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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 09:11:00 2007" /> 9 <meta name="created" content="Thu Nov 22 13:26:17 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 -->
… …
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_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</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
… …
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, representing the 97<p>Libev represents time as a single floating point number, representing the
93(fractional) number of seconds since the (POSIX) epoch (somewhere near 98(fractional) number of seconds since the (POSIX) epoch (somewhere near
94the beginning of 1970, details are complicated, don't ask). This type is 99the beginning of 1970, details are complicated, don't ask). This type is
95called <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
96to 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>
97<dl> 108<dl>
98 <dt>ev_tstamp ev_time ()</dt> 109 <dt>ev_tstamp ev_time ()</dt>
99 <dd> 110 <dd>
100 <p>Returns the current time as libev would use it.</p> 111 <p>Returns the current time as libev would use it. Please note that the
112<code>ev_now</code> function is usually faster and also often returns the timestamp
113you actually want to know.</p>
101 </dd> 114 </dd>
102 <dt>int ev_version_major ()</dt> 115 <dt>int ev_version_major ()</dt>
103 <dt>int ev_version_minor ()</dt> 116 <dt>int ev_version_minor ()</dt>
104 <dd> 117 <dd>
105 <p>You can find out the major and minor version numbers of the library 118 <p>You can find out the major and minor version numbers of the library
106you linked against by calling the functions <code>ev_version_major</code> and 119you linked against by calling the functions <code>ev_version_major</code> and
107<code>ev_version_minor</code>. If you want, you can compare against the global 120<code>ev_version_minor</code>. If you want, you can compare against the global
108symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 121symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
109version of the library your program was compiled against.</p> 122version of the library your program was compiled against.</p>
110 <p>Usually, its a good idea to terminate if the major versions mismatch, 123 <p>Usually, it's a good idea to terminate if the major versions mismatch,
111as this indicates an incompatible change. Minor versions are usually 124as this indicates an incompatible change. Minor versions are usually
112compatible to older versions, so a larger minor version alone is usually 125compatible to older versions, so a larger minor version alone is usually
113not a problem.</p> 126not a problem.</p>
114 </dd> 127 </dd>
115 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 128 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
116 <dd> 129 <dd>
117 <p>Sets the allocation function to use (the prototype is similar to the 130 <p>Sets the allocation function to use (the prototype is similar to the
118realloc function). It is used to allocate and free memory (no surprises 131realloc C function, the semantics are identical). It is used to allocate
119here). If it returns zero when memory needs to be allocated, the library 132and free memory (no surprises here). If it returns zero when memory
120might abort or take some potentially destructive action. The default is 133needs to be allocated, the library might abort or take some potentially
121your system realloc function.</p> 134destructive action. The default is your system realloc function.</p>
122 <p>You could override this function in high-availability programs to, say, 135 <p>You could override this function in high-availability programs to, say,
123free some memory if it cannot allocate memory, to use a special allocator, 136free some memory if it cannot allocate memory, to use a special allocator,
124or even to sleep a while and retry until some memory is available.</p> 137or even to sleep a while and retry until some memory is available.</p>
125 </dd> 138 </dd>
126 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 139 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
127 <dd> 140 <dd>
128 <p>Set the callback function to call on a retryable syscall error (such 141 <p>Set the callback function to call on a retryable syscall error (such
129as failed select, poll, epoll_wait). The message is a printable string 142as failed select, poll, epoll_wait). The message is a printable string
130indicating the system call or subsystem causing the problem. If this 143indicating the system call or subsystem causing the problem. If this
131callback is set, then libev will expect it to remedy the sitution, no 144callback is set, then libev will expect it to remedy the sitution, no
132matter what, when it returns. That is, libev will geenrally retry the 145matter what, when it returns. That is, libev will generally retry the
133requested operation, or, if the condition doesn't go away, do bad stuff 146requested operation, or, if the condition doesn't go away, do bad stuff
134(such as abort).</p> 147(such as abort).</p>
135 </dd> 148 </dd>
136</dl> 149</dl>
137 150
… …
140<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 153<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
141<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 154<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
142types of such loops, the <i>default</i> loop, which supports signals and child 155types of such loops, the <i>default</i> loop, which supports signals and child
143events, and dynamically created loops which do not.</p> 156events, and dynamically created loops which do not.</p>
144<p>If you use threads, a common model is to run the default event loop 157<p>If you use threads, a common model is to run the default event loop
145in your main thread (or in a separate thrad) and for each thread you 158in your main thread (or in a separate thread) and for each thread you
146create, you also create another event loop. Libev itself does no lockign 159create, you also create another event loop. Libev itself does no locking
147whatsoever, so if you mix calls to different event loops, make sure you 160whatsoever, so if you mix calls to the same event loop in different
148lock (this is usually a bad idea, though, even if done right).</p> 161threads, make sure you lock (this is usually a bad idea, though, even if
162done correctly, because it's hideous and inefficient).</p>
149<dl> 163<dl>
150 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 164 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
151 <dd> 165 <dd>
152 <p>This will initialise the default event loop if it hasn't been initialised 166 <p>This will initialise the default event loop if it hasn't been initialised
153yet and return it. If the default loop could not be initialised, returns 167yet and return it. If the default loop could not be initialised, returns
154false. If it already was initialised it simply returns it (and ignores the 168false. If it already was initialised it simply returns it (and ignores the
155flags).</p> 169flags).</p>
156 <p>If you don't know what event loop to use, use the one returned from this 170 <p>If you don't know what event loop to use, use the one returned from this
157function.</p> 171function.</p>
158 <p>The flags argument can be used to specify special behaviour or specific 172 <p>The flags argument can be used to specify special behaviour or specific
159backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p> 173backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>
160 <p>It supports the following flags:</p> 174 <p>It supports the following flags:</p>
161 <p> 175 <p>
162 <dl> 176 <dl>
163 <dt>EVFLAG_AUTO</dt> 177 <dt><code>EVFLAG_AUTO</code></dt>
164 <dd> 178 <dd>
165 <p>The default flags value. Use this if you have no clue (its the right 179 <p>The default flags value. Use this if you have no clue (it's the right
166thing, believe me).</p> 180thing, believe me).</p>
167 </dd> 181 </dd>
168 <dt>EVFLAG_NOENV</dt> 182 <dt><code>EVFLAG_NOENV</code></dt>
169 <dd>
170 <p>If this flag bit is ored into the flag value then libev will <i>not</i> look
171at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this
172environment variable will override the flags completely. This is useful
173to try out specific backends to tets their performance, or to work around
174bugs.</p>
175 </dd> 183 <dd>
176 <dt>EVMETHOD_SELECT portable select backend</dt> 184 <p>If this flag bit is ored into the flag value (or the program runs setuid
177 <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> 185or setgid) then libev will <i>not</i> look at the environment variable
178 <dt>EVMETHOD_EPOLL linux only</dt> 186<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
179 <dt>EVMETHOD_KQUEUE some bsds only</dt> 187override the flags completely if it is found in the environment. This is
180 <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> 188useful to try out specific backends to test their performance, or to work
181 <dt>EVMETHOD_PORT solaris 10 only</dt> 189around bugs.</p>
182 <dd> 190 </dd>
183 <p>If one or more of these are ored into the flags value, then only these 191 <dt><code>EVMETHOD_SELECT</code> (value 1, portable select backend)</dt>
184backends will be tried (in the reverse order as given here). If one are 192 <dd>
185specified, any backend will do.</p> 193 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
194libev tries to roll its own fd_set with no limits on the number of fds,
195but if that fails, expect a fairly low limit on the number of fds when
196using this backend. It doesn't scale too well (O(highest_fd)), but its usually
197the fastest backend for a low number of fds.</p>
198 </dd>
199 <dt><code>EVMETHOD_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
200 <dd>
201 <p>And this is your standard poll(2) backend. It's more complicated than
202select, but handles sparse fds better and has no artificial limit on the
203number of fds you can use (except it will slow down considerably with a
204lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
205 </dd>
206 <dt><code>EVMETHOD_EPOLL</code> (value 4, Linux)</dt>
207 <dd>
208 <p>For few fds, this backend is a bit little slower than poll and select,
209but it scales phenomenally better. While poll and select usually scale like
210O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
211either O(1) or O(active_fds).</p>
212 <p>While stopping and starting an I/O watcher in the same iteration will
213result in some caching, there is still a syscall per such incident
214(because the fd could point to a different file description now), so its
215best to avoid that. Also, dup()ed file descriptors might not work very
216well if you register events for both fds.</p>
217 </dd>
218 <dt><code>EVMETHOD_KQUEUE</code> (value 8, most BSD clones)</dt>
219 <dd>
220 <p>Kqueue deserves special mention, as at the time of this writing, it
221was broken on all BSDs except NetBSD (usually it doesn't work with
222anything but sockets and pipes, except on Darwin, where of course its
223completely useless). For this reason its not being &quot;autodetected&quot; unless
224you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p>
225 <p>It scales in the same way as the epoll backend, but the interface to the
226kernel is more efficient (which says nothing about its actual speed, of
227course). While starting and stopping an I/O watcher does not cause an
228extra syscall as with epoll, it still adds up to four event changes per
229incident, so its best to avoid that.</p>
230 </dd>
231 <dt><code>EVMETHOD_DEVPOLL</code> (value 16, Solaris 8)</dt>
232 <dd>
233 <p>This is not implemented yet (and might never be).</p>
234 </dd>
235 <dt><code>EVMETHOD_PORT</code> (value 32, Solaris 10)</dt>
236 <dd>
237 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
238it's really slow, but it still scales very well (O(active_fds)).</p>
239 </dd>
240 <dt><code>EVMETHOD_ALL</code></dt>
241 <dd>
242 <p>Try all backends (even potentially broken ones). Since this is a mask, you
243can do stuff like <code>EVMETHOD_ALL &amp; ~EVMETHOD_KQUEUE</code>.</p>
186 </dd> 244 </dd>
187 </dl> 245 </dl>
188 </p> 246 </p>
247 <p>If one or more of these are ored into the flags value, then only these
248backends will be tried (in the reverse order as given here). If none are
249specified, most compiled-in backend will be tried, usually in reverse
250order of their flag values :)</p>
189 </dd> 251 </dd>
190 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 252 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
191 <dd> 253 <dd>
192 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 254 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
193always distinct from the default loop. Unlike the default loop, it cannot 255always distinct from the default loop. Unlike the default loop, it cannot
… …
196 </dd> 258 </dd>
197 <dt>ev_default_destroy ()</dt> 259 <dt>ev_default_destroy ()</dt>
198 <dd> 260 <dd>
199 <p>Destroys the default loop again (frees all memory and kernel state 261 <p>Destroys the default loop again (frees all memory and kernel state
200etc.). This stops all registered event watchers (by not touching them in 262etc.). This stops all registered event watchers (by not touching them in
201any way whatsoever, although you cnanot rely on this :).</p> 263any way whatsoever, although you cannot rely on this :).</p>
202 </dd> 264 </dd>
203 <dt>ev_loop_destroy (loop)</dt> 265 <dt>ev_loop_destroy (loop)</dt>
204 <dd> 266 <dd>
205 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 267 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
206earlier call to <code>ev_loop_new</code>.</p> 268earlier call to <code>ev_loop_new</code>.</p>
… …
212after forking, in either the parent or child process (or both, but that 274after forking, in either the parent or child process (or both, but that
213again makes little sense).</p> 275again makes little sense).</p>
214 <p>You <i>must</i> call this function after forking if and only if you want to 276 <p>You <i>must</i> call this function after forking if and only if you want to
215use the event library in both processes. If you just fork+exec, you don't 277use the event library in both processes. If you just fork+exec, you don't
216have to call it.</p> 278have to call it.</p>
217 <p>The function itself is quite fast and its usually not a problem to call 279 <p>The function itself is quite fast and it's usually not a problem to call
218it just in case after a fork. To make this easy, the function will fit in 280it just in case after a fork. To make this easy, the function will fit in
219quite nicely into a call to <code>pthread_atfork</code>:</p> 281quite nicely into a call to <code>pthread_atfork</code>:</p>
220<pre> pthread_atfork (0, 0, ev_default_fork); 282<pre> pthread_atfork (0, 0, ev_default_fork);
221 283
222</pre> 284</pre>
… …
230 <dt>unsigned int ev_method (loop)</dt> 292 <dt>unsigned int ev_method (loop)</dt>
231 <dd> 293 <dd>
232 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 294 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in
233use.</p> 295use.</p>
234 </dd> 296 </dd>
235 <dt>ev_tstamp = ev_now (loop)</dt> 297 <dt>ev_tstamp ev_now (loop)</dt>
236 <dd> 298 <dd>
237 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 299 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
238got events and started processing them. This timestamp does not change 300got events and started processing them. This timestamp does not change
239as long as callbacks are being processed, and this is also the base time 301as long as callbacks are being processed, and this is also the base time
240used for relative timers. You can treat it as the timestamp of the event 302used for relative timers. You can treat it as the timestamp of the event
… …
247events.</p> 309events.</p>
248 <p>If the flags argument is specified as 0, it will not return until either 310 <p>If the flags argument is specified as 0, it will not return until either
249no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 311no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
250 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 312 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
251those events and any outstanding ones, but will not block your process in 313those events and any outstanding ones, but will not block your process in
252case there are no events.</p> 314case there are no events and will return after one iteration of the loop.</p>
253 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 315 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
254neccessary) and will handle those and any outstanding ones. It will block 316neccessary) and will handle those and any outstanding ones. It will block
255your process until at least one new event arrives.</p> 317your process until at least one new event arrives, and will return after
318one iteration of the loop.</p>
256 <p>This flags value could be used to implement alternative looping 319 <p>This flags value could be used to implement alternative looping
257constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 320constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
258more generic mechanism.</p> 321more generic mechanism.</p>
322 <p>Here are the gory details of what ev_loop does:</p>
323<pre> 1. If there are no active watchers (reference count is zero), return.
324 2. Queue and immediately call all prepare watchers.
325 3. If we have been forked, recreate the kernel state.
326 4. Update the kernel state with all outstanding changes.
327 5. Update the &quot;event loop time&quot;.
328 6. Calculate for how long to block.
329 7. Block the process, waiting for events.
330 8. Update the &quot;event loop time&quot; and do time jump handling.
331 9. Queue all outstanding timers.
332 10. Queue all outstanding periodics.
333 11. If no events are pending now, queue all idle watchers.
334 12. Queue all check watchers.
335 13. Call all queued watchers in reverse order (i.e. check watchers first).
336 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
337 was used, return, otherwise continue with step #1.
338
339</pre>
259 </dd> 340 </dd>
260 <dt>ev_unloop (loop, how)</dt> 341 <dt>ev_unloop (loop, how)</dt>
261 <dd> 342 <dd>
262 <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument 343 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
344has processed all outstanding events). The <code>how</code> argument must be either
263must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> 345<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
264call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> 346<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
265calls return.</p>
266 </dd> 347 </dd>
267 <dt>ev_ref (loop)</dt> 348 <dt>ev_ref (loop)</dt>
268 <dt>ev_unref (loop)</dt> 349 <dt>ev_unref (loop)</dt>
269 <dd> 350 <dd>
270 <p>Ref/unref can be used to add or remove a refcount on the event loop: Every 351 <p>Ref/unref can be used to add or remove a reference count on the event
271watcher keeps one reference. If you have a long-runing watcher you never 352loop: Every watcher keeps one reference, and as long as the reference
272unregister that should not keep ev_loop from running, ev_unref() after 353count is nonzero, <code>ev_loop</code> will not return on its own. If you have
273starting, and ev_ref() before stopping it. Libev itself uses this for 354a watcher you never unregister that should not keep <code>ev_loop</code> from
274example for its internal signal pipe: It is not visible to you as a user 355returning, ev_unref() after starting, and ev_ref() before stopping it. For
275and should not keep <code>ev_loop</code> from exiting if the work is done. It is 356example, libev itself uses this for its internal signal pipe: It is not
276also an excellent way to do this for generic recurring timers or from 357visible to the libev user and should not keep <code>ev_loop</code> from exiting if
277within third-party libraries. Just remember to unref after start and ref 358no event watchers registered by it are active. It is also an excellent
278before stop.</p> 359way to do this for generic recurring timers or from within third-party
360libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
279 </dd> 361 </dd>
280</dl> 362</dl>
281 363
282</div> 364</div>
283<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 365<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
284<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 366<div id="ANATOMY_OF_A_WATCHER_CONTENT">
285<p>A watcher is a structure that you create and register to record your 367<p>A watcher is a structure that you create and register to record your
286interest in some event. For instance, if you want to wait for STDIN to 368interest in some event. For instance, if you want to wait for STDIN to
287become readable, you would create an ev_io watcher for that:</p> 369become readable, you would create an <code>ev_io</code> watcher for that:</p>
288<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 370<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
289 { 371 {
290 ev_io_stop (w); 372 ev_io_stop (w);
291 ev_unloop (loop, EVUNLOOP_ALL); 373 ev_unloop (loop, EVUNLOOP_ALL);
292 } 374 }
… …
316*)</code>), and you can stop watching for events at any time by calling the 398*)</code>), and you can stop watching for events at any time by calling the
317corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 399corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
318<p>As long as your watcher is active (has been started but not stopped) you 400<p>As long as your watcher is active (has been started but not stopped) you
319must not touch the values stored in it. Most specifically you must never 401must not touch the values stored in it. Most specifically you must never
320reinitialise it or call its set method.</p> 402reinitialise it or call its set method.</p>
321<p>You cna check whether an event is active by calling the <code>ev_is_active 403<p>You can check whether an event is active by calling the <code>ev_is_active
322(watcher *)</code> macro. To see whether an event is outstanding (but the 404(watcher *)</code> macro. To see whether an event is outstanding (but the
323callback for it has not been called yet) you cna use the <code>ev_is_pending 405callback for it has not been called yet) you can use the <code>ev_is_pending
324(watcher *)</code> macro.</p> 406(watcher *)</code> macro.</p>
325<p>Each and every callback receives the event loop pointer as first, the 407<p>Each and every callback receives the event loop pointer as first, the
326registered watcher structure as second, and a bitset of received events as 408registered watcher structure as second, and a bitset of received events as
327third argument.</p> 409third argument.</p>
328<p>The rceeived events usually include a single bit per event type received 410<p>The received events usually include a single bit per event type received
329(you can receive multiple events at the same time). The possible bit masks 411(you can receive multiple events at the same time). The possible bit masks
330are:</p> 412are:</p>
331<dl> 413<dl>
332 <dt>EV_READ</dt> 414 <dt><code>EV_READ</code></dt>
333 <dt>EV_WRITE</dt> 415 <dt><code>EV_WRITE</code></dt>
334 <dd> 416 <dd>
335 <p>The file descriptor in the ev_io watcher has become readable and/or 417 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
336writable.</p> 418writable.</p>
337 </dd> 419 </dd>
338 <dt>EV_TIMEOUT</dt> 420 <dt><code>EV_TIMEOUT</code></dt>
339 <dd>
340 <p>The ev_timer watcher has timed out.</p>
341 </dd> 421 <dd>
342 <dt>EV_PERIODIC</dt> 422 <p>The <code>ev_timer</code> watcher has timed out.</p>
343 <dd> 423 </dd>
344 <p>The ev_periodic watcher has timed out.</p> 424 <dt><code>EV_PERIODIC</code></dt>
345 </dd> 425 <dd>
346 <dt>EV_SIGNAL</dt> 426 <p>The <code>ev_periodic</code> watcher has timed out.</p>
347 <dd> 427 </dd>
428 <dt><code>EV_SIGNAL</code></dt>
429 <dd>
348 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 430 <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
349 </dd>
350 <dt>EV_CHILD</dt>
351 <dd> 431 </dd>
432 <dt><code>EV_CHILD</code></dt>
433 <dd>
352 <p>The pid specified in the ev_child watcher has received a status change.</p> 434 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
353 </dd>
354 <dt>EV_IDLE</dt>
355 <dd> 435 </dd>
436 <dt><code>EV_IDLE</code></dt>
437 <dd>
356 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 438 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
357 </dd>
358 <dt>EV_PREPARE</dt>
359 <dt>EV_CHECK</dt>
360 <dd> 439 </dd>
440 <dt><code>EV_PREPARE</code></dt>
441 <dt><code>EV_CHECK</code></dt>
442 <dd>
361 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 443 <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
362to gather new events, and all ev_check watchers are invoked just after 444to gather new events, and all <code>ev_check</code> watchers are invoked just after
363<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 445<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
364received events. Callbacks of both watcher types can start and stop as 446received events. Callbacks of both watcher types can start and stop as
365many watchers as they want, and all of them will be taken into account 447many watchers as they want, and all of them will be taken into account
366(for example, a ev_prepare watcher might start an idle watcher to keep 448(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
367<code>ev_loop</code> from blocking).</p> 449<code>ev_loop</code> from blocking).</p>
368 </dd> 450 </dd>
369 <dt>EV_ERROR</dt> 451 <dt><code>EV_ERROR</code></dt>
370 <dd> 452 <dd>
371 <p>An unspecified error has occured, the watcher has been stopped. This might 453 <p>An unspecified error has occured, the watcher has been stopped. This might
372happen because the watcher could not be properly started because libev 454happen because the watcher could not be properly started because libev
373ran out of memory, a file descriptor was found to be closed or any other 455ran out of memory, a file descriptor was found to be closed or any other
374problem. You best act on it by reporting the problem and somehow coping 456problem. You best act on it by reporting the problem and somehow coping
… …
383 465
384</div> 466</div>
385<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 467<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
386<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 468<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
387<p>Each watcher has, by default, a member <code>void *data</code> that you can change 469<p>Each watcher has, by default, a member <code>void *data</code> that you can change
388and read at any time, libev will completely ignore it. This cna be used 470and read at any time, libev will completely ignore it. This can be used
389to associate arbitrary data with your watcher. If you need more data and 471to associate arbitrary data with your watcher. If you need more data and
390don't want to allocate memory and store a pointer to it in that data 472don't want to allocate memory and store a pointer to it in that data
391member, you can also &quot;subclass&quot; the watcher type and provide your own 473member, you can also &quot;subclass&quot; the watcher type and provide your own
392data:</p> 474data:</p>
393<pre> struct my_io 475<pre> struct my_io
… …
420<div id="WATCHER_TYPES_CONTENT"> 502<div id="WATCHER_TYPES_CONTENT">
421<p>This section describes each watcher in detail, but will not repeat 503<p>This section describes each watcher in detail, but will not repeat
422information given in the last section.</p> 504information given in the last section.</p>
423 505
424</div> 506</div>
425<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 507<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
426<div id="struct_ev_io_is_my_file_descriptor_r-2"> 508<div id="code_ev_io_code_is_this_file_descrip-2">
427<p>I/O watchers check whether a file descriptor is readable or writable 509<p>I/O watchers check whether a file descriptor is readable or writable
428in each iteration of the event loop (This behaviour is called 510in each iteration of the event loop (This behaviour is called
429level-triggering because you keep receiving events as long as the 511level-triggering because you keep receiving events as long as the
430condition persists. Remember you cna stop the watcher if you don't want to 512condition persists. Remember you can stop the watcher if you don't want to
431act on the event and neither want to receive future events).</p> 513act on the event and neither want to receive future events).</p>
514<p>In general you can register as many read and/or write event watchers per
515fd as you want (as long as you don't confuse yourself). Setting all file
516descriptors to non-blocking mode is also usually a good idea (but not
517required if you know what you are doing).</p>
518<p>You have to be careful with dup'ed file descriptors, though. Some backends
519(the linux epoll backend is a notable example) cannot handle dup'ed file
520descriptors correctly if you register interest in two or more fds pointing
521to the same underlying file/socket etc. description (that is, they share
522the same underlying &quot;file open&quot;).</p>
523<p>If you must do this, then force the use of a known-to-be-good backend
524(at the time of this writing, this includes only EVMETHOD_SELECT and
525EVMETHOD_POLL).</p>
432<dl> 526<dl>
433 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 527 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
434 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 528 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
435 <dd> 529 <dd>
436 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 530 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
437events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 531events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
438EV_WRITE</code> to receive the given events.</p> 532EV_WRITE</code> to receive the given events.</p>
439 </dd> 533 </dd>
440</dl> 534</dl>
441 535
442</div> 536</div>
443<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 537<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
444<div id="struct_ev_timer_relative_and_optiona-2"> 538<div id="code_ev_timer_code_relative_and_opti-2">
445<p>Timer watchers are simple relative timers that generate an event after a 539<p>Timer watchers are simple relative timers that generate an event after a
446given time, and optionally repeating in regular intervals after that.</p> 540given time, and optionally repeating in regular intervals after that.</p>
447<p>The timers are based on real time, that is, if you register an event that 541<p>The timers are based on real time, that is, if you register an event that
448times out after an hour and youreset your system clock to last years 542times out after an hour and you reset your system clock to last years
449time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 543time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
450detecting time jumps is hard, and soem inaccuracies are unavoidable (the 544detecting time jumps is hard, and some inaccuracies are unavoidable (the
451monotonic clock option helps a lot here).</p> 545monotonic clock option helps a lot here).</p>
546<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
547time. This is usually the right thing as this timestamp refers to the time
548of the event triggering whatever timeout you are modifying/starting. If
549you suspect event processing to be delayed and you <i>need</i> to base the timeout
550on the current time, use something like this to adjust for this:</p>
551<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
552
553</pre>
554<p>The callback is guarenteed to be invoked only when its timeout has passed,
555but if multiple timers become ready during the same loop iteration then
556order of execution is undefined.</p>
452<dl> 557<dl>
453 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 558 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
454 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 559 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
455 <dd> 560 <dd>
456 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 561 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
458timer will automatically be configured to trigger again <code>repeat</code> seconds 563timer will automatically be configured to trigger again <code>repeat</code> seconds
459later, again, and again, until stopped manually.</p> 564later, again, and again, until stopped manually.</p>
460 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 565 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
461configure a timer to trigger every 10 seconds, then it will trigger at 566configure a timer to trigger every 10 seconds, then it will trigger at
462exactly 10 second intervals. If, however, your program cannot keep up with 567exactly 10 second intervals. If, however, your program cannot keep up with
463the timer (ecause it takes longer than those 10 seconds to do stuff) the 568the timer (because it takes longer than those 10 seconds to do stuff) the
464timer will not fire more than once per event loop iteration.</p> 569timer will not fire more than once per event loop iteration.</p>
465 </dd> 570 </dd>
466 <dt>ev_timer_again (loop)</dt> 571 <dt>ev_timer_again (loop)</dt>
467 <dd> 572 <dd>
468 <p>This will act as if the timer timed out and restart it again if it is 573 <p>This will act as if the timer timed out and restart it again if it is
… …
472value), or reset the running timer to the repeat value.</p> 577value), or reset the running timer to the repeat value.</p>
473 <p>This sounds a bit complicated, but here is a useful and typical 578 <p>This sounds a bit complicated, but here is a useful and typical
474example: Imagine you have a tcp connection and you want a so-called idle 579example: Imagine you have a tcp connection and you want a so-called idle
475timeout, that is, you want to be called when there have been, say, 60 580timeout, that is, you want to be called when there have been, say, 60
476seconds of inactivity on the socket. The easiest way to do this is to 581seconds of inactivity on the socket. The easiest way to do this is to
477configure an ev_timer with after=repeat=60 and calling ev_timer_again each 582configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
478time you successfully read or write some data. If you go into an idle 583time you successfully read or write some data. If you go into an idle
479state where you do not expect data to travel on the socket, you can stop 584state where you do not expect data to travel on the socket, you can stop
480the timer, and again will automatically restart it if need be.</p> 585the timer, and again will automatically restart it if need be.</p>
481 </dd> 586 </dd>
482</dl> 587</dl>
483 588
484</div> 589</div>
485<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2> 590<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
486<div id="ev_periodic_to_cron_or_not_to_cron_i-2"> 591<div id="code_ev_periodic_code_to_cron_or_not-2">
487<p>Periodic watchers are also timers of a kind, but they are very versatile 592<p>Periodic watchers are also timers of a kind, but they are very versatile
488(and unfortunately a bit complex).</p> 593(and unfortunately a bit complex).</p>
489<p>Unlike ev_timer's, they are not based on real time (or relative time) 594<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
490but on wallclock time (absolute time). You can tell a periodic watcher 595but on wallclock time (absolute time). You can tell a periodic watcher
491to trigger &quot;at&quot; some specific point in time. For example, if you tell a 596to trigger &quot;at&quot; some specific point in time. For example, if you tell a
492periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 597periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now ()
493+ 10.&gt;) and then reset your system clock to the last year, then it will 598+ 10.&gt;) and then reset your system clock to the last year, then it will
494take a year to trigger the event (unlike an ev_timer, which would trigger 599take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
495roughly 10 seconds later and of course not if you reset your system time 600roughly 10 seconds later and of course not if you reset your system time
496again).</p> 601again).</p>
497<p>They can also be used to implement vastly more complex timers, such as 602<p>They can also be used to implement vastly more complex timers, such as
498triggering an event on eahc midnight, local time.</p> 603triggering an event on eahc midnight, local time.</p>
604<p>As with timers, the callback is guarenteed to be invoked only when the
605time (<code>at</code>) has been passed, but if multiple periodic timers become ready
606during the same loop iteration then order of execution is undefined.</p>
499<dl> 607<dl>
500 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 608 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
501 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 609 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
502 <dd> 610 <dd>
503 <p>Lots of arguments, lets sort it out... There are basically three modes of 611 <p>Lots of arguments, lets sort it out... There are basically three modes of
504operation, and we will explain them from simplest to complex:</p> 612operation, and we will explain them from simplest to complex:</p>
505
506
507
508
509 <p> 613 <p>
510 <dl> 614 <dl>
511 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 615 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
512 <dd> 616 <dd>
513 <p>In this configuration the watcher triggers an event at the wallclock time 617 <p>In this configuration the watcher triggers an event at the wallclock time
… …
525<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 629<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
526 630
527</pre> 631</pre>
528 <p>This doesn't mean there will always be 3600 seconds in between triggers, 632 <p>This doesn't mean there will always be 3600 seconds in between triggers,
529but only that the the callback will be called when the system time shows a 633but only that the the callback will be called when the system time shows a
530full hour (UTC), or more correct, when the system time is evenly divisible 634full hour (UTC), or more correctly, when the system time is evenly divisible
531by 3600.</p> 635by 3600.</p>
532 <p>Another way to think about it (for the mathematically inclined) is that 636 <p>Another way to think about it (for the mathematically inclined) is that
533ev_periodic will try to run the callback in this mode at the next possible 637<code>ev_periodic</code> will try to run the callback in this mode at the next possible
534time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 638time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
535 </dd> 639 </dd>
536 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 640 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
537 <dd> 641 <dd>
538 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 642 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
539ignored. Instead, each time the periodic watcher gets scheduled, the 643ignored. Instead, each time the periodic watcher gets scheduled, the
540reschedule callback will be called with the watcher as first, and the 644reschedule callback will be called with the watcher as first, and the
541current time as second argument.</p> 645current time as second argument.</p>
542 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 646 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
543periodic watcher, ever, or make any event loop modificstions</i>. If you need 647ever, or make any event loop modifications</i>. If you need to stop it,
544to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 648return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
649starting a prepare watcher).</p>
545 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 650 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
546ev_tstamp now)&gt;, e.g.:</p> 651ev_tstamp now)</code>, e.g.:</p>
547<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 652<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
548 { 653 {
549 return now + 60.; 654 return now + 60.;
550 } 655 }
551 656
552</pre> 657</pre>
553 <p>It must return the next time to trigger, based on the passed time value 658 <p>It must return the next time to trigger, based on the passed time value
554(that is, the lowest time value larger than to the second argument). It 659(that is, the lowest time value larger than to the second argument). It
555will usually be called just before the callback will be triggered, but 660will usually be called just before the callback will be triggered, but
556might be called at other times, too.</p> 661might be called at other times, too.</p>
662 <p>NOTE: <i>This callback must always return a time that is later than the
663passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
557 <p>This can be used to create very complex timers, such as a timer that 664 <p>This can be used to create very complex timers, such as a timer that
558triggers on each midnight, local time. To do this, you would calculate the 665triggers on each midnight, local time. To do this, you would calculate the
559next midnight after <code>now</code> and return the timestamp value for this. How you do this 666next midnight after <code>now</code> and return the timestamp value for this. How
560is, again, up to you (but it is not trivial).</p> 667you do this is, again, up to you (but it is not trivial, which is the main
668reason I omitted it as an example).</p>
561 </dd> 669 </dd>
562 </dl> 670 </dl>
563 </p> 671 </p>
564 </dd> 672 </dd>
565 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 673 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
570program when the crontabs have changed).</p> 678program when the crontabs have changed).</p>
571 </dd> 679 </dd>
572</dl> 680</dl>
573 681
574</div> 682</div>
575<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 683<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
576<div id="ev_signal_signal_me_when_a_signal_ge-2"> 684<div id="code_ev_signal_code_signal_me_when_a-2">
577<p>Signal watchers will trigger an event when the process receives a specific 685<p>Signal watchers will trigger an event when the process receives a specific
578signal one or more times. Even though signals are very asynchronous, libev 686signal one or more times. Even though signals are very asynchronous, libev
579will try its best to deliver signals synchronously, i.e. as part of the 687will try it's best to deliver signals synchronously, i.e. as part of the
580normal event processing, like any other event.</p> 688normal event processing, like any other event.</p>
581<p>You cna configure as many watchers as you like per signal. Only when the 689<p>You can configure as many watchers as you like per signal. Only when the
582first watcher gets started will libev actually register a signal watcher 690first watcher gets started will libev actually register a signal watcher
583with the kernel (thus it coexists with your own signal handlers as long 691with the kernel (thus it coexists with your own signal handlers as long
584as you don't register any with libev). Similarly, when the last signal 692as you don't register any with libev). Similarly, when the last signal
585watcher for a signal is stopped libev will reset the signal handler to 693watcher for a signal is stopped libev will reset the signal handler to
586SIG_DFL (regardless of what it was set to before).</p> 694SIG_DFL (regardless of what it was set to before).</p>
… …
592of the <code>SIGxxx</code> constants).</p> 700of the <code>SIGxxx</code> constants).</p>
593 </dd> 701 </dd>
594</dl> 702</dl>
595 703
596</div> 704</div>
597<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 705<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
598<div id="ev_child_wait_for_pid_status_changes-2"> 706<div id="code_ev_child_code_wait_for_pid_stat-2">
599<p>Child watchers trigger when your process receives a SIGCHLD in response to 707<p>Child watchers trigger when your process receives a SIGCHLD in response to
600some child status changes (most typically when a child of yours dies).</p> 708some child status changes (most typically when a child of yours dies).</p>
601<dl> 709<dl>
602 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 710 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
603 <dt>ev_child_set (ev_child *, int pid)</dt> 711 <dt>ev_child_set (ev_child *, int pid)</dt>
604 <dd> 712 <dd>
605 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 713 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
606<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 714<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
607at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 715at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
608the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 716the status word (use the macros from <code>sys/wait.h</code> and see your systems
717<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
609contains the pid of the process causing the status change.</p> 718process causing the status change.</p>
610 </dd> 719 </dd>
611</dl> 720</dl>
612 721
613</div> 722</div>
614<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 723<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
615<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 724<div id="code_ev_idle_code_when_you_ve_got_no-2">
616<p>Idle watchers trigger events when there are no other I/O or timer (or 725<p>Idle watchers trigger events when there are no other events are pending
617periodic) events pending. That is, as long as your process is busy 726(prepare, check and other idle watchers do not count). That is, as long
618handling sockets or timeouts it will not be called. But when your process 727as your process is busy handling sockets or timeouts (or even signals,
619is idle all idle watchers are being called again and again - until 728imagine) it will not be triggered. But when your process is idle all idle
729watchers are being called again and again, once per event loop iteration -
620stopped, that is, or your process receives more events.</p> 730until stopped, that is, or your process receives more events and becomes
731busy.</p>
621<p>The most noteworthy effect is that as long as any idle watchers are 732<p>The most noteworthy effect is that as long as any idle watchers are
622active, the process will not block when waiting for new events.</p> 733active, the process will not block when waiting for new events.</p>
623<p>Apart from keeping your process non-blocking (which is a useful 734<p>Apart from keeping your process non-blocking (which is a useful
624effect on its own sometimes), idle watchers are a good place to do 735effect on its own sometimes), idle watchers are a good place to do
625&quot;pseudo-background processing&quot;, or delay processing stuff to after the 736&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
632believe me.</p> 743believe me.</p>
633 </dd> 744 </dd>
634</dl> 745</dl>
635 746
636</div> 747</div>
637<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 748<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
638<div id="prepare_and_check_your_hooks_into_th-2"> 749<div id="code_ev_prepare_code_and_code_ev_che-2">
639<p>Prepare and check watchers usually (but not always) are used in 750<p>Prepare and check watchers are usually (but not always) used in tandem:
640tandom. Prepare watchers get invoked before the process blocks and check 751prepare watchers get invoked before the process blocks and check watchers
641watchers afterwards.</p> 752afterwards.</p>
642<p>Their main purpose is to integrate other event mechanisms into libev. This 753<p>Their main purpose is to integrate other event mechanisms into libev. This
643could be used, for example, to track variable changes, implement your own 754could be used, for example, to track variable changes, implement your own
644watchers, integrate net-snmp or a coroutine library and lots more.</p> 755watchers, integrate net-snmp or a coroutine library and lots more.</p>
645<p>This is done by examining in each prepare call which file descriptors need 756<p>This is done by examining in each prepare call which file descriptors need
646to be watched by the other library, registering ev_io watchers for them 757to be watched by the other library, registering <code>ev_io</code> watchers for
647and starting an ev_timer watcher for any timeouts (many libraries provide 758them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
648just this functionality). Then, in the check watcher you check for any 759provide just this functionality). Then, in the check watcher you check for
649events that occured (by making your callbacks set soem flags for example) 760any events that occured (by checking the pending status of all watchers
650and call back into the library.</p> 761and stopping them) and call back into the library. The I/O and timer
762callbacks will never actually be called (but must be valid nevertheless,
763because you never know, you know?).</p>
651<p>As another example, the perl Coro module uses these hooks to integrate 764<p>As another example, the Perl Coro module uses these hooks to integrate
652coroutines into libev programs, by yielding to other active coroutines 765coroutines into libev programs, by yielding to other active coroutines
653during each prepare and only letting the process block if no coroutines 766during each prepare and only letting the process block if no coroutines
654are ready to run.</p> 767are ready to run (it's actually more complicated: it only runs coroutines
768with priority higher than or equal to the event loop and one coroutine
769of lower priority, but only once, using idle watchers to keep the event
770loop from blocking if lower-priority coroutines are active, thus mapping
771low-priority coroutines to idle/background tasks).</p>
655<dl> 772<dl>
656 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 773 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
657 <dt>ev_check_init (ev_check *, callback)</dt> 774 <dt>ev_check_init (ev_check *, callback)</dt>
658 <dd> 775 <dd>
659 <p>Initialises and configures the prepare or check watcher - they have no 776 <p>Initialises and configures the prepare or check watcher - they have no
660parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 777parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
661macros, but using them is utterly, utterly pointless.</p> 778macros, but using them is utterly, utterly and completely pointless.</p>
662 </dd> 779 </dd>
663</dl> 780</dl>
664 781
665</div> 782</div>
666<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 783<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
667<div id="OTHER_FUNCTIONS_CONTENT"> 784<div id="OTHER_FUNCTIONS_CONTENT">
668<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 785<p>There are some other functions of possible interest. Described. Here. Now.</p>
669<dl> 786<dl>
670 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 787 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
671 <dd> 788 <dd>
672 <p>This function combines a simple timer and an I/O watcher, calls your 789 <p>This function combines a simple timer and an I/O watcher, calls your
673callback on whichever event happens first and automatically stop both 790callback on whichever event happens first and automatically stop both
674watchers. This is useful if you want to wait for a single event on an fd 791watchers. This is useful if you want to wait for a single event on an fd
675or timeout without havign to allocate/configure/start/stop/free one or 792or timeout without having to allocate/configure/start/stop/free one or
676more watchers yourself.</p> 793more watchers yourself.</p>
677 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 794 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
678ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 795is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
679will be craeted and started.</p> 796<code>events</code> set will be craeted and started.</p>
680 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 797 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
681started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 798started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
682= 0) will be started.</p> 799repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
800dubious value.</p>
683 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 801 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
684gets passed an events set (normally a combination of EV_ERROR, EV_READ, 802passed an <code>revents</code> set like normal event callbacks (a combination of
685EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 803<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
804value passed to <code>ev_once</code>:</p>
686<pre> static void stdin_ready (int revents, void *arg) 805<pre> static void stdin_ready (int revents, void *arg)
687 { 806 {
688 if (revents &amp; EV_TIMEOUT) 807 if (revents &amp; EV_TIMEOUT)
689 /* doh, nothing entered */ 808 /* doh, nothing entered */;
690 else if (revents &amp; EV_READ) 809 else if (revents &amp; EV_READ)
691 /* stdin might have data for us, joy! */ 810 /* stdin might have data for us, joy! */;
692 } 811 }
693 812
694 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 813 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
695 814
696</pre> 815</pre>
697 </dd> 816 </dd>
698 <dt>ev_feed_event (loop, watcher, int events)</dt> 817 <dt>ev_feed_event (loop, watcher, int events)</dt>
699 <dd> 818 <dd>
700 <p>Feeds the given event set into the event loop, as if the specified event 819 <p>Feeds the given event set into the event loop, as if the specified event
701has happened for the specified watcher (which must be a pointer to an 820had happened for the specified watcher (which must be a pointer to an
702initialised but not necessarily active event watcher).</p> 821initialised but not necessarily started event watcher).</p>
703 </dd> 822 </dd>
704 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 823 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
705 <dd> 824 <dd>
706 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 825 <p>Feed an event on the given fd, as if a file descriptor backend detected
826the given events it.</p>
707 </dd> 827 </dd>
708 <dt>ev_feed_signal_event (loop, int signum)</dt> 828 <dt>ev_feed_signal_event (loop, int signum)</dt>
709 <dd> 829 <dd>
710 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 830 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
711 </dd> 831 </dd>
712</dl> 832</dl>
833
834</div>
835<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
836<div id="LIBEVENT_EMULATION_CONTENT">
837<p>Libev offers a compatibility emulation layer for libevent. It cannot
838emulate the internals of libevent, so here are some usage hints:</p>
839<dl>
840 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
841 <dt>* The following members are fully supported: ev_base, ev_callback,
842ev_arg, ev_fd, ev_res, ev_events.</dt>
843 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
844maintained by libev, it does not work exactly the same way as in libevent (consider
845it a private API).</dt>
846 <dt>* Priorities are not currently supported. Initialising priorities
847will fail and all watchers will have the same priority, even though there
848is an ev_pri field.</dt>
849 <dt>* Other members are not supported.</dt>
850 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
851to use the libev header file and library.</dt>
852</dl>
853
854</div>
855<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
856<div id="C_SUPPORT_CONTENT">
857<p>TBD.</p>
713 858
714</div> 859</div>
715<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 860<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
716<div id="AUTHOR_CONTENT"> 861<div id="AUTHOR_CONTENT">
717<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 862<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

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