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4	<head>	4	<head>
5	<title>libev</title>	5	<title>libev</title>
6	<meta name="description" content="Pod documentation for libev" />	6	<meta name="description" content="Pod documentation for libev" />
7	<meta name="inputfile" content="<standard input>" />	7	<meta name="inputfile" content="<standard input>" />
8	<meta name="outputfile" content="<standard output>" />	8	<meta name="outputfile" content="<standard output>" />
9	<meta name="created" content="Fri Nov 23 09:26:40 2007" />	9	<meta name="created" content="Sat Nov 24 05:58:35 2007" />
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12	<body>	12	<body>
13	<div class="pod">	13	<div class="pod">
14	<!-- INDEX START -->	14	<!-- INDEX START -->
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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="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</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="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</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="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</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="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</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	<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>
		37	<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li>
37	</ul>	38	</ul>
38	</li>	39	</li>
39	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>	40	<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>	41	<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>	42	<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
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96	<div id="TIME_REPRESENTATION_CONTENT">	97	<div id="TIME_REPRESENTATION_CONTENT">
97	<p>Libev represents time as a single floating point number, representing the	98	<p>Libev represents time as a single floating point number, representing the
98	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
99	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
100	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases	101	called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
101	to the double type in C.</p>	102	to the <code>double</code> type in C, and when you need to do any calculations on
		103	it, you should treat it as such.</p>
		104
		105
		106
		107
102		108
103	</div>	109	</div>
104	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	110	<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105	<div id="GLOBAL_FUNCTIONS_CONTENT">	111	<div id="GLOBAL_FUNCTIONS_CONTENT">
106	<p>These functions can be called anytime, even before initialising the	112	<p>These functions can be called anytime, even before initialising the
…		…
122	version of the library your program was compiled against.</p>	128	version of the library your program was compiled against.</p>
123	<p>Usually, it's a good idea to terminate if the major versions mismatch,	129	<p>Usually, it's a good idea to terminate if the major versions mismatch,
124	as this indicates an incompatible change. Minor versions are usually	130	as this indicates an incompatible change. Minor versions are usually
125	compatible to older versions, so a larger minor version alone is usually	131	compatible to older versions, so a larger minor version alone is usually
126	not a problem.</p>	132	not a problem.</p>
		133	<p>Example: make sure we haven't accidentally been linked against the wrong
		134	version:</p>
		135	<pre> assert (("libev version mismatch",
		136	ev_version_major () == EV_VERSION_MAJOR
		137	&& ev_version_minor () >= EV_VERSION_MINOR));
		138
		139	</pre>
127	</dd>	140	</dd>
128	<dt>unsigned int ev_supported_backends ()</dt>	141	<dt>unsigned int ev_supported_backends ()</dt>
129	<dd>	142	<dd>
130	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>	143	<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
131	value) compiled into this binary of libev (independent of their	144	value) compiled into this binary of libev (independent of their
132	availability on the system you are running on). See <code>ev_default_loop</code> for	145	availability on the system you are running on). See <code>ev_default_loop</code> for
133	a description of the set values.</p>	146	a description of the set values.</p>
		147	<p>Example: make sure we have the epoll method, because yeah this is cool and
		148	a must have and can we have a torrent of it please!!!11</p>
		149	<pre> assert (("sorry, no epoll, no sex",
		150	ev_supported_backends () & EVBACKEND_EPOLL));
		151
		152	</pre>
134	</dd>	153	</dd>
135	<dt>unsigned int ev_recommended_backends ()</dt>	154	<dt>unsigned int ev_recommended_backends ()</dt>
136	<dd>	155	<dd>
137	<p>Return the set of all backends compiled into this binary of libev and also	156	<p>Return the set of all backends compiled into this binary of libev and also
138	recommended for this platform. This set is often smaller than the one	157	recommended for this platform. This set is often smaller than the one
139	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on	158	returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
140	most BSDs and will not be autodetected unless you explicitly request it	159	most 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	160	(assuming you know what you are doing). This is the set of backends that
142	<code>EVFLAG_AUTO</code> will probe for.</p>	161	libev will probe for if you specify no backends explicitly.</p>
		162	</dd>
		163	<dt>unsigned int ev_embeddable_backends ()</dt>
		164	<dd>
		165	<p>Returns the set of backends that are embeddable in other event loops. This
		166	is the theoretical, all-platform, value. To find which backends
		167	might be supported on the current system, you would need to look at
		168	<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for
		169	recommended ones.</p>
		170	<p>See the description of <code>ev_embed</code> watchers for more info.</p>
143	</dd>	171	</dd>
144	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>	172	<dt>ev_set_allocator (void (cb)(void *ptr, long size))</dt>
145	<dd>	173	<dd>
146	<p>Sets the allocation function to use (the prototype is similar to the	174	<p>Sets the allocation function to use (the prototype is similar to the
147	realloc C function, the semantics are identical). It is used to allocate	175	realloc C function, the semantics are identical). It is used to allocate
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149	needs to be allocated, the library might abort or take some potentially	177	needs to be allocated, the library might abort or take some potentially
150	destructive action. The default is your system realloc function.</p>	178	destructive action. The default is your system realloc function.</p>
151	<p>You could override this function in high-availability programs to, say,	179	<p>You could override this function in high-availability programs to, say,
152	free some memory if it cannot allocate memory, to use a special allocator,	180	free some memory if it cannot allocate memory, to use a special allocator,
153	or even to sleep a while and retry until some memory is available.</p>	181	or even to sleep a while and retry until some memory is available.</p>
		182	<p>Example: replace the libev allocator with one that waits a bit and then
		183	retries: better than mine).</p>
		184	<pre> static void *
		185	persistent_realloc (void *ptr, long size)
		186	{
		187	for (;;)
		188	{
		189	void *newptr = realloc (ptr, size);
		190
		191	if (newptr)
		192	return newptr;
		193
		194	sleep (60);
		195	}
		196	}
		197
		198	...
		199	ev_set_allocator (persistent_realloc);
		200
		201	</pre>
154	</dd>	202	</dd>
155	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>	203	<dt>ev_set_syserr_cb (void (cb)(const char msg));</dt>
156	<dd>	204	<dd>
157	<p>Set the callback function to call on a retryable syscall error (such	205	<p>Set the callback function to call on a retryable syscall error (such
158	as failed select, poll, epoll_wait). The message is a printable string	206	as failed select, poll, epoll_wait). The message is a printable string
159	indicating the system call or subsystem causing the problem. If this	207	indicating the system call or subsystem causing the problem. If this
160	callback is set, then libev will expect it to remedy the sitution, no	208	callback is set, then libev will expect it to remedy the sitution, no
161	matter what, when it returns. That is, libev will generally retry the	209	matter what, when it returns. That is, libev will generally retry the
162	requested operation, or, if the condition doesn't go away, do bad stuff	210	requested operation, or, if the condition doesn't go away, do bad stuff
163	(such as abort).</p>	211	(such as abort).</p>
		212	<p>Example: do the same thing as libev does internally:</p>
		213	<pre> static void
		214	fatal_error (const char *msg)
		215	{
		216	perror (msg);
		217	abort ();
		218	}
		219
		220	...
		221	ev_set_syserr_cb (fatal_error);
		222
		223	</pre>
164	</dd>	224	</dd>
165	</dl>	225	</dl>
166		226
167	</div>	227	</div>
168	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>	228	<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
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184	false. If it already was initialised it simply returns it (and ignores the	244	false. If it already was initialised it simply returns it (and ignores the
185	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>	245	flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
186	<p>If you don't know what event loop to use, use the one returned from this	246	<p>If you don't know what event loop to use, use the one returned from this
187	function.</p>	247	function.</p>
188	<p>The flags argument can be used to specify special behaviour or specific	248	<p>The flags argument can be used to specify special behaviour or specific
189	backends to use, and is usually specified as <code>0</code> (or EVFLAG_AUTO).</p>	249	backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
190	<p>It supports the following flags:</p>	250	<p>The following flags are supported:</p>
191	<p>	251	<p>
192	<dl>	252	<dl>
193	<dt><code>EVFLAG_AUTO</code></dt>	253	<dt><code>EVFLAG_AUTO</code></dt>
194	<dd>	254	<dd>
195	<p>The default flags value. Use this if you have no clue (it's the right	255	<p>The default flags value. Use this if you have no clue (it's the right
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237	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>	297	<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
238	<dd>	298	<dd>
239	<p>Kqueue deserves special mention, as at the time of this writing, it	299	<p>Kqueue deserves special mention, as at the time of this writing, it
240	was broken on all BSDs except NetBSD (usually it doesn't work with	300	was broken on all BSDs except NetBSD (usually it doesn't work with
241	anything but sockets and pipes, except on Darwin, where of course its	301	anything but sockets and pipes, except on Darwin, where of course its
242	completely useless). For this reason its not being "autodetected" unless	302	completely useless). For this reason its not being "autodetected"
243	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p>	303	unless you explicitly specify it explicitly in the flags (i.e. using
		304	<code>EVBACKEND_KQUEUE</code>).</p>
244	<p>It scales in the same way as the epoll backend, but the interface to the	305	<p>It scales in the same way as the epoll backend, but the interface to the
245	kernel is more efficient (which says nothing about its actual speed, of	306	kernel is more efficient (which says nothing about its actual speed, of
246	course). While starting and stopping an I/O watcher does not cause an	307	course). While starting and stopping an I/O watcher does not cause an
247	extra syscall as with epoll, it still adds up to four event changes per	308	extra syscall as with epoll, it still adds up to four event changes per
248	incident, so its best to avoid that.</p>	309	incident, so its best to avoid that.</p>
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269	</p>	330	</p>
270	<p>If one or more of these are ored into the flags value, then only these	331	<p>If one or more of these are ored into the flags value, then only these
271	backends will be tried (in the reverse order as given here). If none are	332	backends will be tried (in the reverse order as given here). If none are
272	specified, most compiled-in backend will be tried, usually in reverse	333	specified, most compiled-in backend will be tried, usually in reverse
273	order of their flag values :)</p>	334	order of their flag values :)</p>
		335	<p>The most typical usage is like this:</p>
		336	<pre> if (!ev_default_loop (0))
		337	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		338
		339	</pre>
		340	<p>Restrict libev to the select and poll backends, and do not allow
		341	environment settings to be taken into account:</p>
		342	<pre> ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		343
		344	</pre>
		345	<p>Use whatever libev has to offer, but make sure that kqueue is used if
		346	available (warning, breaks stuff, best use only with your own private
		347	event loop and only if you know the OS supports your types of fds):</p>
		348	<pre> ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		349
		350	</pre>
274	</dd>	351	</dd>
275	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>	352	<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
276	<dd>	353	<dd>
277	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is	354	<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
278	always distinct from the default loop. Unlike the default loop, it cannot	355	always distinct from the default loop. Unlike the default loop, it cannot
279	handle signal and child watchers, and attempts to do so will be greeted by	356	handle signal and child watchers, and attempts to do so will be greeted by
280	undefined behaviour (or a failed assertion if assertions are enabled).</p>	357	undefined behaviour (or a failed assertion if assertions are enabled).</p>
		358	<p>Example: try to create a event loop that uses epoll and nothing else.</p>
		359	<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		360	if (!epoller)
		361	fatal ("no epoll found here, maybe it hides under your chair");
		362
		363	</pre>
281	</dd>	364	</dd>
282	<dt>ev_default_destroy ()</dt>	365	<dt>ev_default_destroy ()</dt>
283	<dd>	366	<dd>
284	<p>Destroys the default loop again (frees all memory and kernel state	367	<p>Destroys the default loop again (frees all memory and kernel state
285	etc.). This stops all registered event watchers (by not touching them in	368	etc.). This stops all registered event watchers (by not touching them in
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321	use.</p>	404	use.</p>
322	</dd>	405	</dd>
323	<dt>ev_tstamp ev_now (loop)</dt>	406	<dt>ev_tstamp ev_now (loop)</dt>
324	<dd>	407	<dd>
325	<p>Returns the current "event loop time", which is the time the event loop	408	<p>Returns the current "event loop time", which is the time the event loop
326	got events and started processing them. This timestamp does not change	409	received events and started processing them. This timestamp does not
327	as long as callbacks are being processed, and this is also the base time	410	change as long as callbacks are being processed, and this is also the base
328	used for relative timers. You can treat it as the timestamp of the event	411	time used for relative timers. You can treat it as the timestamp of the
329	occuring (or more correctly, the mainloop finding out about it).</p>	412	event occuring (or more correctly, libev finding out about it).</p>
330	</dd>	413	</dd>
331	<dt>ev_loop (loop, int flags)</dt>	414	<dt>ev_loop (loop, int flags)</dt>
332	<dd>	415	<dd>
333	<p>Finally, this is it, the event handler. This function usually is called	416	<p>Finally, this is it, the event handler. This function usually is called
334	after you initialised all your watchers and you want to start handling	417	after you initialised all your watchers and you want to start handling
335	events.</p>	418	events.</p>
336	<p>If the flags argument is specified as 0, it will not return until either	419	<p>If the flags argument is specified as <code>0</code>, it will not return until
337	no event watchers are active anymore or <code>ev_unloop</code> was called.</p>	420	either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
		421	<p>Please note that an explicit <code>ev_unloop</code> is usually better than
		422	relying on all watchers to be stopped when deciding when a program has
		423	finished (especially in interactive programs), but having a program that
		424	automatically loops as long as it has to and no longer by virtue of
		425	relying on its watchers stopping correctly is a thing of beauty.</p>
338	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle	426	<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
339	those events and any outstanding ones, but will not block your process in	427	those events and any outstanding ones, but will not block your process in
340	case there are no events and will return after one iteration of the loop.</p>	428	case there are no events and will return after one iteration of the loop.</p>
341	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if	429	<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
342	neccessary) and will handle those and any outstanding ones. It will block	430	neccessary) and will handle those and any outstanding ones. It will block
343	your process until at least one new event arrives, and will return after	431	your process until at least one new event arrives, and will return after
344	one iteration of the loop.</p>	432	one iteration of the loop. This is useful if you are waiting for some
345	<p>This flags value could be used to implement alternative looping	433	external event in conjunction with something not expressible using other
346	constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and	434	libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
347	more generic mechanism.</p>	435	usually a better approach for this kind of thing.</p>
348	<p>Here are the gory details of what ev_loop does:</p>	436	<p>Here are the gory details of what <code>ev_loop</code> does:</p>
349	<pre> 1. If there are no active watchers (reference count is zero), return.	437	<pre> * If there are no active watchers (reference count is zero), return.
350	2. Queue and immediately call all prepare watchers.	438	- Queue prepare watchers and then call all outstanding watchers.
351	3. If we have been forked, recreate the kernel state.	439	- If we have been forked, recreate the kernel state.
352	4. Update the kernel state with all outstanding changes.	440	- Update the kernel state with all outstanding changes.
353	5. Update the "event loop time".	441	- Update the "event loop time".
354	6. Calculate for how long to block.	442	- Calculate for how long to block.
355	7. Block the process, waiting for events.	443	- Block the process, waiting for any events.
		444	- Queue all outstanding I/O (fd) events.
356	8. Update the "event loop time" and do time jump handling.	445	- Update the "event loop time" and do time jump handling.
357	9. Queue all outstanding timers.	446	- Queue all outstanding timers.
358	10. Queue all outstanding periodics.	447	- Queue all outstanding periodics.
359	11. If no events are pending now, queue all idle watchers.	448	- If no events are pending now, queue all idle watchers.
360	12. Queue all check watchers.	449	- Queue all check watchers.
361	13. Call all queued watchers in reverse order (i.e. check watchers first).	450	- Call all queued watchers in reverse order (i.e. check watchers first).
		451	Signals and child watchers are implemented as I/O watchers, and will
		452	be handled here by queueing them when their watcher gets executed.
362	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	453	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
363	was used, return, otherwise continue with step #1.	454	were used, return, otherwise continue with step *.
		455
		456	</pre>
		457	<p>Example: queue some jobs and then loop until no events are outsanding
		458	anymore.</p>
		459	<pre> ... queue jobs here, make sure they register event watchers as long
		460	... as they still have work to do (even an idle watcher will do..)
		461	ev_loop (my_loop, 0);
		462	... jobs done. yeah!
364		463
365	</pre>	464	</pre>
366	</dd>	465	</dd>
367	<dt>ev_unloop (loop, how)</dt>	466	<dt>ev_unloop (loop, how)</dt>
368	<dd>	467	<dd>
…		…
382	example, libev itself uses this for its internal signal pipe: It is not	481	example, libev itself uses this for its internal signal pipe: It is not
383	visible to the libev user and should not keep <code>ev_loop</code> from exiting if	482	visible to the libev user and should not keep <code>ev_loop</code> from exiting if
384	no event watchers registered by it are active. It is also an excellent	483	no event watchers registered by it are active. It is also an excellent
385	way to do this for generic recurring timers or from within third-party	484	way to do this for generic recurring timers or from within third-party
386	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>	485	libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
		486	<p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
		487	running when nothing else is active.</p>
		488	<pre> struct dv_signal exitsig;
		489	ev_signal_init (&exitsig, sig_cb, SIGINT);
		490	ev_signal_start (myloop, &exitsig);
		491	evf_unref (myloop);
		492
		493	</pre>
		494	<p>Example: for some weird reason, unregister the above signal handler again.</p>
		495	<pre> ev_ref (myloop);
		496	ev_signal_stop (myloop, &exitsig);
		497
		498	</pre>
387	</dd>	499	</dd>
388	</dl>	500	</dl>
389		501
390	</div>	502	</div>
391	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>	503	<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
…		…
527	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>	639	<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
528	<div id="WATCHER_TYPES_CONTENT">	640	<div id="WATCHER_TYPES_CONTENT">
529	<p>This section describes each watcher in detail, but will not repeat	641	<p>This section describes each watcher in detail, but will not repeat
530	information given in the last section.</p>	642	information given in the last section.</p>
531		643
		644
		645
		646
		647
532	</div>	648	</div>
533	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>	649	<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
534	<div id="code_ev_io_code_is_this_file_descrip-2">	650	<div id="code_ev_io_code_is_this_file_descrip-2">
535	<p>I/O watchers check whether a file descriptor is readable or writable	651	<p>I/O watchers check whether a file descriptor is readable or writable
536	in each iteration of the event loop (This behaviour is called	652	in each iteration of the event loop (This behaviour is called
…		…
566	when the readyness condition is no longer valid even when employing	682	when the readyness condition is no longer valid even when employing
567	typical ways of handling events, so its a good idea to use non-blocking	683	typical ways of handling events, so its a good idea to use non-blocking
568	I/O unconditionally.</p>	684	I/O unconditionally.</p>
569	</dd>	685	</dd>
570	</dl>	686	</dl>
		687	<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
		688	readable, but only once. Since it is likely line-buffered, you could
		689	attempt to read a whole line in the callback:</p>
		690	<pre> static void
		691	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		692	{
		693	ev_io_stop (loop, w);
		694	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		695	}
		696
		697	...
		698	struct ev_loop *loop = ev_default_init (0);
		699	struct ev_io stdin_readable;
		700	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		701	ev_io_start (loop, &stdin_readable);
		702	ev_loop (loop, 0);
		703
		704
		705
		706
		707	</pre>
571		708
572	</div>	709	</div>
573	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>	710	<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
574	<div id="code_ev_timer_code_relative_and_opti-2">	711	<div id="code_ev_timer_code_relative_and_opti-2">
575	<p>Timer watchers are simple relative timers that generate an event after a	712	<p>Timer watchers are simple relative timers that generate an event after a
…		…
619	time you successfully read or write some data. If you go into an idle	756	time you successfully read or write some data. If you go into an idle
620	state where you do not expect data to travel on the socket, you can stop	757	state where you do not expect data to travel on the socket, you can stop
621	the timer, and again will automatically restart it if need be.</p>	758	the timer, and again will automatically restart it if need be.</p>
622	</dd>	759	</dd>
623	</dl>	760	</dl>
		761	<p>Example: create a timer that fires after 60 seconds.</p>
		762	<pre> static void
		763	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		764	{
		765	.. one minute over, w is actually stopped right here
		766	}
		767
		768	struct ev_timer mytimer;
		769	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		770	ev_timer_start (loop, &mytimer);
		771
		772	</pre>
		773	<p>Example: create a timeout timer that times out after 10 seconds of
		774	inactivity.</p>
		775	<pre> static void
		776	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		777	{
		778	.. ten seconds without any activity
		779	}
		780
		781	struct ev_timer mytimer;
		782	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		783	ev_timer_again (&mytimer); /* start timer */
		784	ev_loop (loop, 0);
		785
		786	// and in some piece of code that gets executed on any "activity":
		787	// reset the timeout to start ticking again at 10 seconds
		788	ev_timer_again (&mytimer);
		789
		790
		791
		792
		793	</pre>
624		794
625	</div>	795	</div>
626	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>	796	<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
627	<div id="code_ev_periodic_code_to_cron_or_not-2">	797	<div id="code_ev_periodic_code_to_cron_or_not-2">
628	<p>Periodic watchers are also timers of a kind, but they are very versatile	798	<p>Periodic watchers are also timers of a kind, but they are very versatile
…		…
712	when you changed some parameters or the reschedule callback would return	882	when you changed some parameters or the reschedule callback would return
713	a different time than the last time it was called (e.g. in a crond like	883	a different time than the last time it was called (e.g. in a crond like
714	program when the crontabs have changed).</p>	884	program when the crontabs have changed).</p>
715	</dd>	885	</dd>
716	</dl>	886	</dl>
		887	<p>Example: call a callback every hour, or, more precisely, whenever the
		888	system clock is divisible by 3600. The callback invocation times have
		889	potentially a lot of jittering, but good long-term stability.</p>
		890	<pre> static void
		891	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		892	{
		893	... its now a full hour (UTC, or TAI or whatever your clock follows)
		894	}
		895
		896	struct ev_periodic hourly_tick;
		897	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		898	ev_periodic_start (loop, &hourly_tick);
		899
		900	</pre>
		901	<p>Example: the same as above, but use a reschedule callback to do it:</p>
		902	<pre> #include <math.h>
		903
		904	static ev_tstamp
		905	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		906	{
		907	return fmod (now, 3600.) + 3600.;
		908	}
		909
		910	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		911
		912	</pre>
		913	<p>Example: call a callback every hour, starting now:</p>
		914	<pre> struct ev_periodic hourly_tick;
		915	ev_periodic_init (&hourly_tick, clock_cb,
		916	fmod (ev_now (loop), 3600.), 3600., 0);
		917	ev_periodic_start (loop, &hourly_tick);
		918
		919
		920
		921
		922	</pre>
717		923
718	</div>	924	</div>
719	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>	925	<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
720	<div id="code_ev_signal_code_signal_me_when_a-2">	926	<div id="code_ev_signal_code_signal_me_when_a-2">
721	<p>Signal watchers will trigger an event when the process receives a specific	927	<p>Signal watchers will trigger an event when the process receives a specific
…		…
735	<p>Configures the watcher to trigger on the given signal number (usually one	941	<p>Configures the watcher to trigger on the given signal number (usually one
736	of the <code>SIGxxx</code> constants).</p>	942	of the <code>SIGxxx</code> constants).</p>
737	</dd>	943	</dd>
738	</dl>	944	</dl>
739		945
		946
		947
		948
		949
740	</div>	950	</div>
741	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>	951	<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
742	<div id="code_ev_child_code_wait_for_pid_stat-2">	952	<div id="code_ev_child_code_wait_for_pid_stat-2">
743	<p>Child watchers trigger when your process receives a SIGCHLD in response to	953	<p>Child watchers trigger when your process receives a SIGCHLD in response to
744	some child status changes (most typically when a child of yours dies).</p>	954	some child status changes (most typically when a child of yours dies).</p>
…		…
752	the status word (use the macros from <code>sys/wait.h</code> and see your systems	962	the status word (use the macros from <code>sys/wait.h</code> and see your systems
753	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the	963	<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
754	process causing the status change.</p>	964	process causing the status change.</p>
755	</dd>	965	</dd>
756	</dl>	966	</dl>
		967	<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
		968	<pre> static void
		969	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		970	{
		971	ev_unloop (loop, EVUNLOOP_ALL);
		972	}
		973
		974	struct ev_signal signal_watcher;
		975	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		976	ev_signal_start (loop, &sigint_cb);
		977
		978
		979
		980
		981	</pre>
757		982
758	</div>	983	</div>
759	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>	984	<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
760	<div id="code_ev_idle_code_when_you_ve_got_no-2">	985	<div id="code_ev_idle_code_when_you_ve_got_no-2">
761	<p>Idle watchers trigger events when there are no other events are pending	986	<p>Idle watchers trigger events when there are no other events are pending
…		…
777	<p>Initialises and configures the idle watcher - it has no parameters of any	1002	<p>Initialises and configures the idle watcher - it has no parameters of any
778	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,	1003	kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
779	believe me.</p>	1004	believe me.</p>
780	</dd>	1005	</dd>
781	</dl>	1006	</dl>
		1007	<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
		1008	callback, free it. Alos, use no error checking, as usual.</p>
		1009	<pre> static void
		1010	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1011	{
		1012	free (w);
		1013	// now do something you wanted to do when the program has
		1014	// no longer asnything immediate to do.
		1015	}
		1016
		1017	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1018	ev_idle_init (idle_watcher, idle_cb);
		1019	ev_idle_start (loop, idle_cb);
		1020
		1021
		1022
		1023
		1024	</pre>
782		1025
783	</div>	1026	</div>
784	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>	1027	<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
785	<div id="code_ev_prepare_code_and_code_ev_che-2">	1028	<div id="code_ev_prepare_code_and_code_ev_che-2">
786	<p>Prepare and check watchers are usually (but not always) used in tandem:	1029	<p>Prepare and check watchers are usually (but not always) used in tandem:
787	prepare watchers get invoked before the process blocks and check watchers	1030	prepare watchers get invoked before the process blocks and check watchers
788	afterwards.</p>	1031	afterwards.</p>
789	<p>Their main purpose is to integrate other event mechanisms into libev. This	1032	<p>Their main purpose is to integrate other event mechanisms into libev and
790	could be used, for example, to track variable changes, implement your own	1033	their use is somewhat advanced. This could be used, for example, to track
791	watchers, integrate net-snmp or a coroutine library and lots more.</p>	1034	variable changes, implement your own watchers, integrate net-snmp or a
		1035	coroutine library and lots more.</p>
792	<p>This is done by examining in each prepare call which file descriptors need	1036	<p>This is done by examining in each prepare call which file descriptors need
793	to be watched by the other library, registering <code>ev_io</code> watchers for	1037	to be watched by the other library, registering <code>ev_io</code> watchers for
794	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries	1038	them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
795	provide just this functionality). Then, in the check watcher you check for	1039	provide just this functionality). Then, in the check watcher you check for
796	any events that occured (by checking the pending status of all watchers	1040	any events that occured (by checking the pending status of all watchers
…		…
812	<p>Initialises and configures the prepare or check watcher - they have no	1056	<p>Initialises and configures the prepare or check watcher - they have no
813	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>	1057	parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
814	macros, but using them is utterly, utterly and completely pointless.</p>	1058	macros, but using them is utterly, utterly and completely pointless.</p>
815	</dd>	1059	</dd>
816	</dl>	1060	</dl>
		1061	<p>Example: TODO.</p>
		1062
		1063
		1064
		1065
		1066
		1067	</div>
		1068	<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2>
		1069	<div id="code_ev_embed_code_when_one_backend_-2">
		1070	<p>This is a rather advanced watcher type that lets you embed one event loop
		1071	into another.</p>
		1072	<p>There are primarily two reasons you would want that: work around bugs and
		1073	prioritise I/O.</p>
		1074	<p>As an example for a bug workaround, the kqueue backend might only support
		1075	sockets on some platform, so it is unusable as generic backend, but you
		1076	still want to make use of it because you have many sockets and it scales
		1077	so nicely. In this case, you would create a kqueue-based loop and embed it
		1078	into your default loop (which might use e.g. poll). Overall operation will
		1079	be a bit slower because first libev has to poll and then call kevent, but
		1080	at least you can use both at what they are best.</p>
		1081	<p>As for prioritising I/O: rarely you have the case where some fds have
		1082	to be watched and handled very quickly (with low latency), and even
		1083	priorities and idle watchers might have too much overhead. In this case
		1084	you would put all the high priority stuff in one loop and all the rest in
		1085	a second one, and embed the second one in the first.</p>
		1086	<p>As long as the watcher is started it will automatically handle events. The
		1087	callback will be invoked whenever some events have been handled. You can
		1088	set the callback to <code>0</code> to avoid having to specify one if you are not
		1089	interested in that.</p>
		1090	<p>Also, there have not currently been made special provisions for forking:
		1091	when you fork, you not only have to call <code>ev_loop_fork</code> on both loops,
		1092	but you will also have to stop and restart any <code>ev_embed</code> watchers
		1093	yourself.</p>
		1094	<p>Unfortunately, not all backends are embeddable, only the ones returned by
		1095	<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any
		1096	portable one.</p>
		1097	<p>So when you want to use this feature you will always have to be prepared
		1098	that you cannot get an embeddable loop. The recommended way to get around
		1099	this is to have a separate variables for your embeddable loop, try to
		1100	create it, and if that fails, use the normal loop for everything:</p>
		1101	<pre> struct ev_loop *loop_hi = ev_default_init (0);
		1102	struct ev_loop *loop_lo = 0;
		1103	struct ev_embed embed;
		1104
		1105	// see if there is a chance of getting one that works
		1106	// (remember that a flags value of 0 means autodetection)
		1107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1109	: 0;
		1110
		1111	// if we got one, then embed it, otherwise default to loop_hi
		1112	if (loop_lo)
		1113	{
		1114	ev_embed_init (&embed, 0, loop_lo);
		1115	ev_embed_start (loop_hi, &embed);
		1116	}
		1117	else
		1118	loop_lo = loop_hi;
		1119
		1120	</pre>
		1121	<dl>
		1122	<dt>ev_embed_init (ev_embed , callback, struct ev_loop loop)</dt>
		1123	<dt>ev_embed_set (ev_embed , callback, struct ev_loop loop)</dt>
		1124	<dd>
		1125	<p>Configures the watcher to embed the given loop, which must be embeddable.</p>
		1126	</dd>
		1127	</dl>
		1128
		1129
		1130
		1131
817		1132
818	</div>	1133	</div>
819	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>	1134	<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
820	<div id="OTHER_FUNCTIONS_CONTENT">	1135	<div id="OTHER_FUNCTIONS_CONTENT">
821	<p>There are some other functions of possible interest. Described. Here. Now.</p>	1136	<p>There are some other functions of possible interest. Described. Here. Now.</p>
…		…
865	<dd>	1180	<dd>
866	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>	1181	<p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
867	</dd>	1182	</dd>
868	</dl>	1183	</dl>
869		1184
		1185
		1186
		1187
		1188
870	</div>	1189	</div>
871	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>	1190	<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
872	<div id="LIBEVENT_EMULATION_CONTENT">	1191	<div id="LIBEVENT_EMULATION_CONTENT">
873	<p>Libev offers a compatibility emulation layer for libevent. It cannot	1192	<p>Libev offers a compatibility emulation layer for libevent. It cannot
874	emulate the internals of libevent, so here are some usage hints:</p>	1193	emulate the internals of libevent, so here are some usage hints:</p>

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Revision 1.33 by root, Fri Nov 23 08:36:35 2007 UTC vs.
Revision 1.36 by root, Sat Nov 24 06:23:27 2007 UTC