more.</p> 685watchers, integrate net-snmp or a coroutine library and lots more.</p>
643<p>This is done by examining in each prepare call which file descriptors need 686<p>This is done by examining in each prepare call which file descriptors need
644to be watched by the other library, registering ev_io watchers for them 687to be watched by the other library, registering <code>ev_io</code> watchers for
645and starting an ev_timer watcher for any timeouts (many libraries provide 688them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
646just this functionality). Then, in the check watcher you check for any 689provide just this functionality). Then, in the check watcher you check for
647events that occured (by making your callbacks set soem flags for example) 690any events that occured (by checking the pending status of all watchers
648and call back into the library.</p> 691and stopping them) and call back into the library. The I/O and timer
692callbacks will never actually be called (but must be valid nevertheless,
693because you never know, you know?).</p>
649<p>As another example, the perl Coro module uses these hooks to integrate 694<p>As another example, the Perl Coro module uses these hooks to integrate
650coroutines into libev programs, by yielding to other active coroutines 695coroutines into libev programs, by yielding to other active coroutines
651during each prepare and only letting the process block if no coroutines 696during each prepare and only letting the process block if no coroutines
652are ready to run.</p> 697are ready to run (it's actually more complicated: it only runs coroutines
698with priority higher than or equal to the event loop and one coroutine
699of lower priority, but only once, using idle watchers to keep the event
700loop from blocking if lower-priority coroutines are active, thus mapping
701low-priority coroutines to idle/background tasks).</p>
653<dl> 702<dl>
654 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 703 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
655 <dt>ev_check_init (ev_check *, callback)</dt> 704 <dt>ev_check_init (ev_check *, callback)</dt>
656 <dd> 705 <dd>
657 <p>Initialises and configures the prepare or check watcher - they have no 706 <p>Initialises and configures the prepare or check watcher - they have no
658parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 707parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
659macros, but using them is utterly, utterly pointless.</p> 708macros, but using them is utterly, utterly and completely pointless.</p>
660 </dd> 709 </dd>
661</dl> 710</dl>
662 711
663</div> 712</div>
664<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 713<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
665<div id="OTHER_FUNCTIONS_CONTENT"> 714<div id="OTHER_FUNCTIONS_CONTENT">
666<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 715<p>There are some other functions of possible interest. Described. Here. Now.</p>
667<dl> 716<dl>
668 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 717 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
669 <dd> 718 <dd>
670 <p>This function combines a simple timer and an I/O watcher, calls your 719 <p>This function combines a simple timer and an I/O watcher, calls your
671callback on whichever event happens first and automatically stop both 720callback on whichever event happens first and automatically stop both
672watchers. This is useful if you want to wait for a single event on an fd 721watchers. This is useful if you want to wait for a single event on an fd
673or timeout without havign to allocate/configure/start/stop/free one or 722or timeout without havign to allocate/configure/start/stop/free one or
674more watchers yourself.</p> 723more watchers yourself.</p>
675 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 724 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
676ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 725is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
677will be craeted and started.</p> 726<code>events</code> set will be craeted and started.</p>
678 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 727 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
679started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 728started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
680= 0) will be started.</p> 729repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
730dubious value.</p>
681 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 731 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
682gets passed an events set (normally a combination of EV_ERROR, EV_READ, 732passed an <code>revents</code> set like normal event callbacks (a combination of
683EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 733<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
734value passed to <code>ev_once</code>:</p>
684<pre> static void stdin_ready (int revents, void *arg) 735<pre> static void stdin_ready (int revents, void *arg)
685 { 736 {
686 if (revents &amp; EV_TIMEOUT) 737 if (revents &amp; EV_TIMEOUT)
687 /* doh, nothing entered */ 738 /* doh, nothing entered */;
688 else if (revents &amp; EV_READ) 739 else if (revents &amp; EV_READ)
689 /* stdin might have data for us, joy! */ 740 /* stdin might have data for us, joy! */;
690 } 741 }
691 742
692 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 743 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
693 744
694</pre> 745</pre>
695 </dd> 746 </dd>
696 <dt>ev_feed_event (loop, watcher, int events)</dt> 747 <dt>ev_feed_event (loop, watcher, int events)</dt>
697 <dd> 748 <dd>
698 <p>Feeds the given event set into the event loop, as if the specified event 749 <p>Feeds the given event set into the event loop, as if the specified event
699has happened for the specified watcher (which must be a pointer to an 750had happened for the specified watcher (which must be a pointer to an
700initialised but not necessarily active event watcher).</p> 751initialised but not necessarily started event watcher).</p>
701 </dd> 752 </dd>
702 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 753 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
703 <dd> 754 <dd>
704 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 755 <p>Feed an event on the given fd, as if a file descriptor backend detected
756the given events it.</p>
705 </dd> 757 </dd>
706 <dt>ev_feed_signal_event (loop, int signum)</dt> 758 <dt>ev_feed_signal_event (loop, int signum)</dt>
707 <dd> 759 <dd>
708 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 760 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
709 </dd> 761 </dd>
710</dl> 762</dl>
763
764</div>
765<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
766<div id="LIBEVENT_EMULATION_CONTENT">
767<p>TBD.</p>
768
769</div>
770<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
771<div id="C_SUPPORT_CONTENT">
772<p>TBD.</p>
711 773
712</div> 774</div>
713<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 775<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
714<div id="AUTHOR_CONTENT"> 776<div id="AUTHOR_CONTENT">
715<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 777<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

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