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

Comparing libev/ev.html (file contents):
Revision 1.1 by root, Mon Nov 12 07:58:13 2007 UTC vs.
Revision 1.34 by root, Fri Nov 23 15:26:08 2007 UTC

… …
4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Mon Nov 12 08:58:02 2007" /> 9 <meta name="created" content="Fri Nov 23 16:26:06 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">ev_periodic</a></li> 32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
32<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li> 33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
33<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li> 34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>
34<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li> 35<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>
35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> 36<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>
36</ul> 37</ul>
37</li> 38</li>
38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
39<li><a href="#AUTHOR">AUTHOR</a> 42<li><a href="#AUTHOR">AUTHOR</a>
40</li> 43</li>
41</ul><hr /> 44</ul><hr />
42<!-- INDEX END --> 45<!-- INDEX END -->
43 46
… …
55</div> 58</div>
56<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 59<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>
57<div id="DESCRIPTION_CONTENT"> 60<div id="DESCRIPTION_CONTENT">
58<p>Libev is an event loop: you register interest in certain events (such as a 61<p>Libev is an event loop: you register interest in certain events (such as a
59file descriptor being readable or a timeout occuring), and it will manage 62file descriptor being readable or a timeout occuring), and it will manage
60these event sources and provide your program events.</p> 63these event sources and provide your program with events.</p>
61<p>To do this, it must take more or less complete control over your process 64<p>To do this, it must take more or less complete control over your process
62(or thread) by executing the <i>event loop</i> handler, and will then 65(or thread) by executing the <i>event loop</i> handler, and will then
63communicate events via a callback mechanism.</p> 66communicate events via a callback mechanism.</p>
64<p>You register interest in certain events by registering so-called <i>event 67<p>You register interest in certain events by registering so-called <i>event
65watchers</i>, which are relatively small C structures you initialise with the 68watchers</i>, which are relatively small C structures you initialise with the
… …
71<div id="FEATURES_CONTENT"> 74<div id="FEATURES_CONTENT">
72<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 75<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific
73kqueue mechanisms for file descriptor events, relative timers, absolute 76kqueue mechanisms for file descriptor events, relative timers, absolute
74timers with customised rescheduling, signal events, process status change 77timers with customised rescheduling, signal events, process status change
75events (related to SIGCHLD), and event watchers dealing with the event 78events (related to SIGCHLD), and event watchers dealing with the event
76loop mechanism itself (idle, prepare and check watchers).</p> 79loop mechanism itself (idle, prepare and check watchers). It also is quite
80fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing
81it to libevent for example).</p>
77 82
78</div> 83</div>
79<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 84<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
80<div id="CONVENTIONS_CONTENT"> 85<div id="CONVENTIONS_CONTENT">
81<p>Libev is very configurable. In this manual the default configuration 86<p>Libev is very configurable. In this manual the default configuration
82will be described, which supports multiple event loops. For more info 87will be described, which supports multiple event loops. For more info
83about various configuraiton options please have a look at the file 88about various configuration options please have a look at the file
84<cite>README.embed</cite> in the libev distribution. If libev was configured without 89<cite>README.embed</cite> in the libev distribution. If libev was configured without
85support for multiple event loops, then all functions taking an initial 90support for multiple event loops, then all functions taking an initial
86argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 91argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
87will not have this argument.</p> 92will not have this argument.</p>
88 93
89</div> 94</div>
90<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 95<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
91<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> 96<div id="TIME_REPRESENTATION_CONTENT">
92<p>Libev represents time as a single floating point number. This type is 97<p>Libev represents time as a single floating point number, representing the
98(fractional) number of seconds since the (POSIX) epoch (somewhere near
99the beginning of 1970, details are complicated, don't ask). This type is
93called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 100called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
94to the double type in C.</p> 101to the double type in C.</p>
102
103</div>
104<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105<div id="GLOBAL_FUNCTIONS_CONTENT">
106<p>These functions can be called anytime, even before initialising the
107library in any way.</p>
95<dl> 108<dl>
96 <dt>ev_tstamp ev_time ()</dt> 109 <dt>ev_tstamp ev_time ()</dt>
97 <dd> 110 <dd>
98 <p>Returns the current time as libev would use it.</p> 111 <p>Returns the current time as libev would use it. 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>
99 </dd> 114 </dd>
100 <dt>int ev_version_major ()</dt> 115 <dt>int ev_version_major ()</dt>
101 <dt>int ev_version_minor ()</dt> 116 <dt>int ev_version_minor ()</dt>
102 <dd> 117 <dd>
103 <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
104you 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
105<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
106symbols <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
107version of the library your program was compiled against.</p> 122version of the library your program was compiled against.</p>
108 <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,
109as this indicates an incompatible change. Minor versions are usually 124as this indicates an incompatible change. Minor versions are usually
110compatible to older versions, so a larger minor version alone is usually 125compatible to older versions, so a larger minor version alone is usually
111not a problem.</p> 126not a problem.</p>
112 </dd> 127 </dd>
128 <dt>unsigned int ev_supported_backends ()</dt>
129 <dd>
130 <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
131value) compiled into this binary of libev (independent of their
132availability on the system you are running on). See <code>ev_default_loop</code> for
133a description of the set values.</p>
134 </dd>
135 <dt>unsigned int ev_recommended_backends ()</dt>
136 <dd>
137 <p>Return the set of all backends compiled into this binary of libev and also
138recommended for this platform. This set is often smaller than the one
139returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
140most BSDs and will not be autodetected unless you explicitly request it
141(assuming you know what you are doing). This is the set of backends that
142libev will probe for if you specify no backends explicitly.</p>
143 </dd>
113 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 144 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
114 <dd> 145 <dd>
115 <p>Sets the allocation function to use (the prototype is similar to the 146 <p>Sets the allocation function to use (the prototype is similar to the
116realloc function). It is used to allocate and free memory (no surprises 147realloc C function, the semantics are identical). It is used to allocate
117here). If it returns zero when memory needs to be allocated, the library 148and free memory (no surprises here). If it returns zero when memory
118might abort or take some potentially destructive action. The default is 149needs to be allocated, the library might abort or take some potentially
119your system realloc function.</p> 150destructive action. The default is your system realloc function.</p>
120 <p>You could override this function in high-availability programs to, say, 151 <p>You could override this function in high-availability programs to, say,
121free some memory if it cannot allocate memory, to use a special allocator, 152free some memory if it cannot allocate memory, to use a special allocator,
122or even to sleep a while and retry until some memory is available.</p> 153or even to sleep a while and retry until some memory is available.</p>
123 </dd> 154 </dd>
124 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 155 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
125 <dd> 156 <dd>
126 <p>Set the callback function to call on a retryable syscall error (such 157 <p>Set the callback function to call on a retryable syscall error (such
127as failed select, poll, epoll_wait). The message is a printable string 158as failed select, poll, epoll_wait). The message is a printable string
128indicating the system call or subsystem causing the problem. If this 159indicating the system call or subsystem causing the problem. If this
129callback is set, then libev will expect it to remedy the sitution, no 160callback is set, then libev will expect it to remedy the sitution, no
130matter what, when it returns. That is, libev will geenrally retry the 161matter what, when it returns. That is, libev will generally retry the
131requested operation, or, if the condition doesn't go away, do bad stuff 162requested operation, or, if the condition doesn't go away, do bad stuff
132(such as abort).</p> 163(such as abort).</p>
133 </dd> 164 </dd>
134</dl> 165</dl>
135 166
… …
138<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 169<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
139<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 170<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
140types of such loops, the <i>default</i> loop, which supports signals and child 171types of such loops, the <i>default</i> loop, which supports signals and child
141events, and dynamically created loops which do not.</p> 172events, and dynamically created loops which do not.</p>
142<p>If you use threads, a common model is to run the default event loop 173<p>If you use threads, a common model is to run the default event loop
143in your main thread (or in a separate thrad) and for each thread you 174in your main thread (or in a separate thread) and for each thread you
144create, you also create another event loop. Libev itself does no lockign 175create, you also create another event loop. Libev itself does no locking
145whatsoever, so if you mix calls to different event loops, make sure you 176whatsoever, so if you mix calls to the same event loop in different
146lock (this is usually a bad idea, though, even if done right).</p> 177threads, make sure you lock (this is usually a bad idea, though, even if
178done correctly, because it's hideous and inefficient).</p>
147<dl> 179<dl>
148 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 180 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
149 <dd> 181 <dd>
150 <p>This will initialise the default event loop if it hasn't been initialised 182 <p>This will initialise the default event loop if it hasn't been initialised
151yet and return it. If the default loop could not be initialised, returns 183yet and return it. If the default loop could not be initialised, returns
152false. If it already was initialised it simply returns it (and ignores the 184false. If it already was initialised it simply returns it (and ignores the
153flags).</p> 185flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
154 <p>If you don't know what event loop to use, use the one returned from this 186 <p>If you don't know what event loop to use, use the one returned from this
155function.</p> 187function.</p>
156 <p>The flags argument can be used to specify special behaviour or specific 188 <p>The flags argument can be used to specify special behaviour or specific
157backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p> 189backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
158 <p>It supports the following flags:</p> 190 <p>The following flags are supported:</p>
159 <p> 191 <p>
160 <dl> 192 <dl>
161 <dt>EVFLAG_AUTO</dt> 193 <dt><code>EVFLAG_AUTO</code></dt>
162 <dd> 194 <dd>
163 <p>The default flags value. Use this if you have no clue (its the right 195 <p>The default flags value. Use this if you have no clue (it's the right
164thing, believe me).</p> 196thing, believe me).</p>
165 </dd> 197 </dd>
166 <dt>EVFLAG_NOENV</dt> 198 <dt><code>EVFLAG_NOENV</code></dt>
167 <dd>
168 <p>If this flag bit is ored into the flag value then libev will <i>not</i> look
169at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this
170environment variable will override the flags completely. This is useful
171to try out specific backends to tets their performance, or to work around
172bugs.</p>
173 </dd> 199 <dd>
174 <dt>EVMETHOD_SELECT portable select backend</dt> 200 <p>If this flag bit is ored into the flag value (or the program runs setuid
175 <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> 201or setgid) then libev will <i>not</i> look at the environment variable
176 <dt>EVMETHOD_EPOLL linux only</dt> 202<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
177 <dt>EVMETHOD_KQUEUE some bsds only</dt> 203override the flags completely if it is found in the environment. This is
178 <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> 204useful to try out specific backends to test their performance, or to work
179 <dt>EVMETHOD_PORT solaris 10 only</dt> 205around bugs.</p>
180 <dd> 206 </dd>
181 <p>If one or more of these are ored into the flags value, then only these 207 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
182backends will be tried (in the reverse order as given here). If one are 208 <dd>
183specified, any backend will do.</p> 209 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
210libev tries to roll its own fd_set with no limits on the number of fds,
211but if that fails, expect a fairly low limit on the number of fds when
212using this backend. It doesn't scale too well (O(highest_fd)), but its usually
213the fastest backend for a low number of fds.</p>
214 </dd>
215 <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
216 <dd>
217 <p>And this is your standard poll(2) backend. It's more complicated than
218select, but handles sparse fds better and has no artificial limit on the
219number of fds you can use (except it will slow down considerably with a
220lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
221 </dd>
222 <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
223 <dd>
224 <p>For few fds, this backend is a bit little slower than poll and select,
225but it scales phenomenally better. While poll and select usually scale like
226O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
227either O(1) or O(active_fds).</p>
228 <p>While stopping and starting an I/O watcher in the same iteration will
229result in some caching, there is still a syscall per such incident
230(because the fd could point to a different file description now), so its
231best to avoid that. Also, dup()ed file descriptors might not work very
232well if you register events for both fds.</p>
233 <p>Please note that epoll sometimes generates spurious notifications, so you
234need to use non-blocking I/O or other means to avoid blocking when no data
235(or space) is available.</p>
236 </dd>
237 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
238 <dd>
239 <p>Kqueue deserves special mention, as at the time of this writing, it
240was broken on all BSDs except NetBSD (usually it doesn't work with
241anything but sockets and pipes, except on Darwin, where of course its
242completely useless). For this reason its not being &quot;autodetected&quot;
243unless you explicitly specify it explicitly in the flags (i.e. using
244<code>EVBACKEND_KQUEUE</code>).</p>
245 <p>It scales in the same way as the epoll backend, but the interface to the
246kernel is more efficient (which says nothing about its actual speed, of
247course). While starting and stopping an I/O watcher does not cause an
248extra syscall as with epoll, it still adds up to four event changes per
249incident, so its best to avoid that.</p>
250 </dd>
251 <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
252 <dd>
253 <p>This is not implemented yet (and might never be).</p>
254 </dd>
255 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
256 <dd>
257 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
258it's really slow, but it still scales very well (O(active_fds)).</p>
259 <p>Please note that solaris ports can result in a lot of spurious
260notifications, so you need to use non-blocking I/O or other means to avoid
261blocking when no data (or space) is available.</p>
262 </dd>
263 <dt><code>EVBACKEND_ALL</code></dt>
264 <dd>
265 <p>Try all backends (even potentially broken ones that wouldn't be tried
266with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
267<code>EVBACKEND_ALL &amp; ~EVBACKEND_KQUEUE</code>.</p>
184 </dd> 268 </dd>
185 </dl> 269 </dl>
186 </p> 270 </p>
271 <p>If one or more of these are ored into the flags value, then only these
272backends will be tried (in the reverse order as given here). If none are
273specified, most compiled-in backend will be tried, usually in reverse
274order of their flag values :)</p>
275 <p>The most typical usage is like this:</p>
276<pre> if (!ev_default_loop (0))
277 fatal (&quot;could not initialise libev, bad $LIBEV_FLAGS in environment?&quot;);
278
279</pre>
280 <p>Restrict libev to the select and poll backends, and do not allow
281environment settings to be taken into account:</p>
282<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
283
284</pre>
285 <p>Use whatever libev has to offer, but make sure that kqueue is used if
286available (warning, breaks stuff, best use only with your own private
287event loop and only if you know the OS supports your types of fds):</p>
288<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
289
290</pre>
187 </dd> 291 </dd>
188 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 292 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
189 <dd> 293 <dd>
190 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 294 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
191always distinct from the default loop. Unlike the default loop, it cannot 295always distinct from the default loop. Unlike the default loop, it cannot
… …
194 </dd> 298 </dd>
195 <dt>ev_default_destroy ()</dt> 299 <dt>ev_default_destroy ()</dt>
196 <dd> 300 <dd>
197 <p>Destroys the default loop again (frees all memory and kernel state 301 <p>Destroys the default loop again (frees all memory and kernel state
198etc.). This stops all registered event watchers (by not touching them in 302etc.). This stops all registered event watchers (by not touching them in
199any way whatsoever, although you cnanot rely on this :).</p> 303any way whatsoever, although you cannot rely on this :).</p>
200 </dd> 304 </dd>
201 <dt>ev_loop_destroy (loop)</dt> 305 <dt>ev_loop_destroy (loop)</dt>
202 <dd> 306 <dd>
203 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 307 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
204earlier call to <code>ev_loop_new</code>.</p> 308earlier call to <code>ev_loop_new</code>.</p>
… …
207 <dd> 311 <dd>
208 <p>This function reinitialises the kernel state for backends that have 312 <p>This function reinitialises the kernel state for backends that have
209one. Despite the name, you can call it anytime, but it makes most sense 313one. Despite the name, you can call it anytime, but it makes most sense
210after forking, in either the parent or child process (or both, but that 314after forking, in either the parent or child process (or both, but that
211again makes little sense).</p> 315again makes little sense).</p>
212 <p>You <i>must</i> call this function after forking if and only if you want to 316 <p>You <i>must</i> call this function in the child process after forking if and
213use the event library in both processes. If you just fork+exec, you don't 317only if you want to use the event library in both processes. If you just
214have to call it.</p> 318fork+exec, you don't have to call it.</p>
215 <p>The function itself is quite fast and its usually not a problem to call 319 <p>The function itself is quite fast and it's usually not a problem to call
216it just in case after a fork. To make this easy, the function will fit in 320it just in case after a fork. To make this easy, the function will fit in
217quite nicely into a call to <code>pthread_atfork</code>:</p> 321quite nicely into a call to <code>pthread_atfork</code>:</p>
218<pre> pthread_atfork (0, 0, ev_default_fork); 322<pre> pthread_atfork (0, 0, ev_default_fork);
219 323
220</pre> 324</pre>
325 <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
326without calling this function, so if you force one of those backends you
327do not need to care.</p>
221 </dd> 328 </dd>
222 <dt>ev_loop_fork (loop)</dt> 329 <dt>ev_loop_fork (loop)</dt>
223 <dd> 330 <dd>
224 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 331 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
225<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 332<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
226after fork, and how you do this is entirely your own problem.</p> 333after fork, and how you do this is entirely your own problem.</p>
227 </dd> 334 </dd>
228 <dt>unsigned int ev_method (loop)</dt> 335 <dt>unsigned int ev_backend (loop)</dt>
229 <dd> 336 <dd>
230 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 337 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
231use.</p> 338use.</p>
232 </dd> 339 </dd>
233 <dt>ev_tstamp = ev_now (loop)</dt> 340 <dt>ev_tstamp ev_now (loop)</dt>
234 <dd> 341 <dd>
235 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 342 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
236got events and started processing them. This timestamp does not change 343got events and started processing them. This timestamp does not change
237as long as callbacks are being processed, and this is also the base time 344as long as callbacks are being processed, and this is also the base time
238used for relative timers. You can treat it as the timestamp of the event 345used for relative timers. You can treat it as the timestamp of the event
… …
241 <dt>ev_loop (loop, int flags)</dt> 348 <dt>ev_loop (loop, int flags)</dt>
242 <dd> 349 <dd>
243 <p>Finally, this is it, the event handler. This function usually is called 350 <p>Finally, this is it, the event handler. This function usually is called
244after you initialised all your watchers and you want to start handling 351after you initialised all your watchers and you want to start handling
245events.</p> 352events.</p>
246 <p>If the flags argument is specified as 0, it will not return until either 353 <p>If the flags argument is specified as <code>0</code>, it will not return until
247no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 354either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
248 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 355 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
249those events and any outstanding ones, but will not block your process in 356those events and any outstanding ones, but will not block your process in
250case there are no events.</p> 357case there are no events and will return after one iteration of the loop.</p>
251 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 358 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
252neccessary) and will handle those and any outstanding ones. It will block 359neccessary) and will handle those and any outstanding ones. It will block
253your process until at least one new event arrives.</p> 360your process until at least one new event arrives, and will return after
254 <p>This flags value could be used to implement alternative looping 361one iteration of the loop. This is useful if you are waiting for some
255constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 362external event in conjunction with something not expressible using other
256more generic mechanism.</p> 363libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
364usually a better approach for this kind of thing.</p>
365 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
366<pre> * If there are no active watchers (reference count is zero), return.
367 - Queue prepare watchers and then call all outstanding watchers.
368 - If we have been forked, recreate the kernel state.
369 - Update the kernel state with all outstanding changes.
370 - Update the &quot;event loop time&quot;.
371 - Calculate for how long to block.
372 - Block the process, waiting for any events.
373 - Queue all outstanding I/O (fd) events.
374 - Update the &quot;event loop time&quot; and do time jump handling.
375 - Queue all outstanding timers.
376 - Queue all outstanding periodics.
377 - If no events are pending now, queue all idle watchers.
378 - Queue all check watchers.
379 - Call all queued watchers in reverse order (i.e. check watchers first).
380 Signals and child watchers are implemented as I/O watchers, and will
381 be handled here by queueing them when their watcher gets executed.
382 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
383 were used, return, otherwise continue with step *.
384
385</pre>
257 </dd> 386 </dd>
258 <dt>ev_unloop (loop, how)</dt> 387 <dt>ev_unloop (loop, how)</dt>
259 <dd> 388 <dd>
260 <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument 389 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
390has processed all outstanding events). The <code>how</code> argument must be either
261must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> 391<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
262call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> 392<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
263calls return.</p>
264 </dd> 393 </dd>
265 <dt>ev_ref (loop)</dt> 394 <dt>ev_ref (loop)</dt>
266 <dt>ev_unref (loop)</dt> 395 <dt>ev_unref (loop)</dt>
267 <dd> 396 <dd>
268 <p>Ref/unref can be used to add or remove a refcount on the event loop: Every 397 <p>Ref/unref can be used to add or remove a reference count on the event
269watcher keeps one reference. If you have a long-runing watcher you never 398loop: Every watcher keeps one reference, and as long as the reference
270unregister that should not keep ev_loop from running, ev_unref() after 399count is nonzero, <code>ev_loop</code> will not return on its own. If you have
271starting, and ev_ref() before stopping it. Libev itself uses this for 400a watcher you never unregister that should not keep <code>ev_loop</code> from
272example for its internal signal pipe: It is not visible to you as a user 401returning, ev_unref() after starting, and ev_ref() before stopping it. For
273and should not keep <code>ev_loop</code> from exiting if the work is done. It is 402example, libev itself uses this for its internal signal pipe: It is not
274also an excellent way to do this for generic recurring timers or from 403visible to the libev user and should not keep <code>ev_loop</code> from exiting if
275within third-party libraries. Just remember to unref after start and ref 404no event watchers registered by it are active. It is also an excellent
276before stop.</p> 405way to do this for generic recurring timers or from within third-party
406libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
277 </dd> 407 </dd>
278</dl> 408</dl>
279 409
280</div> 410</div>
281<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 411<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
282<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 412<div id="ANATOMY_OF_A_WATCHER_CONTENT">
283<p>A watcher is a structure that you create and register to record your 413<p>A watcher is a structure that you create and register to record your
284interest in some event. For instance, if you want to wait for STDIN to 414interest in some event. For instance, if you want to wait for STDIN to
285become readable, you would create an ev_io watcher for that:</p> 415become readable, you would create an <code>ev_io</code> watcher for that:</p>
286<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 416<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
287 { 417 {
288 ev_io_stop (w); 418 ev_io_stop (w);
289 ev_unloop (loop, EVUNLOOP_ALL); 419 ev_unloop (loop, EVUNLOOP_ALL);
290 } 420 }
… …
313with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 443with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
314*)</code>), and you can stop watching for events at any time by calling the 444*)</code>), and you can stop watching for events at any time by calling the
315corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 445corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
316<p>As long as your watcher is active (has been started but not stopped) you 446<p>As long as your watcher is active (has been started but not stopped) you
317must not touch the values stored in it. Most specifically you must never 447must not touch the values stored in it. Most specifically you must never
318reinitialise it or call its set method.</p> 448reinitialise it or call its set macro.</p>
319<p>You cna check wether an event is active by calling the <code>ev_is_active 449<p>You can check whether an event is active by calling the <code>ev_is_active
320(watcher *)</code> macro. To see wether an event is outstanding (but the 450(watcher *)</code> macro. To see whether an event is outstanding (but the
321callback for it has not been called yet) you cna use the <code>ev_is_pending 451callback for it has not been called yet) you can use the <code>ev_is_pending
322(watcher *)</code> macro.</p> 452(watcher *)</code> macro.</p>
323<p>Each and every callback receives the event loop pointer as first, the 453<p>Each and every callback receives the event loop pointer as first, the
324registered watcher structure as second, and a bitset of received events as 454registered watcher structure as second, and a bitset of received events as
325third argument.</p> 455third argument.</p>
326<p>The rceeived events usually include a single bit per event type received 456<p>The received events usually include a single bit per event type received
327(you can receive multiple events at the same time). The possible bit masks 457(you can receive multiple events at the same time). The possible bit masks
328are:</p> 458are:</p>
329<dl> 459<dl>
330 <dt>EV_READ</dt> 460 <dt><code>EV_READ</code></dt>
331 <dt>EV_WRITE</dt> 461 <dt><code>EV_WRITE</code></dt>
332 <dd> 462 <dd>
333 <p>The file descriptor in the ev_io watcher has become readable and/or 463 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
334writable.</p> 464writable.</p>
335 </dd> 465 </dd>
336 <dt>EV_TIMEOUT</dt> 466 <dt><code>EV_TIMEOUT</code></dt>
337 <dd>
338 <p>The ev_timer watcher has timed out.</p>
339 </dd> 467 <dd>
340 <dt>EV_PERIODIC</dt> 468 <p>The <code>ev_timer</code> watcher has timed out.</p>
341 <dd> 469 </dd>
342 <p>The ev_periodic watcher has timed out.</p> 470 <dt><code>EV_PERIODIC</code></dt>
343 </dd> 471 <dd>
344 <dt>EV_SIGNAL</dt> 472 <p>The <code>ev_periodic</code> watcher has timed out.</p>
345 <dd> 473 </dd>
474 <dt><code>EV_SIGNAL</code></dt>
475 <dd>
346 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 476 <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
347 </dd>
348 <dt>EV_CHILD</dt>
349 <dd> 477 </dd>
478 <dt><code>EV_CHILD</code></dt>
479 <dd>
350 <p>The pid specified in the ev_child watcher has received a status change.</p> 480 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
351 </dd>
352 <dt>EV_IDLE</dt>
353 <dd> 481 </dd>
482 <dt><code>EV_IDLE</code></dt>
483 <dd>
354 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 484 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
355 </dd>
356 <dt>EV_PREPARE</dt>
357 <dt>EV_CHECK</dt>
358 <dd> 485 </dd>
486 <dt><code>EV_PREPARE</code></dt>
487 <dt><code>EV_CHECK</code></dt>
488 <dd>
359 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 489 <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
360to gather new events, and all ev_check watchers are invoked just after 490to gather new events, and all <code>ev_check</code> watchers are invoked just after
361<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 491<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
362received events. Callbacks of both watcher types can start and stop as 492received events. Callbacks of both watcher types can start and stop as
363many watchers as they want, and all of them will be taken into account 493many watchers as they want, and all of them will be taken into account
364(for example, a ev_prepare watcher might start an idle watcher to keep 494(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
365<code>ev_loop</code> from blocking).</p> 495<code>ev_loop</code> from blocking).</p>
366 </dd> 496 </dd>
367 <dt>EV_ERROR</dt> 497 <dt><code>EV_ERROR</code></dt>
368 <dd> 498 <dd>
369 <p>An unspecified error has occured, the watcher has been stopped. This might 499 <p>An unspecified error has occured, the watcher has been stopped. This might
370happen because the watcher could not be properly started because libev 500happen because the watcher could not be properly started because libev
371ran out of memory, a file descriptor was found to be closed or any other 501ran out of memory, a file descriptor was found to be closed or any other
372problem. You best act on it by reporting the problem and somehow coping 502problem. You best act on it by reporting the problem and somehow coping
… …
381 511
382</div> 512</div>
383<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 513<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
384<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 514<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
385<p>Each watcher has, by default, a member <code>void *data</code> that you can change 515<p>Each watcher has, by default, a member <code>void *data</code> that you can change
386and read at any time, libev will completely ignore it. This cna be used 516and read at any time, libev will completely ignore it. This can be used
387to associate arbitrary data with your watcher. If you need more data and 517to associate arbitrary data with your watcher. If you need more data and
388don't want to allocate memory and store a pointer to it in that data 518don't want to allocate memory and store a pointer to it in that data
389member, you can also &quot;subclass&quot; the watcher type and provide your own 519member, you can also &quot;subclass&quot; the watcher type and provide your own
390data:</p> 520data:</p>
391<pre> struct my_io 521<pre> struct my_io
… …
418<div id="WATCHER_TYPES_CONTENT"> 548<div id="WATCHER_TYPES_CONTENT">
419<p>This section describes each watcher in detail, but will not repeat 549<p>This section describes each watcher in detail, but will not repeat
420information given in the last section.</p> 550information given in the last section.</p>
421 551
422</div> 552</div>
423<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 553<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
424<div id="struct_ev_io_is_my_file_descriptor_r-2"> 554<div id="code_ev_io_code_is_this_file_descrip-2">
425<p>I/O watchers check wether a file descriptor is readable or writable 555<p>I/O watchers check whether a file descriptor is readable or writable
426in each iteration of the event loop (This behaviour is called 556in each iteration of the event loop (This behaviour is called
427level-triggering because you keep receiving events as long as the 557level-triggering because you keep receiving events as long as the
428condition persists. Remember you cna stop the watcher if you don't want to 558condition persists. Remember you can stop the watcher if you don't want to
429act on the event and neither want to receive future events).</p> 559act on the event and neither want to receive future events).</p>
560<p>In general you can register as many read and/or write event watchers per
561fd as you want (as long as you don't confuse yourself). Setting all file
562descriptors to non-blocking mode is also usually a good idea (but not
563required if you know what you are doing).</p>
564<p>You have to be careful with dup'ed file descriptors, though. Some backends
565(the linux epoll backend is a notable example) cannot handle dup'ed file
566descriptors correctly if you register interest in two or more fds pointing
567to the same underlying file/socket etc. description (that is, they share
568the same underlying &quot;file open&quot;).</p>
569<p>If you must do this, then force the use of a known-to-be-good backend
570(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
571<code>EVBACKEND_POLL</code>).</p>
430<dl> 572<dl>
431 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 573 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
432 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 574 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
433 <dd> 575 <dd>
434 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 576 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
435events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 577events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
436EV_WRITE</code> to receive the given events.</p> 578EV_WRITE</code> to receive the given events.</p>
579 <p>Please note that most of the more scalable backend mechanisms (for example
580epoll and solaris ports) can result in spurious readyness notifications
581for file descriptors, so you practically need to use non-blocking I/O (and
582treat callback invocation as hint only), or retest separately with a safe
583interface before doing I/O (XLib can do this), or force the use of either
584<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
585problem. Also note that it is quite easy to have your callback invoked
586when the readyness condition is no longer valid even when employing
587typical ways of handling events, so its a good idea to use non-blocking
588I/O unconditionally.</p>
437 </dd> 589 </dd>
438</dl> 590</dl>
439 591
440</div> 592</div>
441<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 593<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
442<div id="struct_ev_timer_relative_and_optiona-2"> 594<div id="code_ev_timer_code_relative_and_opti-2">
443<p>Timer watchers are simple relative timers that generate an event after a 595<p>Timer watchers are simple relative timers that generate an event after a
444given time, and optionally repeating in regular intervals after that.</p> 596given time, and optionally repeating in regular intervals after that.</p>
445<p>The timers are based on real time, that is, if you register an event that 597<p>The timers are based on real time, that is, if you register an event that
446times out after an hour and youreset your system clock to last years 598times out after an hour and you reset your system clock to last years
447time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 599time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
448detecting time jumps is hard, and soem inaccuracies are unavoidable (the 600detecting time jumps is hard, and some inaccuracies are unavoidable (the
449monotonic clock option helps a lot here).</p> 601monotonic clock option helps a lot here).</p>
602<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
603time. This is usually the right thing as this timestamp refers to the time
604of the event triggering whatever timeout you are modifying/starting. If
605you suspect event processing to be delayed and you <i>need</i> to base the timeout
606on the current time, use something like this to adjust for this:</p>
607<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
608
609</pre>
610<p>The callback is guarenteed to be invoked only when its timeout has passed,
611but if multiple timers become ready during the same loop iteration then
612order of execution is undefined.</p>
450<dl> 613<dl>
451 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 614 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
452 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 615 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
453 <dd> 616 <dd>
454 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 617 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
456timer will automatically be configured to trigger again <code>repeat</code> seconds 619timer will automatically be configured to trigger again <code>repeat</code> seconds
457later, again, and again, until stopped manually.</p> 620later, again, and again, until stopped manually.</p>
458 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 621 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
459configure a timer to trigger every 10 seconds, then it will trigger at 622configure a timer to trigger every 10 seconds, then it will trigger at
460exactly 10 second intervals. If, however, your program cannot keep up with 623exactly 10 second intervals. If, however, your program cannot keep up with
461the timer (ecause it takes longer than those 10 seconds to do stuff) the 624the timer (because it takes longer than those 10 seconds to do stuff) the
462timer will not fire more than once per event loop iteration.</p> 625timer will not fire more than once per event loop iteration.</p>
463 </dd> 626 </dd>
464 <dt>ev_timer_again (loop)</dt> 627 <dt>ev_timer_again (loop)</dt>
465 <dd> 628 <dd>
466 <p>This will act as if the timer timed out and restart it again if it is 629 <p>This will act as if the timer timed out and restart it again if it is
… …
470value), or reset the running timer to the repeat value.</p> 633value), or reset the running timer to the repeat value.</p>
471 <p>This sounds a bit complicated, but here is a useful and typical 634 <p>This sounds a bit complicated, but here is a useful and typical
472example: Imagine you have a tcp connection and you want a so-called idle 635example: Imagine you have a tcp connection and you want a so-called idle
473timeout, that is, you want to be called when there have been, say, 60 636timeout, that is, you want to be called when there have been, say, 60
474seconds of inactivity on the socket. The easiest way to do this is to 637seconds of inactivity on the socket. The easiest way to do this is to
475configure an ev_timer with after=repeat=60 and calling ev_timer_again each 638configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
476time you successfully read or write some data. If you go into an idle 639time you successfully read or write some data. If you go into an idle
477state where you do not expect data to travel on the socket, you can stop 640state where you do not expect data to travel on the socket, you can stop
478the timer, and again will automatically restart it if need be.</p> 641the timer, and again will automatically restart it if need be.</p>
479 </dd> 642 </dd>
480</dl> 643</dl>
481 644
482</div> 645</div>
483<h2 id="ev_periodic">ev_periodic</h2> 646<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
484<div id="ev_periodic_CONTENT"> 647<div id="code_ev_periodic_code_to_cron_or_not-2">
485<p>Periodic watchers are also timers of a kind, but they are very versatile 648<p>Periodic watchers are also timers of a kind, but they are very versatile
486(and unfortunately a bit complex).</p> 649(and unfortunately a bit complex).</p>
487<p>Unlike ev_timer's, they are not based on real time (or relative time) 650<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
488but on wallclock time (absolute time). You can tell a periodic watcher 651but on wallclock time (absolute time). You can tell a periodic watcher
489to trigger &quot;at&quot; some specific point in time. For example, if you tell a 652to trigger &quot;at&quot; some specific point in time. For example, if you tell a
490periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 653periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now ()
491+ 10.&gt;) and then reset your system clock to the last year, then it will 654+ 10.&gt;) and then reset your system clock to the last year, then it will
492take a year to trigger the event (unlike an ev_timer, which would trigger 655take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
493roughly 10 seconds later and of course not if you reset your system time 656roughly 10 seconds later and of course not if you reset your system time
494again).</p> 657again).</p>
495<p>They can also be used to implement vastly more complex timers, such as 658<p>They can also be used to implement vastly more complex timers, such as
496triggering an event on eahc midnight, local time.</p> 659triggering an event on eahc midnight, local time.</p>
660<p>As with timers, the callback is guarenteed to be invoked only when the
661time (<code>at</code>) has been passed, but if multiple periodic timers become ready
662during the same loop iteration then order of execution is undefined.</p>
497<dl> 663<dl>
498 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 664 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
499 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 665 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
500 <dd> 666 <dd>
501 <p>Lots of arguments, lets sort it out... There are basically three modes of 667 <p>Lots of arguments, lets sort it out... There are basically three modes of
502operation, and we will explain them from simplest to complex:</p> 668operation, and we will explain them from simplest to complex:</p>
503
504
505
506
507 <p> 669 <p>
508 <dl> 670 <dl>
509 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 671 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
510 <dd> 672 <dd>
511 <p>In this configuration the watcher triggers an event at the wallclock time 673 <p>In this configuration the watcher triggers an event at the wallclock time
… …
523<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 685<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
524 686
525</pre> 687</pre>
526 <p>This doesn't mean there will always be 3600 seconds in between triggers, 688 <p>This doesn't mean there will always be 3600 seconds in between triggers,
527but only that the the callback will be called when the system time shows a 689but only that the the callback will be called when the system time shows a
528full hour (UTC), or more correct, when the system time is evenly divisible 690full hour (UTC), or more correctly, when the system time is evenly divisible
529by 3600.</p> 691by 3600.</p>
530 <p>Another way to think about it (for the mathematically inclined) is that 692 <p>Another way to think about it (for the mathematically inclined) is that
531ev_periodic will try to run the callback in this mode at the next possible 693<code>ev_periodic</code> will try to run the callback in this mode at the next possible
532time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 694time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
533 </dd> 695 </dd>
534 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 696 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
535 <dd> 697 <dd>
536 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 698 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
537ignored. Instead, each time the periodic watcher gets scheduled, the 699ignored. Instead, each time the periodic watcher gets scheduled, the
538reschedule callback will be called with the watcher as first, and the 700reschedule callback will be called with the watcher as first, and the
539current time as second argument.</p> 701current time as second argument.</p>
540 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 702 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
541periodic watcher, ever, or make any event loop modificstions</i>. If you need 703ever, or make any event loop modifications</i>. If you need to stop it,
542to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 704return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
705starting a prepare watcher).</p>
543 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 706 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
544ev_tstamp now)&gt;, e.g.:</p> 707ev_tstamp now)</code>, e.g.:</p>
545<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 708<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
546 { 709 {
547 return now + 60.; 710 return now + 60.;
548 } 711 }
549 712
550</pre> 713</pre>
551 <p>It must return the next time to trigger, based on the passed time value 714 <p>It must return the next time to trigger, based on the passed time value
552(that is, the lowest time value larger than to the second argument). It 715(that is, the lowest time value larger than to the second argument). It
553will usually be called just before the callback will be triggered, but 716will usually be called just before the callback will be triggered, but
554might be called at other times, too.</p> 717might be called at other times, too.</p>
718 <p>NOTE: <i>This callback must always return a time that is later than the
719passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
555 <p>This can be used to create very complex timers, such as a timer that 720 <p>This can be used to create very complex timers, such as a timer that
556triggers on each midnight, local time. To do this, you would calculate the 721triggers on each midnight, local time. To do this, you would calculate the
557next midnight after <code>now</code> and return the timestamp value for this. How you do this 722next midnight after <code>now</code> and return the timestamp value for this. How
558is, again, up to you (but it is not trivial).</p> 723you do this is, again, up to you (but it is not trivial, which is the main
724reason I omitted it as an example).</p>
559 </dd> 725 </dd>
560 </dl> 726 </dl>
561 </p> 727 </p>
562 </dd> 728 </dd>
563 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 729 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
568program when the crontabs have changed).</p> 734program when the crontabs have changed).</p>
569 </dd> 735 </dd>
570</dl> 736</dl>
571 737
572</div> 738</div>
573<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 739<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
574<div id="ev_signal_signal_me_when_a_signal_ge-2"> 740<div id="code_ev_signal_code_signal_me_when_a-2">
575<p>Signal watchers will trigger an event when the process receives a specific 741<p>Signal watchers will trigger an event when the process receives a specific
576signal one or more times. Even though signals are very asynchronous, libev 742signal one or more times. Even though signals are very asynchronous, libev
577will try its best to deliver signals synchronously, i.e. as part of the 743will try it's best to deliver signals synchronously, i.e. as part of the
578normal event processing, like any other event.</p> 744normal event processing, like any other event.</p>
579<p>You cna configure as many watchers as you like per signal. Only when the 745<p>You can configure as many watchers as you like per signal. Only when the
580first watcher gets started will libev actually register a signal watcher 746first watcher gets started will libev actually register a signal watcher
581with the kernel (thus it coexists with your own signal handlers as long 747with the kernel (thus it coexists with your own signal handlers as long
582as you don't register any with libev). Similarly, when the last signal 748as you don't register any with libev). Similarly, when the last signal
583watcher for a signal is stopped libev will reset the signal handler to 749watcher for a signal is stopped libev will reset the signal handler to
584SIG_DFL (regardless of what it was set to before).</p> 750SIG_DFL (regardless of what it was set to before).</p>
… …
590of the <code>SIGxxx</code> constants).</p> 756of the <code>SIGxxx</code> constants).</p>
591 </dd> 757 </dd>
592</dl> 758</dl>
593 759
594</div> 760</div>
595<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 761<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
596<div id="ev_child_wait_for_pid_status_changes-2"> 762<div id="code_ev_child_code_wait_for_pid_stat-2">
597<p>Child watchers trigger when your process receives a SIGCHLD in response to 763<p>Child watchers trigger when your process receives a SIGCHLD in response to
598some child status changes (most typically when a child of yours dies).</p> 764some child status changes (most typically when a child of yours dies).</p>
599<dl> 765<dl>
600 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 766 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
601 <dt>ev_child_set (ev_child *, int pid)</dt> 767 <dt>ev_child_set (ev_child *, int pid)</dt>
602 <dd> 768 <dd>
603 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 769 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
604<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 770<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
605at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 771at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
606the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 772the status word (use the macros from <code>sys/wait.h</code> and see your systems
773<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
607contains the pid of the process causing the status change.</p> 774process causing the status change.</p>
608 </dd> 775 </dd>
609</dl> 776</dl>
610 777
611</div> 778</div>
612<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 779<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
613<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 780<div id="code_ev_idle_code_when_you_ve_got_no-2">
614<p>Idle watchers trigger events when there are no other I/O or timer (or 781<p>Idle watchers trigger events when there are no other events are pending
615periodic) events pending. That is, as long as your process is busy 782(prepare, check and other idle watchers do not count). That is, as long
616handling sockets or timeouts it will not be called. But when your process 783as your process is busy handling sockets or timeouts (or even signals,
617is idle all idle watchers are being called again and again - until 784imagine) it will not be triggered. But when your process is idle all idle
785watchers are being called again and again, once per event loop iteration -
618stopped, that is, or your process receives more events.</p> 786until stopped, that is, or your process receives more events and becomes
787busy.</p>
619<p>The most noteworthy effect is that as long as any idle watchers are 788<p>The most noteworthy effect is that as long as any idle watchers are
620active, the process will not block when waiting for new events.</p> 789active, the process will not block when waiting for new events.</p>
621<p>Apart from keeping your process non-blocking (which is a useful 790<p>Apart from keeping your process non-blocking (which is a useful
622effect on its own sometimes), idle watchers are a good place to do 791effect on its own sometimes), idle watchers are a good place to do
623&quot;pseudo-background processing&quot;, or delay processing stuff to after the 792&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
630believe me.</p> 799believe me.</p>
631 </dd> 800 </dd>
632</dl> 801</dl>
633 802
634</div> 803</div>
635<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 804<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
636<div id="prepare_and_check_your_hooks_into_th-2"> 805<div id="code_ev_prepare_code_and_code_ev_che-2">
637<p>Prepare and check watchers usually (but not always) are used in 806<p>Prepare and check watchers are usually (but not always) used in tandem:
638tandom. Prepare watchers get invoked before the process blocks and check 807prepare watchers get invoked before the process blocks and check watchers
639watchers afterwards.</p> 808afterwards.</p>
640<p>Their main purpose is to integrate other event mechanisms into libev. This 809<p>Their main purpose is to integrate other event mechanisms into libev. This
641could be used, for example, to track variable changes, implement your own 810could be used, for example, to track variable changes, implement your own
642watchers, integrate net-snmp or a coroutine library and lots more.</p> 811watchers, integrate net-snmp or a coroutine library and lots more.</p>
643<p>This is done by examining in each prepare call which file descriptors need 812<p>This is done by examining in each prepare call which file descriptors need
644to be watched by the other library, registering ev_io watchers for them 813to be watched by the other library, registering <code>ev_io</code> watchers for
645and starting an ev_timer watcher for any timeouts (many libraries provide 814them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
646just this functionality). Then, in the check watcher you check for any 815provide just this functionality). Then, in the check watcher you check for
647events that occured (by making your callbacks set soem flags for example) 816any events that occured (by checking the pending status of all watchers
648and call back into the library.</p> 817and stopping them) and call back into the library. The I/O and timer
818callbacks will never actually be called (but must be valid nevertheless,
819because you never know, you know?).</p>
649<p>As another example, the perl Coro module uses these hooks to integrate 820<p>As another example, the Perl Coro module uses these hooks to integrate
650coroutines into libev programs, by yielding to other active coroutines 821coroutines into libev programs, by yielding to other active coroutines
651during each prepare and only letting the process block if no coroutines 822during each prepare and only letting the process block if no coroutines
652are ready to run.</p> 823are ready to run (it's actually more complicated: it only runs coroutines
824with priority higher than or equal to the event loop and one coroutine
825of lower priority, but only once, using idle watchers to keep the event
826loop from blocking if lower-priority coroutines are active, thus mapping
827low-priority coroutines to idle/background tasks).</p>
653<dl> 828<dl>
654 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 829 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
655 <dt>ev_check_init (ev_check *, callback)</dt> 830 <dt>ev_check_init (ev_check *, callback)</dt>
656 <dd> 831 <dd>
657 <p>Initialises and configures the prepare or check watcher - they have no 832 <p>Initialises and configures the prepare or check watcher - they have no
658parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 833parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
659macros, but using them is utterly, utterly pointless.</p> 834macros, but using them is utterly, utterly and completely pointless.</p>
660 </dd> 835 </dd>
661</dl> 836</dl>
662 837
663</div> 838</div>
664<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 839<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
665<div id="OTHER_FUNCTIONS_CONTENT"> 840<div id="OTHER_FUNCTIONS_CONTENT">
666<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 841<p>There are some other functions of possible interest. Described. Here. Now.</p>
667<dl> 842<dl>
668 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 843 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
669 <dd> 844 <dd>
670 <p>This function combines a simple timer and an I/O watcher, calls your 845 <p>This function combines a simple timer and an I/O watcher, calls your
671callback on whichever event happens first and automatically stop both 846callback on whichever event happens first and automatically stop both
672watchers. This is useful if you want to wait for a single event on an fd 847watchers. This is useful if you want to wait for a single event on an fd
673or timeout without havign to allocate/configure/start/stop/free one or 848or timeout without having to allocate/configure/start/stop/free one or
674more watchers yourself.</p> 849more watchers yourself.</p>
675 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 850 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
676ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 851is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
677will be craeted and started.</p> 852<code>events</code> set will be craeted and started.</p>
678 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 853 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
679started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 854started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
680= 0) will be started.</p> 855repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
856dubious value.</p>
681 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 857 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
682gets passed an events set (normally a combination of EV_ERROR, EV_READ, 858passed an <code>revents</code> set like normal event callbacks (a combination of
683EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 859<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
860value passed to <code>ev_once</code>:</p>
684<pre> static void stdin_ready (int revents, void *arg) 861<pre> static void stdin_ready (int revents, void *arg)
685 { 862 {
686 if (revents &amp; EV_TIMEOUT) 863 if (revents &amp; EV_TIMEOUT)
687 /* doh, nothing entered */ 864 /* doh, nothing entered */;
688 else if (revents &amp; EV_READ) 865 else if (revents &amp; EV_READ)
689 /* stdin might have data for us, joy! */ 866 /* stdin might have data for us, joy! */;
690 } 867 }
691 868
692 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 869 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
693 870
694</pre> 871</pre>
695 </dd> 872 </dd>
696 <dt>ev_feed_event (loop, watcher, int events)</dt> 873 <dt>ev_feed_event (loop, watcher, int events)</dt>
697 <dd> 874 <dd>
698 <p>Feeds the given event set into the event loop, as if the specified event 875 <p>Feeds the given event set into the event loop, as if the specified event
699has happened for the specified watcher (which must be a pointer to an 876had happened for the specified watcher (which must be a pointer to an
700initialised but not necessarily active event watcher).</p> 877initialised but not necessarily started event watcher).</p>
701 </dd> 878 </dd>
702 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 879 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
703 <dd> 880 <dd>
704 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 881 <p>Feed an event on the given fd, as if a file descriptor backend detected
882the given events it.</p>
705 </dd> 883 </dd>
706 <dt>ev_feed_signal_event (loop, int signum)</dt> 884 <dt>ev_feed_signal_event (loop, int signum)</dt>
707 <dd> 885 <dd>
708 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 886 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
709 </dd> 887 </dd>
710</dl> 888</dl>
889
890</div>
891<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
892<div id="LIBEVENT_EMULATION_CONTENT">
893<p>Libev offers a compatibility emulation layer for libevent. It cannot
894emulate the internals of libevent, so here are some usage hints:</p>
895<dl>
896 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
897 <dt>* The following members are fully supported: ev_base, ev_callback,
898ev_arg, ev_fd, ev_res, ev_events.</dt>
899 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
900maintained by libev, it does not work exactly the same way as in libevent (consider
901it a private API).</dt>
902 <dt>* Priorities are not currently supported. Initialising priorities
903will fail and all watchers will have the same priority, even though there
904is an ev_pri field.</dt>
905 <dt>* Other members are not supported.</dt>
906 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
907to use the libev header file and library.</dt>
908</dl>
909
910</div>
911<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
912<div id="C_SUPPORT_CONTENT">
913<p>TBD.</p>
711 914
712</div> 915</div>
713<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 916<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
714<div id="AUTHOR_CONTENT"> 917<div id="AUTHOR_CONTENT">
715<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 918<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

Diff Legend

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