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 1.12 by root, Mon Nov 12 08:35:18 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="Mon Nov 12 09:35:17 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
… …
24<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 24<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> 25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
26</ul> 26</ul>
27</li> 27</li>
28<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 28<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> 29<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> 30<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> 31<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</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> 32<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> 33<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> 34<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> 35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li>
36</ul> 36</ul>
37</li> 37</li>
38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
39<li><a href="#AUTHOR">AUTHOR</a> 39<li><a href="#AUTHOR">AUTHOR</a>
… …
55</div> 55</div>
56<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 56<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p>
57<div id="DESCRIPTION_CONTENT"> 57<div id="DESCRIPTION_CONTENT">
58<p>Libev is an event loop: you register interest in certain events (such as a 58<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 59file descriptor being readable or a timeout occuring), and it will manage
60these event sources and provide your program events.</p> 60these 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 61<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 62(or thread) by executing the <i>event loop</i> handler, and will then
63communicate events via a callback mechanism.</p> 63communicate events via a callback mechanism.</p>
64<p>You register interest in certain events by registering so-called <i>event 64<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 65watchers</i>, which are relatively small C structures you initialise with the
… …
71<div id="FEATURES_CONTENT"> 71<div id="FEATURES_CONTENT">
72<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 72<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific
73kqueue mechanisms for file descriptor events, relative timers, absolute 73kqueue mechanisms for file descriptor events, relative timers, absolute
74timers with customised rescheduling, signal events, process status change 74timers with customised rescheduling, signal events, process status change
75events (related to SIGCHLD), and event watchers dealing with the event 75events (related to SIGCHLD), and event watchers dealing with the event
76loop mechanism itself (idle, prepare and check watchers).</p> 76loop mechanism itself (idle, prepare and check watchers). It also is quite
77fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing
78it to libevent for example).</p>
77 79
78</div> 80</div>
79<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 81<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
80<div id="CONVENTIONS_CONTENT"> 82<div id="CONVENTIONS_CONTENT">
81<p>Libev is very configurable. In this manual the default configuration 83<p>Libev is very configurable. In this manual the default configuration
82will be described, which supports multiple event loops. For more info 84will be described, which supports multiple event loops. For more info
83about various configuraiton options please have a look at the file 85about various configuration options please have a look at the file
84<cite>README.embed</cite> in the libev distribution. If libev was configured without 86<cite>README.embed</cite> in the libev distribution. If libev was configured without
85support for multiple event loops, then all functions taking an initial 87support 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>) 88argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
87will not have this argument.</p> 89will not have this argument.</p>
88 90
… …
105 <p>You can find out the major and minor version numbers of the library 107 <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 108you 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 109<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 110symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
109version of the library your program was compiled against.</p> 111version of the library your program was compiled against.</p>
110 <p>Usually, its a good idea to terminate if the major versions mismatch, 112 <p>Usually, it's a good idea to terminate if the major versions mismatch,
111as this indicates an incompatible change. Minor versions are usually 113as this indicates an incompatible change. Minor versions are usually
112compatible to older versions, so a larger minor version alone is usually 114compatible to older versions, so a larger minor version alone is usually
113not a problem.</p> 115not a problem.</p>
114 </dd> 116 </dd>
115 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 117 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
116 <dd> 118 <dd>
117 <p>Sets the allocation function to use (the prototype is similar to the 119 <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 120realloc C function, the semantics are identical). It is used to allocate
119here). If it returns zero when memory needs to be allocated, the library 121and free memory (no surprises here). If it returns zero when memory
120might abort or take some potentially destructive action. The default is 122needs to be allocated, the library might abort or take some potentially
121your system realloc function.</p> 123destructive action. The default is your system realloc function.</p>
122 <p>You could override this function in high-availability programs to, say, 124 <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, 125free 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> 126or even to sleep a while and retry until some memory is available.</p>
125 </dd> 127 </dd>
126 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 128 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
127 <dd> 129 <dd>
128 <p>Set the callback function to call on a retryable syscall error (such 130 <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 131as failed select, poll, epoll_wait). The message is a printable string
130indicating the system call or subsystem causing the problem. If this 132indicating the system call or subsystem causing the problem. If this
131callback is set, then libev will expect it to remedy the sitution, no 133callback is set, then libev will expect it to remedy the sitution, no
132matter what, when it returns. That is, libev will geenrally retry the 134matter what, when it returns. That is, libev will generally retry the
133requested operation, or, if the condition doesn't go away, do bad stuff 135requested operation, or, if the condition doesn't go away, do bad stuff
134(such as abort).</p> 136(such as abort).</p>
135 </dd> 137 </dd>
136</dl> 138</dl>
137 139
… …
141<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 143<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 144types of such loops, the <i>default</i> loop, which supports signals and child
143events, and dynamically created loops which do not.</p> 145events, and dynamically created loops which do not.</p>
144<p>If you use threads, a common model is to run the default event loop 146<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 147in your main thread (or in a separate thrad) and for each thread you
146create, you also create another event loop. Libev itself does no lockign 148create, you also create another event loop. Libev itself does no locking
147whatsoever, so if you mix calls to different event loops, make sure you 149whatsoever, 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> 150threads, make sure you lock (this is usually a bad idea, though, even if
151done correctly, because it's hideous and inefficient).</p>
149<dl> 152<dl>
150 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 153 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
151 <dd> 154 <dd>
152 <p>This will initialise the default event loop if it hasn't been initialised 155 <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 156yet 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 157false. If it already was initialised it simply returns it (and ignores the
155flags).</p> 158flags).</p>
156 <p>If you don't know what event loop to use, use the one returned from this 159 <p>If you don't know what event loop to use, use the one returned from this
157function.</p> 160function.</p>
158 <p>The flags argument can be used to specify special behaviour or specific 161 <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> 162backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>
160 <p>It supports the following flags:</p> 163 <p>It supports the following flags:</p>
161 <p> 164 <p>
162 <dl> 165 <dl>
163 <dt>EVFLAG_AUTO</dt> 166 <dt><code>EVFLAG_AUTO</code></dt>
164 <dd> 167 <dd>
165 <p>The default flags value. Use this if you have no clue (its the right 168 <p>The default flags value. Use this if you have no clue (it's the right
166thing, believe me).</p> 169thing, believe me).</p>
167 </dd> 170 </dd>
168 <dt>EVFLAG_NOENV</dt> 171 <dt><code>EVFLAG_NOENV</code></dt>
169 <dd> 172 <dd>
170 <p>If this flag bit is ored into the flag value then libev will <i>not</i> look 173 <p>If this flag bit is ored into the flag value (or the program runs setuid
171at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this 174or setgid) then libev will <i>not</i> look at the environment variable
172environment variable will override the flags completely. This is useful 175<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
176override the flags completely if it is found in the environment. This is
173to try out specific backends to tets their performance, or to work around 177useful to try out specific backends to test their performance, or to work
174bugs.</p> 178around bugs.</p>
175 </dd> 179 </dd>
176 <dt>EVMETHOD_SELECT portable select backend</dt> 180 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>
177 <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> 181 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
178 <dt>EVMETHOD_EPOLL linux only</dt> 182 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
179 <dt>EVMETHOD_KQUEUE some bsds only</dt> 183 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
180 <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> 184 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
181 <dt>EVMETHOD_PORT solaris 10 only</dt> 185 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
182 <dd> 186 <dd>
183 <p>If one or more of these are ored into the flags value, then only these 187 <p>If one or more of these are ored into the flags value, then only these
184backends will be tried (in the reverse order as given here). If one are 188backends will be tried (in the reverse order as given here). If one are
185specified, any backend will do.</p> 189specified, any backend will do.</p>
186 </dd> 190 </dd>
… …
196 </dd> 200 </dd>
197 <dt>ev_default_destroy ()</dt> 201 <dt>ev_default_destroy ()</dt>
198 <dd> 202 <dd>
199 <p>Destroys the default loop again (frees all memory and kernel state 203 <p>Destroys the default loop again (frees all memory and kernel state
200etc.). This stops all registered event watchers (by not touching them in 204etc.). This stops all registered event watchers (by not touching them in
201any way whatsoever, although you cnanot rely on this :).</p> 205any way whatsoever, although you cannot rely on this :).</p>
202 </dd> 206 </dd>
203 <dt>ev_loop_destroy (loop)</dt> 207 <dt>ev_loop_destroy (loop)</dt>
204 <dd> 208 <dd>
205 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 209 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
206earlier call to <code>ev_loop_new</code>.</p> 210earlier call to <code>ev_loop_new</code>.</p>
… …
212after forking, in either the parent or child process (or both, but that 216after forking, in either the parent or child process (or both, but that
213again makes little sense).</p> 217again makes little sense).</p>
214 <p>You <i>must</i> call this function after forking if and only if you want to 218 <p>You <i>must</i> call this function after forking if and only if you want to
215use the event library in both processes. If you just fork+exec, you don't 219use the event library in both processes. If you just fork+exec, you don't
216have to call it.</p> 220have to call it.</p>
217 <p>The function itself is quite fast and its usually not a problem to call 221 <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 222it 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> 223quite nicely into a call to <code>pthread_atfork</code>:</p>
220<pre> pthread_atfork (0, 0, ev_default_fork); 224<pre> pthread_atfork (0, 0, ev_default_fork);
221 225
222</pre> 226</pre>
… …
230 <dt>unsigned int ev_method (loop)</dt> 234 <dt>unsigned int ev_method (loop)</dt>
231 <dd> 235 <dd>
232 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 236 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in
233use.</p> 237use.</p>
234 </dd> 238 </dd>
235 <dt>ev_tstamp = ev_now (loop)</dt> 239 <dt>ev_tstamp ev_now (loop)</dt>
236 <dd> 240 <dd>
237 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 241 <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 242got events and started processing them. This timestamp does not change
239as long as callbacks are being processed, and this is also the base time 243as 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 244used for relative timers. You can treat it as the timestamp of the event
… …
247events.</p> 251events.</p>
248 <p>If the flags argument is specified as 0, it will not return until either 252 <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> 253no 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 254 <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 255those events and any outstanding ones, but will not block your process in
252case there are no events.</p> 256case 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 257 <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 258neccessary) and will handle those and any outstanding ones. It will block
255your process until at least one new event arrives.</p> 259your process until at least one new event arrives, and will return after
260one iteration of the loop.</p>
256 <p>This flags value could be used to implement alternative looping 261 <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 262constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
258more generic mechanism.</p> 263more generic mechanism.</p>
259 </dd> 264 </dd>
260 <dt>ev_unloop (loop, how)</dt> 265 <dt>ev_unloop (loop, how)</dt>
261 <dd> 266 <dd>
262 <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument 267 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
268has 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> 269<code>EVUNLOOP_ONCE</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> 270<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
265calls return.</p>
266 </dd> 271 </dd>
267 <dt>ev_ref (loop)</dt> 272 <dt>ev_ref (loop)</dt>
268 <dt>ev_unref (loop)</dt> 273 <dt>ev_unref (loop)</dt>
269 <dd> 274 <dd>
270 <p>Ref/unref can be used to add or remove a refcount on the event loop: Every 275 <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 276loop: Every watcher keeps one reference, and as long as the reference
272unregister that should not keep ev_loop from running, ev_unref() after 277count 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 278a 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 279returning, 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 280example, 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 281visible 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 282no event watchers registered by it are active. It is also an excellent
278before stop.</p> 283way to do this for generic recurring timers or from within third-party
284libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
279 </dd> 285 </dd>
280</dl> 286</dl>
281 287
282</div> 288</div>
283<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 289<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"> 290<div id="ANATOMY_OF_A_WATCHER_CONTENT">
285<p>A watcher is a structure that you create and register to record your 291<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 292interest 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> 293become 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) 294<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
289 { 295 {
290 ev_io_stop (w); 296 ev_io_stop (w);
291 ev_unloop (loop, EVUNLOOP_ALL); 297 ev_unloop (loop, EVUNLOOP_ALL);
292 } 298 }
… …
316*)</code>), and you can stop watching for events at any time by calling the 322*)</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> 323corresponding 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 324<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 325must not touch the values stored in it. Most specifically you must never
320reinitialise it or call its set method.</p> 326reinitialise it or call its set method.</p>
321<p>You cna check wether an event is active by calling the <code>ev_is_active 327<p>You cna 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 328(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 329callback for it has not been called yet) you cna use the <code>ev_is_pending
324(watcher *)</code> macro.</p> 330(watcher *)</code> macro.</p>
325<p>Each and every callback receives the event loop pointer as first, the 331<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 332registered watcher structure as second, and a bitset of received events as
327third argument.</p> 333third argument.</p>
328<p>The rceeived events usually include a single bit per event type received 334<p>The rceeived events usually include a single bit per event type received
329(you can receive multiple events at the same time). The possible bit masks 335(you can receive multiple events at the same time). The possible bit masks
330are:</p> 336are:</p>
331<dl> 337<dl>
332 <dt>EV_READ</dt> 338 <dt><code>EV_READ</code></dt>
333 <dt>EV_WRITE</dt> 339 <dt><code>EV_WRITE</code></dt>
334 <dd> 340 <dd>
335 <p>The file descriptor in the ev_io watcher has become readable and/or 341 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
336writable.</p> 342writable.</p>
337 </dd> 343 </dd>
338 <dt>EV_TIMEOUT</dt> 344 <dt><code>EV_TIMEOUT</code></dt>
339 <dd>
340 <p>The ev_timer watcher has timed out.</p>
341 </dd> 345 <dd>
342 <dt>EV_PERIODIC</dt> 346 <p>The <code>ev_timer</code> watcher has timed out.</p>
343 <dd> 347 </dd>
344 <p>The ev_periodic watcher has timed out.</p> 348 <dt><code>EV_PERIODIC</code></dt>
345 </dd> 349 <dd>
346 <dt>EV_SIGNAL</dt> 350 <p>The <code>ev_periodic</code> watcher has timed out.</p>
347 <dd> 351 </dd>
352 <dt><code>EV_SIGNAL</code></dt>
353 <dd>
348 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 354 <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> 355 </dd>
356 <dt><code>EV_CHILD</code></dt>
357 <dd>
352 <p>The pid specified in the ev_child watcher has received a status change.</p> 358 <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> 359 </dd>
360 <dt><code>EV_IDLE</code></dt>
361 <dd>
356 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 362 <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> 363 </dd>
364 <dt><code>EV_PREPARE</code></dt>
365 <dt><code>EV_CHECK</code></dt>
366 <dd>
361 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 367 <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 368to 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 369<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 370received 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 371many 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 372(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
367<code>ev_loop</code> from blocking).</p> 373<code>ev_loop</code> from blocking).</p>
368 </dd> 374 </dd>
369 <dt>EV_ERROR</dt> 375 <dt><code>EV_ERROR</code></dt>
370 <dd> 376 <dd>
371 <p>An unspecified error has occured, the watcher has been stopped. This might 377 <p>An unspecified error has occured, the watcher has been stopped. This might
372happen because the watcher could not be properly started because libev 378happen 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 379ran 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 380problem. You best act on it by reporting the problem and somehow coping
… …
420<div id="WATCHER_TYPES_CONTENT"> 426<div id="WATCHER_TYPES_CONTENT">
421<p>This section describes each watcher in detail, but will not repeat 427<p>This section describes each watcher in detail, but will not repeat
422information given in the last section.</p> 428information given in the last section.</p>
423 429
424</div> 430</div>
425<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 431<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"> 432<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 433<p>I/O watchers check whether a file descriptor is readable or writable
428in each iteration of the event loop (This behaviour is called 434in each iteration of the event loop (This behaviour is called
429level-triggering because you keep receiving events as long as the 435level-triggering because you keep receiving events as long as the
430condition persists. Remember you cna stop the watcher if you don't want to 436condition persists. Remember you cna stop the watcher if you don't want to
431act on the event and neither want to receive future events).</p> 437act on the event and neither want to receive future events).</p>
438<p>In general you can register as many read and/or write event watchers oer
439fd as you want (as long as you don't confuse yourself). Setting all file
440descriptors to non-blocking mode is also usually a good idea (but not
441required if you know what you are doing).</p>
442<p>You have to be careful with dup'ed file descriptors, though. Some backends
443(the linux epoll backend is a notable example) cannot handle dup'ed file
444descriptors correctly if you register interest in two or more fds pointing
445to the same file/socket etc. description.</p>
446<p>If you must do this, then force the use of a known-to-be-good backend
447(at the time of this writing, this includes only EVMETHOD_SELECT and
448EVMETHOD_POLL).</p>
432<dl> 449<dl>
433 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 450 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
434 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 451 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
435 <dd> 452 <dd>
436 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 453 <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 | 454events 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> 455EV_WRITE</code> to receive the given events.</p>
439 </dd> 456 </dd>
440</dl> 457</dl>
441 458
442</div> 459</div>
443<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 460<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"> 461<div id="code_ev_timer_code_relative_and_opti-2">
445<p>Timer watchers are simple relative timers that generate an event after a 462<p>Timer watchers are simple relative timers that generate an event after a
446given time, and optionally repeating in regular intervals after that.</p> 463given 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 464<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 465times out after an hour and youreset your system clock to last years
449time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 466time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
450detecting time jumps is hard, and soem inaccuracies are unavoidable (the 467detecting time jumps is hard, and soem inaccuracies are unavoidable (the
451monotonic clock option helps a lot here).</p> 468monotonic clock option helps a lot here).</p>
469<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
470time. This is usually the right thing as this timestamp refers to the time
471of the event triggering whatever timeout you are modifying/starting. If
472you suspect event processing to be delayed and you *need* to base the timeout
473ion the current time, use something like this to adjust for this:</p>
474<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
475
476</pre>
452<dl> 477<dl>
453 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 478 <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> 479 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
455 <dd> 480 <dd>
456 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 481 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
472value), or reset the running timer to the repeat value.</p> 497value), or reset the running timer to the repeat value.</p>
473 <p>This sounds a bit complicated, but here is a useful and typical 498 <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 499example: 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 500timeout, 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 501seconds 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 502configure 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 503time 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 504state 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> 505the timer, and again will automatically restart it if need be.</p>
481 </dd> 506 </dd>
482</dl> 507</dl>
483 508
484</div> 509</div>
485<h2 id="ev_periodic">ev_periodic</h2> 510<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</h2>
486<div id="ev_periodic_CONTENT"> 511<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 512<p>Periodic watchers are also timers of a kind, but they are very versatile
488(and unfortunately a bit complex).</p> 513(and unfortunately a bit complex).</p>
489<p>Unlike ev_timer's, they are not based on real time (or relative time) 514<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 515but 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 516to 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 () 517periodic 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 518+ 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 519take 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 520roughly 10 seconds later and of course not if you reset your system time
496again).</p> 521again).</p>
497<p>They can also be used to implement vastly more complex timers, such as 522<p>They can also be used to implement vastly more complex timers, such as
498triggering an event on eahc midnight, local time.</p> 523triggering an event on eahc midnight, local time.</p>
499<dl> 524<dl>
… …
525<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 550<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
526 551
527</pre> 552</pre>
528 <p>This doesn't mean there will always be 3600 seconds in between triggers, 553 <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 554but 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 555full hour (UTC), or more correctly, when the system time is evenly divisible
531by 3600.</p> 556by 3600.</p>
532 <p>Another way to think about it (for the mathematically inclined) is that 557 <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 558<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> 559time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
535 </dd> 560 </dd>
536 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 561 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
537 <dd> 562 <dd>
538 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 563 <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 564ignored. Instead, each time the periodic watcher gets scheduled, the
540reschedule callback will be called with the watcher as first, and the 565reschedule callback will be called with the watcher as first, and the
541current time as second argument.</p> 566current time as second argument.</p>
542 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 567 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other
543periodic watcher, ever, or make any event loop modificstions</i>. If you need 568periodic watcher, ever, or make any event loop modifications</i>. If you need
544to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 569to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p>
570 <p>Also, <i>&lt;this callback must always return a time that is later than the
571passed <code>now</code> value </i>&gt;. Not even <code>now</code> itself will be ok.</p>
545 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 572 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
546ev_tstamp now)&gt;, e.g.:</p> 573ev_tstamp now)&gt;, e.g.:</p>
547<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 574<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
548 { 575 {
549 return now + 60.; 576 return now + 60.;
… …
570program when the crontabs have changed).</p> 597program when the crontabs have changed).</p>
571 </dd> 598 </dd>
572</dl> 599</dl>
573 600
574</div> 601</div>
575<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 602<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"> 603<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 604<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 605signal 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 606will try it's best to deliver signals synchronously, i.e. as part of the
580normal event processing, like any other event.</p> 607normal event processing, like any other event.</p>
581<p>You cna configure as many watchers as you like per signal. Only when the 608<p>You cna configure as many watchers as you like per signal. Only when the
582first watcher gets started will libev actually register a signal watcher 609first watcher gets started will libev actually register a signal watcher
583with the kernel (thus it coexists with your own signal handlers as long 610with 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 611as you don't register any with libev). Similarly, when the last signal
… …
592of the <code>SIGxxx</code> constants).</p> 619of the <code>SIGxxx</code> constants).</p>
593 </dd> 620 </dd>
594</dl> 621</dl>
595 622
596</div> 623</div>
597<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 624<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"> 625<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 626<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> 627some child status changes (most typically when a child of yours dies).</p>
601<dl> 628<dl>
602 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 629 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
603 <dt>ev_child_set (ev_child *, int pid)</dt> 630 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
609contains the pid of the process causing the status change.</p> 636contains the pid of the process causing the status change.</p>
610 </dd> 637 </dd>
611</dl> 638</dl>
612 639
613</div> 640</div>
614<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 641<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"> 642<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 643<p>Idle watchers trigger events when there are no other I/O or timer (or
617periodic) events pending. That is, as long as your process is busy 644periodic) events pending. That is, as long as your process is busy
618handling sockets or timeouts it will not be called. But when your process 645handling sockets or timeouts it will not be called. But when your process
619is idle all idle watchers are being called again and again - until 646is idle all idle watchers are being called again and again - until
620stopped, that is, or your process receives more events.</p> 647stopped, that is, or your process receives more events.</p>
… …
641watchers afterwards.</p> 668watchers afterwards.</p>
642<p>Their main purpose is to integrate other event mechanisms into libev. This 669<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 670could be used, for example, to track variable changes, implement your own
644watchers, integrate net-snmp or a coroutine library and lots more.</p> 671watchers, 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 672<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 673to be watched by the other library, registering <code>ev_io</code> watchers for them
647and starting an ev_timer watcher for any timeouts (many libraries provide 674and starting an <code>ev_timer</code> watcher for any timeouts (many libraries provide
648just this functionality). Then, in the check watcher you check for any 675just this functionality). Then, in the check watcher you check for any
649events that occured (by making your callbacks set soem flags for example) 676events that occured (by making your callbacks set soem flags for example)
650and call back into the library.</p> 677and call back into the library.</p>
651<p>As another example, the perl Coro module uses these hooks to integrate 678<p>As another example, the perl Coro module uses these hooks to integrate
652coroutines into libev programs, by yielding to other active coroutines 679coroutines into libev programs, by yielding to other active coroutines
… …
673callback on whichever event happens first and automatically stop both 700callback 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 701watchers. 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 702or timeout without havign to allocate/configure/start/stop/free one or
676more watchers yourself.</p> 703more watchers yourself.</p>
677 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 704 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is
678ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 705ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and <code>events</code> set
679will be craeted and started.</p> 706will be craeted and started.</p>
680 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 707 <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 708started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and repeat
682= 0) will be started.</p> 709= 0) will be started.</p>
683 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 710 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and
684gets passed an events set (normally a combination of EV_ERROR, EV_READ, 711gets passed an events set (normally a combination of <code>EV_ERROR</code>, <code>EV_READ</code>,
685EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 712<code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> value passed to <code>ev_once</code>:</p>
686<pre> static void stdin_ready (int revents, void *arg) 713<pre> static void stdin_ready (int revents, void *arg)
687 { 714 {
688 if (revents &amp; EV_TIMEOUT) 715 if (revents &amp; EV_TIMEOUT)
689 /* doh, nothing entered */ 716 /* doh, nothing entered */
690 else if (revents &amp; EV_READ) 717 else if (revents &amp; EV_READ)

Diff Legend

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