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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 09:12:14 2007" /> 9 <meta name="created" content="Thu Nov 22 13:28:34 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
… …
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). It also is quite 79loop mechanism itself (idle, prepare and check watchers). It also is quite
77fast (see a <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it 80fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing
78to libevent).</p> 81it to libevent for example).</p>
79 82
80</div> 83</div>
81<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>
82<div id="CONVENTIONS_CONTENT"> 85<div id="CONVENTIONS_CONTENT">
83<p>Libev is very configurable. In this manual the default configuration 86<p>Libev is very configurable. In this manual the default configuration
84will be described, which supports multiple event loops. For more info 87will be described, which supports multiple event loops. For more info
85about various configuraiton options please have a look at the file 88about various configuration options please have a look at the file
86<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
87support for multiple event loops, then all functions taking an initial 90support for multiple event loops, then all functions taking an initial
88argument 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>)
89will not have this argument.</p> 92will not have this argument.</p>
90 93
91</div> 94</div>
92<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>
93<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> 96<div id="TIME_REPRESENTATION_CONTENT">
94<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
95(fractional) number of seconds since the (POSIX) epoch (somewhere near 98(fractional) number of seconds since the (POSIX) epoch (somewhere near
96the 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
97called <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
98to 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>
99<dl> 108<dl>
100 <dt>ev_tstamp ev_time ()</dt> 109 <dt>ev_tstamp ev_time ()</dt>
101 <dd> 110 <dd>
102 <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>
103 </dd> 114 </dd>
104 <dt>int ev_version_major ()</dt> 115 <dt>int ev_version_major ()</dt>
105 <dt>int ev_version_minor ()</dt> 116 <dt>int ev_version_minor ()</dt>
106 <dd> 117 <dd>
107 <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
108you 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
109<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
110symbols <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
111version of the library your program was compiled against.</p> 122version of the library your program was compiled against.</p>
112 <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,
113as this indicates an incompatible change. Minor versions are usually 124as this indicates an incompatible change. Minor versions are usually
114compatible to older versions, so a larger minor version alone is usually 125compatible to older versions, so a larger minor version alone is usually
115not a problem.</p> 126not a problem.</p>
116 </dd> 127 </dd>
117 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 128 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
118 <dd> 129 <dd>
119 <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
120realloc function). It is used to allocate and free memory (no surprises 131realloc C function, the semantics are identical). It is used to allocate
121here). If it returns zero when memory needs to be allocated, the library 132and free memory (no surprises here). If it returns zero when memory
122might abort or take some potentially destructive action. The default is 133needs to be allocated, the library might abort or take some potentially
123your system realloc function.</p> 134destructive action. The default is your system realloc function.</p>
124 <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,
125free 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,
126or 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>
127 </dd> 138 </dd>
128 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 139 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
129 <dd> 140 <dd>
130 <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
131as failed select, poll, epoll_wait). The message is a printable string 142as failed select, poll, epoll_wait). The message is a printable string
132indicating the system call or subsystem causing the problem. If this 143indicating the system call or subsystem causing the problem. If this
133callback 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
134matter what, when it returns. That is, libev will geenrally retry the 145matter what, when it returns. That is, libev will generally retry the
135requested 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
136(such as abort).</p> 147(such as abort).</p>
137 </dd> 148 </dd>
138</dl> 149</dl>
139 150
… …
142<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 153<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
143<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
144types 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
145events, and dynamically created loops which do not.</p> 156events, and dynamically created loops which do not.</p>
146<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
147in 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
148create, you also create another event loop. Libev itself does no lockign 159create, you also create another event loop. Libev itself does no locking
149whatsoever, 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
150lock (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>
151<dl> 163<dl>
152 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 164 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
153 <dd> 165 <dd>
154 <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
155yet 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
156false. 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
157flags).</p> 169flags).</p>
158 <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
159function.</p> 171function.</p>
160 <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
161backends 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>
162 <p>It supports the following flags:</p> 174 <p>It supports the following flags:</p>
163 <p> 175 <p>
164 <dl> 176 <dl>
165 <dt>EVFLAG_AUTO</dt> 177 <dt><code>EVFLAG_AUTO</code></dt>
166 <dd> 178 <dd>
167 <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
168thing, believe me).</p> 180thing, believe me).</p>
169 </dd> 181 </dd>
170 <dt>EVFLAG_NOENV</dt> 182 <dt><code>EVFLAG_NOENV</code></dt>
171 <dd>
172 <p>If this flag bit is ored into the flag value then libev will <i>not</i> look
173at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this
174environment variable will override the flags completely. This is useful
175to try out specific backends to tets their performance, or to work around
176bugs.</p>
177 </dd> 183 <dd>
178 <dt>EVMETHOD_SELECT portable select backend</dt> 184 <p>If this flag bit is ored into the flag value (or the program runs setuid
179 <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> 185or setgid) then libev will <i>not</i> look at the environment variable
180 <dt>EVMETHOD_EPOLL linux only</dt> 186<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181 <dt>EVMETHOD_KQUEUE some bsds only</dt> 187override the flags completely if it is found in the environment. This is
182 <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> 188useful to try out specific backends to test their performance, or to work
183 <dt>EVMETHOD_PORT solaris 10 only</dt> 189around bugs.</p>
184 <dd> 190 </dd>
185 <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>
186backends will be tried (in the reverse order as given here). If one are 192 <dd>
187specified, 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 that wouldn't be tried
243with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
244<code>EVMETHOD_ALL &amp; ~EVMETHOD_KQUEUE</code>.</p>
188 </dd> 245 </dd>
189 </dl> 246 </dl>
190 </p> 247 </p>
248 <p>If one or more of these are ored into the flags value, then only these
249backends will be tried (in the reverse order as given here). If none are
250specified, most compiled-in backend will be tried, usually in reverse
251order of their flag values :)</p>
191 </dd> 252 </dd>
192 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 253 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
193 <dd> 254 <dd>
194 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 255 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
195always distinct from the default loop. Unlike the default loop, it cannot 256always distinct from the default loop. Unlike the default loop, it cannot
… …
198 </dd> 259 </dd>
199 <dt>ev_default_destroy ()</dt> 260 <dt>ev_default_destroy ()</dt>
200 <dd> 261 <dd>
201 <p>Destroys the default loop again (frees all memory and kernel state 262 <p>Destroys the default loop again (frees all memory and kernel state
202etc.). This stops all registered event watchers (by not touching them in 263etc.). This stops all registered event watchers (by not touching them in
203any way whatsoever, although you cnanot rely on this :).</p> 264any way whatsoever, although you cannot rely on this :).</p>
204 </dd> 265 </dd>
205 <dt>ev_loop_destroy (loop)</dt> 266 <dt>ev_loop_destroy (loop)</dt>
206 <dd> 267 <dd>
207 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 268 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
208earlier call to <code>ev_loop_new</code>.</p> 269earlier call to <code>ev_loop_new</code>.</p>
… …
214after forking, in either the parent or child process (or both, but that 275after forking, in either the parent or child process (or both, but that
215again makes little sense).</p> 276again makes little sense).</p>
216 <p>You <i>must</i> call this function after forking if and only if you want to 277 <p>You <i>must</i> call this function after forking if and only if you want to
217use the event library in both processes. If you just fork+exec, you don't 278use the event library in both processes. If you just fork+exec, you don't
218have to call it.</p> 279have to call it.</p>
219 <p>The function itself is quite fast and its usually not a problem to call 280 <p>The function itself is quite fast and it's usually not a problem to call
220it just in case after a fork. To make this easy, the function will fit in 281it just in case after a fork. To make this easy, the function will fit in
221quite nicely into a call to <code>pthread_atfork</code>:</p> 282quite nicely into a call to <code>pthread_atfork</code>:</p>
222<pre> pthread_atfork (0, 0, ev_default_fork); 283<pre> pthread_atfork (0, 0, ev_default_fork);
223 284
224</pre> 285</pre>
… …
232 <dt>unsigned int ev_method (loop)</dt> 293 <dt>unsigned int ev_method (loop)</dt>
233 <dd> 294 <dd>
234 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 295 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in
235use.</p> 296use.</p>
236 </dd> 297 </dd>
237 <dt>ev_tstamp = ev_now (loop)</dt> 298 <dt>ev_tstamp ev_now (loop)</dt>
238 <dd> 299 <dd>
239 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 300 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
240got events and started processing them. This timestamp does not change 301got events and started processing them. This timestamp does not change
241as long as callbacks are being processed, and this is also the base time 302as long as callbacks are being processed, and this is also the base time
242used for relative timers. You can treat it as the timestamp of the event 303used for relative timers. You can treat it as the timestamp of the event
… …
249events.</p> 310events.</p>
250 <p>If the flags argument is specified as 0, it will not return until either 311 <p>If the flags argument is specified as 0, it will not return until either
251no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 312no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
252 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 313 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
253those events and any outstanding ones, but will not block your process in 314those events and any outstanding ones, but will not block your process in
254case there are no events.</p> 315case there are no events and will return after one iteration of the loop.</p>
255 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 316 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
256neccessary) and will handle those and any outstanding ones. It will block 317neccessary) and will handle those and any outstanding ones. It will block
257your process until at least one new event arrives.</p> 318your process until at least one new event arrives, and will return after
319one iteration of the loop.</p>
258 <p>This flags value could be used to implement alternative looping 320 <p>This flags value could be used to implement alternative looping
259constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 321constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
260more generic mechanism.</p> 322more generic mechanism.</p>
323 <p>Here are the gory details of what ev_loop does:</p>
324<pre> 1. If there are no active watchers (reference count is zero), return.
325 2. Queue and immediately call all prepare watchers.
326 3. If we have been forked, recreate the kernel state.
327 4. Update the kernel state with all outstanding changes.
328 5. Update the &quot;event loop time&quot;.
329 6. Calculate for how long to block.
330 7. Block the process, waiting for events.
331 8. Update the &quot;event loop time&quot; and do time jump handling.
332 9. Queue all outstanding timers.
333 10. Queue all outstanding periodics.
334 11. If no events are pending now, queue all idle watchers.
335 12. Queue all check watchers.
336 13. Call all queued watchers in reverse order (i.e. check watchers first).
337 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
338 was used, return, otherwise continue with step #1.
339
340</pre>
261 </dd> 341 </dd>
262 <dt>ev_unloop (loop, how)</dt> 342 <dt>ev_unloop (loop, how)</dt>
263 <dd> 343 <dd>
264 <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument 344 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
345has processed all outstanding events). The <code>how</code> argument must be either
265must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> 346<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
266call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> 347<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
267calls return.</p>
268 </dd> 348 </dd>
269 <dt>ev_ref (loop)</dt> 349 <dt>ev_ref (loop)</dt>
270 <dt>ev_unref (loop)</dt> 350 <dt>ev_unref (loop)</dt>
271 <dd> 351 <dd>
272 <p>Ref/unref can be used to add or remove a refcount on the event loop: Every 352 <p>Ref/unref can be used to add or remove a reference count on the event
273watcher keeps one reference. If you have a long-runing watcher you never 353loop: Every watcher keeps one reference, and as long as the reference
274unregister that should not keep ev_loop from running, ev_unref() after 354count is nonzero, <code>ev_loop</code> will not return on its own. If you have
275starting, and ev_ref() before stopping it. Libev itself uses this for 355a watcher you never unregister that should not keep <code>ev_loop</code> from
276example for its internal signal pipe: It is not visible to you as a user 356returning, ev_unref() after starting, and ev_ref() before stopping it. For
277and should not keep <code>ev_loop</code> from exiting if the work is done. It is 357example, libev itself uses this for its internal signal pipe: It is not
278also an excellent way to do this for generic recurring timers or from 358visible to the libev user and should not keep <code>ev_loop</code> from exiting if
279within third-party libraries. Just remember to unref after start and ref 359no event watchers registered by it are active. It is also an excellent
280before stop.</p> 360way to do this for generic recurring timers or from within third-party
361libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
281 </dd> 362 </dd>
282</dl> 363</dl>
283 364
284</div> 365</div>
285<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 366<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
286<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 367<div id="ANATOMY_OF_A_WATCHER_CONTENT">
287<p>A watcher is a structure that you create and register to record your 368<p>A watcher is a structure that you create and register to record your
288interest in some event. For instance, if you want to wait for STDIN to 369interest in some event. For instance, if you want to wait for STDIN to
289become readable, you would create an ev_io watcher for that:</p> 370become readable, you would create an <code>ev_io</code> watcher for that:</p>
290<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 371<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
291 { 372 {
292 ev_io_stop (w); 373 ev_io_stop (w);
293 ev_unloop (loop, EVUNLOOP_ALL); 374 ev_unloop (loop, EVUNLOOP_ALL);
294 } 375 }
… …
318*)</code>), and you can stop watching for events at any time by calling the 399*)</code>), and you can stop watching for events at any time by calling the
319corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 400corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
320<p>As long as your watcher is active (has been started but not stopped) you 401<p>As long as your watcher is active (has been started but not stopped) you
321must not touch the values stored in it. Most specifically you must never 402must not touch the values stored in it. Most specifically you must never
322reinitialise it or call its set method.</p> 403reinitialise it or call its set method.</p>
323<p>You cna check whether an event is active by calling the <code>ev_is_active 404<p>You can check whether an event is active by calling the <code>ev_is_active
324(watcher *)</code> macro. To see whether an event is outstanding (but the 405(watcher *)</code> macro. To see whether an event is outstanding (but the
325callback for it has not been called yet) you cna use the <code>ev_is_pending 406callback for it has not been called yet) you can use the <code>ev_is_pending
326(watcher *)</code> macro.</p> 407(watcher *)</code> macro.</p>
327<p>Each and every callback receives the event loop pointer as first, the 408<p>Each and every callback receives the event loop pointer as first, the
328registered watcher structure as second, and a bitset of received events as 409registered watcher structure as second, and a bitset of received events as
329third argument.</p> 410third argument.</p>
330<p>The rceeived events usually include a single bit per event type received 411<p>The received events usually include a single bit per event type received
331(you can receive multiple events at the same time). The possible bit masks 412(you can receive multiple events at the same time). The possible bit masks
332are:</p> 413are:</p>
333<dl> 414<dl>
334 <dt>EV_READ</dt> 415 <dt><code>EV_READ</code></dt>
335 <dt>EV_WRITE</dt> 416 <dt><code>EV_WRITE</code></dt>
336 <dd> 417 <dd>
337 <p>The file descriptor in the ev_io watcher has become readable and/or 418 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
338writable.</p> 419writable.</p>
339 </dd> 420 </dd>
340 <dt>EV_TIMEOUT</dt> 421 <dt><code>EV_TIMEOUT</code></dt>
341 <dd>
342 <p>The ev_timer watcher has timed out.</p>
343 </dd> 422 <dd>
344 <dt>EV_PERIODIC</dt> 423 <p>The <code>ev_timer</code> watcher has timed out.</p>
345 <dd> 424 </dd>
346 <p>The ev_periodic watcher has timed out.</p> 425 <dt><code>EV_PERIODIC</code></dt>
347 </dd> 426 <dd>
348 <dt>EV_SIGNAL</dt> 427 <p>The <code>ev_periodic</code> watcher has timed out.</p>
349 <dd> 428 </dd>
429 <dt><code>EV_SIGNAL</code></dt>
430 <dd>
350 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 431 <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
351 </dd>
352 <dt>EV_CHILD</dt>
353 <dd> 432 </dd>
433 <dt><code>EV_CHILD</code></dt>
434 <dd>
354 <p>The pid specified in the ev_child watcher has received a status change.</p> 435 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
355 </dd>
356 <dt>EV_IDLE</dt>
357 <dd> 436 </dd>
437 <dt><code>EV_IDLE</code></dt>
438 <dd>
358 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 439 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
359 </dd>
360 <dt>EV_PREPARE</dt>
361 <dt>EV_CHECK</dt>
362 <dd> 440 </dd>
441 <dt><code>EV_PREPARE</code></dt>
442 <dt><code>EV_CHECK</code></dt>
443 <dd>
363 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 444 <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
364to gather new events, and all ev_check watchers are invoked just after 445to gather new events, and all <code>ev_check</code> watchers are invoked just after
365<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 446<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
366received events. Callbacks of both watcher types can start and stop as 447received events. Callbacks of both watcher types can start and stop as
367many watchers as they want, and all of them will be taken into account 448many watchers as they want, and all of them will be taken into account
368(for example, a ev_prepare watcher might start an idle watcher to keep 449(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
369<code>ev_loop</code> from blocking).</p> 450<code>ev_loop</code> from blocking).</p>
370 </dd> 451 </dd>
371 <dt>EV_ERROR</dt> 452 <dt><code>EV_ERROR</code></dt>
372 <dd> 453 <dd>
373 <p>An unspecified error has occured, the watcher has been stopped. This might 454 <p>An unspecified error has occured, the watcher has been stopped. This might
374happen because the watcher could not be properly started because libev 455happen because the watcher could not be properly started because libev
375ran out of memory, a file descriptor was found to be closed or any other 456ran out of memory, a file descriptor was found to be closed or any other
376problem. You best act on it by reporting the problem and somehow coping 457problem. You best act on it by reporting the problem and somehow coping
… …
385 466
386</div> 467</div>
387<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 468<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
388<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 469<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
389<p>Each watcher has, by default, a member <code>void *data</code> that you can change 470<p>Each watcher has, by default, a member <code>void *data</code> that you can change
390and read at any time, libev will completely ignore it. This cna be used 471and read at any time, libev will completely ignore it. This can be used
391to associate arbitrary data with your watcher. If you need more data and 472to associate arbitrary data with your watcher. If you need more data and
392don't want to allocate memory and store a pointer to it in that data 473don't want to allocate memory and store a pointer to it in that data
393member, you can also &quot;subclass&quot; the watcher type and provide your own 474member, you can also &quot;subclass&quot; the watcher type and provide your own
394data:</p> 475data:</p>
395<pre> struct my_io 476<pre> struct my_io
… …
422<div id="WATCHER_TYPES_CONTENT"> 503<div id="WATCHER_TYPES_CONTENT">
423<p>This section describes each watcher in detail, but will not repeat 504<p>This section describes each watcher in detail, but will not repeat
424information given in the last section.</p> 505information given in the last section.</p>
425 506
426</div> 507</div>
427<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 508<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
428<div id="struct_ev_io_is_my_file_descriptor_r-2"> 509<div id="code_ev_io_code_is_this_file_descrip-2">
429<p>I/O watchers check whether a file descriptor is readable or writable 510<p>I/O watchers check whether a file descriptor is readable or writable
430in each iteration of the event loop (This behaviour is called 511in each iteration of the event loop (This behaviour is called
431level-triggering because you keep receiving events as long as the 512level-triggering because you keep receiving events as long as the
432condition persists. Remember you cna stop the watcher if you don't want to 513condition persists. Remember you can stop the watcher if you don't want to
433act on the event and neither want to receive future events).</p> 514act on the event and neither want to receive future events).</p>
515<p>In general you can register as many read and/or write event watchers per
516fd as you want (as long as you don't confuse yourself). Setting all file
517descriptors to non-blocking mode is also usually a good idea (but not
518required if you know what you are doing).</p>
519<p>You have to be careful with dup'ed file descriptors, though. Some backends
520(the linux epoll backend is a notable example) cannot handle dup'ed file
521descriptors correctly if you register interest in two or more fds pointing
522to the same underlying file/socket etc. description (that is, they share
523the same underlying &quot;file open&quot;).</p>
524<p>If you must do this, then force the use of a known-to-be-good backend
525(at the time of this writing, this includes only EVMETHOD_SELECT and
526EVMETHOD_POLL).</p>
434<dl> 527<dl>
435 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 528 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
436 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 529 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
437 <dd> 530 <dd>
438 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 531 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
439events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 532events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
440EV_WRITE</code> to receive the given events.</p> 533EV_WRITE</code> to receive the given events.</p>
441 </dd> 534 </dd>
442</dl> 535</dl>
443 536
444</div> 537</div>
445<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 538<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
446<div id="struct_ev_timer_relative_and_optiona-2"> 539<div id="code_ev_timer_code_relative_and_opti-2">
447<p>Timer watchers are simple relative timers that generate an event after a 540<p>Timer watchers are simple relative timers that generate an event after a
448given time, and optionally repeating in regular intervals after that.</p> 541given time, and optionally repeating in regular intervals after that.</p>
449<p>The timers are based on real time, that is, if you register an event that 542<p>The timers are based on real time, that is, if you register an event that
450times out after an hour and youreset your system clock to last years 543times out after an hour and you reset your system clock to last years
451time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 544time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
452detecting time jumps is hard, and soem inaccuracies are unavoidable (the 545detecting time jumps is hard, and some inaccuracies are unavoidable (the
453monotonic clock option helps a lot here).</p> 546monotonic clock option helps a lot here).</p>
547<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
548time. This is usually the right thing as this timestamp refers to the time
549of the event triggering whatever timeout you are modifying/starting. If
550you suspect event processing to be delayed and you <i>need</i> to base the timeout
551on the current time, use something like this to adjust for this:</p>
552<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
553
554</pre>
555<p>The callback is guarenteed to be invoked only when its timeout has passed,
556but if multiple timers become ready during the same loop iteration then
557order of execution is undefined.</p>
454<dl> 558<dl>
455 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 559 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
456 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 560 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
457 <dd> 561 <dd>
458 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 562 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
460timer will automatically be configured to trigger again <code>repeat</code> seconds 564timer will automatically be configured to trigger again <code>repeat</code> seconds
461later, again, and again, until stopped manually.</p> 565later, again, and again, until stopped manually.</p>
462 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 566 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
463configure a timer to trigger every 10 seconds, then it will trigger at 567configure a timer to trigger every 10 seconds, then it will trigger at
464exactly 10 second intervals. If, however, your program cannot keep up with 568exactly 10 second intervals. If, however, your program cannot keep up with
465the timer (ecause it takes longer than those 10 seconds to do stuff) the 569the timer (because it takes longer than those 10 seconds to do stuff) the
466timer will not fire more than once per event loop iteration.</p> 570timer will not fire more than once per event loop iteration.</p>
467 </dd> 571 </dd>
468 <dt>ev_timer_again (loop)</dt> 572 <dt>ev_timer_again (loop)</dt>
469 <dd> 573 <dd>
470 <p>This will act as if the timer timed out and restart it again if it is 574 <p>This will act as if the timer timed out and restart it again if it is
… …
474value), or reset the running timer to the repeat value.</p> 578value), or reset the running timer to the repeat value.</p>
475 <p>This sounds a bit complicated, but here is a useful and typical 579 <p>This sounds a bit complicated, but here is a useful and typical
476example: Imagine you have a tcp connection and you want a so-called idle 580example: Imagine you have a tcp connection and you want a so-called idle
477timeout, that is, you want to be called when there have been, say, 60 581timeout, that is, you want to be called when there have been, say, 60
478seconds of inactivity on the socket. The easiest way to do this is to 582seconds of inactivity on the socket. The easiest way to do this is to
479configure an ev_timer with after=repeat=60 and calling ev_timer_again each 583configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
480time you successfully read or write some data. If you go into an idle 584time you successfully read or write some data. If you go into an idle
481state where you do not expect data to travel on the socket, you can stop 585state where you do not expect data to travel on the socket, you can stop
482the timer, and again will automatically restart it if need be.</p> 586the timer, and again will automatically restart it if need be.</p>
483 </dd> 587 </dd>
484</dl> 588</dl>
485 589
486</div> 590</div>
487<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2> 591<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
488<div id="ev_periodic_to_cron_or_not_to_cron_i-2"> 592<div id="code_ev_periodic_code_to_cron_or_not-2">
489<p>Periodic watchers are also timers of a kind, but they are very versatile 593<p>Periodic watchers are also timers of a kind, but they are very versatile
490(and unfortunately a bit complex).</p> 594(and unfortunately a bit complex).</p>
491<p>Unlike ev_timer's, they are not based on real time (or relative time) 595<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
492but on wallclock time (absolute time). You can tell a periodic watcher 596but on wallclock time (absolute time). You can tell a periodic watcher
493to trigger &quot;at&quot; some specific point in time. For example, if you tell a 597to trigger &quot;at&quot; some specific point in time. For example, if you tell a
494periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 598periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now ()
495+ 10.&gt;) and then reset your system clock to the last year, then it will 599+ 10.&gt;) and then reset your system clock to the last year, then it will
496take a year to trigger the event (unlike an ev_timer, which would trigger 600take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
497roughly 10 seconds later and of course not if you reset your system time 601roughly 10 seconds later and of course not if you reset your system time
498again).</p> 602again).</p>
499<p>They can also be used to implement vastly more complex timers, such as 603<p>They can also be used to implement vastly more complex timers, such as
500triggering an event on eahc midnight, local time.</p> 604triggering an event on eahc midnight, local time.</p>
605<p>As with timers, the callback is guarenteed to be invoked only when the
606time (<code>at</code>) has been passed, but if multiple periodic timers become ready
607during the same loop iteration then order of execution is undefined.</p>
501<dl> 608<dl>
502 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 609 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
503 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 610 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
504 <dd> 611 <dd>
505 <p>Lots of arguments, lets sort it out... There are basically three modes of 612 <p>Lots of arguments, lets sort it out... There are basically three modes of
506operation, and we will explain them from simplest to complex:</p> 613operation, and we will explain them from simplest to complex:</p>
507
508
509
510
511 <p> 614 <p>
512 <dl> 615 <dl>
513 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 616 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
514 <dd> 617 <dd>
515 <p>In this configuration the watcher triggers an event at the wallclock time 618 <p>In this configuration the watcher triggers an event at the wallclock time
… …
527<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 630<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
528 631
529</pre> 632</pre>
530 <p>This doesn't mean there will always be 3600 seconds in between triggers, 633 <p>This doesn't mean there will always be 3600 seconds in between triggers,
531but only that the the callback will be called when the system time shows a 634but only that the the callback will be called when the system time shows a
532full hour (UTC), or more correct, when the system time is evenly divisible 635full hour (UTC), or more correctly, when the system time is evenly divisible
533by 3600.</p> 636by 3600.</p>
534 <p>Another way to think about it (for the mathematically inclined) is that 637 <p>Another way to think about it (for the mathematically inclined) is that
535ev_periodic will try to run the callback in this mode at the next possible 638<code>ev_periodic</code> will try to run the callback in this mode at the next possible
536time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 639time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
537 </dd> 640 </dd>
538 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 641 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
539 <dd> 642 <dd>
540 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 643 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
541ignored. Instead, each time the periodic watcher gets scheduled, the 644ignored. Instead, each time the periodic watcher gets scheduled, the
542reschedule callback will be called with the watcher as first, and the 645reschedule callback will be called with the watcher as first, and the
543current time as second argument.</p> 646current time as second argument.</p>
544 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 647 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
545periodic watcher, ever, or make any event loop modificstions</i>. If you need 648ever, or make any event loop modifications</i>. If you need to stop it,
546to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 649return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
650starting a prepare watcher).</p>
547 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 651 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
548ev_tstamp now)&gt;, e.g.:</p> 652ev_tstamp now)</code>, e.g.:</p>
549<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 653<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
550 { 654 {
551 return now + 60.; 655 return now + 60.;
552 } 656 }
553 657
554</pre> 658</pre>
555 <p>It must return the next time to trigger, based on the passed time value 659 <p>It must return the next time to trigger, based on the passed time value
556(that is, the lowest time value larger than to the second argument). It 660(that is, the lowest time value larger than to the second argument). It
557will usually be called just before the callback will be triggered, but 661will usually be called just before the callback will be triggered, but
558might be called at other times, too.</p> 662might be called at other times, too.</p>
663 <p>NOTE: <i>This callback must always return a time that is later than the
664passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
559 <p>This can be used to create very complex timers, such as a timer that 665 <p>This can be used to create very complex timers, such as a timer that
560triggers on each midnight, local time. To do this, you would calculate the 666triggers on each midnight, local time. To do this, you would calculate the
561next midnight after <code>now</code> and return the timestamp value for this. How you do this 667next midnight after <code>now</code> and return the timestamp value for this. How
562is, again, up to you (but it is not trivial).</p> 668you do this is, again, up to you (but it is not trivial, which is the main
669reason I omitted it as an example).</p>
563 </dd> 670 </dd>
564 </dl> 671 </dl>
565 </p> 672 </p>
566 </dd> 673 </dd>
567 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 674 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
572program when the crontabs have changed).</p> 679program when the crontabs have changed).</p>
573 </dd> 680 </dd>
574</dl> 681</dl>
575 682
576</div> 683</div>
577<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 684<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
578<div id="ev_signal_signal_me_when_a_signal_ge-2"> 685<div id="code_ev_signal_code_signal_me_when_a-2">
579<p>Signal watchers will trigger an event when the process receives a specific 686<p>Signal watchers will trigger an event when the process receives a specific
580signal one or more times. Even though signals are very asynchronous, libev 687signal one or more times. Even though signals are very asynchronous, libev
581will try its best to deliver signals synchronously, i.e. as part of the 688will try it's best to deliver signals synchronously, i.e. as part of the
582normal event processing, like any other event.</p> 689normal event processing, like any other event.</p>
583<p>You cna configure as many watchers as you like per signal. Only when the 690<p>You can configure as many watchers as you like per signal. Only when the
584first watcher gets started will libev actually register a signal watcher 691first watcher gets started will libev actually register a signal watcher
585with the kernel (thus it coexists with your own signal handlers as long 692with the kernel (thus it coexists with your own signal handlers as long
586as you don't register any with libev). Similarly, when the last signal 693as you don't register any with libev). Similarly, when the last signal
587watcher for a signal is stopped libev will reset the signal handler to 694watcher for a signal is stopped libev will reset the signal handler to
588SIG_DFL (regardless of what it was set to before).</p> 695SIG_DFL (regardless of what it was set to before).</p>
… …
594of the <code>SIGxxx</code> constants).</p> 701of the <code>SIGxxx</code> constants).</p>
595 </dd> 702 </dd>
596</dl> 703</dl>
597 704
598</div> 705</div>
599<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 706<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
600<div id="ev_child_wait_for_pid_status_changes-2"> 707<div id="code_ev_child_code_wait_for_pid_stat-2">
601<p>Child watchers trigger when your process receives a SIGCHLD in response to 708<p>Child watchers trigger when your process receives a SIGCHLD in response to
602some child status changes (most typically when a child of yours dies).</p> 709some child status changes (most typically when a child of yours dies).</p>
603<dl> 710<dl>
604 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 711 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
605 <dt>ev_child_set (ev_child *, int pid)</dt> 712 <dt>ev_child_set (ev_child *, int pid)</dt>
606 <dd> 713 <dd>
607 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 714 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
608<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 715<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
609at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 716at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
610the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 717the status word (use the macros from <code>sys/wait.h</code> and see your systems
718<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
611contains the pid of the process causing the status change.</p> 719process causing the status change.</p>
612 </dd> 720 </dd>
613</dl> 721</dl>
614 722
615</div> 723</div>
616<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 724<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
617<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 725<div id="code_ev_idle_code_when_you_ve_got_no-2">
618<p>Idle watchers trigger events when there are no other I/O or timer (or 726<p>Idle watchers trigger events when there are no other events are pending
619periodic) events pending. That is, as long as your process is busy 727(prepare, check and other idle watchers do not count). That is, as long
620handling sockets or timeouts it will not be called. But when your process 728as your process is busy handling sockets or timeouts (or even signals,
621is idle all idle watchers are being called again and again - until 729imagine) it will not be triggered. But when your process is idle all idle
730watchers are being called again and again, once per event loop iteration -
622stopped, that is, or your process receives more events.</p> 731until stopped, that is, or your process receives more events and becomes
732busy.</p>
623<p>The most noteworthy effect is that as long as any idle watchers are 733<p>The most noteworthy effect is that as long as any idle watchers are
624active, the process will not block when waiting for new events.</p> 734active, the process will not block when waiting for new events.</p>
625<p>Apart from keeping your process non-blocking (which is a useful 735<p>Apart from keeping your process non-blocking (which is a useful
626effect on its own sometimes), idle watchers are a good place to do 736effect on its own sometimes), idle watchers are a good place to do
627&quot;pseudo-background processing&quot;, or delay processing stuff to after the 737&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
634believe me.</p> 744believe me.</p>
635 </dd> 745 </dd>
636</dl> 746</dl>
637 747
638</div> 748</div>
639<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 749<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
640<div id="prepare_and_check_your_hooks_into_th-2"> 750<div id="code_ev_prepare_code_and_code_ev_che-2">
641<p>Prepare and check watchers usually (but not always) are used in 751<p>Prepare and check watchers are usually (but not always) used in tandem:
642tandom. Prepare watchers get invoked before the process blocks and check 752prepare watchers get invoked before the process blocks and check watchers
643watchers afterwards.</p> 753afterwards.</p>
644<p>Their main purpose is to integrate other event mechanisms into libev. This 754<p>Their main purpose is to integrate other event mechanisms into libev. This
645could be used, for example, to track variable changes, implement your own 755could be used, for example, to track variable changes, implement your own
646watchers, integrate net-snmp or a coroutine library and lots more.</p> 756watchers, integrate net-snmp or a coroutine library and lots more.</p>
647<p>This is done by examining in each prepare call which file descriptors need 757<p>This is done by examining in each prepare call which file descriptors need
648to be watched by the other library, registering ev_io watchers for them 758to be watched by the other library, registering <code>ev_io</code> watchers for
649and starting an ev_timer watcher for any timeouts (many libraries provide 759them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
650just this functionality). Then, in the check watcher you check for any 760provide just this functionality). Then, in the check watcher you check for
651events that occured (by making your callbacks set soem flags for example) 761any events that occured (by checking the pending status of all watchers
652and call back into the library.</p> 762and stopping them) and call back into the library. The I/O and timer
763callbacks will never actually be called (but must be valid nevertheless,
764because you never know, you know?).</p>
653<p>As another example, the perl Coro module uses these hooks to integrate 765<p>As another example, the Perl Coro module uses these hooks to integrate
654coroutines into libev programs, by yielding to other active coroutines 766coroutines into libev programs, by yielding to other active coroutines
655during each prepare and only letting the process block if no coroutines 767during each prepare and only letting the process block if no coroutines
656are ready to run.</p> 768are ready to run (it's actually more complicated: it only runs coroutines
769with priority higher than or equal to the event loop and one coroutine
770of lower priority, but only once, using idle watchers to keep the event
771loop from blocking if lower-priority coroutines are active, thus mapping
772low-priority coroutines to idle/background tasks).</p>
657<dl> 773<dl>
658 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 774 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
659 <dt>ev_check_init (ev_check *, callback)</dt> 775 <dt>ev_check_init (ev_check *, callback)</dt>
660 <dd> 776 <dd>
661 <p>Initialises and configures the prepare or check watcher - they have no 777 <p>Initialises and configures the prepare or check watcher - they have no
662parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 778parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
663macros, but using them is utterly, utterly pointless.</p> 779macros, but using them is utterly, utterly and completely pointless.</p>
664 </dd> 780 </dd>
665</dl> 781</dl>
666 782
667</div> 783</div>
668<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 784<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
669<div id="OTHER_FUNCTIONS_CONTENT"> 785<div id="OTHER_FUNCTIONS_CONTENT">
670<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 786<p>There are some other functions of possible interest. Described. Here. Now.</p>
671<dl> 787<dl>
672 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 788 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
673 <dd> 789 <dd>
674 <p>This function combines a simple timer and an I/O watcher, calls your 790 <p>This function combines a simple timer and an I/O watcher, calls your
675callback on whichever event happens first and automatically stop both 791callback on whichever event happens first and automatically stop both
676watchers. This is useful if you want to wait for a single event on an fd 792watchers. This is useful if you want to wait for a single event on an fd
677or timeout without havign to allocate/configure/start/stop/free one or 793or timeout without having to allocate/configure/start/stop/free one or
678more watchers yourself.</p> 794more watchers yourself.</p>
679 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 795 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
680ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 796is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
681will be craeted and started.</p> 797<code>events</code> set will be craeted and started.</p>
682 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 798 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
683started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 799started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
684= 0) will be started.</p> 800repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
801dubious value.</p>
685 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 802 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
686gets passed an events set (normally a combination of EV_ERROR, EV_READ, 803passed an <code>revents</code> set like normal event callbacks (a combination of
687EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 804<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
805value passed to <code>ev_once</code>:</p>
688<pre> static void stdin_ready (int revents, void *arg) 806<pre> static void stdin_ready (int revents, void *arg)
689 { 807 {
690 if (revents &amp; EV_TIMEOUT) 808 if (revents &amp; EV_TIMEOUT)
691 /* doh, nothing entered */ 809 /* doh, nothing entered */;
692 else if (revents &amp; EV_READ) 810 else if (revents &amp; EV_READ)
693 /* stdin might have data for us, joy! */ 811 /* stdin might have data for us, joy! */;
694 } 812 }
695 813
696 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 814 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
697 815
698</pre> 816</pre>
699 </dd> 817 </dd>
700 <dt>ev_feed_event (loop, watcher, int events)</dt> 818 <dt>ev_feed_event (loop, watcher, int events)</dt>
701 <dd> 819 <dd>
702 <p>Feeds the given event set into the event loop, as if the specified event 820 <p>Feeds the given event set into the event loop, as if the specified event
703has happened for the specified watcher (which must be a pointer to an 821had happened for the specified watcher (which must be a pointer to an
704initialised but not necessarily active event watcher).</p> 822initialised but not necessarily started event watcher).</p>
705 </dd> 823 </dd>
706 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 824 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
707 <dd> 825 <dd>
708 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 826 <p>Feed an event on the given fd, as if a file descriptor backend detected
827the given events it.</p>
709 </dd> 828 </dd>
710 <dt>ev_feed_signal_event (loop, int signum)</dt> 829 <dt>ev_feed_signal_event (loop, int signum)</dt>
711 <dd> 830 <dd>
712 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 831 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
713 </dd> 832 </dd>
714</dl> 833</dl>
834
835</div>
836<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
837<div id="LIBEVENT_EMULATION_CONTENT">
838<p>Libev offers a compatibility emulation layer for libevent. It cannot
839emulate the internals of libevent, so here are some usage hints:</p>
840<dl>
841 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
842 <dt>* The following members are fully supported: ev_base, ev_callback,
843ev_arg, ev_fd, ev_res, ev_events.</dt>
844 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
845maintained by libev, it does not work exactly the same way as in libevent (consider
846it a private API).</dt>
847 <dt>* Priorities are not currently supported. Initialising priorities
848will fail and all watchers will have the same priority, even though there
849is an ev_pri field.</dt>
850 <dt>* Other members are not supported.</dt>
851 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
852to use the libev header file and library.</dt>
853</dl>
854
855</div>
856<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
857<div id="C_SUPPORT_CONTENT">
858<p>TBD.</p>
715 859
716</div> 860</div>
717<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 861<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
718<div id="AUTHOR_CONTENT"> 862<div id="AUTHOR_CONTENT">
719<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 863<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

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