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

Comparing libev/ev.html (file contents):
Revision 1.2 by root, Mon Nov 12 08:02:54 2007 UTC vs.
Revision 1.32 by root, Fri Nov 23 05:14:58 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 09:02:48 2007" /> 9 <meta name="created" content="Fri Nov 23 06:14:47 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, representing the 97<p>Libev represents time as a single floating point number, representing the
93(fractional) number of seconds since the (POSIX) epoch (somewhere near 98(fractional) number of seconds since the (POSIX) epoch (somewhere near
94the beginning of 1970, details are complicated, don't ask). This type is 99the beginning of 1970, details are complicated, don't ask). This type is
95called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 100called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
96to the double type in C.</p> 101to the double type in C.</p>
102
103</div>
104<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105<div id="GLOBAL_FUNCTIONS_CONTENT">
106<p>These functions can be called anytime, even before initialising the
107library in any way.</p>
97<dl> 108<dl>
98 <dt>ev_tstamp ev_time ()</dt> 109 <dt>ev_tstamp ev_time ()</dt>
99 <dd> 110 <dd>
100 <p>Returns the current time as libev would use it.</p> 111 <p>Returns the current time as libev would use it. Please note that the
112<code>ev_now</code> function is usually faster and also often returns the timestamp
113you actually want to know.</p>
101 </dd> 114 </dd>
102 <dt>int ev_version_major ()</dt> 115 <dt>int ev_version_major ()</dt>
103 <dt>int ev_version_minor ()</dt> 116 <dt>int ev_version_minor ()</dt>
104 <dd> 117 <dd>
105 <p>You can find out the major and minor version numbers of the library 118 <p>You can find out the major and minor version numbers of the library
106you linked against by calling the functions <code>ev_version_major</code> and 119you linked against by calling the functions <code>ev_version_major</code> and
107<code>ev_version_minor</code>. If you want, you can compare against the global 120<code>ev_version_minor</code>. If you want, you can compare against the global
108symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 121symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
109version of the library your program was compiled against.</p> 122version of the library your program was compiled against.</p>
110 <p>Usually, its a good idea to terminate if the major versions mismatch, 123 <p>Usually, it's a good idea to terminate if the major versions mismatch,
111as this indicates an incompatible change. Minor versions are usually 124as this indicates an incompatible change. Minor versions are usually
112compatible to older versions, so a larger minor version alone is usually 125compatible to older versions, so a larger minor version alone is usually
113not a problem.</p> 126not a problem.</p>
114 </dd> 127 </dd>
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
142<code>EVFLAG_AUTO</code> will probe for.</p>
143 </dd>
115 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 144 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
116 <dd> 145 <dd>
117 <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
118realloc function). It is used to allocate and free memory (no surprises 147realloc C function, the semantics are identical). It is used to allocate
119here). If it returns zero when memory needs to be allocated, the library 148and free memory (no surprises here). If it returns zero when memory
120might abort or take some potentially destructive action. The default is 149needs to be allocated, the library might abort or take some potentially
121your system realloc function.</p> 150destructive action. The default is your system realloc function.</p>
122 <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,
123free 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,
124or 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>
125 </dd> 154 </dd>
126 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 155 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
127 <dd> 156 <dd>
128 <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
129as failed select, poll, epoll_wait). The message is a printable string 158as failed select, poll, epoll_wait). The message is a printable string
130indicating the system call or subsystem causing the problem. If this 159indicating the system call or subsystem causing the problem. If this
131callback 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
132matter what, when it returns. That is, libev will geenrally retry the 161matter what, when it returns. That is, libev will generally retry the
133requested 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
134(such as abort).</p> 163(such as abort).</p>
135 </dd> 164 </dd>
136</dl> 165</dl>
137 166
… …
140<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 169<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
141<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 170<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
142types of such loops, the <i>default</i> loop, which supports signals and child 171types of such loops, the <i>default</i> loop, which supports signals and child
143events, and dynamically created loops which do not.</p> 172events, and dynamically created loops which do not.</p>
144<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
145in 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
146create, you also create another event loop. Libev itself does no lockign 175create, you also create another event loop. Libev itself does no locking
147whatsoever, 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
148lock (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>
149<dl> 179<dl>
150 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 180 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
151 <dd> 181 <dd>
152 <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
153yet 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
154false. 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
155flags).</p> 185flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
156 <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
157function.</p> 187function.</p>
158 <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
159backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p> 189backends to use, and is usually specified as <code>0</code> (or EVFLAG_AUTO).</p>
160 <p>It supports the following flags:</p> 190 <p>It supports the following flags:</p>
161 <p> 191 <p>
162 <dl> 192 <dl>
163 <dt>EVFLAG_AUTO</dt> 193 <dt><code>EVFLAG_AUTO</code></dt>
164 <dd> 194 <dd>
165 <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
166thing, believe me).</p> 196thing, believe me).</p>
167 </dd> 197 </dd>
168 <dt>EVFLAG_NOENV</dt> 198 <dt><code>EVFLAG_NOENV</code></dt>
169 <dd>
170 <p>If this flag bit is ored into the flag value then libev will <i>not</i> look
171at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this
172environment variable will override the flags completely. This is useful
173to try out specific backends to tets their performance, or to work around
174bugs.</p>
175 </dd> 199 <dd>
176 <dt>EVMETHOD_SELECT portable select backend</dt> 200 <p>If this flag bit is ored into the flag value (or the program runs setuid
177 <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> 201or setgid) then libev will <i>not</i> look at the environment variable
178 <dt>EVMETHOD_EPOLL linux only</dt> 202<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
179 <dt>EVMETHOD_KQUEUE some bsds only</dt> 203override the flags completely if it is found in the environment. This is
180 <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> 204useful to try out specific backends to test their performance, or to work
181 <dt>EVMETHOD_PORT solaris 10 only</dt> 205around bugs.</p>
182 <dd> 206 </dd>
183 <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>
184backends will be tried (in the reverse order as given here). If one are 208 <dd>
185specified, 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 </dd>
234 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
235 <dd>
236 <p>Kqueue deserves special mention, as at the time of this writing, it
237was broken on all BSDs except NetBSD (usually it doesn't work with
238anything but sockets and pipes, except on Darwin, where of course its
239completely useless). For this reason its not being &quot;autodetected&quot; unless
240you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p>
241 <p>It scales in the same way as the epoll backend, but the interface to the
242kernel is more efficient (which says nothing about its actual speed, of
243course). While starting and stopping an I/O watcher does not cause an
244extra syscall as with epoll, it still adds up to four event changes per
245incident, so its best to avoid that.</p>
246 </dd>
247 <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
248 <dd>
249 <p>This is not implemented yet (and might never be).</p>
250 </dd>
251 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
252 <dd>
253 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
254it's really slow, but it still scales very well (O(active_fds)).</p>
255 </dd>
256 <dt><code>EVBACKEND_ALL</code></dt>
257 <dd>
258 <p>Try all backends (even potentially broken ones that wouldn't be tried
259with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
260<code>EVBACKEND_ALL &amp; ~EVBACKEND_KQUEUE</code>.</p>
186 </dd> 261 </dd>
187 </dl> 262 </dl>
188 </p> 263 </p>
264 <p>If one or more of these are ored into the flags value, then only these
265backends will be tried (in the reverse order as given here). If none are
266specified, most compiled-in backend will be tried, usually in reverse
267order of their flag values :)</p>
189 </dd> 268 </dd>
190 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 269 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
191 <dd> 270 <dd>
192 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 271 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
193always distinct from the default loop. Unlike the default loop, it cannot 272always distinct from the default loop. Unlike the default loop, it cannot
… …
196 </dd> 275 </dd>
197 <dt>ev_default_destroy ()</dt> 276 <dt>ev_default_destroy ()</dt>
198 <dd> 277 <dd>
199 <p>Destroys the default loop again (frees all memory and kernel state 278 <p>Destroys the default loop again (frees all memory and kernel state
200etc.). This stops all registered event watchers (by not touching them in 279etc.). This stops all registered event watchers (by not touching them in
201any way whatsoever, although you cnanot rely on this :).</p> 280any way whatsoever, although you cannot rely on this :).</p>
202 </dd> 281 </dd>
203 <dt>ev_loop_destroy (loop)</dt> 282 <dt>ev_loop_destroy (loop)</dt>
204 <dd> 283 <dd>
205 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 284 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
206earlier call to <code>ev_loop_new</code>.</p> 285earlier call to <code>ev_loop_new</code>.</p>
… …
209 <dd> 288 <dd>
210 <p>This function reinitialises the kernel state for backends that have 289 <p>This function reinitialises the kernel state for backends that have
211one. Despite the name, you can call it anytime, but it makes most sense 290one. Despite the name, you can call it anytime, but it makes most sense
212after forking, in either the parent or child process (or both, but that 291after forking, in either the parent or child process (or both, but that
213again makes little sense).</p> 292again makes little sense).</p>
214 <p>You <i>must</i> call this function after forking if and only if you want to 293 <p>You <i>must</i> call this function in the child process after forking if and
215use the event library in both processes. If you just fork+exec, you don't 294only if you want to use the event library in both processes. If you just
216have to call it.</p> 295fork+exec, you don't have to call it.</p>
217 <p>The function itself is quite fast and its usually not a problem to call 296 <p>The function itself is quite fast and it's usually not a problem to call
218it just in case after a fork. To make this easy, the function will fit in 297it just in case after a fork. To make this easy, the function will fit in
219quite nicely into a call to <code>pthread_atfork</code>:</p> 298quite nicely into a call to <code>pthread_atfork</code>:</p>
220<pre> pthread_atfork (0, 0, ev_default_fork); 299<pre> pthread_atfork (0, 0, ev_default_fork);
221 300
222</pre> 301</pre>
302 <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
303without calling this function, so if you force one of those backends you
304do not need to care.</p>
223 </dd> 305 </dd>
224 <dt>ev_loop_fork (loop)</dt> 306 <dt>ev_loop_fork (loop)</dt>
225 <dd> 307 <dd>
226 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 308 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
227<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 309<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
228after fork, and how you do this is entirely your own problem.</p> 310after fork, and how you do this is entirely your own problem.</p>
229 </dd> 311 </dd>
230 <dt>unsigned int ev_method (loop)</dt> 312 <dt>unsigned int ev_backend (loop)</dt>
231 <dd> 313 <dd>
232 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 314 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
233use.</p> 315use.</p>
234 </dd> 316 </dd>
235 <dt>ev_tstamp = ev_now (loop)</dt> 317 <dt>ev_tstamp ev_now (loop)</dt>
236 <dd> 318 <dd>
237 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 319 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
238got events and started processing them. This timestamp does not change 320got events and started processing them. This timestamp does not change
239as long as callbacks are being processed, and this is also the base time 321as long as callbacks are being processed, and this is also the base time
240used for relative timers. You can treat it as the timestamp of the event 322used for relative timers. You can treat it as the timestamp of the event
… …
247events.</p> 329events.</p>
248 <p>If the flags argument is specified as 0, it will not return until either 330 <p>If the flags argument is specified as 0, it will not return until either
249no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 331no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
250 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 332 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
251those events and any outstanding ones, but will not block your process in 333those events and any outstanding ones, but will not block your process in
252case there are no events.</p> 334case there are no events and will return after one iteration of the loop.</p>
253 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 335 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
254neccessary) and will handle those and any outstanding ones. It will block 336neccessary) and will handle those and any outstanding ones. It will block
255your process until at least one new event arrives.</p> 337your process until at least one new event arrives, and will return after
338one iteration of the loop.</p>
256 <p>This flags value could be used to implement alternative looping 339 <p>This flags value could be used to implement alternative looping
257constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 340constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
258more generic mechanism.</p> 341more generic mechanism.</p>
342 <p>Here are the gory details of what ev_loop does:</p>
343<pre> 1. If there are no active watchers (reference count is zero), return.
344 2. Queue and immediately call all prepare watchers.
345 3. If we have been forked, recreate the kernel state.
346 4. Update the kernel state with all outstanding changes.
347 5. Update the &quot;event loop time&quot;.
348 6. Calculate for how long to block.
349 7. Block the process, waiting for events.
350 8. Update the &quot;event loop time&quot; and do time jump handling.
351 9. Queue all outstanding timers.
352 10. Queue all outstanding periodics.
353 11. If no events are pending now, queue all idle watchers.
354 12. Queue all check watchers.
355 13. Call all queued watchers in reverse order (i.e. check watchers first).
356 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
357 was used, return, otherwise continue with step #1.
358
359</pre>
259 </dd> 360 </dd>
260 <dt>ev_unloop (loop, how)</dt> 361 <dt>ev_unloop (loop, how)</dt>
261 <dd> 362 <dd>
262 <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument 363 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
364has processed all outstanding events). The <code>how</code> argument must be either
263must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> 365<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
264call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> 366<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
265calls return.</p>
266 </dd> 367 </dd>
267 <dt>ev_ref (loop)</dt> 368 <dt>ev_ref (loop)</dt>
268 <dt>ev_unref (loop)</dt> 369 <dt>ev_unref (loop)</dt>
269 <dd> 370 <dd>
270 <p>Ref/unref can be used to add or remove a refcount on the event loop: Every 371 <p>Ref/unref can be used to add or remove a reference count on the event
271watcher keeps one reference. If you have a long-runing watcher you never 372loop: Every watcher keeps one reference, and as long as the reference
272unregister that should not keep ev_loop from running, ev_unref() after 373count is nonzero, <code>ev_loop</code> will not return on its own. If you have
273starting, and ev_ref() before stopping it. Libev itself uses this for 374a watcher you never unregister that should not keep <code>ev_loop</code> from
274example for its internal signal pipe: It is not visible to you as a user 375returning, ev_unref() after starting, and ev_ref() before stopping it. For
275and should not keep <code>ev_loop</code> from exiting if the work is done. It is 376example, libev itself uses this for its internal signal pipe: It is not
276also an excellent way to do this for generic recurring timers or from 377visible to the libev user and should not keep <code>ev_loop</code> from exiting if
277within third-party libraries. Just remember to unref after start and ref 378no event watchers registered by it are active. It is also an excellent
278before stop.</p> 379way to do this for generic recurring timers or from within third-party
380libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
279 </dd> 381 </dd>
280</dl> 382</dl>
281 383
282</div> 384</div>
283<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 385<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
284<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 386<div id="ANATOMY_OF_A_WATCHER_CONTENT">
285<p>A watcher is a structure that you create and register to record your 387<p>A watcher is a structure that you create and register to record your
286interest in some event. For instance, if you want to wait for STDIN to 388interest in some event. For instance, if you want to wait for STDIN to
287become readable, you would create an ev_io watcher for that:</p> 389become readable, you would create an <code>ev_io</code> watcher for that:</p>
288<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 390<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
289 { 391 {
290 ev_io_stop (w); 392 ev_io_stop (w);
291 ev_unloop (loop, EVUNLOOP_ALL); 393 ev_unloop (loop, EVUNLOOP_ALL);
292 } 394 }
… …
315with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 417with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
316*)</code>), and you can stop watching for events at any time by calling the 418*)</code>), and you can stop watching for events at any time by calling the
317corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 419corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
318<p>As long as your watcher is active (has been started but not stopped) you 420<p>As long as your watcher is active (has been started but not stopped) you
319must not touch the values stored in it. Most specifically you must never 421must not touch the values stored in it. Most specifically you must never
320reinitialise it or call its set method.</p> 422reinitialise it or call its set macro.</p>
321<p>You cna check wether an event is active by calling the <code>ev_is_active 423<p>You can check whether an event is active by calling the <code>ev_is_active
322(watcher *)</code> macro. To see wether an event is outstanding (but the 424(watcher *)</code> macro. To see whether an event is outstanding (but the
323callback for it has not been called yet) you cna use the <code>ev_is_pending 425callback for it has not been called yet) you can use the <code>ev_is_pending
324(watcher *)</code> macro.</p> 426(watcher *)</code> macro.</p>
325<p>Each and every callback receives the event loop pointer as first, the 427<p>Each and every callback receives the event loop pointer as first, the
326registered watcher structure as second, and a bitset of received events as 428registered watcher structure as second, and a bitset of received events as
327third argument.</p> 429third argument.</p>
328<p>The rceeived events usually include a single bit per event type received 430<p>The received events usually include a single bit per event type received
329(you can receive multiple events at the same time). The possible bit masks 431(you can receive multiple events at the same time). The possible bit masks
330are:</p> 432are:</p>
331<dl> 433<dl>
332 <dt>EV_READ</dt> 434 <dt><code>EV_READ</code></dt>
333 <dt>EV_WRITE</dt> 435 <dt><code>EV_WRITE</code></dt>
334 <dd> 436 <dd>
335 <p>The file descriptor in the ev_io watcher has become readable and/or 437 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
336writable.</p> 438writable.</p>
337 </dd> 439 </dd>
338 <dt>EV_TIMEOUT</dt> 440 <dt><code>EV_TIMEOUT</code></dt>
339 <dd>
340 <p>The ev_timer watcher has timed out.</p>
341 </dd> 441 <dd>
342 <dt>EV_PERIODIC</dt> 442 <p>The <code>ev_timer</code> watcher has timed out.</p>
343 <dd> 443 </dd>
344 <p>The ev_periodic watcher has timed out.</p> 444 <dt><code>EV_PERIODIC</code></dt>
345 </dd> 445 <dd>
346 <dt>EV_SIGNAL</dt> 446 <p>The <code>ev_periodic</code> watcher has timed out.</p>
347 <dd> 447 </dd>
448 <dt><code>EV_SIGNAL</code></dt>
449 <dd>
348 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 450 <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
349 </dd>
350 <dt>EV_CHILD</dt>
351 <dd> 451 </dd>
452 <dt><code>EV_CHILD</code></dt>
453 <dd>
352 <p>The pid specified in the ev_child watcher has received a status change.</p> 454 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
353 </dd>
354 <dt>EV_IDLE</dt>
355 <dd> 455 </dd>
456 <dt><code>EV_IDLE</code></dt>
457 <dd>
356 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 458 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
357 </dd>
358 <dt>EV_PREPARE</dt>
359 <dt>EV_CHECK</dt>
360 <dd> 459 </dd>
460 <dt><code>EV_PREPARE</code></dt>
461 <dt><code>EV_CHECK</code></dt>
462 <dd>
361 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 463 <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
362to gather new events, and all ev_check watchers are invoked just after 464to gather new events, and all <code>ev_check</code> watchers are invoked just after
363<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 465<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
364received events. Callbacks of both watcher types can start and stop as 466received events. Callbacks of both watcher types can start and stop as
365many watchers as they want, and all of them will be taken into account 467many watchers as they want, and all of them will be taken into account
366(for example, a ev_prepare watcher might start an idle watcher to keep 468(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
367<code>ev_loop</code> from blocking).</p> 469<code>ev_loop</code> from blocking).</p>
368 </dd> 470 </dd>
369 <dt>EV_ERROR</dt> 471 <dt><code>EV_ERROR</code></dt>
370 <dd> 472 <dd>
371 <p>An unspecified error has occured, the watcher has been stopped. This might 473 <p>An unspecified error has occured, the watcher has been stopped. This might
372happen because the watcher could not be properly started because libev 474happen because the watcher could not be properly started because libev
373ran out of memory, a file descriptor was found to be closed or any other 475ran out of memory, a file descriptor was found to be closed or any other
374problem. You best act on it by reporting the problem and somehow coping 476problem. You best act on it by reporting the problem and somehow coping
… …
383 485
384</div> 486</div>
385<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 487<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
386<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 488<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
387<p>Each watcher has, by default, a member <code>void *data</code> that you can change 489<p>Each watcher has, by default, a member <code>void *data</code> that you can change
388and read at any time, libev will completely ignore it. This cna be used 490and read at any time, libev will completely ignore it. This can be used
389to associate arbitrary data with your watcher. If you need more data and 491to associate arbitrary data with your watcher. If you need more data and
390don't want to allocate memory and store a pointer to it in that data 492don't want to allocate memory and store a pointer to it in that data
391member, you can also &quot;subclass&quot; the watcher type and provide your own 493member, you can also &quot;subclass&quot; the watcher type and provide your own
392data:</p> 494data:</p>
393<pre> struct my_io 495<pre> struct my_io
… …
420<div id="WATCHER_TYPES_CONTENT"> 522<div id="WATCHER_TYPES_CONTENT">
421<p>This section describes each watcher in detail, but will not repeat 523<p>This section describes each watcher in detail, but will not repeat
422information given in the last section.</p> 524information given in the last section.</p>
423 525
424</div> 526</div>
425<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 527<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
426<div id="struct_ev_io_is_my_file_descriptor_r-2"> 528<div id="code_ev_io_code_is_this_file_descrip-2">
427<p>I/O watchers check wether a file descriptor is readable or writable 529<p>I/O watchers check whether a file descriptor is readable or writable
428in each iteration of the event loop (This behaviour is called 530in each iteration of the event loop (This behaviour is called
429level-triggering because you keep receiving events as long as the 531level-triggering because you keep receiving events as long as the
430condition persists. Remember you cna stop the watcher if you don't want to 532condition persists. Remember you can stop the watcher if you don't want to
431act on the event and neither want to receive future events).</p> 533act on the event and neither want to receive future events).</p>
534<p>In general you can register as many read and/or write event watchers per
535fd as you want (as long as you don't confuse yourself). Setting all file
536descriptors to non-blocking mode is also usually a good idea (but not
537required if you know what you are doing).</p>
538<p>You have to be careful with dup'ed file descriptors, though. Some backends
539(the linux epoll backend is a notable example) cannot handle dup'ed file
540descriptors correctly if you register interest in two or more fds pointing
541to the same underlying file/socket etc. description (that is, they share
542the same underlying &quot;file open&quot;).</p>
543<p>If you must do this, then force the use of a known-to-be-good backend
544(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
545<code>EVBACKEND_POLL</code>).</p>
432<dl> 546<dl>
433 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 547 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
434 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 548 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
435 <dd> 549 <dd>
436 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 550 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
437events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 551events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
438EV_WRITE</code> to receive the given events.</p> 552EV_WRITE</code> to receive the given events.</p>
439 </dd> 553 </dd>
440</dl> 554</dl>
441 555
442</div> 556</div>
443<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 557<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
444<div id="struct_ev_timer_relative_and_optiona-2"> 558<div id="code_ev_timer_code_relative_and_opti-2">
445<p>Timer watchers are simple relative timers that generate an event after a 559<p>Timer watchers are simple relative timers that generate an event after a
446given time, and optionally repeating in regular intervals after that.</p> 560given time, and optionally repeating in regular intervals after that.</p>
447<p>The timers are based on real time, that is, if you register an event that 561<p>The timers are based on real time, that is, if you register an event that
448times out after an hour and youreset your system clock to last years 562times out after an hour and you reset your system clock to last years
449time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 563time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
450detecting time jumps is hard, and soem inaccuracies are unavoidable (the 564detecting time jumps is hard, and some inaccuracies are unavoidable (the
451monotonic clock option helps a lot here).</p> 565monotonic clock option helps a lot here).</p>
566<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
567time. This is usually the right thing as this timestamp refers to the time
568of the event triggering whatever timeout you are modifying/starting. If
569you suspect event processing to be delayed and you <i>need</i> to base the timeout
570on the current time, use something like this to adjust for this:</p>
571<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
572
573</pre>
574<p>The callback is guarenteed to be invoked only when its timeout has passed,
575but if multiple timers become ready during the same loop iteration then
576order of execution is undefined.</p>
452<dl> 577<dl>
453 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 578 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
454 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 579 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
455 <dd> 580 <dd>
456 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 581 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
458timer will automatically be configured to trigger again <code>repeat</code> seconds 583timer will automatically be configured to trigger again <code>repeat</code> seconds
459later, again, and again, until stopped manually.</p> 584later, again, and again, until stopped manually.</p>
460 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 585 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
461configure a timer to trigger every 10 seconds, then it will trigger at 586configure a timer to trigger every 10 seconds, then it will trigger at
462exactly 10 second intervals. If, however, your program cannot keep up with 587exactly 10 second intervals. If, however, your program cannot keep up with
463the timer (ecause it takes longer than those 10 seconds to do stuff) the 588the timer (because it takes longer than those 10 seconds to do stuff) the
464timer will not fire more than once per event loop iteration.</p> 589timer will not fire more than once per event loop iteration.</p>
465 </dd> 590 </dd>
466 <dt>ev_timer_again (loop)</dt> 591 <dt>ev_timer_again (loop)</dt>
467 <dd> 592 <dd>
468 <p>This will act as if the timer timed out and restart it again if it is 593 <p>This will act as if the timer timed out and restart it again if it is
… …
472value), or reset the running timer to the repeat value.</p> 597value), or reset the running timer to the repeat value.</p>
473 <p>This sounds a bit complicated, but here is a useful and typical 598 <p>This sounds a bit complicated, but here is a useful and typical
474example: Imagine you have a tcp connection and you want a so-called idle 599example: Imagine you have a tcp connection and you want a so-called idle
475timeout, that is, you want to be called when there have been, say, 60 600timeout, that is, you want to be called when there have been, say, 60
476seconds of inactivity on the socket. The easiest way to do this is to 601seconds of inactivity on the socket. The easiest way to do this is to
477configure an ev_timer with after=repeat=60 and calling ev_timer_again each 602configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
478time you successfully read or write some data. If you go into an idle 603time you successfully read or write some data. If you go into an idle
479state where you do not expect data to travel on the socket, you can stop 604state where you do not expect data to travel on the socket, you can stop
480the timer, and again will automatically restart it if need be.</p> 605the timer, and again will automatically restart it if need be.</p>
481 </dd> 606 </dd>
482</dl> 607</dl>
483 608
484</div> 609</div>
485<h2 id="ev_periodic">ev_periodic</h2> 610<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
486<div id="ev_periodic_CONTENT"> 611<div id="code_ev_periodic_code_to_cron_or_not-2">
487<p>Periodic watchers are also timers of a kind, but they are very versatile 612<p>Periodic watchers are also timers of a kind, but they are very versatile
488(and unfortunately a bit complex).</p> 613(and unfortunately a bit complex).</p>
489<p>Unlike ev_timer's, they are not based on real time (or relative time) 614<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
490but on wallclock time (absolute time). You can tell a periodic watcher 615but on wallclock time (absolute time). You can tell a periodic watcher
491to trigger &quot;at&quot; some specific point in time. For example, if you tell a 616to trigger &quot;at&quot; some specific point in time. For example, if you tell a
492periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 617periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now ()
493+ 10.&gt;) and then reset your system clock to the last year, then it will 618+ 10.&gt;) and then reset your system clock to the last year, then it will
494take a year to trigger the event (unlike an ev_timer, which would trigger 619take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
495roughly 10 seconds later and of course not if you reset your system time 620roughly 10 seconds later and of course not if you reset your system time
496again).</p> 621again).</p>
497<p>They can also be used to implement vastly more complex timers, such as 622<p>They can also be used to implement vastly more complex timers, such as
498triggering an event on eahc midnight, local time.</p> 623triggering an event on eahc midnight, local time.</p>
624<p>As with timers, the callback is guarenteed to be invoked only when the
625time (<code>at</code>) has been passed, but if multiple periodic timers become ready
626during the same loop iteration then order of execution is undefined.</p>
499<dl> 627<dl>
500 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 628 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
501 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 629 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
502 <dd> 630 <dd>
503 <p>Lots of arguments, lets sort it out... There are basically three modes of 631 <p>Lots of arguments, lets sort it out... There are basically three modes of
504operation, and we will explain them from simplest to complex:</p> 632operation, and we will explain them from simplest to complex:</p>
505
506
507
508
509 <p> 633 <p>
510 <dl> 634 <dl>
511 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 635 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
512 <dd> 636 <dd>
513 <p>In this configuration the watcher triggers an event at the wallclock time 637 <p>In this configuration the watcher triggers an event at the wallclock time
… …
525<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 649<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
526 650
527</pre> 651</pre>
528 <p>This doesn't mean there will always be 3600 seconds in between triggers, 652 <p>This doesn't mean there will always be 3600 seconds in between triggers,
529but only that the the callback will be called when the system time shows a 653but only that the the callback will be called when the system time shows a
530full hour (UTC), or more correct, when the system time is evenly divisible 654full hour (UTC), or more correctly, when the system time is evenly divisible
531by 3600.</p> 655by 3600.</p>
532 <p>Another way to think about it (for the mathematically inclined) is that 656 <p>Another way to think about it (for the mathematically inclined) is that
533ev_periodic will try to run the callback in this mode at the next possible 657<code>ev_periodic</code> will try to run the callback in this mode at the next possible
534time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 658time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
535 </dd> 659 </dd>
536 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 660 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
537 <dd> 661 <dd>
538 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 662 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
539ignored. Instead, each time the periodic watcher gets scheduled, the 663ignored. Instead, each time the periodic watcher gets scheduled, the
540reschedule callback will be called with the watcher as first, and the 664reschedule callback will be called with the watcher as first, and the
541current time as second argument.</p> 665current time as second argument.</p>
542 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 666 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
543periodic watcher, ever, or make any event loop modificstions</i>. If you need 667ever, or make any event loop modifications</i>. If you need to stop it,
544to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 668return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
669starting a prepare watcher).</p>
545 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 670 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
546ev_tstamp now)&gt;, e.g.:</p> 671ev_tstamp now)</code>, e.g.:</p>
547<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 672<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
548 { 673 {
549 return now + 60.; 674 return now + 60.;
550 } 675 }
551 676
552</pre> 677</pre>
553 <p>It must return the next time to trigger, based on the passed time value 678 <p>It must return the next time to trigger, based on the passed time value
554(that is, the lowest time value larger than to the second argument). It 679(that is, the lowest time value larger than to the second argument). It
555will usually be called just before the callback will be triggered, but 680will usually be called just before the callback will be triggered, but
556might be called at other times, too.</p> 681might be called at other times, too.</p>
682 <p>NOTE: <i>This callback must always return a time that is later than the
683passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
557 <p>This can be used to create very complex timers, such as a timer that 684 <p>This can be used to create very complex timers, such as a timer that
558triggers on each midnight, local time. To do this, you would calculate the 685triggers on each midnight, local time. To do this, you would calculate the
559next midnight after <code>now</code> and return the timestamp value for this. How you do this 686next midnight after <code>now</code> and return the timestamp value for this. How
560is, again, up to you (but it is not trivial).</p> 687you do this is, again, up to you (but it is not trivial, which is the main
688reason I omitted it as an example).</p>
561 </dd> 689 </dd>
562 </dl> 690 </dl>
563 </p> 691 </p>
564 </dd> 692 </dd>
565 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 693 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
570program when the crontabs have changed).</p> 698program when the crontabs have changed).</p>
571 </dd> 699 </dd>
572</dl> 700</dl>
573 701
574</div> 702</div>
575<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 703<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
576<div id="ev_signal_signal_me_when_a_signal_ge-2"> 704<div id="code_ev_signal_code_signal_me_when_a-2">
577<p>Signal watchers will trigger an event when the process receives a specific 705<p>Signal watchers will trigger an event when the process receives a specific
578signal one or more times. Even though signals are very asynchronous, libev 706signal one or more times. Even though signals are very asynchronous, libev
579will try its best to deliver signals synchronously, i.e. as part of the 707will try it's best to deliver signals synchronously, i.e. as part of the
580normal event processing, like any other event.</p> 708normal event processing, like any other event.</p>
581<p>You cna configure as many watchers as you like per signal. Only when the 709<p>You can configure as many watchers as you like per signal. Only when the
582first watcher gets started will libev actually register a signal watcher 710first watcher gets started will libev actually register a signal watcher
583with the kernel (thus it coexists with your own signal handlers as long 711with the kernel (thus it coexists with your own signal handlers as long
584as you don't register any with libev). Similarly, when the last signal 712as you don't register any with libev). Similarly, when the last signal
585watcher for a signal is stopped libev will reset the signal handler to 713watcher for a signal is stopped libev will reset the signal handler to
586SIG_DFL (regardless of what it was set to before).</p> 714SIG_DFL (regardless of what it was set to before).</p>
… …
592of the <code>SIGxxx</code> constants).</p> 720of the <code>SIGxxx</code> constants).</p>
593 </dd> 721 </dd>
594</dl> 722</dl>
595 723
596</div> 724</div>
597<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 725<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
598<div id="ev_child_wait_for_pid_status_changes-2"> 726<div id="code_ev_child_code_wait_for_pid_stat-2">
599<p>Child watchers trigger when your process receives a SIGCHLD in response to 727<p>Child watchers trigger when your process receives a SIGCHLD in response to
600some child status changes (most typically when a child of yours dies).</p> 728some child status changes (most typically when a child of yours dies).</p>
601<dl> 729<dl>
602 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 730 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
603 <dt>ev_child_set (ev_child *, int pid)</dt> 731 <dt>ev_child_set (ev_child *, int pid)</dt>
604 <dd> 732 <dd>
605 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 733 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
606<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 734<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
607at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 735at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
608the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 736the status word (use the macros from <code>sys/wait.h</code> and see your systems
737<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
609contains the pid of the process causing the status change.</p> 738process causing the status change.</p>
610 </dd> 739 </dd>
611</dl> 740</dl>
612 741
613</div> 742</div>
614<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 743<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
615<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 744<div id="code_ev_idle_code_when_you_ve_got_no-2">
616<p>Idle watchers trigger events when there are no other I/O or timer (or 745<p>Idle watchers trigger events when there are no other events are pending
617periodic) events pending. That is, as long as your process is busy 746(prepare, check and other idle watchers do not count). That is, as long
618handling sockets or timeouts it will not be called. But when your process 747as your process is busy handling sockets or timeouts (or even signals,
619is idle all idle watchers are being called again and again - until 748imagine) it will not be triggered. But when your process is idle all idle
749watchers are being called again and again, once per event loop iteration -
620stopped, that is, or your process receives more events.</p> 750until stopped, that is, or your process receives more events and becomes
751busy.</p>
621<p>The most noteworthy effect is that as long as any idle watchers are 752<p>The most noteworthy effect is that as long as any idle watchers are
622active, the process will not block when waiting for new events.</p> 753active, the process will not block when waiting for new events.</p>
623<p>Apart from keeping your process non-blocking (which is a useful 754<p>Apart from keeping your process non-blocking (which is a useful
624effect on its own sometimes), idle watchers are a good place to do 755effect on its own sometimes), idle watchers are a good place to do
625&quot;pseudo-background processing&quot;, or delay processing stuff to after the 756&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
632believe me.</p> 763believe me.</p>
633 </dd> 764 </dd>
634</dl> 765</dl>
635 766
636</div> 767</div>
637<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 768<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
638<div id="prepare_and_check_your_hooks_into_th-2"> 769<div id="code_ev_prepare_code_and_code_ev_che-2">
639<p>Prepare and check watchers usually (but not always) are used in 770<p>Prepare and check watchers are usually (but not always) used in tandem:
640tandom. Prepare watchers get invoked before the process blocks and check 771prepare watchers get invoked before the process blocks and check watchers
641watchers afterwards.</p> 772afterwards.</p>
642<p>Their main purpose is to integrate other event mechanisms into libev. This 773<p>Their main purpose is to integrate other event mechanisms into libev. This
643could be used, for example, to track variable changes, implement your own 774could be used, for example, to track variable changes, implement your own
644watchers, integrate net-snmp or a coroutine library and lots more.</p> 775watchers, integrate net-snmp or a coroutine library and lots more.</p>
645<p>This is done by examining in each prepare call which file descriptors need 776<p>This is done by examining in each prepare call which file descriptors need
646to be watched by the other library, registering ev_io watchers for them 777to be watched by the other library, registering <code>ev_io</code> watchers for
647and starting an ev_timer watcher for any timeouts (many libraries provide 778them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
648just this functionality). Then, in the check watcher you check for any 779provide just this functionality). Then, in the check watcher you check for
649events that occured (by making your callbacks set soem flags for example) 780any events that occured (by checking the pending status of all watchers
650and call back into the library.</p> 781and stopping them) and call back into the library. The I/O and timer
782callbacks will never actually be called (but must be valid nevertheless,
783because you never know, you know?).</p>
651<p>As another example, the perl Coro module uses these hooks to integrate 784<p>As another example, the Perl Coro module uses these hooks to integrate
652coroutines into libev programs, by yielding to other active coroutines 785coroutines into libev programs, by yielding to other active coroutines
653during each prepare and only letting the process block if no coroutines 786during each prepare and only letting the process block if no coroutines
654are ready to run.</p> 787are ready to run (it's actually more complicated: it only runs coroutines
788with priority higher than or equal to the event loop and one coroutine
789of lower priority, but only once, using idle watchers to keep the event
790loop from blocking if lower-priority coroutines are active, thus mapping
791low-priority coroutines to idle/background tasks).</p>
655<dl> 792<dl>
656 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 793 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
657 <dt>ev_check_init (ev_check *, callback)</dt> 794 <dt>ev_check_init (ev_check *, callback)</dt>
658 <dd> 795 <dd>
659 <p>Initialises and configures the prepare or check watcher - they have no 796 <p>Initialises and configures the prepare or check watcher - they have no
660parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 797parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
661macros, but using them is utterly, utterly pointless.</p> 798macros, but using them is utterly, utterly and completely pointless.</p>
662 </dd> 799 </dd>
663</dl> 800</dl>
664 801
665</div> 802</div>
666<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 803<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
667<div id="OTHER_FUNCTIONS_CONTENT"> 804<div id="OTHER_FUNCTIONS_CONTENT">
668<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 805<p>There are some other functions of possible interest. Described. Here. Now.</p>
669<dl> 806<dl>
670 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 807 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
671 <dd> 808 <dd>
672 <p>This function combines a simple timer and an I/O watcher, calls your 809 <p>This function combines a simple timer and an I/O watcher, calls your
673callback on whichever event happens first and automatically stop both 810callback on whichever event happens first and automatically stop both
674watchers. This is useful if you want to wait for a single event on an fd 811watchers. This is useful if you want to wait for a single event on an fd
675or timeout without havign to allocate/configure/start/stop/free one or 812or timeout without having to allocate/configure/start/stop/free one or
676more watchers yourself.</p> 813more watchers yourself.</p>
677 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 814 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
678ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 815is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
679will be craeted and started.</p> 816<code>events</code> set will be craeted and started.</p>
680 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 817 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
681started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 818started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
682= 0) will be started.</p> 819repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
820dubious value.</p>
683 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 821 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
684gets passed an events set (normally a combination of EV_ERROR, EV_READ, 822passed an <code>revents</code> set like normal event callbacks (a combination of
685EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 823<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
824value passed to <code>ev_once</code>:</p>
686<pre> static void stdin_ready (int revents, void *arg) 825<pre> static void stdin_ready (int revents, void *arg)
687 { 826 {
688 if (revents &amp; EV_TIMEOUT) 827 if (revents &amp; EV_TIMEOUT)
689 /* doh, nothing entered */ 828 /* doh, nothing entered */;
690 else if (revents &amp; EV_READ) 829 else if (revents &amp; EV_READ)
691 /* stdin might have data for us, joy! */ 830 /* stdin might have data for us, joy! */;
692 } 831 }
693 832
694 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 833 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
695 834
696</pre> 835</pre>
697 </dd> 836 </dd>
698 <dt>ev_feed_event (loop, watcher, int events)</dt> 837 <dt>ev_feed_event (loop, watcher, int events)</dt>
699 <dd> 838 <dd>
700 <p>Feeds the given event set into the event loop, as if the specified event 839 <p>Feeds the given event set into the event loop, as if the specified event
701has happened for the specified watcher (which must be a pointer to an 840had happened for the specified watcher (which must be a pointer to an
702initialised but not necessarily active event watcher).</p> 841initialised but not necessarily started event watcher).</p>
703 </dd> 842 </dd>
704 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 843 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
705 <dd> 844 <dd>
706 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 845 <p>Feed an event on the given fd, as if a file descriptor backend detected
846the given events it.</p>
707 </dd> 847 </dd>
708 <dt>ev_feed_signal_event (loop, int signum)</dt> 848 <dt>ev_feed_signal_event (loop, int signum)</dt>
709 <dd> 849 <dd>
710 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 850 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
711 </dd> 851 </dd>
712</dl> 852</dl>
853
854</div>
855<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
856<div id="LIBEVENT_EMULATION_CONTENT">
857<p>Libev offers a compatibility emulation layer for libevent. It cannot
858emulate the internals of libevent, so here are some usage hints:</p>
859<dl>
860 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
861 <dt>* The following members are fully supported: ev_base, ev_callback,
862ev_arg, ev_fd, ev_res, ev_events.</dt>
863 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
864maintained by libev, it does not work exactly the same way as in libevent (consider
865it a private API).</dt>
866 <dt>* Priorities are not currently supported. Initialising priorities
867will fail and all watchers will have the same priority, even though there
868is an ev_pri field.</dt>
869 <dt>* Other members are not supported.</dt>
870 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
871to use the libev header file and library.</dt>
872</dl>
873
874</div>
875<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
876<div id="C_SUPPORT_CONTENT">
877<p>TBD.</p>
713 878
714</div> 879</div>
715<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 880<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
716<div id="AUTHOR_CONTENT"> 881<div id="AUTHOR_CONTENT">
717<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 882<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

Diff Legend

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